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Sample records for hmqc heteronuclear multiple-quantum

  1. Population transfer HMQC for half-integer quadrupolar nuclei

    International Nuclear Information System (INIS)

    Wang, Qiang; Xu, Jun; Feng, Ningdong; Deng, Feng; Li, Yixuan; Trébosc, Julien; Lafon, Olivier; Hu, Bingwen; Chen, Qun; Amoureux, Jean-Paul

    2015-01-01

    This work presents a detailed analysis of a recently proposed nuclear magnetic resonance method [Wang et al., Chem. Commun. 49(59), 6653-6655 (2013)] for accelerating heteronuclear coherence transfers involving half-integer spin quadrupolar nuclei by manipulating their satellite transitions. This method, called Population Transfer Heteronuclear Multiple Quantum Correlation (PT-HMQC), is investigated in details by combining theoretical analyses, numerical simulations, and experimental investigations. We find that compared to instant inversion or instant saturation, continuous saturation is the most practical strategy to accelerate coherence transfers on half-integer quadrupolar nuclei. We further demonstrate that this strategy is efficient to enhance the sensitivity of J-mediated heteronuclear correlation experiments between two half-integer quadrupolar isotopes (e.g., 27 Al- 17 O). In this case, the build-up is strongly affected by relaxation for small T 2 ′ and J coupling values, and shortening the mixing time makes a huge signal enhancement. Moreover, this concept of population transfer can also be applied to dipolar-mediated HMQC experiments. Indeed, on the AlPO 4 -14 sample, one still observes experimentally a 2-fold shortening of the optimum mixing time albeit with no significant signal gain in the 31 P-( 27 Al) experiments

  2. Complete resonance assignment for the polypeptide backbone of interleukin 1β using three-dimensional heteronuclear NMR spectroscopy

    International Nuclear Information System (INIS)

    Driscoll, P.C.; Clore, G.M.; Marion, D.; Gronenborn, A.M.; Wingfield, P.T.

    1990-01-01

    The complete sequence-specific assignment of the 15 N and 1 H backbone resonances of the NMR spectrum of recombinant human interleukin 1β has been obtained by using primarily 15 N- 1 H heteronuclear three-dimensional (3D) NMR techniques in combination with 15 N- 1 H heteronuclear and 1 H homonuclear two-dimensional NMR. The fingerprint region of the spectrum was analyzed by using a combination of 3D heteronuclear 1 H Hartmann-Hahn 15 N- 1 H multiple quantum coherence (3D HOHAHA-HMQC) and 3D heteronuclear 1 H nuclear Overhauser 15 N- 1 H multiple quantum coherence (3D NOESY-HMQC) spectroscopies. The authors show that the problems of amide NH and C α H chemical shift degeneracy that are prevalent for proteins of the size are readily overcome by using the 3D heteronuclear NMR technique. A doubling of some peaks in the spectrum was found to be due to N-terminal heterogeneity of the 15 N-labeled protein, corresponding to a mixture of wild-type and des-Ala-1-interleukin 1β. The complete list of 15 N and 1 H assignments is given for all the amide NH and C α H resonances of all non-proline residues, as well as the 1 H assignments for some of the amino acid side chains. This first example of the sequence-specific assignment of a protein using heteronuclear 3D NMR provides a basis for further conformational and dynamic studies of interleukin 1β

  3. Mixed-time parallel evolution in multiple quantum NMR experiments: sensitivity and resolution enhancement in heteronuclear NMR

    International Nuclear Information System (INIS)

    Ying Jinfa; Chill, Jordan H.; Louis, John M.; Bax, Ad

    2007-01-01

    A new strategy is demonstrated that simultaneously enhances sensitivity and resolution in three- or higher-dimensional heteronuclear multiple quantum NMR experiments. The approach, referred to as mixed-time parallel evolution (MT-PARE), utilizes evolution of chemical shifts of the spins participating in the multiple quantum coherence in parallel, thereby reducing signal losses relative to sequential evolution. The signal in a given PARE dimension, t 1 , is of a non-decaying constant-time nature for a duration that depends on the length of t 2 , and vice versa, prior to the onset of conventional exponential decay. Line shape simulations for the 1 H- 15 N PARE indicate that this strategy significantly enhances both sensitivity and resolution in the indirect 1 H dimension, and that the unusual signal decay profile results in acceptable line shapes. Incorporation of the MT-PARE approach into a 3D HMQC-NOESY experiment for measurement of H N -H N NOEs in KcsA in SDS micelles at 50 o C was found to increase the experimental sensitivity by a factor of 1.7±0.3 with a concomitant resolution increase in the indirectly detected 1 H dimension. The method is also demonstrated for a situation in which homonuclear 13 C- 13 C decoupling is required while measuring weak H3'-2'OH NOEs in an RNA oligomer

  4. Biological activities of a new compound isolated from the aerial parts ...

    African Journals Online (AJOL)

    A new compound trivially named vitexcarpan was isolated from the ethyl acetate fraction of Vitex agnus castus. The structure of compound was elucidated with the help of spectroscopic techniques: 13C NMR, 1H NMR, heteronuclear multiple bond correlation (HMBC), heteronuclear multiple quantum coherence (HMQC), ...

  5. Quantum atom-heteronuclear molecule dark state: Role of population imbalance

    International Nuclear Information System (INIS)

    Jing Hui; Cui Shuai

    2010-01-01

    Recently, the finite-number effect of initial atoms in coherent atom-molecule conversion was investigated by Zhao et al. [Phys. Rev. Lett. 101, 010401 (2008)]. Here, by extending to the atom-heteronuclear molecule dark state, we find that the initial populations imbalance of the atoms plays a significant role in quantum conversion rate and adiabatic fidelity. In particular, even for the finite total number of imbalanced two-species atoms, the mean-field conversion rate, contrary to the general belief, still can be remarkably close to the exact quantum results.

  6. Trace level detection of compounds related to the chemical weapons convention by 1H-detected 13C NMR spectroscopy executed with a sensitivity-enhanced, cryogenic probehead.

    Science.gov (United States)

    Cullinan, David B; Hondrogiannis, George; Henderson, Terry J

    2008-04-15

    Two-dimensional 1H-13C HSQC (heteronuclear single quantum correlation) and fast-HMQC (heteronuclear multiple quantum correlation) pulse sequences were implemented using a sensitivity-enhanced, cryogenic probehead for detecting compounds relevant to the Chemical Weapons Convention present in complex mixtures. The resulting methods demonstrated exceptional sensitivity for detecting the analytes at trace level concentrations. 1H-13C correlations of target analytes at chemical shift information could be derived quickly and simultaneously from the resulting spectra. The fast-HMQC pulse sequences generated magnitude mode spectra suitable for detailed analysis in approximately 4.5 h and can be used in experiments to efficiently screen a large number of samples. The HSQC pulse sequences, on the other hand, required roughly twice the data acquisition time to produce suitable spectra. These spectra, however, were phase-sensitive, contained considerably more resolution in both dimensions, and proved to be superior for detecting analyte 1H-13C correlations. Furthermore, a HSQC spectrum collected with a multiplicity-edited pulse sequence provided additional structural information valuable for identifying target analytes. The HSQC pulse sequences are ideal for collecting high-quality data sets with overnight acquisitions and logically follow the use of fast-HMQC pulse sequences to rapidly screen samples for potential target analytes. Use of the pulse sequences considerably improves the performance of NMR spectroscopy as a complimentary technique for the screening, identification, and validation of chemical warfare agents and other small-molecule analytes present in complex mixtures and environmental samples.

  7. Detailed 1H and 13C NMR spectral data assignment for two dihydrobenzofuran neolignans

    International Nuclear Information System (INIS)

    Medeiros, Talita C.T.; Dias, Herbert J.; Crotti, Antônio E.M.

    2016-01-01

    In this work we present a complete proton ( 1 H) and carbon 13 ( 13 C) nuclear magnetic resonance (NMR) spectral analysis of two synthetic dihydrofuran neolignans (±)-trans-dehydrodicoumarate dimethyl ester and (±)-trans-dehydrodiferulate dimethyl ester. Unequivocal assignments were achieved by 1 H NMR, proton decoupled 13 C ( 13 C{ 1 H}) NMR spectra, gradient-selected correlation spectroscopy (gCOSY), J-resolved, gradient-selected heteronuclear multiple quantum coherence (gHMQC), gradient-selected heteronuclear multiple bond coherence (gHMBC) and nuclear Overhauser effect spectroscopy (NOESY) experiments. All hydrogen coupling constants were measured, clarifying all the hydrogen signals multiplicities. Computational methods were also used to simulate the 1 H and 13 C chemical shifts and showed good agreement with the trans configuration of the substituents at C 7 and C 8 . (author)

  8. Microbial transformation of Isopimpinellin by Glomerella cingulata.

    Science.gov (United States)

    Marumoto, Shinsuke; Miyazawa, Mitsuo

    2011-01-01

    Microbial transformation studies conducted on isopimpinellin (1) by the fungus Glomerella cingulata have revealed that 1 was metabolized to give the corresponding reduced acid, 5,8-dimethoxy-6,7-furano-hydrocoumaric acid (2). The structure of metabolite 2 was elucidated by high-resolution mass spectrometry (HR-MS), extensive NMR techniques, including (1)H NMR, (13)C NMR, (1)H-(1)H correlation spectroscopy (COSY), heteronuclear multiple quantum coherence (HMQC) and heteonuclear multiple bond coherence (HMBC). The biotransformed product 2 showed weak a in vitro β-secretase (BACE1) inhibitory effect.

  9. Detailed {sup 1}H and {sup 13}C NMR spectral data assignment for two dihydrobenzofuran neolignans

    Energy Technology Data Exchange (ETDEWEB)

    Medeiros, Talita C.T.; Dias, Herbert J.; Crotti, Antônio E.M., E-mail: millercrotti@ffclrp.usp.br [Universidade de São Paulo (USP), Ribeirão Preto, SP (Brazil). Faculdade de Filosofia, Ciências e Letras. Departamento de Química

    2016-07-01

    In this work we present a complete proton ({sup 1}H) and carbon 13 ({sup 13}C) nuclear magnetic resonance (NMR) spectral analysis of two synthetic dihydrofuran neolignans (±)-trans-dehydrodicoumarate dimethyl ester and (±)-trans-dehydrodiferulate dimethyl ester. Unequivocal assignments were achieved by 1 H NMR, proton decoupled {sup 13}C ({sup 13}C{"1H}) NMR spectra, gradient-selected correlation spectroscopy (gCOSY), J-resolved, gradient-selected heteronuclear multiple quantum coherence (gHMQC), gradient-selected heteronuclear multiple bond coherence (gHMBC) and nuclear Overhauser effect spectroscopy (NOESY) experiments. All hydrogen coupling constants were measured, clarifying all the hydrogen signals multiplicities. Computational methods were also used to simulate the {sup 1}H and {sup 13}C chemical shifts and showed good agreement with the trans configuration of the substituents at C{sub 7} and C{sub 8}. (author)

  10. {sup 15}N and {sup 13}C- SOFAST-HMQC editing enhances 3D-NOESY sensitivity in highly deuterated, selectively [{sup 1}H,{sup 13}C]-labeled proteins

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Paolo, E-mail: rossip@umn.edu; Xia, Youlin; Khanra, Nandish; Veglia, Gianluigi, E-mail: vegli001@umn.edu; Kalodimos, Charalampos G., E-mail: ckalodim@umn.edu [University of Minnesota, Department of Biochemistry, Molecular Biology and Biophysics (United States)

    2016-12-15

    The ongoing NMR method development effort strives for high quality multidimensional data with reduced collection time. Here, we apply ‘SOFAST-HMQC’ to frequency editing in 3D NOESY experiments and demonstrate the sensitivity benefits using highly deuterated and {sup 15}N, methyl labeled samples in H{sub 2}O. The experiments benefit from a combination of selective T{sub 1} relaxation (or L-optimized effect), from Ernst angle optimization and, in certain types of experiments, from using the mixing time for both NOE buildup and magnetization recovery. This effect enhances sensitivity by up to 2.4× at fast pulsing versus reference HMQC sequences of same overall length and water suppression characteristics. Representative experiments designed to address interesting protein NMR challenges are detailed. Editing capabilities are exploited with heteronuclear {sup 15}N,{sup 13}C-edited, or with diagonal-free {sup 13}C aromatic/methyl-resolved 3D-SOFAST-HMQC–NOESY–HMQC. The latter experiment is used here to elucidate the methyl-aromatic NOE network in the hydrophobic core of the 19 kDa FliT-FliJ flagellar protein complex. Incorporation of fast pulsing to reference experiments such as 3D-NOESY–HMQC boosts digital resolution, simplifies the process of NOE assignment and helps to automate protein structure determination.

  11. Pumping vortex into a Bose-Einstein condensate of heteronuclear molecules

    International Nuclear Information System (INIS)

    Xu, Z F; Wang, R Q; You, L

    2009-01-01

    Heteronuclear molecules have attracted wide attention due to their permanent electric dipole moments. Analogous to atoms with magnetic dipoles, the existence of nonzero electric dipoles significantly enhances the possibilities and mechanisms for the control and design of quantum degenerate molecule systems with electric (E) fields. This work proposes a vortex creation mechanism inside a condensate of heteronuclear molecules through the adiabatic flipping of the axial bias of an analogous E-field Ioffe-Pritchard trap (IPT), extending the original protocol of Isoshima et al (2000 Phys. Rev. A 61 063610) for an atomic spinor condensate inside a magnetic (B)-field IPT. We provide both analytic proof and numerical simulations to illustrate the high fidelity operation of this vortex pump protocol. We hope our work provides stimulating experimental possibilities for active investigations in quantum degenerate molecule systems.

  12. Application of heteronuclear couplings to conformational analysis of oligonucleotides

    International Nuclear Information System (INIS)

    Zhu, G.; Live, D.; Bax, A.

    1994-01-01

    The value of vicinal coupling constants extracted from NMR spectra in deducing torsion angles for conformational analysis is well recognized. Due to the abundance of protons, their couplings have been mostly widely used. In many instances, couplings between protons and other nuclei may be a valuable complement to proton-proton couplings or, in some instances, may be the only coupling available to characterize the torsion angle about a bond. Recently, heteronuclear couplings have been used to great benefit in studies of isotopically enriched proteins, and this general approach has been extended to peptides at natural abundance. The possibility of using this approach to study oligonucleotides is also attractive but has not as yet been widely exploited. With the development of strategies for labeling such molecules, particularly RNAs, this may become an important component in conformational analysis. For DNA, labeling is less accessible, but sufficient quantities of unlabeled material are readily available for measuring these couplings at natural abundance. We chose several DNA systems to explore the usefulness of heteronuclear couplings in addressing the sugar conformation and the glycosidic torsion angle. Intensities of cross peaks in long-range HMQC experiments can be related to the couplings. Crosspeaks involving H1' and C1' atoms have been emphasized because of the superior shift dispersion at these positions between sugar protons and carbon atoms. Results will be shown for the self-complementary Dickerson duplex dodecamer sequence d(CGCGAATTCGCG) and for d(GGTCGG), which dimerizes to form a G-tetrad structure incorporating both syn and anti base orientations. The couplings provide a clear discrimination between presence of C3'-endo and C2'-endo conformations of the sugars and syn and anti bases arrangements

  13. Application of heteronuclear couplings to conformational analysis of oligonucleotides

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, G. [Univ. of Maryland, College Park, MD (United States); Live, D. [Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Bax, A. [NIDDK National Institutes of Health, Bethesda, MD (United States)

    1994-12-01

    The value of vicinal coupling constants extracted from NMR spectra in deducing torsion angles for conformational analysis is well recognized. Due to the abundance of protons, their couplings have been mostly widely used. In many instances, couplings between protons and other nuclei may be a valuable complement to proton-proton couplings or, in some instances, may be the only coupling available to characterize the torsion angle about a bond. Recently, heteronuclear couplings have been used to great benefit in studies of isotopically enriched proteins, and this general approach has been extended to peptides at natural abundance. The possibility of using this approach to study oligonucleotides is also attractive but has not as yet been widely exploited. With the development of strategies for labeling such molecules, particularly RNAs, this may become an important component in conformational analysis. For DNA, labeling is less accessible, but sufficient quantities of unlabeled material are readily available for measuring these couplings at natural abundance. We chose several DNA systems to explore the usefulness of heteronuclear couplings in addressing the sugar conformation and the glycosidic torsion angle. Intensities of cross peaks in long-range HMQC experiments can be related to the couplings. Crosspeaks involving H1{prime} and C1{prime} atoms have been emphasized because of the superior shift dispersion at these positions between sugar protons and carbon atoms. Results will be shown for the self-complementary Dickerson duplex dodecamer sequence d(CGCGAATTCGCG) and for d(GGTCGG), which dimerizes to form a G-tetrad structure incorporating both syn and anti base orientations. The couplings provide a clear discrimination between presence of C3{prime}-endo and C2{prime}-endo conformations of the sugars and syn and anti bases arrangements.

  14. Projected [1H,15N]-HMQC-[1H,1H]-NOESY for large molecular systems: application to a 121 kDa protein-DNA complex

    International Nuclear Information System (INIS)

    Galius, Veniamin; Leontiou, Chrysoula; Richmond, Timothy; Wider, Gerhard

    2008-01-01

    We present a projected [ 1 H, 15 N]-HMQC-[ 1 H, 1 H]-NOESY experiment for observation of NOE interactions between amide protons with degenerate 15 N chemical shifts in large molecular systems. The projection is achieved by simultaneous evolution of the multiple quantum coherence of the nitrogen spin and the attached proton spin. In this way NOE signals can be separated from direct-correlation peaks also in spectra with low resolution by fully exploiting both 1 H and 15 N frequency differences, such that sensitivity can be increased by using short maximum evolution times. The sensitivity of the experiment is not dependent on the projection angle for projections up to 45 deg. and no additional pulses or delays are required as compared to the conventional 2D [ 1 H, 15 N]-HMQC-NOESY. The experiment provides two distinct 2D spectra corresponding to the positive and negative angle projections, respectively. With a linear combination of 1D cross-sections from the two projections the unavoidable sensitivity loss in projection spectra can be compensated for each particular NOE interaction. We demonstrate the application of the novel projection experiment for the observation of an NOE interaction between two sequential glycines with degenerate 15 N chemical shifts in a 121.3 kDa complex of the linker H1 histone protein with a 152 bp linear DNA

  15. Antiinflammatory and Antioxidant Flavonoids and Phenols from Cardiospermum halicacabum (倒地鈴 Dào Dì Líng

    Directory of Open Access Journals (Sweden)

    Hui-Ling Cheng

    2013-01-01

    Full Text Available Seventeen compounds, quercetin-3-O-α-l-rhamnoside (1, kaempferol-3-O-α-l-rhamnoside (2, apigenin-7-O-β-d-glucuronide (3, apigenin 7-O-β-d-glucuronide methyl ester (4, apigenin 7-O-β-d-glucuronide ethyl ester (5, chrysoeriol (6, apigenin (7, kaempferol (8, luteolin (9, quercetin (10, methyl 3,4-dihydroxybenzoate (11, p-coumaric acid (12, 4-hydroxybenzoic acid (13, hydroquinone (14, protocathehuic acid (15, gallic acid (16, and indole-3-carboxylic acid (17, were isolated from the ethanol extract of Taiwanese Cardiospermum halicabum. All chemical structures were determined by physical and extensive spectroscopic analyses such as 1H Nuclear Magnetic Resonance spectroscopy (NMR, 13C NMR, 1H-1H Correlation spectroscopy (1H-1H COSY, Heteronuclear Multiple Quantum Coherence spectroscopy (HMQC, Heteronuclear Multiple-bond Correlation spectroscopy (HMBC, and Nuclear Overhauser Effect spectroscopy (NOESY, as well as comparison with literature values. Furthermore, the High-Performance Liquid Chromatography-Photodiode Array Detector (HPLC-DAD fingerprint profile was established for the determination of major constituents in the EtOAc extract and retention times of the isolated compounds. All isolated compounds were also evaluated for antiinflammatory and antioxidant activities.

  16. Line-narrowing in proton-detected nitrogen-14 NMR

    Science.gov (United States)

    Cavadini, Simone; Vitzthum, Veronika; Ulzega, Simone; Abraham, Anuji; Bodenhausen, Geoffrey

    2010-01-01

    In solids spinning at the magic angle, the indirect detection of single-quantum (SQ) and double-quantum (DQ) 14N spectra ( I = 1) via spy nuclei S = 1/2 such as protons can be achieved in the manner of heteronuclear single- or multiple-quantum correlation (HSQC or HMQC) spectroscopy. The HMQC method relies on the excitation of two-spin coherences of the type T11IT11S and T21IT11S at the beginning of the evolution interval t1. The spectra obtained by Fourier transformation from t1 to ω1 may be broadened by the homogenous decay of the transverse terms of the spy nuclei S. This broadening is mostly due to homonuclear dipolar S- S' interactions between the proton spy nuclei. In this work we have investigated the possibility of inserting rotor-synchronized symmetry-based C or R sequences and decoupling schemes such as Phase-Modulated Lee-Goldburg (PMLG) sequences in the evolution period. These schemes reduce the homonuclear proton-proton interactions and lead to an enhancement of the resolution of both SQ and DQ proton-detected 14N HMQC spectra. In addition, we have investigated the combination of HSQC with symmetry-based sequences and PMLG and shown that the highest resolution in the 14N dimension is achieved by using HSQC in combination with symmetry-based sequences of the R-type. We show improvements in resolution in samples of L-alanine and the tripeptide ala-ala-gly (AAG). In particular, for L-alanine the width of the 14N SQ peak is reduced from 2 to 1.2 kHz, in agreement with simulations. We report accurate measurements of quadrupolar coupling constants and asymmetry parameters for amide 14N in AAG peptide bonds.

  17. Interaction-induced decay of a heteronuclear two-atom system

    Science.gov (United States)

    Xu, Peng; Yang, Jiaheng; Liu, Min; He, Xiaodong; Zeng, Yong; Wang, Kunpeng; Wang, Jin; Papoular, D. J.; Shlyapnikov, G. V.; Zhan, Mingsheng

    2015-01-01

    Two-atom systems in small traps are of fundamental interest for understanding the role of interactions in degenerate cold gases and for the creation of quantum gates in quantum information processing with single-atom traps. One of the key quantities is the inelastic relaxation (decay) time when one of the atoms or both are in a higher hyperfine state. Here we measure this quantity in a heteronuclear system of 87Rb and 85Rb in a micro optical trap and demonstrate experimentally and theoretically the presence of both fast and slow relaxation processes, depending on the choice of the initial hyperfine states. This experimental method allows us to single out a particular relaxation process thus provides an extremely clean platform for collisional physics studies. Our results have also implications for engineering of quantum states via controlled collisions and creation of two-qubit quantum gates. PMID:26199051

  18. Simplifying the complex 1H NMR spectra of fluorine-substituted benzamides by spin system filtering and spin-state selection: multiple-quantum-single-quantum correlation.

    Science.gov (United States)

    Baishya, Bikash; Reddy, G N Manjunatha; Prabhu, Uday Ramesh; Row, T N Guru; Suryaprakash, N

    2008-10-23

    The proton NMR spectra of fluorine-substituted benzamides are very complex (Figure 1) due to severe overlap of (1)H resonances from the two aromatic rings, in addition to several short and long-range scalar couplings experienced by each proton. With no detectable scalar couplings between the inter-ring spins, the (1)H NMR spectra can be construed as an overlap of spectra from two independent phenyl rings. In the present study we demonstrate that it is possible to separate the individual spectrum for each aromatic ring by spin system filtering employing the multiple-quantum-single-quantum correlation methodology. Furthermore, the two spin states of fluorine are utilized to simplify the spectrum corresponding to each phenyl ring by the spin-state selection. The demonstrated technique reduces spectral complexity by a factor of 4, in addition to permitting the determination of long-range couplings of less than 0.2 Hz and the relative signs of heteronuclear couplings. The technique also aids the judicious choice of the spin-selective double-quantum-single-quantum J-resolved experiment to determine the long-range homonuclear couplings of smaller magnitudes.

  19. PSYCHE CPMG-HSQMBC: An NMR Spectroscopic Method for Precise and Simple Measurement of Long-Range Heteronuclear Coupling Constants.

    Science.gov (United States)

    Timári, István; Szilágyi, László; Kövér, Katalin E

    2015-09-28

    Among the NMR spectroscopic parameters, long-range heteronuclear coupling constants convey invaluable information on torsion angles relevant to glycosidic linkages of carbohydrates. A broadband homonuclear decoupled PSYCHE CPMG-HSQMBC method for the precise and direct measurement of multiple-bond heteronuclear couplings is presented. The PSYCHE scheme built into the pulse sequence efficiently eliminates unwanted proton-proton splittings from the heteronuclear multiplets so that the desired heteronuclear couplings can be determined simply by measuring frequency differences between peak maxima of pure antiphase doublets. Moreover, PSYCHE CPMG-HSQMBC can provide significant improvement in sensitivity as compared to an earlier Zangger-Sterk-based method. Applications of the proposed pulse sequence are demonstrated for the extraction of (n)J((1)H,(77)Se) and (n)J((1)H,(13)C) values, respectively, in carbohydrates; further extensions can be envisioned in any J-based structural and conformational studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Heteronuclear proton assisted recoupling

    Science.gov (United States)

    De Paëpe, Gaël; Lewandowski, Józef R.; Loquet, Antoine; Eddy, Matt; Megy, Simon; Böckmann, Anja; Griffin, Robert G.

    2011-03-01

    We describe a theoretical framework for understanding the heteronuclear version of the third spin assisted recoupling polarization transfer mechanism and demonstrate its potential for detecting long-distance intramolecular and intermolecular 15N-13C contacts in biomolecular systems. The pulse sequence, proton assisted insensitive nuclei cross polarization (PAIN-CP) relies on a cross term between 1H-15N and 1H-13C dipolar couplings to mediate zero- and/or double-quantum 15N-13C recoupling. In particular, using average Hamiltonian theory we derive effective Hamiltonians for PAIN-CP and show that the transfer is mediated by trilinear terms of the form N±C∓Hz (ZQ) or N±C±Hz (DQ) depending on the rf field strengths employed. We use analytical and numerical simulations to explain the structure of the PAIN-CP optimization maps and to delineate the appropriate matching conditions. We also detail the dependence of the PAIN-CP polarization transfer with respect to local molecular geometry and explain the observed reduction in dipolar truncation. In addition, we demonstrate the utility of PAIN-CP in structural studies with 15N-13C spectra of two uniformly 13C,15N labeled model microcrystalline proteins—GB1, a 56 amino acid peptide, and Crh, a 85 amino acid domain swapped dimer (MW = 2 × 10.4 kDa). The spectra acquired at high magic angle spinning frequencies (ωr/2π > 20 kHz) and magnetic fields (ω0H/2π = 700-900 MHz) using moderate rf fields, yield multiple long-distance intramonomer and intermonomer 15N-13C contacts. We use these distance restraints, in combination with the available x-ray structure as a homology model, to perform a calculation of the monomer subunit of the Crh protein.

  1. Complete structure of the cell surface polysaccharide of Streptococcus oralis ATCC 10557: A receptor for lectin-mediated interbacterial adherence

    International Nuclear Information System (INIS)

    Abeygunawardana, C.; Bush, C.A.; Cisar, J.O.

    1991-01-01

    Lectin-carbohydrate binding is known to play an important role in a number of different cell-cell interactions including those between certain species of oral streptococci and actinomyces that colonize teeth. The cell wall polysaccharides of Streptococcus oralis ATCC 10557, S. oralis 34, and Streptococcus mitis J22, although not identical antigenically, each function as a receptor molecule for the galactose and N-acetylgalactosamine reactive fimbrial lectins of Actinomyces viscosus and Actinomyces naeslundii. Carbohydrate analysis of the receptor polysaccharide isolated from S. oralis ATCC 10557 shows galactose (3 mol), glucose (1 mol), GalNAc (1 mol), and rhamnose (1 mol). 1 H NMR spectra of the polysaccharide show that is partially O-acetylated. Analysis of the 1 H NMR spectrum of the de-O-acetylated polysaccharide shows that it is composed of repeating subunits containing six monosaccharides and that the subunits are joined by a phosphodiester linkage. The 1 H and 13 C NMR spectra were completely assigned by two-dimensional homonuclear correlation methods and by 1 H-detected heteronuclear multiple-quantum correlation ( 1 H[ 13 C]HMQC). The complete 1 H and 13 C assignment of the native polysaccharide was carried out by the same techniques augmented by a 13 C-coupled hybrid HMQC-COSY method, which is shown to be especially useful for carbohydrates in which strong coupling and overlapping peaks in the 1 H spectrum pose difficulties

  2. Multiplicative properties of quantum channels

    Science.gov (United States)

    Rahaman, Mizanur

    2017-08-01

    In this paper, we study the multiplicative behaviour of quantum channels, mathematically described by trace preserving, completely positive maps on matrix algebras. It turns out that the multiplicative domain of a unital quantum channel has a close connection to its spectral properties. A structure theorem (theorem 2.5), which reveals the automorphic property of an arbitrary unital quantum channel on a subalgebra, is presented. Various classes of quantum channels (irreducible, primitive, etc) are then analysed in terms of this stabilising subalgebra. The notion of the multiplicative index of a unital quantum channel is introduced, which measures the number of times a unital channel needs to be composed with itself for the multiplicative algebra to stabilise. We show that the maps that have trivial multiplicative domains are dense in completely bounded norm topology in the set of all unital completely positive maps. Some applications in quantum information theory are discussed.

  3. Heteronuclear Long-Range Correlation

    DEFF Research Database (Denmark)

    Sørensen, Ole W.

    The lecture will cover heteronuclear long-range correlation techniques like HMBC, H2BC, and HAT HMBC with the emphasis on determining the number of covalent bonds between two spins being correlated. H2BC and HMBC spectra are quite complementary as a peak can be strong in one of the two spectra...

  4. Spin-orbit interaction in multiple quantum wells

    International Nuclear Information System (INIS)

    Hao, Ya-Fei

    2015-01-01

    In this paper, we investigate how the structure of multiple quantum wells affects spin-orbit interactions. To increase the interface-related Rashba spin splitting and the strength of the interface-related Rashba spin-orbit interaction, we designed three kinds of multiple quantum wells. We demonstrate that the structure of the multiple quantum wells strongly affected the interface-related Rashba spin-orbit interaction, increasing the interface-related Rashba spin splitting to up to 26% larger in multiple quantum wells than in a stepped quantum well. We also show that the cubic Dresselhaus spin-orbit interaction similarly influenced the spin relaxation time of multiple quantum wells and that of a stepped quantum well. The increase in the interface-related Rashba spin splitting originates from the relationship between interface-related Rashba spin splitting and electron probability density. Our results suggest that multiple quantum wells can be good candidates for spintronic devices

  5. Spin-orbit interaction in multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Ya-Fei, E-mail: haoyafei@zjnu.cn [Physics Department, Zhejiang Normal University, Zhejiang 321004 (China)

    2015-01-07

    In this paper, we investigate how the structure of multiple quantum wells affects spin-orbit interactions. To increase the interface-related Rashba spin splitting and the strength of the interface-related Rashba spin-orbit interaction, we designed three kinds of multiple quantum wells. We demonstrate that the structure of the multiple quantum wells strongly affected the interface-related Rashba spin-orbit interaction, increasing the interface-related Rashba spin splitting to up to 26% larger in multiple quantum wells than in a stepped quantum well. We also show that the cubic Dresselhaus spin-orbit interaction similarly influenced the spin relaxation time of multiple quantum wells and that of a stepped quantum well. The increase in the interface-related Rashba spin splitting originates from the relationship between interface-related Rashba spin splitting and electron probability density. Our results suggest that multiple quantum wells can be good candidates for spintronic devices.

  6. Perfect quantum multiple-unicast network coding protocol

    Science.gov (United States)

    Li, Dan-Dan; Gao, Fei; Qin, Su-Juan; Wen, Qiao-Yan

    2018-01-01

    In order to realize long-distance and large-scale quantum communication, it is natural to utilize quantum repeater. For a general quantum multiple-unicast network, it is still puzzling how to complete communication tasks perfectly with less resources such as registers. In this paper, we solve this problem. By applying quantum repeaters to multiple-unicast communication problem, we give encoding-decoding schemes for source nodes, internal ones and target ones, respectively. Source-target nodes share EPR pairs by using our encoding-decoding schemes over quantum multiple-unicast network. Furthermore, quantum communication can be accomplished perfectly via teleportation. Compared with existed schemes, our schemes can reduce resource consumption and realize long-distance transmission of quantum information.

  7. Time-domain multiple-quantum NMR

    International Nuclear Information System (INIS)

    Weitekamp, D.P.

    1982-11-01

    The development of time-domain multiple-quantum nuclear magnetic resonance is reviewed through mid 1982 and some prospects for future development are indicated. Particular attention is given to the problem of obtaining resolved, interpretable, many-quantum spectra for anisotropic magnetically isolated systems of coupled spins. New results are presented on a number of topics including the optimization of multiple-quantum-line intensities, analysis of noise in two-dimensional spectroscopy, and the use of order-selective excitation for cross polarization between nuclear-spin species

  8. Multiple-Access Quantum-Classical Networks

    Science.gov (United States)

    Razavi, Mohsen

    2011-10-01

    A multi-user network that supports both classical and quantum communication is proposed. By relying on optical code-division multiple access techniques, this system offers simultaneous key exchange between multiple pairs of network users. A lower bound on the secure key generation rate will be derived for decoy-state quantum key distribution protocols.

  9. Immobilization of (dd)heteronuclear hexacyanoferrates(II) in a gelatin matrix

    International Nuclear Information System (INIS)

    Mikhajlov, O.V.

    2008-01-01

    Data pertinent to potentiality of preparing salts of (dd)heteronuclear hexacyanoferrates(II) with(M 1 ) II and (M 2 ) II (M 1 , M 2 = Mn, Co, Ni, Cu, Zn, Cd) as a result of contact between M 1 2 [Fe(CN) 6 ] immobilized in a gelatin matrix and aqueous solutions of metal chlorides have been systematized and summarized. The decisive role of the gelatin matrix, performing the function of an organizing system in formation of (dd)heteronuclear hexacyanoferrates(II) of metals, has been pointed out [ru

  10. Collisional properties of weakly bound heteronuclear dimers

    NARCIS (Netherlands)

    Marcelis, B.; Kokkelmans, S.J.J.M.F.; Shlyapnikov, G.V.; Petrov, D.S.

    2008-01-01

    We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating

  11. Experimental benchmarking of quantum control in zero-field nuclear magnetic resonance.

    Science.gov (United States)

    Jiang, Min; Wu, Teng; Blanchard, John W; Feng, Guanru; Peng, Xinhua; Budker, Dmitry

    2018-06-01

    Demonstration of coherent control and characterization of the control fidelity is important for the development of quantum architectures such as nuclear magnetic resonance (NMR). We introduce an experimental approach to realize universal quantum control, and benchmarking thereof, in zero-field NMR, an analog of conventional high-field NMR that features less-constrained spin dynamics. We design a composite pulse technique for both arbitrary one-spin rotations and a two-spin controlled-not (CNOT) gate in a heteronuclear two-spin system at zero field, which experimentally demonstrates universal quantum control in such a system. Moreover, using quantum information-inspired randomized benchmarking and partial quantum process tomography, we evaluate the quality of the control, achieving single-spin control for 13 C with an average fidelity of 0.9960(2) and two-spin control via a CNOT gate with a fidelity of 0.9877(2). Our method can also be extended to more general multispin heteronuclear systems at zero field. The realization of universal quantum control in zero-field NMR is important for quantum state/coherence preparation, pulse sequence design, and is an essential step toward applications to materials science, chemical analysis, and fundamental physics.

  12. Quantum internet using code division multiple access

    Science.gov (United States)

    Zhang, Jing; Liu, Yu-xi; Özdemir, Şahin Kaya; Wu, Re-Bing; Gao, Feifei; Wang, Xiang-Bin; Yang, Lan; Nori, Franco

    2013-01-01

    A crucial open problem inS large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content, and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels. PMID:23860488

  13. Quantum Optical Multiple Scattering

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær

    . In the first part we use a scattering-matrix formalism combined with results from random-matrix theory to investigate the interference of quantum optical states on a multiple scattering medium. We investigate a single realization of a scattering medium thereby showing that it is possible to create entangled...... states by interference of squeezed beams. Mixing photon states on the single realization also shows that quantum interference naturally arises by interfering quantum states. We further investigate the ensemble averaged transmission properties of the quantized light and see that the induced quantum...... interference survives even after disorder averaging. The quantum interference manifests itself through increased photon correlations. Furthermore, the theoretical description of a measurement procedure is presented. In this work we relate the noise power spectrum of the total transmitted or reflected light...

  14. Quantum theory of NMR adiabatic pulses and their applications

    International Nuclear Information System (INIS)

    Ke, Y.

    1993-01-01

    Recently explosive developments of in vivo NMR spectroscopy (NMRS) and imaging (NMRI) in biological and medical sciences have resulted in the establishment of NMR as one of the most advanced major technique in life sciences. These developments have created huge demands for a variety of NMR adiabatic pulses with play a very important role in NMR experiments in vivo. In order to develop new NMR adiabatic pulses, a rigorous systematical quantum theory for this kind of pulses is greatly needed. Providing such a theory is one of the important goals of this dissertation. Quantum density matrix theory and product operator method have been used throughout this dissertation. Another goal, which is the major goal of this thesis research, is to use the quantum theory as a guide to develop new NMR adiabatic pulses and their applications. To fill this goal, a technique to construct a new type of adiabatic pulses, narrow band selective adiabatic pulses, has been invented, which is described through the example of constructing an adiabatic DANTE inversion pulse. This new adiabatic pulse is the first narrow band selective adiabatic pulses: Adiabatic homonuclear and heteronuclear spectral editing sequences. Unique to the first pulse sequence is a B 1 -field filter which is built by using two non-refocusing adiabatic full passage pulses to refocus the wanted signal and dephase unwanted signals. This extra filter greatly enhance the editing efficiency. Unlike commonly used heteronuclear spectral editing sequences which depend on the polarization transfer or spectral subtraction by phase cycling techniques, the second pulse sequences accomplishes the editing of heteronuclear J-coupled signals based on the fact that this sequence is transparent to the uncoupled spins and is equivalent a 90 degrees excitation pulse to the heteronuclear J-coupled spins. Experimental results have confirmed the ability of spectral editing with these two new sequences

  15. Computer studies of multiple-quantum spin dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Murdoch, J.B.

    1982-11-01

    The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment.

  16. Computer studies of multiple-quantum spin dynamics

    International Nuclear Information System (INIS)

    Murdoch, J.B.

    1982-11-01

    The excitation and detection of multiple-quantum (MQ) transitions in Fourier transform NMR spectroscopy is an interesting problem in the quantum mechanical dynamics of spin systems as well as an important new technique for investigation of molecular structure. In particular, multiple-quantum spectroscopy can be used to simplify overly complex spectra or to separate the various interactions between a nucleus and its environment. The emphasis of this work is on computer simulation of spin-system evolution to better relate theory and experiment

  17. New sesquiterpenes from Euonymus europaeus (Celastraceae).

    Science.gov (United States)

    Descoins, Charles; Bazzocchi, Isabel López; Ravelo, Angel Gutiérrez

    2002-02-01

    A new sesquiterpene evoninate alkaloid (1), and two sesquiterpenes (2, 3) with a dihydro-beta-agarofuran skeleton, along with three known sesquiterpenes (4-6), were isolated from the seeds of Euonymus europaeus. Their structures were elucidated by high resolution mass analysis, and one- and two-dimensional (1D and 2D) NMR spectroscopy, including homonuclear and heteronuclear correlation [correlation spectroscopy (COSY), rotating frame Overhauser enhancement spectroscopy (ROESY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC)] experiments.

  18. Selectivity in multiple quantum nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Warren, W.S.

    1980-11-01

    The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible

  19. Selectivity in multiple quantum nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Warren Sloan [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division

    1980-11-01

    The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.

  20. Deterministically entangling multiple remote quantum memories inside an optical cavity

    Science.gov (United States)

    Yan, Zhihui; Liu, Yanhong; Yan, Jieli; Jia, Xiaojun

    2018-01-01

    Quantum memory for the nonclassical state of light and entanglement among multiple remote quantum nodes hold promise for a large-scale quantum network, however, continuous-variable (CV) memory efficiency and entangled degree are limited due to imperfect implementation. Here we propose a scheme to deterministically entangle multiple distant atomic ensembles based on CV cavity-enhanced quantum memory. The memory efficiency can be improved with the help of cavity-enhanced electromagnetically induced transparency dynamics. A high degree of entanglement among multiple atomic ensembles can be obtained by mapping the quantum state from multiple entangled optical modes into a collection of atomic spin waves inside optical cavities. Besides being of interest in terms of unconditional entanglement among multiple macroscopic objects, our scheme paves the way towards the practical application of quantum networks.

  1. Secure Multiparty Quantum Computation for Summation and Multiplication.

    Science.gov (United States)

    Shi, Run-hua; Mu, Yi; Zhong, Hong; Cui, Jie; Zhang, Shun

    2016-01-21

    As a fundamental primitive, Secure Multiparty Summation and Multiplication can be used to build complex secure protocols for other multiparty computations, specially, numerical computations. However, there is still lack of systematical and efficient quantum methods to compute Secure Multiparty Summation and Multiplication. In this paper, we present a novel and efficient quantum approach to securely compute the summation and multiplication of multiparty private inputs, respectively. Compared to classical solutions, our proposed approach can ensure the unconditional security and the perfect privacy protection based on the physical principle of quantum mechanics.

  2. Quantum theory of multiple-input-multiple-output Markovian feedback with diffusive measurements

    International Nuclear Information System (INIS)

    Chia, A.; Wiseman, H. M.

    2011-01-01

    Feedback control engineers have been interested in multiple-input-multiple-output (MIMO) extensions of single-input-single-output (SISO) results of various kinds due to its rich mathematical structure and practical applications. An outstanding problem in quantum feedback control is the extension of the SISO theory of Markovian feedback by Wiseman and Milburn [Phys. Rev. Lett. 70, 548 (1993)] to multiple inputs and multiple outputs. Here we generalize the SISO homodyne-mediated feedback theory to allow for multiple inputs, multiple outputs, and arbitrary diffusive quantum measurements. We thus obtain a MIMO framework which resembles the SISO theory and whose additional mathematical structure is highlighted by the extensive use of vector-operator algebra.

  3. Continuous-wave spatial quantum correlations of light induced by multiple scattering

    DEFF Research Database (Denmark)

    Smolka, Stephan; Ott, Johan Raunkjær; Huck, Alexander

    2012-01-01

    and reflectance. Utilizing frequency-resolved quantum noise measurements, we observe that the strength of the spatial quantum correlation function can be controlled by changing the quantum state of an incident bright squeezed-light source. Our results are found to be in excellent agreement with the developed......We present theoretical and experimental results on spatial quantum correlations induced by multiple scattering of nonclassical light. A continuous-mode quantum theory is derived that enables determining the spatial quantum correlation function from the fluctuations of the total transmittance...... theory and form a basis for future research on, e. g., quantum interference of multiple quantum states in a multiple scattering medium....

  4. Nonadditivity of quantum capacities of quantum multiple-access channels and the butterfly network

    International Nuclear Information System (INIS)

    Huang Peng; He Guangqiang; Zhu Jun; Zeng Guihua

    2011-01-01

    Multipartite quantum information transmission without additional classical resources is investigated. We show purely quantum superadditivity of quantum capacity regions of quantum memoryless multiple-access (MA) channels, which are not entanglement breaking. Also, we find that the superadditivity holds when the MA channel extends to the quantum butterfly network, which can achieve quantum network coding. The present widespread effects for the channels which enable entanglement distribution have not been revealed for multipartite scenarios.

  5. 71Ga-77Se connectivities and proximities in gallium selenide crystal and glass probed by solid-state NMR

    Science.gov (United States)

    Nagashima, Hiroki; Trébosc, Julien; Calvez, Laurent; Pourpoint, Frédérique; Mear, François; Lafon, Olivier; Amoureux, Jean-Paul

    2017-09-01

    We introduce two-dimensional (2D) 71Ga-77Se through-bond and through-space correlation experiments. Such correlations are achieved using (i) the J-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer (J-RINEPT) method with 71Ga excitation and 77Se Carr-Purcell-Meiboon-Gill (CPMG) detection, as well as (ii) the J- or dipolar-mediated Hetero-nuclear Multiple-Quantum Correlation (J- or D-HMQC) schemes with 71Ga excitation and quadrupolar CPMG (QCPMG) detection. These methods are applied to the crystalline β-Ga2Se3 and the 0.2Ga2Se3-0.8GeSe2 glass. Such glass leads to a homogeneous and reproducible glass-ceramic, which is a good alternative to single-crystalline Ge and polycrystalline ZnSe materials for making lenses transparent in the IR range for thermal imaging applications. We show that 2D 71Ga-77Se correlation experiments allow resolving the 77Se signals of molecular units, which are not resolved in the 1D 77Se CPMG spectrum. Additionally, the build-up curves of the J-RINEPT and the J-HMQC experiments allow the estimate of the 71Ga-77Se J-couplings via one and three-bonds in the three-dimensional network of β-Ga2Se3. Furthermore, these build-up curves show that the one-bond 1J71Ga-77Se couplings in the 0.2Ga2Se3-0.8GeSe2 glass are similar to those measured for β-Ga2Se3. We also report 2D 71Ga Satellite Transition Magic-Angle Spinning (STMAS) spectrum of β-Ga2Se3 using QCPMG detection at high magnetic field and high Magic-Angle Spinning frequency using large radio frequency field. Such spectrum allows separating the signal of β-Ga2Se3 and that of an impurity.

  6. Multiplicative formulation of quantum mechanics

    International Nuclear Information System (INIS)

    Voros, A.; Leboeuf, P.

    1991-01-01

    A general semi-classical description for the eigenfunctions of the multidimensional Schroedinger operator cannot be based on the WKB method which is incompatible with classically ergodic behavior. An alternative, more general multiplicative parametrization of quantum wave functions is suggested, whereby the semi-classical behavior of eigenfunctions can be traced in the presence of classical ergodicity, in the form of diffusive patterns of phase-space zeros in the quantum wave functions. (author) 24 refs.; 4 figs

  7. Electron Raman scattering in asymmetrical multiple quantum wells

    International Nuclear Information System (INIS)

    Betancourt-Riera, R; Rosas, R; Marin-Enriquez, I; Riera, R; Marin, J L

    2005-01-01

    Optical properties of asymmetrical multiple quantum wells for the construction of quantum cascade lasers are calculated, and expressions for the electronic states of asymmetrical multiple quantum wells are presented. The gain and differential cross-section for an electron Raman scattering process are obtained. Also, the emission spectra for several scattering configurations are discussed, and the corresponding selection rules for the processes involved are studied; an interpretation of the singularities found in the spectra is given. The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers

  8. Fundamental principles of nanostructures and multiple exciton generation effect in quantum dots

    International Nuclear Information System (INIS)

    Turaeva, N.; Oksengendler, B.; Rashidova, S.

    2011-01-01

    In this work the theoretical aspects of the effect of multiple exciton generation in QDs has been studied. The statistic theory of multiple exciton generation in quantum dots is presented based on the Fermi approach to the problem of multiple generation of elementary particles at nucleon-nucleon collisions. Our calculations show that the quantum efficiencies of multiple exciton generation in various quantum dots at absorption of single photon are in a good agreement with the experimental data. The microscopic mechanism of this effect is based on the theory of electronic 'shaking'. In the work the deviation of averaged multiplicity of MEG effect from the Poisson law of fluctuations has been investigated. Besides, the role of interface electronic states of quantum dot and ligand has been considered by means of quantum mechanics. The size optimization of quantum dot has been arranged to receive the maximum multiplicity of MEG effect. (authors)

  9. Multiple exciton generation in quantum dot-based solar cells

    Science.gov (United States)

    Goodwin, Heather; Jellicoe, Tom C.; Davis, Nathaniel J. L. K.; Böhm, Marcus L.

    2018-01-01

    Multiple exciton generation (MEG) in quantum-confined semiconductors is the process by which multiple bound charge-carrier pairs are generated after absorption of a single high-energy photon. Such charge-carrier multiplication effects have been highlighted as particularly beneficial for solar cells where they have the potential to increase the photocurrent significantly. Indeed, recent research efforts have proved that more than one charge-carrier pair per incident solar photon can be extracted in photovoltaic devices incorporating quantum-confined semiconductors. While these proof-of-concept applications underline the potential of MEG in solar cells, the impact of the carrier multiplication effect on the device performance remains rather low. This review covers recent advancements in the understanding and application of MEG as a photocurrent-enhancing mechanism in quantum dot-based photovoltaics.

  10. On Multiplicative Linear Logic, Modality and Quantum Circuits

    Directory of Open Access Journals (Sweden)

    Ugo Dal Lago

    2012-10-01

    Full Text Available A logical system derived from linear logic and called QMLL is introduced and shown able to capture all unitary quantum circuits. Conversely, any proof is shown to compute, through a concrete GoI interpretation, some quantum circuits. The system QMLL, which enjoys cut-elimination, is obtained by endowing multiplicative linear logic with a quantum modality.

  11. Observation of spatial quantum correlations induced by multiple scattering of nonclassical light

    DEFF Research Database (Denmark)

    Smolka, Stephan; Huck, Alexander; Andersen, Ulrik Lund

    2009-01-01

    and negative spatial quantum correlations are observed when varying the quantum state incident to the multiple scattering medium, and the strength of the correlations is controlled by the number of photons. The experimental results are in excellent agreement with recent theoretical proposals by implementing......We present the experimental realization of spatial quantum correlations of photons that are induced by multiple scattering of squeezed light. The quantum correlation relates photons propagating along two different light paths through the random medium and is infinite in range. Both positive...... the full quantum model of multiple scattering....

  12. Isolation and characterisation of three new anthraquinone secondary metabolites from Symplocos racemosa.

    Science.gov (United States)

    Farooq, Umar; Naz, Sadia; Khan, Ajmal; Khan, Sara; Khan, Afsar; Ali, Mumtaz; Khan, Saleha Suleman

    2016-01-01

    Three new anthraquinone secondary metabolites were isolated from Symplocos racemosa, a small tree of family symplocaceae. The structures of compounds (1-3) were elucidated to be 1,4-dihydroxy-6-(ethoxymethyl)-8-propylanthracene-9,10-dione (1), 1,4-dihydroxy-6-(hydroxymethyl)-8-butylanthracene-9,10-dione (2) and 1,4-dihydroxy-6-(hydroxymethyl)-8-propyl anthracene-9,10-dione (3) using their spectral data, i.e. through IR, UV, (1)H NMR, (13)C NMR and two-dimensional (2D) NMR techniques including heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation and correlation spectroscopy.

  13. ESTRUCTURA TRIDIMENSIONAL DE LA CITOQUININA N-BENZIL 9 (2 TETRAHIDROPIRANYL ADENINE UTILIZANDO EL MÉTODO DE RESONANCIA MAGNÉTICA NUCLEAR

    Directory of Open Access Journals (Sweden)

    Carlos Rojas

    2004-06-01

    Full Text Available Para comprender la función biológica de las moléculas que conforman los seres vivos es necesario conocer la estructura tridimensional de ellas, pues está comprobado que la función depende más de la distribución espacial que de los mismos componentes. El objetivo del presente trabajo es determinar la estructura de una fitohormona. Uno de los métodos que existen para determinar estas estructuras es la resonancia magnética nuclear pulsada el cual se escogió para este trabajo. Este método se diferencia de la resonancia de onda continua en el hecho de que el campo magnético variable es aplicado en forma de pulsos y su amplitud no puede ser considerada como una perturbación al sistema. La determinación de la estructura exigió la toma de los espectros unidimensionales de H1, C13 y los Distortionless Enhacement by Polarization Transfer (DEPT; este último es una secuencia de pulsos que permite diferenciar entre carbonos unidos a tres, a dos y a un hidrógeno. Con la ayuda del espectro C13 también se pueden distinguir los carbonos que no están enlazados con ningún hidrógeno. Además de éstos, fueron necesarios los siguientes espectros bidimensionales: 1 Heteronuclear Multiple Quantum Correlation (HMQC el cual correlaciona hidrógenos con carbonos que se encuentren enlazados; 2 Heteronuclear Multiple Bond Correlation (HMBC que correlaciona carbonos con hidrógenos que se encuentren a dos o tres enlaces; 3 Correlation Spectroscopy (COSY el cual muestra la correlación entre hidrógenos que se encuentren a dos o tres enlaces; y 4 Nuclear Overhauser Effect Spectroscopy (NOESY el cual correlaciona hidrógenos que distan entre sí menos de 5 Å. A partir de la información obtenida del análisis de estos espectros se dedujo el modelo de la fitohormona que se presenta como resultado del trabajo.

  14. Analysis of the backbone dynamics of interleukin-1β using two-dimensional inverse detected heteronuclear 15N-1H NMR spectroscopy

    International Nuclear Information System (INIS)

    Clore, G.M.; Driscoll, P.C.; Wingfield, P.T.; Gronenborn, A.M.

    1990-01-01

    The backbone dynamics of uniformly 15 N-labeled interleukin-1β are investigated by using two-dimensional inverse detected heteronuclear 15 N- 1 H NMR spectroscopy. 15 N T 1 , T 2 , and NOE data at a spectrometer frequency of 600 MHz are obtained for 90% of the backbone amide groups. The data provide evidence for motions on three time scales. All the residues exhibit very fast motions on a time scale of approx-lt 20-50 ps that can be characterized by a single-order parameter with an average value of 0.82 ± 0.05. Thirty-two residues also display motions on a time scale of 0.5-4 ns, slightly less than the overall rotational correlation time of the protein (8.3 ns). While the simple formulation can account for the 15 N T 1 and T 2 data, it fails to account for the 15 N- 1 H NOE data and yields calculated values for the NOEs that are either too small or negative, whereas the observed NOEs are positive. Another 42 residues are characterized by some sort of motion on the 30-ns-10-ms time scale, which results in 15 N line broadening due to chemical exchange between different conformational substates with distinct 15 N chemical shifts. In general, the motions on both the 0.5-4-ns and 30-ns-10-ms time scales are localized in surface-accessible loops and turns connecting the β-strands, as well as at the beginning and end of strands. Finally, the kinetic and equilibrium properties of a slow conformational equilibrium between a major and a minor species, involving at least 19 residues and located on one contiguous face of the molecule, are characterized by using 1 H- 15 N correlation spectroscopy, 1 H- 15 N heteronuclear multiple quantum coherence-nuclear Overhauser enhancement spectroscopy, and 1 H- 1 H nuclear Overhauser enhancement spectroscopy

  15. Performance analysis of quantum access network using code division multiple access model

    International Nuclear Information System (INIS)

    Hu Linxi; Yang Can; He Guangqiang

    2017-01-01

    A quantum access network has been implemented by frequency division multiple access and time division multiple access, while code division multiple access is limited for its difficulty to realize the orthogonality of the code. Recently, the chaotic phase shifters were proposed to guarantee the orthogonality by different chaotic signals and spread the spectral content of the quantum states. In this letter, we propose to implement the code division multiple access quantum network by using chaotic phase shifters and synchronization. Due to the orthogonality of the different chaotic phase shifter, every pair of users can faithfully transmit quantum information through a common channel and have little crosstalk between different users. Meanwhile, the broadband spectra of chaotic signals efficiently help the quantum states to defend against channel loss and noise. (paper)

  16. Quantum critical matter. Quantum phase transitions with multiple dynamics and Weyl superconductors

    International Nuclear Information System (INIS)

    Meng, Tobias

    2012-01-01

    In this PhD thesis, the physics of quantum critical matter and exotic quantum state close to quantum phase transitions is investigated. We will focus on three different examples that highlight some of the interesting phenomena related to quantum phase transitions. Firstly, we discuss the physics of quantum phase transitions in quantum wires as a function of an external gate voltage when new subbands are activated. We find that at these transitions, strong correlations lead to the formation of an impenetrable gas of polarons, and identify criteria for possible instabilities in the spin- and charge sectors of the model. Our analysis is based on the combination of exact resummations, renormalization group techniques and Luttinger liquid approaches. Secondly, we turn to the physics of multiple divergent time scales close to a quantum critical point. Using an appropriately generalized renormalization group approach, we identify that the presence of multiple dynamics at a quantum phase transition can lead to the emergence of new critical scaling exponents and thus to the breakdown of the usual scaling schemes. We calculate the critical behavior of various thermodynamic properties and detail how unusual physics can arise. It is hoped that these results might be helpful for the interpretation of experimental scaling puzzles close to quantum critical points. Thirdly, we turn to the physics of topological transitions, and more precisely the physics of Weyl superconductors. The latter are the superconducting variant of the topologically non-trivial Weyl semimetals, and emerge at the quantum phase transition between a topological superconductor and a normal insulator upon perturbing the transition with a time reversal symmetry breaking perturbation, such as magnetism. We characterize the topological properties of Weyl superconductors and establish a topological phase diagram for a particular realization in heterostructures. We discuss the physics of vortices in Weyl

  17. Heteronuclear three-dimensional NMR spectroscopy. Natural abundance 13C chemical shift editing of 1H-1H COSY spectra

    International Nuclear Information System (INIS)

    Fesik, S.W.; Gampe, R.T. Jr.; Zuiderweg, E.R.P.

    1989-01-01

    It has been demonstrated that heteronuclear 3D NMR spectroscopy can be effectively applied to small molecules with 13 C at natural abundance. A 78mM solution of the aminoglycoside, kanamycin A was used for this experiment. The heteronuclear 3D NMR spectroscopy is shown to be a useful method for resolving spectral overlap in all frequency domains. 10 refs., 2 figs

  18. Multiple-state quantum Otto engine, 1D box system

    Energy Technology Data Exchange (ETDEWEB)

    Latifah, E., E-mail: enylatifah@um.ac.id [Laboratory of Theoretical Physics and Natural Philosophy, Physics Department, Institut Teknologi Sepuluh Nopember, ITS, Surabaya, Indonesia and Physics Department, Malang State University (Indonesia); Purwanto, A. [Laboratory of Theoretical Physics and Natural Philosophy, Physics Department, Institut Teknologi Sepuluh Nopember, ITS, Surabaya (Indonesia)

    2014-03-24

    Quantum heat engines produce work using quantum matter as their working substance. We studied adiabatic and isochoric processes and defined the general force according to quantum system. The processes and general force are used to evaluate a quantum Otto engine based on multiple-state of one dimensional box system and calculate the efficiency. As a result, the efficiency depends on the ratio of initial and final width of system under adiabatic processes.

  19. Fine hierarchy of the V-O bonds by advanced solid state NMR: novel Pb4(VO2)(PO4)3 structure as a textbook case.

    Science.gov (United States)

    Tricot, Grégory; Mentré, Olivier; Cristol, Sylvain; Delevoye, Laurent

    2012-12-17

    We report here a complete structural characterization of a new lead Pb(4)(VO(2))(PO(4))(3) vanadophosphate compound by single crystal X-ray diffraction and (51)V and (31)P solid-state NMR spectroscopy. Although structural data are commonly used for the estimation of bond lengths and further delimitation of the true coordination number (e.g., octahedral: 6 versus 5 + 1 versus 4 + 2), we show here for the first time by solid-state NMR a more accurate appreciation of the V-O bonding scheme in this complex oxide which appears well adapted to the full series of vanado-phosphate materials. The direct characterization of V-O-P bridges through the J-mediated correlation (51)V{(31)P} heteronuclear multiple quantum coherence (J-HMQC) technique allows a contrasted hierarchy of the V-O electronic delocalization and indirectly supports the presence or not of the V-O bond. In the reported lead vanado-phosphate structure, the two vanadium polyhedra that have been assigned to octahedra from a bond length point of view have been finally reclassified as tetra- and penta-coordinated units on the basis of the solid-state NMR results. More generally, we believe that the improved characterization of interatomic bonds in various vanado-phosphate structures by solid-state NMR will contribute to a better understanding of the structure/property relationships in this important class of materials.

  20. Long-range dispersion interactions. I. Formalism for two heteronuclear atoms

    International Nuclear Information System (INIS)

    Zhang, J.-Y.; Mitroy, J.

    2007-01-01

    A general procedure for systematically evaluating the long-range dispersion interaction between two heteronuclear atoms in arbitrary states is outlined. The C 6 dispersion parameter can always be written in terms of sum rules involving oscillator strengths only and formulas for a number of symmetry cases are given. The dispersion coefficients for excited alkali-metal atoms interacting with the ground-state H and He are tabulated

  1. Heteronuclear three-dimensional NMR spectroscopy of the inflammatory protein C5a

    International Nuclear Information System (INIS)

    Zuiderweg, E.R.P.; Fesik, S.W.

    1989-01-01

    The utility of three-dimensional heteronuclear NMR spectroscopy for the assignment of 1 H and 15 N resonances of the inflammatory protein C5a (MW 8500), uniformly labeled with 15 N, is demonstrated at a protein concentration of 0.7 mM. It is shown that dramatic simplification of the 2D nuclear Overhauser effect spectrum (NOESY) is obtained by editing with respect to the frequency of the 15 N heteronucleus in a third dimension. The improved resolution in the 3D experiment largely facilitates the assignment of protein NMR spectra and allows for the determination of distance constraints from otherwise overlapping NOE cross peaks for purposes of 3D structure determination. The results show that 15 N heteronuclear 3D NMR can facilitate the structure determination of small proteins and promises to be a useful tool for the study of larger systems that cannot be studied by conventional 2D NMR techniques

  2. Heteronuclear three-dimensional NMR spectroscopy of the inflammatory protein C5a

    Energy Technology Data Exchange (ETDEWEB)

    Zuiderweg, E.R.P.; Fesik, S.W. (Abbott Laboratories, Abbott Park, IL (USA))

    1989-03-21

    The utility of three-dimensional heteronuclear NMR spectroscopy for the assignment of {sup 1}H and {sup 15}N resonances of the inflammatory protein C5a (MW 8500), uniformly labeled with {sup 15}N, is demonstrated at a protein concentration of 0.7 mM. It is shown that dramatic simplification of the 2D nuclear Overhauser effect spectrum (NOESY) is obtained by editing with respect to the frequency of the {sup 15}N heteronucleus in a third dimension. The improved resolution in the 3D experiment largely facilitates the assignment of protein NMR spectra and allows for the determination of distance constraints from otherwise overlapping NOE cross peaks for purposes of 3D structure determination. The results show that {sup 15}N heteronuclear 3D NMR can facilitate the structure determination of small proteins and promises to be a useful tool for the study of larger systems that cannot be studied by conventional 2D NMR techniques.

  3. Chemical study of ethyl Acetate fraction of Picrasma Javanica Bl.

    Directory of Open Access Journals (Sweden)

    Sri Hainil

    2015-12-01

    Full Text Available N-1 main compound from ethyl acetate fraction of kayu pahit bark (Picrasma Javanica B1 has been isolated and characterized with colom chromatography and continued with preparative chromatography. According to analized from spectrum data used ultraviolet (UV spectroscopy, infra red (IR, 1H RMI (Resonansi Magnet Inti, 13 C RMI, Massa , COSY (Correlated Spectroscopy, HSQC (Heteronuclear Single Quantum Correlation, HMBC ( Heteronuclear Multiple Bond Correlation and literature study showed that the compound of isolation was javanicin A.

  4. Quantum key distribution network for multiple applications

    Science.gov (United States)

    Tajima, A.; Kondoh, T.; Ochi, T.; Fujiwara, M.; Yoshino, K.; Iizuka, H.; Sakamoto, T.; Tomita, A.; Shimamura, E.; Asami, S.; Sasaki, M.

    2017-09-01

    The fundamental architecture and functions of secure key management in a quantum key distribution (QKD) network with enhanced universal interfaces for smooth key sharing between arbitrary two nodes and enabling multiple secure communication applications are proposed. The proposed architecture consists of three layers: a quantum layer, key management layer and key supply layer. We explain the functions of each layer, the key formats in each layer and the key lifecycle for enabling a practical QKD network. A quantum key distribution-advanced encryption standard (QKD-AES) hybrid system and an encrypted smartphone system were developed as secure communication applications on our QKD network. The validity and usefulness of these systems were demonstrated on the Tokyo QKD Network testbed.

  5. Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory

    Science.gov (United States)

    Tang, Jian-Shun; Zhou, Zong-Quan; Wang, Yi-Tao; Li, Yu-Long; Liu, Xiao; Hua, Yi-Lin; Zou, Yang; Wang, Shuang; He, De-Yong; Chen, Geng; Sun, Yong-Nan; Yu, Ying; Li, Mi-Feng; Zha, Guo-Wei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Li, Chuan-Feng; Guo, Guang-Can

    2015-01-01

    Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by the Duan–Lukin–Cirac–Zoller protocol, many improved quantum repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multiple photons (or multiple photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with 1, 20 and 100 narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devices. PMID:26468996

  6. Exact non-Markovian master equations for multiple qubit systems: Quantum-trajectory approach

    Science.gov (United States)

    Chen, Yusui; You, J. Q.; Yu, Ting

    2014-11-01

    A wide class of exact master equations for a multiple qubit system can be explicitly constructed by using the corresponding exact non-Markovian quantum-state diffusion equations. These exact master equations arise naturally from the quantum decoherence dynamics of qubit system as a quantum memory coupled to a collective colored noisy source. The exact master equations are also important in optimal quantum control, quantum dissipation, and quantum thermodynamics. In this paper, we show that the exact non-Markovian master equation for a dissipative N -qubit system can be derived explicitly from the statistical average of the corresponding non-Markovian quantum trajectories. We illustrated our general formulation by an explicit construction of a three-qubit system coupled to a non-Markovian bosonic environment. This multiple qubit master equation offers an accurate time evolution of quantum systems in various domains, and paves the way to investigate the memory effect of an open system in a non-Markovian regime without any approximation.

  7. Quantum Interference and Entanglement Induced by Multiple Scattering of Light

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær; Mortensen, Asger; Lodahl, Peter

    2010-01-01

    We report on the effects of quantum interference induced by the transmission of an arbitrary number of optical quantum states through a multiple-scattering medium. We identify the role of quantum interference on the photon correlations and the degree of continuous variable entanglement between two...... output modes. It is shown that quantum interference survives averaging over all ensembles of disorder and manifests itself as increased photon correlations due to photon antibunching. Furthermore, the existence of continuous variable entanglement correlations in a volume speckle pattern is predicted. Our...

  8. Theoretical investigations of quantum correlations in NMR multiple-pulse spin-locking experiments

    Science.gov (United States)

    Gerasev, S. A.; Fedorova, A. V.; Fel'dman, E. B.; Kuznetsova, E. I.

    2018-04-01

    Quantum correlations are investigated theoretically in a two-spin system with the dipole-dipole interactions in the NMR multiple-pulse spin-locking experiments. We consider two schemes of the multiple-pulse spin-locking. The first scheme consists of π /2-pulses only and the delays between the pulses can differ. The second scheme contains φ-pulses (0Quantum discord is obtained for the first scheme of the multiple-pulse spin-locking experiment at different temperatures.

  9. Skyrmion burst and multiple quantum walk in thin ferromagnetic films

    International Nuclear Information System (INIS)

    Ezawa, Motohiko

    2011-01-01

    We propose a new type of quantum walk in thin ferromagnetic films. A giant Skyrmion collapses to a singular point in a thin ferromagnetic film, emitting spin waves, when external magnetic field is increased beyond the critical one. After the collapse the remnant is a quantum walker carrying spin S. We determine its time evolution and show the diffusion process is a continuous-time quantum walk. We also analyze an interference of two quantum walkers after two Skyrmion bursts. The system presents a new type of quantum walk for S>1/2, where a quantum walker breaks into 2S quantum walkers. -- Highlights: → A giant Skyrmion collapses to a singular point by applying strong magnetic field. → Quantum walk is realized in thin ferromagnetic films by Skyrmion collapsing. → Quantum walks for S=1/2 and 1 are exact solvable, where S represents the spin. → Quantum walks for >1/2 presents a new type of quantum walks, i.e., 'multiple quantum walks'. → Skyrmion bursts which occur simultaneously exhibit an interference as a manifestation of quantum walk.

  10. Multiple quantum spin dynamics of entanglement

    International Nuclear Information System (INIS)

    Doronin, Serge I.

    2003-01-01

    The dynamics of entanglement is investigated on the basis of exactly solvable models of multiple quantum (MQ) NMR spin dynamics. It is shown that the time evolution of MQ coherences of systems of coupled nuclear spins in solids is directly connected with dynamics of the quantum entanglement. We studied analytically the dynamics of entangled states for two- and three-spin systems coupled by the dipole-dipole interaction. In this case the dynamics of the quantum entanglement is uniquely determined by the time evolution of MQ coherences of the second order. The real part of the density matrix describing MQ dynamics in solids is responsible for MQ coherences of the zeroth order while its imaginary part is responsible for the second order. Thus, one can conclude that the dynamics of the entanglement is connected with transitions from the real part of the density matrix to the imaginary one, and vice versa. A pure state which generalizes the Greenberger-Horne-Zeilinger (GHZ) and W states is found. Different measures of the entanglement of this state are analyzed for tripartite systems

  11. Heteronuclear relaxation in time-dependent spin systems: 15N-T1ρ dispersion during adiabatic fast passage

    International Nuclear Information System (INIS)

    Konrat, Robert; Tollinger, Martin

    1999-01-01

    A novel NMR experiment comprising adiabatic fast passage techniques for the measurement of heteronuclear self-relaxation rates in fully 15N-enriched proteins is described. Heteronuclear self-relaxation is monitored by performing adiabatic fast passage (AFP) experiments at variable adiabaticity (e.g., variation of RF spin-lock field intensity). The experiment encompasses gradient- selection and sensitivity-enhancement. It is shown that transverse relaxation rates derived with this method are in good agreement with the ones measured by the classical Carr-Purcell-Meiboom-Gill (CPMG) sequences. An application of this method to the study of the carboxyl-terminal LIM domain of quail cysteine and glycine-rich protein qCRP2(LIM2) is presented

  12. Two new 24-isopropenyl-lanostanoids from Tillandsia brachycaulos.

    Science.gov (United States)

    Cantillo-Ciau, Zulema; Mena-Rejón, Gonzalo J; Quintero-Mármol, Esther; Jiménez-Díaz, Antonio; Quijano, Leovigildo

    2003-01-01

    The leaves of Tillandsia brachycaulos afforded two novel tetracyclic triterpenoids identified as (24S)-24-isopropenyl-29-nor-5alpha-lanosta-7-en-3beta-ol (1) and (24S)-24-isopropenyl-29-nor-5alpha-lanosta-7-en-3-one (2), in addition to the known isopimaric acid (3) and chlorogenic acid (4). Their structures were elucidated on the basis of spectral analysis, including homo- and heteronuclear correlation NMR experiments (COSY, ROESY, HMQC and HMBC) and by comparison with data in the literature. The antimicrobial and antifungal activities were studied. The compounds did not show significant activity.

  13. Assessment of protein solution versus crystal structure determination using spin- diffusion-suppressed NOE and heteronuclear relaxation data

    International Nuclear Information System (INIS)

    LeMaster, David M.

    1997-01-01

    A spin-diffusion-suppressed NOE buildup series has been measured for E. coli thioredoxin.The extensive 13C and 15N relaxation data previously reported for this protein allow for direct interpretation of dynamical contributions to the 1H-1H cross-relaxation rates for a large proportion of the NOE cross peaks. Estimates of the average accuracy for these derived NOE distances are bounded by 4% and 10%, based on a comparison to the corresponding X-ray distances. An independent fluctuation model is proposed for prediction of the dynamical corrections to 1H-1H cross-relaxation rates, based solely on experimental structural and heteronuclear relaxation data. This analysis is aided by the demonstration that heteronuclear order parameters greater than 0.6 depend only on the variance of the H-X bond orientation,independent of the motional model in either one- or two-dimensional diffusion (i.e., 1- S2 = 3/4 sin2 2 θσ). The combination of spin-diffusion-suppressed NOE data and analysis of dynamical corrections to 1H-1H cross-relaxation rates based on heteronuclear relaxation data has allowed for a detailed interpretation of various discrepancies between the reported solution and crystal structures

  14. Demonstration of quantum logic gates in liquid crystal nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Marjanska, Malgorzata; Chuang, Isaac L.; Kubinec, Mark G.

    2000-01-01

    1 H- 13 C heteronuclear dipolar couplings are used to produce the NMR (nuclear magnetic resonance) version of a two bit controlled-NOT quantum logic gate. This gate is coupled with the Hadamard gate to complete a circuit which generates the Einstein-Podolsky-Rosen (EPR) state which is the maximally entangled state of a pair of spins. The EPR state is crucial for the potential exponential speed advantage of quantum computers over their classical counterparts. We sample the deviation density matrix of the two spin system to verify the presence of the EPR state. EPR state lifetimes are also measured with this technique, thereby demonstrating the viability of liquid crystals as a platform for quantum computing. (c) 2000 American Institute of Physics

  15. Interface and photoluminescence characteristics of graphene-(GaN/InGaN){sub n} multiple quantum wells hybrid structure

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liancheng, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn [Engineering Product Development Pillar (EPD), Singapore University of Technology & Design (SUTD), 8 Somapah Road, Singapore 487372 (Singapore); Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Mind Star (Beijing) Technology Co., Ltd., Zhongguancun South Street, Haidian District, No. 45 Hing Fat Building 1001, Beijing 100872 (China); Liu, Zhiqiang, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn; Tian, Ying Dong; Yi, Xiaoyan; Wang, Junxi; Li, Jinmin; Wang, Guohong [Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Zhang, Zi-Hui, E-mail: wanglc@semi.ac.cn, E-mail: lzq@semi.ac.cn, E-mail: zh.zhang@hebut.edu.cn [Key Laboratory of Electronic Materials and Devices of Tianjin, School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401 (China)

    2016-04-14

    The effects of graphene on the optical properties of active system, e.g., the InGaN/GaN multiple quantum wells, are thoroughly investigated and clarified. Here, we have investigated the mechanisms accounting for the photoluminescence reduction for the graphene covered GaN/InGaN multiple quantum wells hybrid structure. Compared to the bare multiple quantum wells, the photoluminescence intensity of graphene covered multiple quantum wells showed a 39% decrease after excluding the graphene absorption losses. The responsible mechanisms have been identified with the following factors: (1) the graphene two dimensional hole gas intensifies the polarization field in multiple quantum wells, thus steepening the quantum well band profile and causing hole-electron pairs to further separate; (2) a lower affinity of graphene compared to air leading to a weaker capability to confine the excited hot electrons in multiple quantum wells; and (3) exciton transfer through non-radiative energy transfer process. These factors are theoretically analysed based on advanced physical models of semiconductor devices calculations and experimentally verified by varying structural parameters, such as the indium fraction in multiple quantum wells and the thickness of the last GaN quantum barrier spacer layer.

  16. Exact quantum cross sections for a three dimensional angle dependent model for three body reactions.

    Science.gov (United States)

    Baer, M.; Kouri, D. J.

    1971-01-01

    Exact quantum mechanical reactive cross sections are reported for a three dimensional angle dependent model surface. The surface simulates an atom-heteronuclear diatom system A + BC leading to AB + C where atom B is much heavier than A or C. The molecules BC and AB are taken to be rotating vibrators which can dissociate. Results for two angle dependent potentials are given.

  17. Study of optical non-linear properties of a constant total effective length multiple quantum wells system

    International Nuclear Information System (INIS)

    Solaimani, M.; Morteza, Izadifard; Arabshahi, H.; Reza, Sarkardehi Mohammad

    2013-01-01

    In this work, we have studied the effect of the number of the wells, in a multiple quantum wells structure with constant total effective length, on the optical properties of multiple quantum wells like the absorption coefficient and the refractive index by means of compact density matrix approach. GaAs/Al x Ga (1−x) As multiple quantum wells systems was selected as an example. Besides, the effect of varying number of wells on the subband energies, wave functions, number of bound states, and the Fermi energy have been also investigated. Our calculation revealed that the number of wells in a multiple quantum well is a criterion with which we can control the amount of nonlinearity. This study showed that for the third order refractive index change there is two regimes of variations and the critical well number was six. In our calculations, we have used the same wells and barrier thicknesses to construct the multiple quantum wells system. - Highlights: ► OptiOptical Non-Linear. ► Total Effective Length. ► Multiple Quantum Wells System - genetic algorithm ► Schrödinger equation solution. ► Nanostructure.

  18. Some double resonance and multiple quantum NMR studies in solids

    International Nuclear Information System (INIS)

    Wemmer, D.E.

    1978-08-01

    The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of 13 C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D 2 O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, Δsigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO 3 .D 2 O, α,β d-2 HMB and α,β,γ d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules Δm = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made

  19. Frequency doubling of an InGaAs multiple quantum wells semiconductor disk laser

    Science.gov (United States)

    Lidan, Jiang; Renjiang, Zhu; Maohua, Jiang; Dingke, Zhang; Yuting, Cui; Peng, Zhang; Yanrong, Song

    2018-01-01

    We demonstrate a good beam quality 483 nm blue coherent radiation from a frequency doubled InGaAs multiple quantum wells semiconductor disk laser. The gain chip is consisted of 6 repeats of strain uncompensated InGaAs/GaAs quantum wells and 25 pairs of GaAs/AlAs distributed Bragg reflector. A 4 × 4 × 7 mm3 type I phase-matched BBO nonlinear crystal is used in a V-shaped laser cavity for the second harmonic generation, and 210 mW blue output power is obtained when the absorbed pump power is 3.5 W. The M2 factors of the laser beam in x and y directions are about 1.04 and 1.01, respectively. The output power of the blue laser is limited by the relatively small number of the multiple quantum wells, and higher power can be expected by increasing the number of the multiple quantum wells and improving the heat management of the laser.

  20. Some double resonance and multiple quantum NMR studies in solids

    Energy Technology Data Exchange (ETDEWEB)

    Wemmer, D.E.

    1978-08-01

    The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.

  1. Parallel magnetotransport in multiple quantum well structures

    International Nuclear Information System (INIS)

    Sheregii, E.M.; Ploch, D.; Marchewka, M.; Tomaka, G.; Kolek, A.; Stadler, A.; Mleczko, K.; Strupinski, W.; Jasik, A.; Jakiela, R.

    2004-01-01

    The results of investigations of parallel magnetotransport in AlGaAs/GaAs and InGaAs/InAlAs/InP multiple quantum wells structures (MQW's) are presented in this paper. The MQW's were obtained by metalorganic vapour phase epitaxy with different shapes of QW, numbers of QW and levels of doping. The magnetotransport measurements were performed in wide region of temperatures (0.5-300 K) and at high magnetic fields up to 30 T (B is perpendicular and current is parallel to the plane of the QW). Three types of observed effects are analyzed: quantum Hall effect and Shubnikov-de Haas oscillations at low temperatures (0.5-6 K) as well as magnetophonon resonance at higher temperatures (77-300 K)

  2. Highly efficient F-19 heteronuclear decoupling in solid-state NMR spectroscopy using supercycled refocused-CW irradiation

    DEFF Research Database (Denmark)

    Equbal, Asif; Basse, Kristoffer; Nielsen, Niels Christian

    2016-01-01

    We present heteronuclear F-19 refocused CW (rCW) decoupling pulse sequences for solid-state magic-angle- spinning NMR applications. The decoupling sequences have been designed specifically to ensure suppression of the pertinent C-13-F-19 dipolar coupling interactions while simultaneously suppress...

  3. The direct measurement of the heteronuclear chemical shifts relative to tetramethylsilane

    International Nuclear Information System (INIS)

    Moritz, A.G.

    1988-12-01

    The measurement of heteronuclear chemical shifts using absolute frequencies of the heteronucleus and the 1 H resonance of tetramethylsilane has been examined. This method avoids the problems associated with external standards and gives results which can be obtained quickly and with high precision. The method has a number of advantages in the accurate measurement of chemical shifts, as for example 31 P in chemical warfare agents and related chemicals and allows multinuclear data to be obtained without dynamic range or potential interference problems. 15 refs., 4 tabs

  4. Quantum correlation approach to criticality in the XX spin chain with multiple interaction

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, W.W., E-mail: weien.cheng@gmail.com [Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunication, Nanjing 210003 (China); Department of Physics, Hubei Normal University, Huangshi 435002 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education (China); Shan, C.J. [Department of Physics, Hubei Normal University, Huangshi 435002 (China); Sheng, Y.B.; Gong, L.Y.; Zhao, S.M. [Institute of Signal Processing and Transmission, Nanjing University of Posts and Telecommunication, Nanjing 210003 (China); Key Lab of Broadband Wireless Communication and Sensor Network Technology, Ministry of Education (China)

    2012-09-01

    We investigate the quantum critical behavior in the XX spin chain with a XZY-YZX type multiple interaction by means of quantum correlation (Concurrence C, quantum discord D{sub Q} and geometric discord D{sub G}). Around the critical point, the values of these quantum correlations and corresponding derivatives are investigated numerically and analytically. The results show that the non-analyticity property of the concurrence cannot signal well the quantum phase transition, but both the quantum discord and geometric discord can characterize the critical behavior in such model exactly.

  5. Luminescence of quantum-well exciton polaritons from microstructured AlxGa1-xAs-GaAs multiple quantum wells

    Science.gov (United States)

    Kohl, M.; Heitmann, D.; Grambow, P.; Ploog, K.

    1988-06-01

    Periodic multiple-quantum-well wires have been prepared by etching five-layer quantum-well structures through a holographically prepared mask. The periodicity was 380 nm, the lateral confinement 180 nm, and the quantum-well width 13, nm. The luminescence from these microstructured systems in the frequency regime of the one-electron-one-heavy-hole transition was strongly polarized with the electric field perpendicular to the periodic structure. This effect was caused by the resonantly enhanced emission of quantum-well-exciton (QWE) polaritons. Excitation of QWE polaritons was also observed in reflection measurements on the microstructured samples.

  6. Quantum correlations induced by multiple scattering of quadrature squeezed light

    DEFF Research Database (Denmark)

    Lodahl, Peter

    2006-01-01

    Propagating quadrature squeezed light through a multiple scattering random medium is found to induce pronounced spatial quantum correlations that have no classical analogue. The correlations are revealed in the number of photons transported through the sample that can be measured from the intensity...... fluctuations of the total transmission or reflection. In contrast, no pronounced spatial quantum correlations appear in the quadrature amplitudes where excess noise above the shot noise level is found....

  7. Electroluminescence property improvement by adjusting quantum wells’ position relative to p-doped region in InGaN/GaN multiple-quantum-well light emitting diodes

    Directory of Open Access Journals (Sweden)

    P. Chen

    2017-03-01

    Full Text Available The hole distribution and electroluminescence property improvement by adjusting the relative position between quantum wells and p-doped region in InGaN/GaN multiple-quantum-well structures are experimentally and theoretically investigated. Five designed samples with different barrier layer parameters of multiple-quantum-well structure are grown by MOCVD and then fabricated into devices. The electroluminescence properties of these samples are measured and compared. It is found that the output electroluminescence intensity of samples is enhanced if the position of quantum wells shifts towards p-side, while the output power is reduced if their position is shifted towards the n-side. The theoretical calculation of characteristics of these devices using the simulation program APSYS agrees well with the experimental data, illustrating that the effect of relative position between p-doped region and quantum wells on the improvement of hole distribution and electroluminescence performance is significant, especially for InGaN/GaN multiple-quantum-well devices operated under high injection condition.

  8. Multiple network alignment on quantum computers

    Science.gov (United States)

    Daskin, Anmer; Grama, Ananth; Kais, Sabre

    2014-12-01

    Comparative analyses of graph-structured datasets underly diverse problems. Examples of these problems include identification of conserved functional components (biochemical interactions) across species, structural similarity of large biomolecules, and recurring patterns of interactions in social networks. A large class of such analyses methods quantify the topological similarity of nodes across networks. The resulting correspondence of nodes across networks, also called node alignment, can be used to identify invariant subgraphs across the input graphs. Given graphs as input, alignment algorithms use topological information to assign a similarity score to each -tuple of nodes, with elements (nodes) drawn from each of the input graphs. Nodes are considered similar if their neighbors are also similar. An alternate, equivalent view of these network alignment algorithms is to consider the Kronecker product of the input graphs and to identify high-ranked nodes in the Kronecker product graph. Conventional methods such as PageRank and HITS (Hypertext-Induced Topic Selection) can be used for this purpose. These methods typically require computation of the principal eigenvector of a suitably modified Kronecker product matrix of the input graphs. We adopt this alternate view of the problem to address the problem of multiple network alignment. Using the phase estimation algorithm, we show that the multiple network alignment problem can be efficiently solved on quantum computers. We characterize the accuracy and performance of our method and show that it can deliver exponential speedups over conventional (non-quantum) methods.

  9. Degenerate ground states and multiple bifurcations in a two-dimensional q-state quantum Potts model.

    Science.gov (United States)

    Dai, Yan-Wei; Cho, Sam Young; Batchelor, Murray T; Zhou, Huan-Qiang

    2014-06-01

    We numerically investigate the two-dimensional q-state quantum Potts model on the infinite square lattice by using the infinite projected entangled-pair state (iPEPS) algorithm. We show that the quantum fidelity, defined as an overlap measurement between an arbitrary reference state and the iPEPS ground state of the system, can detect q-fold degenerate ground states for the Z_{q} broken-symmetry phase. Accordingly, a multiple bifurcation of the quantum ground-state fidelity is shown to occur as the transverse magnetic field varies from the symmetry phase to the broken-symmetry phase, which means that a multiple-bifurcation point corresponds to a critical point. A (dis)continuous behavior of quantum fidelity at phase transition points characterizes a (dis)continuous phase transition. Similar to the characteristic behavior of the quantum fidelity, the magnetizations, as order parameters, obtained from the degenerate ground states exhibit multiple bifurcation at critical points. Each order parameter is also explicitly demonstrated to transform under the Z_{q} subgroup of the symmetry group of the Hamiltonian. We find that the q-state quantum Potts model on the square lattice undergoes a discontinuous (first-order) phase transition for q=3 and q=4 and a continuous phase transition for q=2 (the two-dimensional quantum transverse Ising model).

  10. Fabrication of InN/InGaN multiple quantum well structures by RF-MBE

    Energy Technology Data Exchange (ETDEWEB)

    Kurouchi, M.; Muto, D.; Takado, S.; Araki, T.; Nanishi, Y. [Department of Photonics, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan); Na, H.; Naoi, H. [Center for Promotion of The 21st Century COE Program, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu, Shiga 525-8577 (Japan); Miyajima, T. [Optoelectronics Laboratory, Materials Laboratories, Sony Corporation, 4-14-1 Asahi, Atsugi, Kanagawa 243-0014 (Japan)

    2006-06-15

    InN/InGaN multiple quantum well structures have been fabricated on InN templates grown on (0 0 0 1) sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy. The structures were confirmed by X-ray diffraction, and satellite peaks up to the 3rd order were observed. From InN/InGaN multiple quantum well structures with different well widths, photoluminescence (PL) emission from the well layers was observed at 77 K, and the PL peak energy slightly blueshifted with decreasing the well width. This dependence can be explained by combined effects of quantum size effect, quantum confined Stark effect, and band filling effect. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Quantum theory of dynamic multiple light scattering in fluctuating disordered media

    International Nuclear Information System (INIS)

    Skipetrov, S. E.

    2007-01-01

    We formulate a quantum theory of dynamic multiple light scattering in fluctuating disordered media and calculate the fluctuation and the autocorrelation function of the photon number operator for light transmitted through a disordered slab. The effect of disorder on the information capacity of a quantum communication channel operating in a disordered environment is estimated, and the use of squeezed light in diffusing-wave spectroscopy is discussed

  12. Enhancement of optical Kerr effect in quantum-cascade lasers with multiple resonance levels.

    Science.gov (United States)

    Bai, Jing; Citrin, D S

    2008-08-18

    In this paper, we investigated the optical Kerr lensing effect in quantum-cascade lasers with multiple resonance levels. The Kerr refractive index n2 is obtained through the third-order susceptibility at the fundamental frequency chi(3)( omega; omega, omega,-omega). Resonant two-photon processes are found to have almost equal contributions to chi(3)( omega; omega, omega,-omega) as the single-photon processes, which result in the predicted enhancement of the positive nonlinear (Kerr) refractive index, and thus may enhance mode-locking of quantum-cascade lasers. Moreover, we also demonstrate an isospectral optimization strategy for further improving n2 through the band-structure design, in order to boost the multimode performance of quantum-cascade lasers. Simulation results show that the optimized stepwise multiple-quantum-well structure has n2 approximately 10-8 cm2/W, a twofold enhancement over the original flat quantum-well structure. This leads to a refractive-index change (delta)n of about 0.01, which is at the upper bound of those reported for typical Kerr medium. This stronger Kerr refractive index may be important for quantum-cascade lasers ultimately to demonstrate self-mode-locking.

  13. Electron-electron interaction in Multiple Quantum Wells

    Science.gov (United States)

    Zybert, M.; Marchewka, M.; Tomaka, G.; Sheregii, E. M.

    2012-07-01

    The complex investigation of the magneto-transport effects in structures containing multiple quantum well (MQWs) based on the GaAs/AlGaAs-heterostructures has been performed. The MQWs investigated have different electron densities in QWs. The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH) observed at low temperatures (0.6-4.2 K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D. Płoch et al., Phys. Rev. B 79 (2009) 195434) including the screening of this interaction. The IQHE and SdH observed in these multilayer structures with the third degree of freedom for electrons are interpreted from this.

  14. Detection of electromagnetic radiation using micromechanical multiple quantum wells structures

    Science.gov (United States)

    Datskos, Panagiotis G [Knoxville, TN; Rajic, Slobodan [Knoxville, TN; Datskou, Irene [Knoxville, TN

    2007-07-17

    An apparatus and method for detecting electromagnetic radiation employs a deflectable micromechanical apparatus incorporating multiple quantum wells structures. When photons strike the quantum-well structure, physical stresses are created within the sensor, similar to a "bimetallic effect." The stresses cause the sensor to bend. The extent of deflection of the sensor can be measured through any of a variety of conventional means to provide a measurement of the photons striking the sensor. A large number of such sensors can be arranged in a two-dimensional array to provide imaging capability.

  15. Neuroprotective Properties of Compounds Extracted from Dianthus superbus L. against Glutamate-induced Cell Death in HT22 Cells.

    Science.gov (United States)

    Yun, Bo-Ra; Yang, Hye Jin; Weon, Jin Bae; Lee, Jiwoo; Eom, Min Rye; Ma, Choong Je

    2016-01-01

    ) were isolated from D. superbus extract4-hydroxy-benzeneacetic acid and 4-methoxybenzeneacetic acid showed significant protective activity against glutamate-induced toxicity in HT22 cells. Abbreviations used: CNS: Central nervous system, ROS: Reactive oxygen species, CHCl3: Chloroform, EtOAc: Ethyl acetate, BuOH: Butanol, HPLC: High performance liquid chromatography, TLC: Thin layer chromatography, MPLC: Middle performance liquid chromatography, MeOH: Methanol, OD: Optical density, COSY: Correlation spectroscopy, HMQC: Heteronuclear multiple-quantum correlation, HMBC: Heteronuclear multiple-bond correlation, HR-MS: High-resolution molecular spectroscopy, MTT: 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

  16. Classical Logic and Quantum Logic with Multiple and Common Lattice Models

    Directory of Open Access Journals (Sweden)

    Mladen Pavičić

    2016-01-01

    Full Text Available We consider a proper propositional quantum logic and show that it has multiple disjoint lattice models, only one of which is an orthomodular lattice (algebra underlying Hilbert (quantum space. We give an equivalent proof for the classical logic which turns out to have disjoint distributive and nondistributive ortholattices. In particular, we prove that both classical logic and quantum logic are sound and complete with respect to each of these lattices. We also show that there is one common nonorthomodular lattice that is a model of both quantum and classical logic. In technical terms, that enables us to run the same classical logic on both a digital (standard, two-subset, 0-1-bit computer and a nondigital (say, a six-subset computer (with appropriate chips and circuits. With quantum logic, the same six-element common lattice can serve us as a benchmark for an efficient evaluation of equations of bigger lattice models or theorems of the logic.

  17. Two dimensional NMR of liquids and oriented molecules

    International Nuclear Information System (INIS)

    Gochin, M.

    1987-02-01

    Chapter 1 discusses the quantum mechanical formalism used for describing the interaction between magnetic dipoles that dictates the appearance of a spectrum. The NMR characteristics of liquids and liquid crystals are stressed. Chapter 2 reviews the theory of multiple quantum and two dimensional NMR. Properties of typical spectra and phase cycling procedures are discussed. Chapter 3 describes a specific application of heteronuclear double quantum coherence to the removal of inhomogeneous broadening in liquids. Pulse sequences have been devised which cancel out any contribution from this inhomogeneity to the final spectrum. An interpretation of various pulse sequences for the case of 13 C and 1 H is given, together with methods of spectral editing by removal or retention of the homo- or heteronuclear J coupling. The technique is applied to a demonstration of high resolution in both frequency and spatial dimensions with a surface coil. In Chapter 4, multiple quantum filtered 2-D spectroscopy is demonstrated as an effective means of studying randomly deuterated molecules dissolved in a nematic liquid crystal. Magnitudes of dipole coupling constants have been determined for benzene and hexane, and their signs and assignments found from high order multiple quantum spectra. For the first time, a realistic impression of the conformation of hexane can be estimated from these results. Chapter 5 is a technical description of the MDB DCHIB-DR11W parallel interface which has been set up to transfer data between the Data General Nova 820 minicomputer, interfaced to the 360 MHz spectrometer, and the Vax 11/730. It covers operation of the boards, physical specifications and installation, and programs for testing and running the interface

  18. Two dimensional NMR of liquids and oriented molecules

    Energy Technology Data Exchange (ETDEWEB)

    Gochin, M.

    1987-02-01

    Chapter 1 discusses the quantum mechanical formalism used for describing the interaction between magnetic dipoles that dictates the appearance of a spectrum. The NMR characteristics of liquids and liquid crystals are stressed. Chapter 2 reviews the theory of multiple quantum and two dimensional NMR. Properties of typical spectra and phase cycling procedures are discussed. Chapter 3 describes a specific application of heteronuclear double quantum coherence to the removal of inhomogeneous broadening in liquids. Pulse sequences have been devised which cancel out any contribution from this inhomogeneity to the final spectrum. An interpretation of various pulse sequences for the case of /sup 13/C and /sup 1/H is given, together with methods of spectral editing by removal or retention of the homo- or heteronuclear J coupling. The technique is applied to a demonstration of high resolution in both frequency and spatial dimensions with a surface coil. In Chapter 4, multiple quantum filtered 2-D spectroscopy is demonstrated as an effective means of studying randomly deuterated molecules dissolved in a nematic liquid crystal. Magnitudes of dipole coupling constants have been determined for benzene and hexane, and their signs and assignments found from high order multiple quantum spectra. For the first time, a realistic impression of the conformation of hexane can be estimated from these results. Chapter 5 is a technical description of the MDB DCHIB-DR11W parallel interface which has been set up to transfer data between the Data General Nova 820 minicomputer, interfaced to the 360 MHz spectrometer, and the Vax 11/730. It covers operation of the boards, physical specifications and installation, and programs for testing and running the interface.

  19. Efficiency dip observed with InGaN-based multiple quantum well solar cells

    KAUST Repository

    Lai, Kunyu; Lin, G. J.; Wu, Yuhrenn; Tsai, Menglun; He, Jr-Hau

    2014-01-01

    The dip of external quantum efficiency (EQE) is observed on In0.15Ga0.85N/GaN multiple quantum well (MQW) solar cells upon the increase of incident optical power density. With indium composition increased to 25%, the EQE dip becomes much less noticeable. The composition dependence of EQE dip is ascribed to the competition between radiative recombination and photocurrent generation in the active region, which are dictated by quantum-confined Stark effect (QCSE) and composition fluctuation in the MQWs.

  20. Harmonic Quantum Coherence of Multiple Excitons in PbS/CdS Core-Shell Nanocrystals

    Science.gov (United States)

    Tahara, Hirokazu; Sakamoto, Masanori; Teranishi, Toshiharu; Kanemitsu, Yoshihiko

    2017-12-01

    The generation and recombination dynamics of multiple excitons in nanocrystals (NCs) have attracted much attention from the viewpoints of fundamental physics and device applications. However, the quantum coherence of multiple exciton states in NCs still remains unclear due to a lack of experimental support. Here, we report the first observation of harmonic dipole oscillations in PbS/CdS core-shell NCs using a phase-locked interference detection method for transient absorption. From the ultrafast coherent dynamics and excitation-photon-fluence dependence of the oscillations, we found that multiple excitons cause the harmonic dipole oscillations with ω , 2 ω , and 3 ω oscillations, even though the excitation pulse energy is set to the exciton resonance frequency, ω . This observation is closely related to the quantum coherence of multiple exciton states in NCs, providing important insights into multiple exciton generation mechanisms.

  1. Differential multiple quantum relaxation caused by chemical exchange outside the fast exchange limit

    International Nuclear Information System (INIS)

    Wang Chunyu; Palmer, Arthur G.

    2002-01-01

    Differential relaxation of multiple quantum coherences is a signature for chemical exchange processes in proteins. Previous analyses of experimental data have used theoretical descriptions applicable only in the limit of fast exchange. Theoretical expressions for differential relaxation rate constants that are accurate outside fast exchange are presented for two-spin-system subject to two-site chemical exchange. The theoretical expressions are validated using experimental results for 15 N- 1 H relaxation in basic pancreatic trypsin inhibitor. The new theoretical expression is valuable for identification and characterization of exchange processes in proteins using differential relaxation of multiple quantum coherences

  2. Multiple-event probability in general-relativistic quantum mechanics. II. A discrete model

    International Nuclear Information System (INIS)

    Mondragon, Mauricio; Perez, Alejandro; Rovelli, Carlo

    2007-01-01

    We introduce a simple quantum mechanical model in which time and space are discrete and periodic. These features avoid the complications related to continuous-spectrum operators and infinite-norm states. The model provides a tool for discussing the probabilistic interpretation of generally covariant quantum systems, without the confusion generated by spurious infinities. We use the model to illustrate the formalism of general-relativistic quantum mechanics, and to test the definition of multiple-event probability introduced in a companion paper [Phys. Rev. D 75, 084033 (2007)]. We consider a version of the model with unitary time evolution and a version without unitary time evolution

  3. Memory-assisted quantum key distribution resilient against multiple-excitation effects

    Science.gov (United States)

    Lo Piparo, Nicolò; Sinclair, Neil; Razavi, Mohsen

    2018-01-01

    Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) has recently been proposed as a technique to improve the rate-versus-distance behavior of QKD systems by using existing, or nearly-achievable, quantum technologies. The promise is that MA-MDI-QKD would require less demanding quantum memories than the ones needed for probabilistic quantum repeaters. Nevertheless, early investigations suggest that, in order to beat the conventional memory-less QKD schemes, the quantum memories used in the MA-MDI-QKD protocols must have high bandwidth-storage products and short interaction times. Among different types of quantum memories, ensemble-based memories offer some of the required specifications, but they typically suffer from multiple excitation effects. To avoid the latter issue, in this paper, we propose two new variants of MA-MDI-QKD both relying on single-photon sources for entangling purposes. One is based on known techniques for entanglement distribution in quantum repeaters. This scheme turns out to offer no advantage even if one uses ideal single-photon sources. By finding the root cause of the problem, we then propose another setup, which can outperform single memory-less setups even if we allow for some imperfections in our single-photon sources. For such a scheme, we compare the key rate for different types of ensemble-based memories and show that certain classes of atomic ensembles can improve the rate-versus-distance behavior.

  4. The Over-Barrier Resonant States and Multi-Channel Scattering in Multiple Quantum Wells

    Directory of Open Access Journals (Sweden)

    A Polupanov

    2016-09-01

    Full Text Available We demonstrate an explicit numerical method for accurate calculation of the scattering matrix and its poles, and apply this method to describe the multi-channel scattering in the multiple quantum-wells structures. The S-matrix is continued analytically to the unphysical region of complex energy values. Results of calculations show that there exist one or more S-matrix poles, corresponding to the over-barrier resonant states critical for the effect of the absolute reflection of holes in the energy range where only the heavy ones may propagate over barriers in a structure. Light- and heavy-hole states are described by the Luttinger Hamiltonian matrix. In contrast to the single quantum-well case, at some parameters of a multiple quantum-wells structure the number of S-matrix poles may exceed that of the absolute reflection peaks, and at different values of parameters the absolute reflection peak corresponds to different resonant states. The imaginary parts of the S-matrix poles and hence the lifetimes of resonant states as well as the widths of resonant peaks of absolute reflection depend drastically on the quantum-well potential depth. In the case of shallow quantum wells there is in fact a long-living over-barrier resonant hole state.

  5. Quantum optics in multiple scattering random media

    DEFF Research Database (Denmark)

    Lodahl, Peter; Lagendijk, Ad

    2005-01-01

    Quantum Optics in Multiple Scattering Random Media Peter Lodahl Research Center COM, Technical University of Denmark, Dk-2800 Lyngby, Denmark. Coherent transport of light in a disordered random medium has attracted enormous attention both from a fundamental and application point of view. Coherent......-tions that should be readily attainable experimentally is devised. Figure 1. Inverse total transmission of shot noise (left) and technical noise (right) as a function of the thickness of the ran-dom medium. The experimental data are well explained by theory (curves). [1] J. Tworzydlo and C.W.J. Beenakker, Phys. Rev...

  6. Nonadditivity of quantum and classical capacities for entanglement breaking multiple-access channels and the butterfly network

    International Nuclear Information System (INIS)

    Grudka, Andrzej; Horodecki, Pawel

    2010-01-01

    We analyze quantum network primitives which are entanglement breaking. We show superadditivity of quantum and classical capacity regions for quantum multiple-access channels and the quantum butterfly network. Since the effects are especially visible at high noise they suggest that quantum information effects may be particularly helpful in the case of the networks with occasional high noise rates. The present effects provide a qualitative borderline between superadditivities of bipartite and multipartite systems.

  7. S3 HMBC hetero: Spin-State-Selective HMBC for accurate measurement of long-range heteronuclear coupling constants

    DEFF Research Database (Denmark)

    Hoeck, Casper; Gotfredsen, Charlotte Held; Sørensen, Ole W.

    2017-01-01

    A novel method, Spin-State-Selective (S3) HMBC hetero, for accurate measurement of heteronuclear coupling constants is introduced. The method extends the S3 HMBC technique for measurement of homonuclear coupling constants by appending a pulse sequence element that interchanges the polarization...

  8. Structural and optical characteristics of InN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Kim, Je Won; Lee, Kyu Han; Hong, Sangsu

    2007-01-01

    The structural and electrical properties of InN/GaN multiple quantum wells, which were grown by metalorganic chemical vapor deposition, were characterized by transmission electron microscopy (TEM) and electroluminescence measurements. From the TEM micrographs, it was shown that the well layer was grown like a quantum dot. The well layer is expected to be the nano-size structures in the InN multiple quantum well layers. The multi-photon confocal laser scanning microscopy was used to investigate the optical properties of the light emitting diode (LED) structures with InN active layers. It was found that the two-photon excitation was possible in InN system. The pit density was measured by using the far-field optical technique. In the varied current conditions, the blue LED with the InN multiple quantum well structures did not have the wavelength shift. With this result, we can expect that the white LEDs with the InN multiple quantum well structures do not show the color temperature changes with the variations of applied currents

  9. Relating Out-of-Time-Order Correlations to Entanglement via Multiple-Quantum Coherences.

    Science.gov (United States)

    Gärttner, Martin; Hauke, Philipp; Rey, Ana Maria

    2018-01-26

    Out-of-time-order correlations (OTOCs) characterize the scrambling, or delocalization, of quantum information over all the degrees of freedom of a system and thus have been proposed as a proxy for chaos in quantum systems. Recent experimental progress in measuring OTOCs calls for a more thorough understanding of how these quantities characterize complex quantum systems, most importantly in terms of the buildup of entanglement. Although a connection between OTOCs and entanglement entropy has been derived, the latter only quantifies entanglement in pure systems and is hard to access experimentally. In this work, we formally demonstrate that the multiple-quantum coherence spectra, a specific family of OTOCs well known in NMR, can be used as an entanglement witness and as a direct probe of multiparticle entanglement. Our results open a path to experimentally testing the fascinating idea that entanglement is the underlying glue that links thermodynamics, statistical mechanics, and quantum gravity.

  10. Relating Out-of-Time-Order Correlations to Entanglement via Multiple-Quantum Coherences

    Science.gov (United States)

    Gärttner, Martin; Hauke, Philipp; Rey, Ana Maria

    2018-01-01

    Out-of-time-order correlations (OTOCs) characterize the scrambling, or delocalization, of quantum information over all the degrees of freedom of a system and thus have been proposed as a proxy for chaos in quantum systems. Recent experimental progress in measuring OTOCs calls for a more thorough understanding of how these quantities characterize complex quantum systems, most importantly in terms of the buildup of entanglement. Although a connection between OTOCs and entanglement entropy has been derived, the latter only quantifies entanglement in pure systems and is hard to access experimentally. In this work, we formally demonstrate that the multiple-quantum coherence spectra, a specific family of OTOCs well known in NMR, can be used as an entanglement witness and as a direct probe of multiparticle entanglement. Our results open a path to experimentally testing the fascinating idea that entanglement is the underlying glue that links thermodynamics, statistical mechanics, and quantum gravity.

  11. Phase behaviour of heteronuclear dimers in three-dimensional systems-a Monte Carlo study

    International Nuclear Information System (INIS)

    Rzysko, W; Binder, K

    2008-01-01

    Monte Carlo simulation in the grand canonical ensemble, the histogram reweighting technique and finite size scaling are used to study the phase behaviour of dimers in three-dimensional systems. A single molecule is composed of two segments A and B, and the bond between them cannot be broken. The phase diagrams have been estimated for a set of model systems. Different structures formed by heteronuclear dimers have been found. The results show a great variety of vapour-liquid coexistence behaviour depending on the strength of the interactions between segments

  12. Hydrothermal liquefaction oil and hydrotreated product from pine feedstock characterized by heteronuclear two-dimensional NMR spectroscopy and FT-ICR mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Sudasinghe, Nilusha; Cort, John R.; Hallen, Richard T.; Olarte, Mariefel V.; Schmidt, Andrew J.; Schaub, Tanner

    2014-12-01

    Hydrothermal liquefaction (HTL) crude oil and hydrotreated product from pine tree farm waste (forest product residual, FPR) have been analyzed by direct infusion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) in both positive- and negative-ionization modes and high-resolution twodimensional heteronuclear 1H-13C NMR spectroscopy. FT-ICR MS resolves thousands of compounds in complex oils and provides unparalleled compositional details for individual molecules for identification of compound class (heteroatom content), type (number of rings plus double bonds to carbon or double bond equivalents (DBE) and carbon number (degree of alkylation). Heteronuclear 1H-13C NMR spectroscopy provides one-bond and multiple-bond correlations between pairs of 1H and 13C chemical shifts that are characteristic of different organic functional groups. Taken together this information provides a picture of the chemical composition of these oils. Pyrolysis crude oil product from pine wood was characterized for comparison. Generally, pyrolysis oil is comprised of a more diverse distribution of heteroatom classes with higher oxygen number relative to HTL oil as shown by both positive- and negative-ion ESI FT-ICR MS. A total of 300 N1, 594 O1 and 267 O2 compounds were observed as products of hydrotreatment. The relative abundance of N1O1, N1O2, N1O3, N2, N2O1, N2O2 and O3 compounds are reduced to different degrees after hydrotreatment and other higher heteroatom containing species (O4-O10, N1O4, N1O5 and N2O3) are completely removed by hydrotreatment.

  13. Heteronuclear long-range correlation, what’s new and how far can it take us?

    DEFF Research Database (Denmark)

    Sørensen, Ole W.

    : A novel experiment for small-molecule and biomolecular NMR at natural isotopic abundance. Sebastian Meier, Andrew J. Benie, Jens Ø. Duus and Ole W. Sørensen, Journal of Magnetic Resonance, in press, doi:10.1016/j.jmr.2009.06.017 Recent progress in heteronuclear long-range NMR of complex carbohydrates: 3D...... H2BC and clean HMBC. Sebastian Meier, Bent O. Petersen, Jens Ø. Duus, Ole W. Sørensen. Carbohydrate Research, in press, doi:10.1016/j.carres.2009.08.013...

  14. Resonant Rayleigh scattering of exciton-polaritons in multiple quantum wells

    DEFF Research Database (Denmark)

    Malpuech, Guillaume; Kavokin, Alexey; Langbein, Wolfgang Werner

    2000-01-01

    A theoretical concept of resonant Rayleigh scattering (RRS) of exciton-polaritons in multiple quantum wells (QWs) is presented. The optical coupling between excitons in different QWs can strongly affect the RRS dynamics, giving rise to characteristic temporal oscillations on a picosecond scale....... Bragg and anti-Bragg arranged QW structures with the same excitonic parameters are predicted to have drastically different RRS spectra. Experimental data on the RRS from multiple QWs show the predicted strong temporal oscillations at small scattering angles, which are well explained by the presented...

  15. Quantum partial search for uneven distribution of multiple target items

    Science.gov (United States)

    Zhang, Kun; Korepin, Vladimir

    2018-06-01

    Quantum partial search algorithm is an approximate search. It aims to find a target block (which has the target items). It runs a little faster than full Grover search. In this paper, we consider quantum partial search algorithm for multiple target items unevenly distributed in a database (target blocks have different number of target items). The algorithm we describe can locate one of the target blocks. Efficiency of the algorithm is measured by number of queries to the oracle. We optimize the algorithm in order to improve efficiency. By perturbation method, we find that the algorithm runs the fastest when target items are evenly distributed in database.

  16. Trifasciatosides A-J, Steroidal Saponins from Sansevieria trifasciata.

    Science.gov (United States)

    Teponno, Rémy Bertrand; Tanaka, Chiaki; Jie, Bai; Tapondjou, Léon Azefack; Miyamoto, Tomofumi

    2016-01-01

    Four previously unreported steroidal saponins, trifasciatosides A-D (1-4), three pairs of previously undescribed steroidal saponins, trifasciatosides E-J (5a, b-7a, b) including acetylated ones, together with twelve known compounds were isolated from the n-butanol soluble fraction of the methanol extract of Sansevieria trifasciata. Their structures were elucidated on the basis of detailed spectroscopic analysis, including (1)H-NMR, (13)C-NMR, (1)H-(1)H correlated spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC), total correlated spectroscopy (TOCSY), nuclear Overhauser enhancement and exchange spectroscopy (NOESY), electrospray ionization-time of flight (ESI-TOF)-MS and chemical methods. Compounds 2, 4, and 7a, b exhibited moderate antiproliferative activity against HeLa cells.

  17. NMR-Assisted Structure Elucidation of an Anticancer Steroid-β-Enaminone Derivative

    Directory of Open Access Journals (Sweden)

    Donald Poirier

    2017-11-01

    Full Text Available The fortuitous modification of a quinoline-proline-piperazine side chain linked to a steroid in the presence of lithium (trimethylsilyl acetylide has generated an unknown product that is more active than its precursor. After having characterized two β-enaminones (two-carbon homologation compounds that were generated from a simplified model side chain, we have identified the unknown product as being the β-enaminone steroid derivative 1. NMR analysis, especially two-dimensional (2D experiments (correlation spectroscopy (COSY, NOE spectroscopy (NOESY, heteronuclear single-quantum correlation (HSQC and heteronuclear multiple-bond correlation (HMBC provided crucial information that was found essential in the characterization of enaminone 1. We also proposed a mechanism to rationalize the formation of this biologically active compound.

  18. Statistics, synergy, and mechanism of multiple photogeneration of excitons in quantum dots: Fundamental and applied aspects

    International Nuclear Information System (INIS)

    Oksengendler, B. L.; Turaeva, N. N.; Uralov, I.; Marasulov, M. B.

    2012-01-01

    The effect of multiple exciton generation is analyzed based on statistical physics, quantum mechanics, and synergetics. Statistical problems of the effect of multiple exciton generation (MEG) are broadened and take into account not only exciton generation, but also background excitation. The study of the role of surface states of quantum dots is based on the synergy of self-catalyzed electronic reactions. An analysis of the MEG mechanism is based on the idea of electronic shaking using the sudden perturbation method in quantum mechanics. All of the above-mentioned results are applied to the problem of calculating the limiting efficiency to transform solar energy into electric energy. (authors)

  19. Faraday rotation in multiple quantum wells of GaAs/AlGaAs

    International Nuclear Information System (INIS)

    Dudziak, E.; Bozym, J.; Prochnik, D.; Wasilewski, Z.R.

    1996-01-01

    We report on the results of first measurements on the Faraday rotation of modulated n-doped multiple quantum wells of GaAs/Al x Ga 1-x As (x = 0.312). The measurements have been performed in the magnetic fields up to 13 T at the temperature of 2 K, in the spectral region of interband transitions. A rich structure of magneto-excitons has been found in the measured spectra. Faraday rotation (phase) measurements are proposed as an alternative method to the photoluminescence excitation for investigations of magneto-excitons in quantum wells. The dependence of measured Faraday rotation on magnetic field and hypothetical connections with quantum Hall effect are also discussed. (author)

  20. Synthesis and magnetic properties of heteronuclear 3d-4f compound

    International Nuclear Information System (INIS)

    Cristovao, B.; Ferenc, W.

    2007-01-01

    A novel heteronuclear 3d-4f compound having formula NdCu 3 L 3 ·13H 2 O (where H 3 L = Schiff base derived from 5-bromosalicylaldehyde and glycylglycine and L 3 = C 11 H 8 N 2 O 4 Br) was obtained. It was characterized by elemental and thermal analyses and magnetic measurements. The Cu(II)-Nd(III) compound is stable up to 323 K. During dehydration process the water molecules are lost in two stages. The magnetic susceptibility data for this complex change with temperature according to the Curie-Weiss law with Θ = -35 K. The magnetic moment values decrease from 5.00μ B at 303 K to 4.38μB at 76 K. (author)

  1. Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions.

    Science.gov (United States)

    Weng, Z F; Smidman, M; Jiao, L; Lu, Xin; Yuan, H Q

    2016-09-01

    Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.

  2. Time evolution of multiple quantum coherences in NMR

    International Nuclear Information System (INIS)

    Sanchez, Claudia M.; Pastawski, Horacio M.; Levstein, Patricia R.

    2007-01-01

    In multiple quantum NMR, individual spins become correlated with one another over time through their dipolar couplings. In this way, the usual Zeeman selection rule can be overcome and forbidden transitions can be excited. Experimentally, these multiple quantum coherences (MQC) are formed by the application of appropriate sequences of radio frequency pulses that force the spins to act collectively. 1 H spin coherences of even order up to 16 were excited in a polycrystalline sample of ferrocene (C 5 H 5 ) 2 Fe and up to 32 in adamantane (C 10 H 16 ) and their evolutions studied in different conditions: (a) under the natural dipolar Hamiltonian, H ZZ (free evolution) and with H ZZ canceled out by (b) time reversion or (c) with the MREV8 sequence. The results show that when canceling H ZZ the coherences decay with characteristic times (τ c ∼200 μs), which are more than one order of magnitude longer than those under free evolution (τ c ∼10 μs). In addition, it is observed that with both MREV8 and time reversion sequences, the higher the order of the coherence (larger number of correlated spins) the faster the speed of degradation, as it happens during the evolution with H ZZ . In both systems, it is observed that the sequence of time reversion of the dipolar Hamiltonian preserves coherences for longer times than MREV8

  3. Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

    Energy Technology Data Exchange (ETDEWEB)

    Hammersley, S.; Dawson, P. [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Kappers, M. J.; Massabuau, F. C.-P.; Sahonta, S.-L.; Oliver, R. A.; Humphreys, C. J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2015-09-28

    InGaN-based light emitting diodes and multiple quantum wells designed to emit in the green spectral region exhibit, in general, lower internal quantum efficiencies than their blue-emitting counter parts, a phenomenon referred to as the “green gap.” One of the main differences between green-emitting and blue-emitting samples is that the quantum well growth temperature is lower for structures designed to emit at longer wavelengths, in order to reduce the effects of In desorption. In this paper, we report on the impact of the quantum well growth temperature on the optical properties of InGaN/GaN multiple quantum wells designed to emit at 460 nm and 530 nm. It was found that for both sets of samples increasing the temperature at which the InGaN quantum well was grown, while maintaining the same indium composition, led to an increase in the internal quantum efficiency measured at 300 K. These increases in internal quantum efficiency are shown to be due reductions in the non-radiative recombination rate which we attribute to reductions in point defect incorporation.

  4. Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

    International Nuclear Information System (INIS)

    Hammersley, S.; Dawson, P.; Kappers, M. J.; Massabuau, F. C.-P.; Sahonta, S.-L.; Oliver, R. A.; Humphreys, C. J.

    2015-01-01

    InGaN-based light emitting diodes and multiple quantum wells designed to emit in the green spectral region exhibit, in general, lower internal quantum efficiencies than their blue-emitting counter parts, a phenomenon referred to as the “green gap.” One of the main differences between green-emitting and blue-emitting samples is that the quantum well growth temperature is lower for structures designed to emit at longer wavelengths, in order to reduce the effects of In desorption. In this paper, we report on the impact of the quantum well growth temperature on the optical properties of InGaN/GaN multiple quantum wells designed to emit at 460 nm and 530 nm. It was found that for both sets of samples increasing the temperature at which the InGaN quantum well was grown, while maintaining the same indium composition, led to an increase in the internal quantum efficiency measured at 300 K. These increases in internal quantum efficiency are shown to be due reductions in the non-radiative recombination rate which we attribute to reductions in point defect incorporation

  5. Coexistence of different vacua in the effective quantum field theory and multiple point principle

    International Nuclear Information System (INIS)

    Volovik, G.E.

    2004-01-01

    According to the multiple point principle our Universe in on the coexistence curve of two or more phases of the quantum vacuum. The coexistence of different quantum vacua can be regulated by the exchange of the global fermionic charges between the vacua. If the coexistence is regulated by the baryonic charge, all the coexisting vacua exhibit the baryonic asymmetry. Due to the exchange of the baryonic charge between the vacuum and matter which occurs above the electroweak transition, the baryonic asymmetry of the vacuum induces the baryonic asymmetry of matter in our Standard-Model phase of the quantum vacuum [ru

  6. Phenolic Glycosides from Capsella bursa-pastoris (L. Medik and Their Anti-Inflammatory Activity

    Directory of Open Access Journals (Sweden)

    Joon Min Cha

    2017-06-01

    Full Text Available A new sesquilignan glycoside 1, together with seven known phenolic glycosides 2–8 were isolated from the aerial parts of Capsella bursa-pastoris. The chemical structure of the new compound 1 was elucidated by extensive nuclear magnetic resonance (NMR data (1H- and 13C-NMR, 1H-1H correlation spectroscopy (1H-1H COSY, heteronuclear single-quantum correlation (HSQC, heteronuclear multiple bond correlation (HMBC, and nuclear overhauser effect spectroscopy (NOESY and HR-FABMS analysis. The anti-inflammatory effects of 1–8 were evaluated in lipopolysaccharide (LPS-stimulated murine microglia BV-2 cells. Compounds 4 and 7 exhibited moderate inhibitory effects on nitric oxide production in LPS-activated BV-2 cells, with IC50 values of 17.80 and 27.91 µM, respectively.

  7. Anti-ulcerogenic Activity of Extract and Some Isolated Flavonoids from Desmostachia bipinnata (L. Stapf

    Directory of Open Access Journals (Sweden)

    Amani, S. Awaad

    2008-08-01

    Full Text Available Five main flavonoid glycosides were isolated, for the first time, from the ethanol extract of Desmostachia bipinnata (L.Stapf ( Gramineae . They were identified as kaempferol(1, quercetin(2, quercetin-3-glucoside(3, trycin(4 and trycin-7-glucoside(5. The structure elucidation was based on UV, Electrospray ionization mass spectrometry (ESIMS, 1H and 13C NMR, proton- proton correlation spectroscopy ( 1H- 1H Cosy, distortionless enhancement by polarization transfer (DEPT, heteronuclear single quantum coherence (HSQC, and heteronuclear multiple bond correlations spectrum (HMBC. The total extract (200 and 300 mg/kg and two of the isolated compounds (trycin and trycin-7-glucoside.100 mg/kg each showed a very promising antiulcerogenic activity with curative ratios; 68.31, 70.54, 77.39 and 78.93%, respectively.

  8. Generation of multiple excitons in Ag2S quantum dots: Single high-energy versus multiple-photon excitation

    KAUST Repository

    Sun, Jingya; Yu, Weili; Usman, Anwar; Isimjan, Tayirjan T.; Del Gobbo, Silvano; Alarousu, Erkki; Takanabe, Kazuhiro; Mohammed, Omar F.

    2014-01-01

    We explored biexciton generation via carrier multiplication (or multiple-exciton generation) by high-energy photons and by multiple-photon absorption in Ag2S quantum dots (QDs) using femtosecond broad-band transient absorption spectroscopy. Irrespective of the size of the QDs and how the multiple excitons are generated in the Ag2S QDs, two distinct characteristic time constants of 9.6-10.2 and 135-175 ps are obtained for the nonradiative Auger recombination of the multiple excitons, indicating the existence of two binding excitons, namely, tightly bound and weakly bound excitons. More importantly, the lifetimes of multiple excitons in Ag 2S QDs were about 1 and 2 orders of magnitude longer than those of comparable size PbS QDs and single-walled carbon nanotubes, respectively. This result is significant because it suggests that by utilizing an appropriate electron acceptor, there is a higher possibility to extract multiple electron-hole pairs in Ag2S QDs, which should improve the performance of QD-based solar cell devices. © 2014 American Chemical Society.

  9. Generation of multiple excitons in Ag2S quantum dots: Single high-energy versus multiple-photon excitation

    KAUST Repository

    Sun, Jingya

    2014-02-20

    We explored biexciton generation via carrier multiplication (or multiple-exciton generation) by high-energy photons and by multiple-photon absorption in Ag2S quantum dots (QDs) using femtosecond broad-band transient absorption spectroscopy. Irrespective of the size of the QDs and how the multiple excitons are generated in the Ag2S QDs, two distinct characteristic time constants of 9.6-10.2 and 135-175 ps are obtained for the nonradiative Auger recombination of the multiple excitons, indicating the existence of two binding excitons, namely, tightly bound and weakly bound excitons. More importantly, the lifetimes of multiple excitons in Ag 2S QDs were about 1 and 2 orders of magnitude longer than those of comparable size PbS QDs and single-walled carbon nanotubes, respectively. This result is significant because it suggests that by utilizing an appropriate electron acceptor, there is a higher possibility to extract multiple electron-hole pairs in Ag2S QDs, which should improve the performance of QD-based solar cell devices. © 2014 American Chemical Society.

  10. Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David

    We studied the THz conductivity of InGaN/GaN multiple quantum wells (MQWs)by time-resolved terahertz spectroscopy. A nonexponential carrier density decay is observed due to the restoration of a built-in piezoelectric field. Terahertz conductivity spectra show a nonmetallic behavior of the carriers....

  11. Multiple-valued logic-protected coding for an optical non-quantum communication line

    NARCIS (Netherlands)

    Antipov, A. L.; Bykovsky, A. Yu.; Vasiliev, N. A.; Egorov, A. A.

    2006-01-01

    A simple and cheap method of secret coding in an optical line is proposed based on multiple-valued logic. This method is shown to have very high cryptography resources and is designated for bidirectional information exchange in a team of mobile robots, where quantum teleportation coding cannot yet

  12. Reaction monitoring using hyperpolarized NMR with scaling of heteronuclear couplings by optimal tracking

    Science.gov (United States)

    Zhang, Guannan; Schilling, Franz; Glaser, Steffen J.; Hilty, Christian

    2016-11-01

    Off-resonance decoupling using the method of Scaling of Heteronuclear Couplings by Optimal Tracking (SHOT) enables determination of heteronuclear correlations of chemical shifts in single scan NMR spectra. Through modulation of J-coupling evolution by shaped radio frequency pulses, off resonance decoupling using SHOT pulses causes a user-defined dependence of the observed J-splitting, such as the splitting of 13C peaks, on the chemical shift offset of coupled nuclei, such as 1H. Because a decoupling experiment requires only a single scan, this method is suitable for characterizing on-going chemical reactions using hyperpolarization by dissolution dynamic nuclear polarization (D-DNP). We demonstrate the calculation of [13C, 1H] chemical shift correlations of the carbanionic active sites from hyperpolarized styrene polymerized using sodium naphthalene as an initiator. While off resonance decoupling by SHOT pulses does not enhance the resolution in the same way as a 2D NMR spectrum would, the ability to obtain the correlations in single scans makes this method ideal for determination of chemical shifts in on-going reactions on the second time scale. In addition, we present a novel SHOT pulse that allows to scale J-splittings 50% larger than the respective J-coupling constant. This feature can be used to enhance the resolution of the indirectly detected chemical shift and reduce peak overlap, as demonstrated in a model reaction between p-anisaldehyde and isobutylamine. For both pulses, the accuracy is evaluated under changing signal-to-noise ratios (SNR) of the peaks from reactants and reaction products, with an overall standard deviation of chemical shift differences compared to reference spectra of 0.02 ppm when measured on a 400 MHz NMR spectrometer. Notably, the appearance of decoupling side-bands, which scale with peak intensity, appears to be of secondary importance.

  13. Simultaneous nano-tracking of multiple motor proteins via spectral discrimination of quantum dots.

    Science.gov (United States)

    Kakizuka, Taishi; Ikezaki, Keigo; Kaneshiro, Junichi; Fujita, Hideaki; Watanabe, Tomonobu M; Ichimura, Taro

    2016-07-01

    Simultaneous nanometric tracking of multiple motor proteins was achieved by combining multicolor fluorescent labeling of target proteins and imaging spectroscopy, revealing dynamic behaviors of multiple motor proteins at the sub-diffraction-limit scale. Using quantum dot probes of distinct colors, we experimentally verified the localization precision to be a few nanometers at temporal resolution of 30 ms or faster. One-dimensional processive movement of two heads of a single myosin molecule and multiple myosin molecules was successfully traced. Furthermore, the system was modified for two-dimensional measurement and applied to tracking of multiple myosin molecules. Our approach is useful for investigating cooperative movement of proteins in supramolecular nanomachinery.

  14. Isotopic and spin-nuclear effects in solid hydrogens (Review Article)

    Science.gov (United States)

    Freiman, Yuri A.; Crespo, Yanier

    2017-12-01

    The multiple isotopic family of hydrogens (H2, HD, D2, HT, DT, T2) due to large differences in the de Boer quantum parameter and inertia moments displays a diversity of pronounced quantum isotopic solid-state effects. The homonuclear members of this family (H2, D2, T2) due to the permutation symmetry are subjects of the constraints of quantum mechanics which link the possible rotational states of these molecules to their total nuclear spin giving rise to the existence of two spin-nuclear modifications, ortho- and parahydrogens, possessing substantially different properties. Consequently, hydrogen solids present an unique opportunity for studying both isotope and spin-nuclear effects. The rotational spectra of heteronuclear hydrogens (HD, HT, DT) are free from limitations imposed by the permutation symmetry. As a result, the ground state of these species in solid state is virtually degenerate. The most dramatic consequence of this fact is an effect similar to the Pomeranchuk effect in 3He which in the case of the solid heteronuclear hydrogens manifests itself as the reentrant broken symmetry phase transitions. In this review article we discuss thermodynamic and kinetic effects pertaining to different isotopic and spin-nuclear species, as well as problems that still remain to be solved.

  15. Carrier multiplication and its reduction by photodoping in colloidal InAs quantum dots

    NARCIS (Netherlands)

    Pijpers, J. J. H.; Hendry, E.; Milder, M.T.W.; Fanciulli, R.; Savolainen, J.; Herek, J.L.; Vanmaekelbergh, D.A.M.|info:eu-repo/dai/nl/304829137; Ruhman, S.; Mocatta, D.; Oron, D.; Aharoni, A.; Banin, U.; Bonn, M.

    2007-01-01

    Carrier (exciton) multiplication in colloidal InAs/CdSe/ZnSe core-shell quantum dots (QDs) is investigated using terahertz time-domain spectroscopy, time-resolved transient absorption, and quasi-continuous wave excitation spectroscopy. For excitation by high-energy photons (~2.7 times the band gap

  16. Two New Stilbenoids from the Aerial Parts of Arundina graminifolia (Orchidaceae

    Directory of Open Access Journals (Sweden)

    Florence Auberon

    2016-10-01

    Full Text Available Two new phenanthrene derivatives, a phenanthrenequinone named arundiquinone (1 and a 9,10-dihydrophenanthrene named arundigramin (2 together with a known lignin dimer (3 and seven known stilbenoids (4–10 were isolated from the aerial parts of the Asian orchid Arundina graminifolia. The structures of the isolated compounds were elucidated by spectroscopic methods, including extensive 1D, 2D NMR (heteronuclear single quantum coherence (HSQC, heteronuclear multiple-bond correlation spectroscopy (HMBC, and HR-ESI-MS techniques, as well as comparison with respective literature reports. The cytoprotective activity of the isolated compounds were evaluated for their ability to reduce beta amyloid induced toxicity on undifferentiated PC12 cells. Compound 8 showed moderate cytoprotective activity at 0.5 µmol/L (71% of cell viability while the other compounds showed no significant activity at the highest concentration tested.

  17. Multiple defects in GaInN multiple quantum wells grown on ELO GaN layers and on GaN substrates

    International Nuclear Information System (INIS)

    Tomiya, S.; Goto, O.; Hoshina, Y.; Tanaka, T.; Ikeda, M.

    2006-01-01

    A new type of structural defects was observed in GaInN multiple quantum well structures with higher In concentrations that were grown on low-threading-dislocation-density templates. The defects were investigated by using various kinds of transmission electron microscopy techniques, and were found to consist of planar defects and associated dislocations. The planar defects nucleate at the interfaces between the quantum well layers and barrier layers. The dislocations are created at the edge boundary of the planar defects and run almost along the c-axis towards the epi-surface. The planar defects are revealed to be inversion domains which are thought to be caused by the segregation of excess In-In bonds at the interface between the quantum well layer and the barrier layer. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Multiple defects in GaInN multiple quantum wells grown on ELO GaN layers and on GaN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tomiya, S. [Materials Analysis Laboratory, Sony Corporation, Kanagawa (Japan); Goto, O.; Hoshina, Y.; Tanaka, T.; Ikeda, M. [Shiroishi Laser Center, Semiconductor Laser Division, MSNC, Sony Corporation, Miyagi (Japan)

    2006-06-15

    A new type of structural defects was observed in GaInN multiple quantum well structures with higher In concentrations that were grown on low-threading-dislocation-density templates. The defects were investigated by using various kinds of transmission electron microscopy techniques, and were found to consist of planar defects and associated dislocations. The planar defects nucleate at the interfaces between the quantum well layers and barrier layers. The dislocations are created at the edge boundary of the planar defects and run almost along the c-axis towards the epi-surface. The planar defects are revealed to be inversion domains which are thought to be caused by the segregation of excess In-In bonds at the interface between the quantum well layer and the barrier layer. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Optical transitions in Ge/SiGe multiple quantum wells with Ge-rich barriers

    Science.gov (United States)

    Bonfanti, M.; Grilli, E.; Guzzi, M.; Virgilio, M.; Grosso, G.; Chrastina, D.; Isella, G.; von Känel, H.; Neels, A.

    2008-07-01

    Direct-gap and indirect-gap transitions in strain-compensated Ge/SiGe multiple quantum wells with Ge-rich SiGe barriers have been studied by optical transmission spectroscopy and photoluminescence experiments. An sp3d5s∗ tight-binding model has been adopted to interpret the experimental results. Photoluminescence spectra and their comparison with theoretical calculations prove the existence of type-I band alignment in compressively strained Ge quantum wells grown on relaxed Ge-rich SiGe buffers. The high quality of the transmission spectra opens up other perspectives for application of these structures in near-infrared optical modulators.

  20. Luminescence of highly excited nonpolar a-plane GaN and AlGaN/GaN multiple quantum wells

    International Nuclear Information System (INIS)

    Jursenas, S.; Kuokstis, E.; Miasojedovas, S.; Kurilcik, G.; Zukauskas, A.; Chen, C.Q.; Yang, J.W.; Adivarahan, V.; Asif Khan, M.

    2004-01-01

    Carrier recombination dynamics in polar and nonpolar GaN epilayers and GaN/AlGaN multiple quantum wells grown over sapphire substrates with a various crystallographic orientation were studied under high photoexcitation by 20 ps laser pulses. The transient luminescence featured a significant enhancement on nonradiative recombination of free carriers for nonpolar a-plane GaN epilayers compared to conventional c-plane samples. The epitaxial layer overgrowth technique was demonstrated to significantly improve the quality of nonpolar a-plane films. This was proved by more than 40-fold increase in luminescence decay time (430 ps compared to ≤ 10 ps in the ordinary a-plane epilayer). Under high-excitation regime, a complete screening of built-in electric field by free carriers in multiple quantum wells grown on c-plane and r-plane sapphire substrates was achieved. Under such high excitation, luminescence efficiency and carrier lifetime of multiple quantum wells were shown to be determined by the substrate quality. (author)

  1. Significant internal quantum efficiency enhancement of GaN/AlGaN multiple quantum wells emitting at ~350 nm via step quantum well structure design

    KAUST Repository

    Wu, Feng; Sun, Haiding; Ajia, Idris A.; Roqan, Iman S.; Zhang, Daliang; Dai, Jiangnan; Chen, Changqing; Feng, Zhe Chuan; Li, Xiaohang

    2017-01-01

    Significant internal quantum efficiency (IQE) enhancement of GaN/AlGaN multiple quantum wells (MQWs) emitting at similar to 350 nm was achieved via a step quantum well (QW) structure design. The MQW structures were grown on AlGaN/AlN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). High resolution x-ray diffraction (HR-XRD) and scanning transmission electron microscopy (STEM) were performed, showing sharp interface of the MQWs. Weak beam dark field imaging was conducted, indicating a similar dislocation density of the investigated MQWs samples. The IQE of GaN/AlGaN MQWs was estimated by temperature dependent photoluminescence (TDPL). An IQE enhancement of about two times was observed for the GaN/AlGaN step QW structure, compared with conventional QW structure. Based on the theoretical calculation, this IQE enhancement was attributed to the suppressed polarization-induced field, and thus the improved electron-hole wave-function overlap in the step QW.

  2. Significant internal quantum efficiency enhancement of GaN/AlGaN multiple quantum wells emitting at ~350 nm via step quantum well structure design

    KAUST Repository

    Wu, Feng

    2017-05-03

    Significant internal quantum efficiency (IQE) enhancement of GaN/AlGaN multiple quantum wells (MQWs) emitting at similar to 350 nm was achieved via a step quantum well (QW) structure design. The MQW structures were grown on AlGaN/AlN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). High resolution x-ray diffraction (HR-XRD) and scanning transmission electron microscopy (STEM) were performed, showing sharp interface of the MQWs. Weak beam dark field imaging was conducted, indicating a similar dislocation density of the investigated MQWs samples. The IQE of GaN/AlGaN MQWs was estimated by temperature dependent photoluminescence (TDPL). An IQE enhancement of about two times was observed for the GaN/AlGaN step QW structure, compared with conventional QW structure. Based on the theoretical calculation, this IQE enhancement was attributed to the suppressed polarization-induced field, and thus the improved electron-hole wave-function overlap in the step QW.

  3. Tailoring the spin polarization in Ge/SiGe multiple quantum wells

    International Nuclear Information System (INIS)

    Giorgioni, Anna; Pezzoli, Fabio; Gatti, Eleonora; Grilli, Emanuele; Guzzi, Mario; Bottegoni, Federico; Cecchi, Stefano; Ciccacci, Franco; Isella, Giovanni; Trivedi, Dhara; Song, Yang; Li, Pengki; Dery, Hanan

    2013-01-01

    We performed spin-resolved photoluminescence measurements on Ge/SiGe multiple quantum wells with different well thickness and using different exciting power densities. The polarization of the direct emission strongly depends on the relative weight of electrons photoexcited from the light and the heavy hole subbands. The study of the polarization as a function of the exciting power highlights the role of the carrier-carrier interactions in determining spin depolarization

  4. Adsorption of asymmetric rigid rods or heteronuclear diatomic moleculeson homogeneous surfaces

    Science.gov (United States)

    Engl, W.; Courbin, L.; Panizza, P.

    2004-10-01

    We treat the adsorption on homogeneous surfaces of asymmetric rigid rods (like for instance heteronuclear diatomic molecules). We show that the n→0 vector spin formalism is well suited to describe such a problem. We establish an isomorphism between the coupling constants of the magnetic Hamiltonian and the adsorption parameters of the rigid rods. By solving this Hamiltonian within a mean-field approximation, we obtain analytical expressions for the densities of the different rod’s configurations, both isotherm and isobar adsorptions curves. The most probable configurations of the molecules (normal or parallel to the surface) which depends on temperature and energy parameters are summarized in a diagram. We derive that the variation of Qv , the heat of adsorption at constant volume, with the temperature is a direct signature of the adsorbed molecules configuration change. We show that this formalism can be generalized to more complicated problems such as for instance the adsorption of symmetric and asymmetric rigid rods mixtures in the presence or not of interactions.

  5. Multiple-scale approach for the expansion scaling of superfluid quantum gases

    International Nuclear Information System (INIS)

    Egusquiza, I. L.; Valle Basagoiti, M. A.; Modugno, M.

    2011-01-01

    We present a general method, based on a multiple-scale approach, for deriving the perturbative solutions of the scaling equations governing the expansion of superfluid ultracold quantum gases released from elongated harmonic traps. We discuss how to treat the secular terms appearing in the usual naive expansion in the trap asymmetry parameter ε and calculate the next-to-leading correction for the asymptotic aspect ratio, with significant improvement over the previous proposals.

  6. Isolation and characterization of metabolites from Croton linearis Jacq. leaves

    International Nuclear Information System (INIS)

    García-Díaz, Jesús; Escalona-Arranz, Julio C.; Rojas-Vargas, Julio; Machado-García, Roberto; Carvallo, Mario G. do; Vega-Acosta, Jorge de la

    2015-01-01

    From an ethanolic extract of Croton linearis Jacq. leaves were isolated and identified a total of 7 compounds: two long chain alcohols: 2-methyl-tretradecan-2-ol (1) y el hexacosanol (3); a linear saturated hydrocarbon: tetracosane (2); three fatty acids: stearic (4), 5,8-dien-tetradecanoic (6) and oleic acid (7); as well as a tri-methoxylated flavone: 5-hydroxy-3,7,4'-trimethoxyflavone (5). Structures of the compounds were elucidated by spectroscopic techniques as Nuclear Magnetic Resonance 1D and 2D (1H and 13C), as well as Gas Chromatography/Mass Spectrometry and Kovats retention indexes when necessary. The substituent positions were assigned based on combination of heteronuclear HMBC and HMQC as well as homonuclear 1H-1H-COSY experiments. All identified compounds constitute a first report for the specie in study. (author)

  7. Exact solutions in the dynamics of alternating open chains of spins s = 1/2 with the XY Hamiltonian and their application to problems of multiple-quantum dynamics and quantum information theory

    International Nuclear Information System (INIS)

    Kuznetsova, E. I.; Fel'dman, E. B.

    2006-01-01

    A method for exactly diagonalizing the XY Hamiltonian of an alternating open chain of spins s = 1/2 has been proposed on the basis of the Jordan-Wigner transformation and analysis of the dynamics of spinless fermions. The multiple-quantum spin dynamics of alternating open chains at high temperatures has been analyzed and the intensities of multiple-quantum coherences have been calculated. The problem of the transfer of a quantum state from one end of the alternating chain to the other is studied. It has been shown that the ideal transfer of qubits is possible in alternating chains with a larger number of spins than that in homogeneous chains

  8. Luminescence and ultrafast phenomena in InGaN multiple quantum wells

    International Nuclear Information System (INIS)

    Viswanath, Annamraju Kasi; Lee, J.I.; Kim, S.T.; Yang, G.M.; Lee, H.J.; Kim, Dongho

    2007-01-01

    High quality In 0.13 Ga 0.87 N/GaN multiple quantum wells (MQWs) on (0001) sapphire substrate were fabricated by MOCVD method. The quantum well thickness is as thin as 10 A, and the barrier thickness is 50 A. We have investigated these ultrathin MQWs by continuous wave (cw) and time-resolved spectroscopy in the picosecond time scales in a wide temperature range from 10 to 290 K. In the luminescence spectrum at 10 K, we observed a broad peak at 3.134 eV which was attributed to the quantum wells emission of InGaN. The full width at half maximum of this peak was 129 meV at 10 K and the broadening at low temperatures which was mostly inhomogeneous was thought to be due to compositional fluctuations and interfacial disorder in the alloy. We also observed an intense and narrow peak at 3.471 eV due to the GaN barrier. The temperature dependence of the luminescence was studied and the peak positions and the intensities of the different peaks were obtained. The activation energy of the InGaN quantum well emission peak was estimated as 69 meV. From the measurements of luminescence intensities and lifetimes at various temperatures, radiative and non-radiative recombination lifetimes were deduced. The results were explained by considering only the localization of the excitons due to potential fluctuations

  9. The rigorous stochastic matrix multiplication scheme for the calculations of reduced equilibrium density matrices of open multilevel quantum systems

    International Nuclear Information System (INIS)

    Chen, Xin

    2014-01-01

    Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, i.e., how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernon influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems

  10. Heteronuclear cross-polarization in multinuclear multidimensional NMR: Prospects for triple-resonance CP

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, A.; Zuiderweg, E.R.P. [Univ. of Michigan, Ann Arbor, MI (United States)

    1994-12-01

    Heteronuclear multiple-pulse-based Cross Polarization (HECP) between scalar coupled spins is gaining an important role in high-resolution multidimensional NMR of isotopically labeled biomolecules, especially in experiments involving net magnetization transfer. It has generally been observed that in these situations, the performance of HECP is superior to that of INEPT-based sequences. In particular, HECP-based three-dimensional HCCH spectroscopy is more efficient than the INEPT version of the same experiment. Differences in sensitivity have been intuitively attributed to relaxation effects and technical factors such as radiofrequency (rf) inhomogeneity We present theoretical analyses and computer simulations to probe the effects of these factors. Relaxation effects were treated phenomenologically; we found that relaxation differences are relatively small (up to 25%) between pulsed-free-precession (INEPT) and HECP-although always in favor of HECP. We explored the rf effects by employing a Gaussian distribution of rf amplitude over sample volume. We found that inhomogeneity effects significantly favor HECP over INEPT, especially under conditions of {open_quotes}matched {close_quotes} inhomogeneity in the two rf coils. The differences in favor of HECP indicate that an extension of HECP to triple resonance experiments (TRCP) in I -> S -> Q net transfers might yield better results relative to analogous INEPT-based net transfers. We theoretically analyze the possibilities of TRCP and find that transfer functions are critically dependent on the ratio J{sub IS}/J{sub SQ}. When J{sub IS} equals J{sub SQ}, we find that 100% transfer is possible for truly simultaneous TRCP and this transfer is obtained in a time 1.41 /J. The TRCP time requirement compares favorably with optimally concatenated INEPT-transfers, where net transfer I -> S -> Q is complete at 1.5 /J.

  11. Two dimensional NMR studies of polysaccharides

    International Nuclear Information System (INIS)

    Byrd, R.A.; Egan, W.; Summers, M.F.

    1987-01-01

    Polysaccharides are very important components in the immune response system. Capsular polysaccharides and lipopolysaccharides occupy cell surface sites of bacteria, play key roles in recognition and some have been used to develop vaccines. Consequently, the ability to determine chemical structures of these systems is vital to an understanding of their immunogenic action. The authors have been utilizing recently developed two-dimensional homonuclear and heteronuclear correlation spectroscopy for unambiguous assignment and structure determination of a number of polysaccharides. In particular, the 1 H-detected heteronuclear correlation experiments are essential to the rapid and sensitive determination of these structures. Linkage sites are determined by independent polarization transfer experiments and multiple quantum correlation experiments. These methods permit the complete structure determination on very small amounts of the polysaccharides. They present the results of a number of structural determinations and discuss the limits of these experiments in terms of their applications to polysaccharides

  12. Investigation of reactive-ion-etch-induced damage of InP/InGaAs multiple quantum wells by photoluminescence

    DEFF Research Database (Denmark)

    Steffensen, O. M.; Birkedal, Dan; Hanberg, J.

    1995-01-01

    The effects of CH4/H2 reactive ion etching (RIE) on the optical properties of an InP/InGaAs multiple-quantum-well structure have been investigated by low-temperature photoluminescence (PL). The structure consisted of eight InGaAs quantum wells, lattice matched to InP, with nominal thicknesses of 0...

  13. Polyad quantum numbers and multiple resonances in anharmonic vibrational studies of polyatomic molecules.

    Science.gov (United States)

    Krasnoshchekov, Sergey V; Stepanov, Nikolay F

    2013-11-14

    In the theory of anharmonic vibrations of a polyatomic molecule, mixing the zero-order vibrational states due to cubic, quartic and higher-order terms in the potential energy expansion leads to the appearance of more-or-less isolated blocks of states (also called polyads), connected through multiple resonances. Such polyads of states can be characterized by a common secondary integer quantum number. This polyad quantum number is defined as a linear combination of the zero-order vibrational quantum numbers, attributed to normal modes, multiplied by non-negative integer polyad coefficients, which are subject to definition for any particular molecule. According to Kellman's method [J. Chem. Phys. 93, 6630 (1990)], the corresponding formalism can be conveniently described using vector algebra. In the present work, a systematic consideration of polyad quantum numbers is given in the framework of the canonical Van Vleck perturbation theory (CVPT) and its numerical-analytic operator implementation for reducing the Hamiltonian to the quasi-diagonal form, earlier developed by the authors. It is shown that CVPT provides a convenient method for the systematic identification of essential resonances and the definition of a polyad quantum number. The method presented is generally suitable for molecules of significant size and complexity, as illustrated by several examples of molecules up to six atoms. The polyad quantum number technique is very useful for assembling comprehensive basis sets for the matrix representation of the Hamiltonian after removal of all non-resonance terms by CVPT. In addition, the classification of anharmonic energy levels according to their polyad quantum numbers provides an additional means for the interpretation of observed vibrational spectra.

  14. Efficiency enhancement of InGaN/GaN multiple quantum wells with graphene layer

    International Nuclear Information System (INIS)

    Deng, Zhen; Li, Zishen; Jiang, Yang; Ma, Ziguang; Fang, Yutao; Li, Yangfeng; Wang, Wenxin; Jia, Haiqiang; Chen, Hong

    2015-01-01

    In this work, a novel hybrid graphene/InGaN-based multiple quantum wells (MQWs) structure has been fabricated. Compared to the sample conventional structure (CS), the utilization of graphene transferred on top GaN layer significantly enhances the internal quantum efficiency and relatively photoluminescence intensity. Furthermore, the excitons in the MQWs of sample hybrid structure (HS) have a shorter decay lifetime of 3.4 ns than that of 6.7 ns for sample CS. These results are probably attributed to the free carriers in the graphene layer, which can screen the piezoelectric field in the active region and thus present a free quantum-confined Stark effect-like behavior. Our work demonstrates that the graphene on the top GaN layer can effectively increase the recombination rate in sample HS, which may further improve LEDs' performance. (orig.)

  15. Multiple-event probability in general-relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Hellmann, Frank; Mondragon, Mauricio; Perez, Alejandro; Rovelli, Carlo

    2007-01-01

    We discuss the definition of quantum probability in the context of 'timeless' general-relativistic quantum mechanics. In particular, we study the probability of sequences of events, or multievent probability. In conventional quantum mechanics this can be obtained by means of the 'wave function collapse' algorithm. We first point out certain difficulties of some natural definitions of multievent probability, including the conditional probability widely considered in the literature. We then observe that multievent probability can be reduced to single-event probability, by taking into account the quantum nature of the measuring apparatus. In fact, by exploiting the von-Neumann freedom of moving the quantum/classical boundary, one can always trade a sequence of noncommuting quantum measurements at different times, with an ensemble of simultaneous commuting measurements on the joint system+apparatus system. This observation permits a formulation of quantum theory based only on single-event probability, where the results of the wave function collapse algorithm can nevertheless be recovered. The discussion also bears on the nature of the quantum collapse

  16. Multiple particle production processes in the ''light'' of quantum optics

    International Nuclear Information System (INIS)

    Friedlander, E.M.

    1990-09-01

    Ever since the observation that high-energy ''nuclear active'' cosmic-ray particles create bunches of penetrating particles upon hitting targets, a controversy has raged about whether these secondaries are created in a ''single act'' or whether many hadrons are just the result of an intra-nuclear cascade, yielding one meson in every step. I cannot escape the impression that: the latter kind of model appeals naturally as a consequence of an innate bio-morphism in our way of thinking and that in one guise or another it has tenaciously survived to this day, also for hadron-hadron collisions, via multi-peripheral models to the modern parton shower approach. Indeed, from the very beginning of theoretical consideration of multiparticle production, the possibility of many particles arising from a single ''hot'' system has been explored, with many fruitful results, not the least of which are the s 1/4 dependence of the mean produced particle multiplicity and the ''thermal'' shape of the P T spectra. An important consequence of the thermodynamical-hydrodynamical models is that particle emission is treated in analogy to black-body radiation, implying for the secondaries a set of specific Quantum-Statistical properties, very similar to those observed in quantum optics. From here on I shall try to review a number of implications and applications of this QS analogy in the study of multiplicity distributions of the produced secondaries. I will touch only in passing another very important topic of this class, the Bose-Einstein two-particle correlations

  17. The quantum double in integrable quantum field theory

    International Nuclear Information System (INIS)

    Bernard, D.; LeClair, A.

    1993-01-01

    Various aspects of recent works on affine quantum group symmetry of integrable 2D quantum field theory are reviewed and further clarified. A geometrical meaning is given to the quantum double, and other properties of quantum groups. The S-matrix is identified with the universal R-matrix. Multiplicative presentations of the yangian double are analyzed. (orig.)

  18. On the effect of ballistic overflow on the temperature dependence of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Prudaev, I. A., E-mail: funcelab@gmail.com; Kopyev, V. V.; Romanov, I. S.; Oleynik, V. L. [National Research Tomsk State University (Russian Federation)

    2017-02-15

    The dependences of the quantum efficiency of InGaN/GaN multiple quantum well light-emitting diodes on the temperature and excitation level are studied. The experiment is performed for two luminescence excitation modes. A comparison of the results obtained during photo- and electroluminescence shows an additional (to the loss associated with Auger recombination) low-temperature loss in the high-density current region. This causes inversion of the temperature dependence of the quantum efficiency at temperatures lower than 220–300 K. Analysis shows that the loss is associated with electron leakage from the light-emitting-diode active region. The experimental data are explained using the ballistic-overflow model. The simulation results are in qualitative agreement with the experimental dependences of the quantum efficiency on temperature and current density.

  19. Observation of Resonant Effects in Ultracold Collisions between Heteronuclear Feshbach Molecules

    Science.gov (United States)

    Ye, Xin; Wang, Fudong; Zhu, Bing; Guo, Mingyang; Lu, Bo; Wang, Dajun

    2016-05-01

    Magnetic field dependent dimer-dimer collisional losses are studied with ultracold 23 Na87 Rb Feshbach molecules. By ramping the magnetic field across the 347.8 G inter-species Feshbach resonance and removing residual atoms with a magnetic field gradient, ~ 8000 pure NaRb Feshbach molecules with a temperature below 1 μK are produced. By holding the pure molecule sample in a crossed optical dipole trap and measuring the time-dependent loss curves under different magnetic fields near the Feshbach resonance, the dimer-dimer loss rates with respect to the atomic scattering length a are mapped out. We observe a resonant feature at around a = 600a0 and a rising tail at above a = 1600a0 . This behavior resembles previous theoretical works on homonuclear Feshbach molecule, where resonant effects between dimer-dimer collisions tied to tetramer bound states were predicted. Our work shows the possibility of exploring four-body physics within a heteronuclear system. We are supported by Hong Kong RGC General Research Fund no. CUHK403813.

  20. Estimating side-chain order in methyl-protonated, perdeuterated proteins via multiple-quantum relaxation violated coherence transfer NMR spectroscopy

    International Nuclear Information System (INIS)

    Sun Hechao; Godoy-Ruiz, Raquel; Tugarinov, Vitali

    2012-01-01

    Relaxation violated coherence transfer NMR spectroscopy (Tugarinov et al. in J Am Chem Soc 129:1743–1750, 2007) is an established experimental tool for quantitative estimation of the amplitudes of side-chain motions in methyl-protonated, highly deuterated proteins. Relaxation violated coherence transfer experiments monitor the build-up of methyl proton multiple-quantum coherences that can be created in magnetically equivalent spin-systems as long as their transverse magnetization components relax with substantially different rates. The rate of this build-up is a reporter of the methyl-bearing side-chain mobility. Although the build-up of multiple-quantum 1 H coherences is monitored in these experiments, the decay of the methyl signal during relaxation delays occurs when methyl proton magnetization is in a single-quantum state. We describe a relaxation violated coherence transfer approach where the relaxation of multiple-quantum 1 H– 13 C methyl coherences during the relaxation delay period is quantified. The NMR experiment and the associated fitting procedure that models the time-dependence of the signal build-up, are applicable to the characterization of side-chain order in [ 13 CH 3 ]-methyl-labeled, highly deuterated protein systems up to ∼100 kDa in molecular weight. The feasibility of extracting reliable measures of side-chain order is experimentally verified on methyl-protonated, perdeuterated samples of an 8.5-kDa ubiquitin at 10°C and an 82-kDa Malate Synthase G at 37°C.

  1. Dicke states in multiple quantum dots

    Science.gov (United States)

    Sitek, Anna; Manolescu, Andrei

    2013-10-01

    We present a theoretical study of the collective optical effects which can occur in groups of three and four quantum dots. We define conditions for stable subradiant (dark) states, rapidly decaying super-radiant states, and spontaneous trapping of excitation. Each quantum dot is treated like a two-level system. The quantum dots are, however, realistic, meaning that they may have different transition energies and dipole moments. The dots interact via a short-range coupling which allows excitation transfer across the dots, but conserves the total population of the system. We calculate the time evolution of single-exciton and biexciton states using the Lindblad equation. In the steady state the individual populations of each dot may have permanent oscillations with frequencies given by the energy separation between the subradiant eigenstates.

  2. Some analogies between quantum cloning and quantum deleting

    International Nuclear Information System (INIS)

    Qiu Daowen

    2002-01-01

    We further verify the impossibility of deleting an arbitrary unknown quantum state, and also show it is impossible to delete two nonorthogonal quantum states as a consequence of unitarity of quantum mechanics. A quantum approximate (deterministic) deleting machine and a probabilistic (exact) deleting machine are constructed. The estimation for the global fidelity characterizing the efficiency of the quantum approximate deleting is given. We then demonstrate that unknown nonorthogonal states chosen from a set with their multiple copies can evolve into a linear superposition of multiple deletions and failure branches by a unitary process if and only if the states are linearly independent. It is notable that the proof for necessity is somewhat different from Pati's [Phys. Rev. Lett. 83, 2849 (1999)]. Another deleting machine for the input states that are unnecessarily linearly independent is also presented. The bounds on the success probabilities of these deleting machines are derived. So we expound some preliminary analogies between quantum cloning and deleting

  3. Electrical and optical properties of multiple quantum well structures and their applications to infrared detectors

    International Nuclear Information System (INIS)

    Helgesen, P.

    1992-04-01

    In this work the author investigate the subband nature of multiple quantum well structures by photoconductance spectroscopy, optical absorption measurements and tunneling experiments. Both interband and intraband transitions have been studied. The work is aimed at making an infrared detector using wide band gap semiconductors. 14 refs

  4. A Novel Diterpene Glycoside with Nine Glucose Units from Stevia rebaudiana Bertoni

    Directory of Open Access Journals (Sweden)

    Indra Prakash

    2017-01-01

    Full Text Available Following our interest in new diterpene glycosides with better taste profiles than that of Rebaudioside M, we have recently isolated and characterized Rebaudioside IX—a novel steviol glycoside—from a commercially‐supplied extract of Stevia rebaudiana Bertoni. This molecule contains a hexasaccharide group attached at C‐13 of the central diterpene core, and contains three additional glucose units when compared with Rebaudioside M. Here we report the complete structure elucidation—based on extensive Nuclear Magnetic Resonance (NMR analysis (1H, 13C, Correlation Spectroscopy (COSY, Heteronuclear Single Quantum Coherence‐Distortionless Enhancement Polarization Transfer (HSQC‐DEPT, Heteronuclear Multiple Bond Correlation (HMBC, 1D Total Correlation Spectroscopy (TOCSY, Nuclear Overhauser Effect Spectroscopy (NOESY and mass spectral data—of this novel diterpene glycoside with nine sugar moieties and containing a relatively rare 16 α‐linked glycoside. A steviol glycoside bearing nine glucose units is unprecedented in the literature, and could have an impact on the natural sweetener catalog.

  5. A Novel Diterpene Glycoside with Nine Glucose Units from Stevia rebaudiana Bertoni.

    Science.gov (United States)

    Prakash, Indra; Ma, Gil; Bunders, Cynthia; Charan, Romila D; Ramirez, Catherine; Devkota, Krishna P; Snyder, Tara M

    2017-01-31

    Following our interest in new diterpene glycosides with better taste profiles than that of Rebaudioside M, we have recently isolated and characterized Rebaudioside IX-a novel steviol glycoside-from a commercially-supplied extract of Stevia rebaudiana Bertoni. This molecule contains a hexasaccharide group attached at C-13 of the central diterpene core, and contains three additional glucose units when compared with Rebaudioside M. Here we report the complete structure elucidation-based on extensive Nuclear Magnetic Resonance (NMR) analysis (1H, 13C, Correlation Spectroscopy (COSY), Heteronuclear Single Quantum Coherence-Distortionless Enhancement Polarization Transfer (HSQC-DEPT), Heteronuclear Multiple Bond Correlation (HMBC), 1D Total Correlation Spectroscopy (TOCSY), Nuclear Overhauser Effect Spectroscopy (NOESY)) and mass spectral data-of this novel diterpene glycoside with nine sugar moieties and containing a relatively rare 16 α-linked glycoside. A steviol glycoside bearing nine glucose units is unprecedented in the literature, and could have an impact on the natural sweetener catalog.

  6. Compositional disordering of GaAs/AlGaAs multiple quantum wells using ion bombardment at elevated temperatures

    International Nuclear Information System (INIS)

    Anderson, K.K.; Donnelly, J.P.; Wang, C.A.; Woodhouse, J.D.; Haus, H.A.

    1988-01-01

    A new method has been developed for compositional mixing of heterostructures by ion bombardment at elevated temperatures. Complete mixing of a 1-μm-thick GaAs/AlGaAs 40-period multiple quantum well layer has been achieved by bombardment with 380 keV Ne + ions for 1 h with the sample at 700 0 C. This temperature is much lower than the annealing temperatures used in other vacancy-enhanced disordering techniques, and even lower temperatures and shorter durations should be possible. Compositional disordering is verified by sputter-profile Auger electron spectroscopy and transmission electron microscopy. Complete mixing is also demonstrated by optical transmission spectra of the disordered material, which exhibit the same band edge as a uniform alloy with the average aluminum mole fraction of the multiple quantum well layer

  7. Enhanced life time and suppressed efficiency roll-off in phosphorescent organic light-emitting diodes with multiple quantum well structures

    Directory of Open Access Journals (Sweden)

    Ja-Ryong Koo

    2012-03-01

    Full Text Available We demonstrate red phosphorescent organic light-emitting diodes (OLEDs with multiple quantum well structures which confine triplet exciton inside an emitting layer (EML region. Five types of OLEDs, from a single to five quantum wells, are fabricated with charge control layers to produce high efficiencies, and the performance of the devices is investigated. The improved quantum efficiency and lifetime of the OLED with four quantum wells, and its suppressed quantum efficiency roll-off of 17.6%, can be described by the increased electron–hole charge balance owing to the bipolar property as well as the efficient triplet exciton confinement within each EML, and by prevention of serious triplet–triplet and/or triplet–polaron annihilation as well as the Förster self-quenching due to charge control layers.

  8. Ordered quantum-ring chains grown on a quantum-dot superlattice template

    International Nuclear Information System (INIS)

    Wu Jiang; Wang, Zhiming M.; Holmes, Kyland; Marega, Euclydes; Mazur, Yuriy I.; Salamo, Gregory J.

    2012-01-01

    One-dimensional ordered quantum-ring chains are fabricated on a quantum-dot superlattice template by molecular beam epitaxy. The quantum-dot superlattice template is prepared by stacking multiple quantum-dot layers and quantum-ring chains are formed by partially capping quantum dots. Partially capping InAs quantum dots with a thin layer of GaAs introduces a morphological change from quantum dots to quantum rings. The lateral ordering is introduced by engineering the strain field of a multi-layer InGaAs quantum-dot superlattice.

  9. Detected-jump-error-correcting quantum codes, quantum error designs, and quantum computation

    International Nuclear Information System (INIS)

    Alber, G.; Mussinger, M.; Beth, Th.; Charnes, Ch.; Delgado, A.; Grassl, M.

    2003-01-01

    The recently introduced detected-jump-correcting quantum codes are capable of stabilizing qubit systems against spontaneous decay processes arising from couplings to statistically independent reservoirs. These embedded quantum codes exploit classical information about which qubit has emitted spontaneously and correspond to an active error-correcting code embedded in a passive error-correcting code. The construction of a family of one-detected-jump-error-correcting quantum codes is shown and the optimal redundancy, encoding, and recovery as well as general properties of detected-jump-error-correcting quantum codes are discussed. By the use of design theory, multiple-jump-error-correcting quantum codes can be constructed. The performance of one-jump-error-correcting quantum codes under nonideal conditions is studied numerically by simulating a quantum memory and Grover's algorithm

  10. Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn1-xMgxO layers by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Xia, Y.; Vinter, B.; Chauveau, J.-M.; Brault, J.; Nemoz, M.; Teisseire, M.; Leroux, M.

    2011-01-01

    Nonpolar (1120) Al 0.2 Ga 0.8 N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (1120) Zn 0.74 Mg 0.26 O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.

  11. Strain-balanced InGaN/GaN multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Van Den Broeck, D. M.; Hosalli, A. M.; Bedair, S. M. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Bharrat, D.; El-Masry, N. A. [Department of Material Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2014-07-21

    InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of In{sub x}Ga{sub 1−x}N/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick In{sub y}Ga{sub 1−y}N templates for x > y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of In{sub x}Ga{sub 1−x}N wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick In{sub y}Ga{sub 1−y}N template. Growth of the In{sub y}Ga{sub 1−y}N template is also detailed in order to achieve thick, relaxed In{sub y}Ga{sub 1−y}N grown on GaN without the presence of V-grooves. When compared to conventional In{sub x}Ga{sub 1−x}N/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the In{sub y}Ga{sub 1−y}N template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”.

  12. Ultrafast dynamics in ZnO/ZnMgO multiple quantum wells

    International Nuclear Information System (INIS)

    Wen, X M; Davis, J A; McDonald, D; Dao, L V; Hannaford, P; Coleman, V A; Tan, H H; Jagadish, C; Koike, K; Sasa, S; Inoue, M; Yano, M

    2007-01-01

    We have investigated carrier relaxation and exciton recombination dynamics in ZnO/ZnMgO multiple quantum wells using femtosecond pump-probe techniques at room temperature. For a probe energy above the band gap, the hot carriers exhibit an effective relaxation by longitudinal optical phonon scattering with a cooling time of 700-850 fs. By detecting the emission near the band-gap, a longer decay time of a few picoseconds was observed which is attributed to acoustic phonon scattering. As the probe energy is decreased further, the decay time continues to increase due to the transitions of exciton recombination or localized carrier recombination

  13. Quantum Query Complexity for Searching Multiple Marked States from an Unsorted Database

    International Nuclear Information System (INIS)

    Shang Bin

    2007-01-01

    An important and usual sort of search problems is to find all marked states from an unsorted database with a large number of states. Grover's original quantum search algorithm is for finding single marked state with uncertainty, and it has been generalized to the case of multiple marked states, as well as been modified to find single marked state with certainty. However, the query complexity for finding all multiple marked states has not been addressed. We use a generalized Long's algorithm with high precision to solve such a problem. We calculate the approximate query complexity, which increases with the number of marked states and with the precision that we demand. In the end we introduce an algorithm for the problem on a 'duality computer' and show its advantage over other algorithms.

  14. Identification of Hepatoprotective Constituents in Limonium tetragonum and Development of Simultaneous Analysis Method using High-performance Liquid Chromatography

    Science.gov (United States)

    Lee, Jae Sun; Kim, Yun Na; Kim, Na-Hyun; Heo, Jeong-Doo; Yang, Min Hye; Rho, Jung-Rae; Jeong, Eun Ju

    2017-01-01

    Background: Limonium tetragonum, a naturally salt-tolerant halophyte, has been studied recently and is of much interest to researchers due to its potent antioxidant and hepatoprotective activities. Objective: In the present study, we attempted to elucidate bioactive compounds from ethyl acetate (EtOAc) soluble fraction of L. tetragonum extract. Furthermore, the simultaneous analysis method of bioactive EtOAc fraction of L. tetragonum has been developed using high-performance liquid chromatography (HPLC). Materials and Methods: Thirteen compounds have been successfully isolated from EtOAc fraction of L. tetragonum, and the structures of 1–13 were elucidated by extensive one-dimensional and two-dimensional spectroscopic methods including 1H-NMR, 13C-NMR, 1H-1H COSY, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser effect spectroscopy. Hepatoprotection of the isolated compounds against liver fibrosis was evaluated by measuring inhibition on hepatic stellate cells (HSCs) undergoing proliferation. Results: Compounds 1–13 were identified as gallincin (1), apigenin-3-O-β-D-galactopyranoside (2), quercetin (3), quercetin-3-O-β-D-galactopyranoside (4), (−)-epigallocatechin (5), (−)-epigallocatechin-3-gallate (6), (−)-epigallocatechin-3-(3″-O-methyl) gallate (7), myricetin-3-O-β-D-galactopyranoside (8), myricetin-3-O-(6″-O-galloyl)-β-D-galactopyranoside (9), myricetin-3-O-α-L-rhamnopyranoside (10), myricetin-3-O-(2″-O-galloyl)-α-L-rhamnopyranoside (11), myricetin-3-O-(3″-O-galloyl)-α-L-rhamnopyranoside (12), and myricetin-3-O-α-L-arabinopyranoside (13), respectively. All compounds except for 4, 8, and 10 are reported for the first time from this plant. Conclusion: Myricetin glycosides which possess galloyl substituent (9, 11, and 12) showed most potent inhibitory effects on the proliferation of HSCs. SUMMARY In the present study, we have successfully isolated 13 compounds from bioactive fraction

  15. Nanoroughness localization of excitons in GaAs multiple quantum wells studied by transient four-wave mixing

    DEFF Research Database (Denmark)

    Birkedal, Dan; Vadim, Lyssenko; Pantke, Karl-Heinz

    1995-01-01

    The interface roughness on a nanometer scale plays a decisive role in dephasing of excitons in GaAs multiple quantum wells. The excitonic four-wave mixing signal shows a free polarization decay and a corresponding homogeneously broadened line from areas with interface roughness on a scale larger...

  16. Optimization of carrier multiplication for more effcient solar cells: the case of Sn quantum dots.

    Science.gov (United States)

    Allan, Guy; Delerue, Christophe

    2011-09-27

    We present calculations of impact ionization rates, carrier multiplication yields, and solar-power conversion efficiencies in solar cells based on quantum dots (QDs) of a semimetal, α-Sn. Using these results and previous ones on PbSe and PbS QDs, we discuss a strategy to select QDs with the highest carrier multiplication rate for more efficient solar cells. We suggest using QDs of materials with a close to zero band gap and a high multiplicity of the bands in order to favor the relaxation of photoexcited carriers by impact ionization. Even in that case, the improvement of the maximum solar-power conversion efficiency appears to be a challenging task. © 2011 American Chemical Society

  17. Effect of barrier height and indium composition on the internal quantum efficiency of (In)AlGaN multiple quantum well structures

    Energy Technology Data Exchange (ETDEWEB)

    Ledentsov, Nikolay Jr.; Reich, Christoph; Mehnke, Frank; Kuhn, Christian; Wernicke, Tim; Kolbe, Tim; Lobo Ploch, Neysha; Rass, Jens [Institute of Solid State Physics, Technische Universitaet Berlin (Germany); Kueller, Viola [Ferdinand-Braun-Institut, Berlin (Germany); Kneissl, Michael [Institute of Solid State Physics, Technische Universitaet Berlin (Germany); Ferdinand-Braun-Institut, Berlin (Germany)

    2013-07-01

    We studied (In)AlGaN multiple quantum wells (MQWs) emitting in the UV-B spectral region with photoluminescence and electroluminescence spectroscopy. The internal quantum efficiency (IQE) was determined by temperature dependent measurements (5 K-300 K). The quantum confined Stark effect (QCSE) was investigated by studying the shift of the emission energy with increasing excitation power density. In the first series, Al{sub 0.27}Ga{sub 0.73}N MQWs with different Al{sub x}Ga{sub 1-x}N barriers (0.32

  18. Temperature and current dependent electroluminescence measurements on colour-coded multiple quantum well light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Bergbauer, Werner [OSRAM Opto Semiconductors GmbH, Regensburg (Germany); FH Deggendorf (Germany); Laubsch, Ansgar; Peter, Matthias; Mayer, Tobias; Bader, Stefan; Oberschmid, Raimund; Hahn, Berthold [OSRAM Opto Semiconductors GmbH, Regensburg (Germany); Benstetter, Guenther [FH Deggendorf (Germany)

    2008-07-01

    As the efficiency and the luminous flux have been increased enormously in the last few years, today Light Emitting Diodes (LEDs) are even pushed to applications like general lighting and Home Cinema Projection. Still, InGaN/GaN heterostructure based LEDs suffer from loss-mechanisms like non-radiative defect and Auger recombination, carrier leakage and piezo-field induced carrier separation. To optimize the high current efficiency we evaluated the benefit of Multiple Quantum Well (MQW) compared to Single Quantum Well (SQW) LEDs. Temperature dependent electroluminescence of colour-coded structures with different Indium content in certain Quantum Wells was measured. The experiments demonstrated a strong temperature and current dependence of the MQW operation. The comparison between different LED structures showed effectively the increased LED performance of those structures which operate with a well adjusted MQW active area. Due to the enhanced carrier distribution in the high current range, these LEDs show a higher light output and additionally a reduced wavelength shift.

  19. Temperature and current dependent electroluminescence measurements on colour-coded multiple quantum well light emitting diodes

    International Nuclear Information System (INIS)

    Bergbauer, Werner; Laubsch, Ansgar; Peter, Matthias; Mayer, Tobias; Bader, Stefan; Oberschmid, Raimund; Hahn, Berthold; Benstetter, Guenther

    2008-01-01

    As the efficiency and the luminous flux have been increased enormously in the last few years, today Light Emitting Diodes (LEDs) are even pushed to applications like general lighting and Home Cinema Projection. Still, InGaN/GaN heterostructure based LEDs suffer from loss-mechanisms like non-radiative defect and Auger recombination, carrier leakage and piezo-field induced carrier separation. To optimize the high current efficiency we evaluated the benefit of Multiple Quantum Well (MQW) compared to Single Quantum Well (SQW) LEDs. Temperature dependent electroluminescence of colour-coded structures with different Indium content in certain Quantum Wells was measured. The experiments demonstrated a strong temperature and current dependence of the MQW operation. The comparison between different LED structures showed effectively the increased LED performance of those structures which operate with a well adjusted MQW active area. Due to the enhanced carrier distribution in the high current range, these LEDs show a higher light output and additionally a reduced wavelength shift

  20. Quantum demultiplexer of quantum parameter-estimation information in quantum networks

    Science.gov (United States)

    Xie, Yanqing; Huang, Yumeng; Wu, Yinzhong; Hao, Xiang

    2018-05-01

    The quantum demultiplexer is constructed by a series of unitary operators and multipartite entangled states. It is used to realize information broadcasting from an input node to multiple output nodes in quantum networks. The scheme of quantum network communication with respect to phase estimation is put forward through the demultiplexer subjected to amplitude damping noises. The generalized partial measurements can be applied to protect the transferring efficiency from environmental noises in the protocol. It is found out that there are some optimal coherent states which can be prepared to enhance the transmission of phase estimation. The dynamics of state fidelity and quantum Fisher information are investigated to evaluate the feasibility of the network communication. While the state fidelity deteriorates rapidly, the quantum Fisher information can be enhanced to a maximum value and then decreases slowly. The memory effect of the environment induces the oscillations of fidelity and quantum Fisher information. The adjustment of the strength of partial measurements is helpful to increase quantum Fisher information.

  1. InGaN/GaN multiple-quantum well heterostructures for solar cells grown by MOVPE: case studies

    Energy Technology Data Exchange (ETDEWEB)

    Mukhtarova, Anna; Valdueza-Felip, Sirona; Durand, Christophe; Pan, Qing; Monroy, Eva; Eymery, Joel [CEA-CNRS-UJF Group ' ' Nanophysique et semi-conducteurs' ' , CEA/INAC/SP2M, Grenoble (France); Grenet, Louis [CEA-LITEN, Grenoble (France); Peyrade, David [Laboratoire des Technologies de la Microelectronique (LTM/CNRS), Grenoble (France); Bougerol, Catherine [CEA-CNRS-UJF Group ' ' Nanophysique et semi-conducteurs' ' , Institut Neel-CNRS, Grenoble (France); Chikhaoui, Walf [CEA-LETI, Grenoble (France)

    2013-03-15

    We investigate the influence of growth temperature, p -doping with bis-cyclopentadienyl magnesium (Cp{sub 2}Mg) and number N of multi-quantum wells on the surface morphology, the electrical and optical properties of InGaN-based solar cells grown by metal-organic vapour phase epitaxy. Atomic force microscopy measurements show no influence of multiple-quantum well number on the surface morphology, but a smoothing with the increase of the Cp{sub 2}Mg flow. Electrochemical capacitance-voltage profiling exhibits an increase of the N{sub a}-N{sub d} concentration when increasing the Cp{sub 2}Mg flow from 250 to 700 sccm. X-ray diffraction analysis and transmission electron microscopy measurements confirm completely strained quantum wells with similar superlattice period for N=5 to 30. Finally, first solar cells have been demonstrated with a maximum external quantum efficiency of 38% at 380 nm wavelength for N=30. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Optical properties of the semiconductor quantum structure

    International Nuclear Information System (INIS)

    Haratizadeh, H.; Holtz, P.O.; Monemar, B.; Karlsoon, K.F.; Moskalenko, E.S.; Amano, H.; Akasaki, I.; Schoenfeld, W.V.; Garcia, J.M.; Petroff, P.M.

    2004-01-01

    Optical properties of the quantum structures have been discussed with emphasize of the AlGaN/GaN multiple quantum wells and InAs/GaAs quantum dot structures. We report on a detailed study of low temperature photoluminescence in Al 0 .07Ga 0 .93 N/GaN multiple quantum wells. The structures were nominally undoped multiple quantum well grown on sapphire substrate. The structure from discrete well width variations is here resolved in photoluminescence spectra. The results demonstrate that the theoretically estimated fields in this work are consistent with the experimental spectra

  3. Optimal Measurements for Simultaneous Quantum Estimation of Multiple Phases.

    Science.gov (United States)

    Pezzè, Luca; Ciampini, Mario A; Spagnolo, Nicolò; Humphreys, Peter C; Datta, Animesh; Walmsley, Ian A; Barbieri, Marco; Sciarrino, Fabio; Smerzi, Augusto

    2017-09-29

    A quantum theory of multiphase estimation is crucial for quantum-enhanced sensing and imaging and may link quantum metrology to more complex quantum computation and communication protocols. In this Letter, we tackle one of the key difficulties of multiphase estimation: obtaining a measurement which saturates the fundamental sensitivity bounds. We derive necessary and sufficient conditions for projective measurements acting on pure states to saturate the ultimate theoretical bound on precision given by the quantum Fisher information matrix. We apply our theory to the specific example of interferometric phase estimation using photon number measurements, a convenient choice in the laboratory. Our results thus introduce concepts and methods relevant to the future theoretical and experimental development of multiparameter estimation.

  4. Optimal Measurements for Simultaneous Quantum Estimation of Multiple Phases

    Science.gov (United States)

    Pezzè, Luca; Ciampini, Mario A.; Spagnolo, Nicolò; Humphreys, Peter C.; Datta, Animesh; Walmsley, Ian A.; Barbieri, Marco; Sciarrino, Fabio; Smerzi, Augusto

    2017-09-01

    A quantum theory of multiphase estimation is crucial for quantum-enhanced sensing and imaging and may link quantum metrology to more complex quantum computation and communication protocols. In this Letter, we tackle one of the key difficulties of multiphase estimation: obtaining a measurement which saturates the fundamental sensitivity bounds. We derive necessary and sufficient conditions for projective measurements acting on pure states to saturate the ultimate theoretical bound on precision given by the quantum Fisher information matrix. We apply our theory to the specific example of interferometric phase estimation using photon number measurements, a convenient choice in the laboratory. Our results thus introduce concepts and methods relevant to the future theoretical and experimental development of multiparameter estimation.

  5. Identification of a novel structure in heparin generated by potassium permanganate oxidation

    Science.gov (United States)

    Beccati, Daniela; Roy, Sucharita; Yu, Fei; Gunay, Nur Sibel; Capila, Ishan; Lech, Miroslaw; Linhardt, Robert J.; Venkataraman, Ganesh

    2012-01-01

    The worldwide heparin contamination crisis in 2008 led health authorities to take fundamental steps to better control heparin manufacture, including implementing appropriate analytical and bio-analytical methods to ensure production and release of high quality heparin sodium product. Consequently, there is an increased interest in the identification and structural elucidation of unusually modified structures that may be present in heparin. Our study focuses on the structural elucidation of species that give rise to a signal observed at 2.10 ppm in the N-acetyl region of the 1H NMR spectrum of some pharmaceutical grade heparin preparations. Structural elucidation experiments were carried out using homonuclear (COSY, TOSCY and NOESY) and heteronuclear (HSQC, HSQC-DEPT, HMQC-COSY, HSQC-TOCSY, and HMBC) 2D NMR spectroscopy on both heparin as well as heparin-like model compounds. Our results identify a novel type of oxidative modification of the heparin chain that results from a specific step in the manufacturing process used to prepare heparin. PMID:25147414

  6. Jumping magneto-electric states of electrons in semiconductor multiple quantum wells

    International Nuclear Information System (INIS)

    Pfeffer, Pawel; Zawadzki, Wlodek

    2011-01-01

    Orbital and spin electron states in semiconductor multiple quantum wells in the presence of an external magnetic field transverse to the growth direction are considered. Rectangular wells of GaAs/GaAlAs and InAs/AlSb are taken as examples. It is shown that, in addition to magneto-electric states known from one-well systems, there appear magneto-electric states having a much stronger dependence of energies on a magnetic field and exhibiting an interesting anti-crossing behavior. The origin of these states is investigated and it is shown that the strong field dependence of the energies is related to an unusual 'jumping' behavior of their wavefunctions between quantum wells as the field increases. The ways of investigating the jumping states by means of interband magneto-luminescence transitions or intraband cyclotron-like transitions are considered and it is demonstrated that the jumping states can be observed. The spin g factors of electrons in the jumping states are calculated using the real values of the spin–orbit interaction and bands' nonparabolicity for the semiconductors in question. It is demonstrated that the jumping states offer a wide variety of the spin g factors

  7. RNA-PAIRS: RNA probabilistic assignment of imino resonance shifts

    International Nuclear Information System (INIS)

    Bahrami, Arash; Clos, Lawrence J.; Markley, John L.; Butcher, Samuel E.; Eghbalnia, Hamid R.

    2012-01-01

    The significant biological role of RNA has further highlighted the need for improving the accuracy, efficiency and the reach of methods for investigating RNA structure and function. Nuclear magnetic resonance (NMR) spectroscopy is vital to furthering the goals of RNA structural biology because of its distinctive capabilities. However, the dispersion pattern in the NMR spectra of RNA makes automated resonance assignment, a key step in NMR investigation of biomolecules, remarkably challenging. Herein we present RNA Probabilistic Assignment of Imino Resonance Shifts (RNA-PAIRS), a method for the automated assignment of RNA imino resonances with synchronized verification and correction of predicted secondary structure. RNA-PAIRS represents an advance in modeling the assignment paradigm because it seeds the probabilistic network for assignment with experimental NMR data, and predicted RNA secondary structure, simultaneously and from the start. Subsequently, RNA-PAIRS sets in motion a dynamic network that reverberates between predictions and experimental evidence in order to reconcile and rectify resonance assignments and secondary structure information. The procedure is halted when assignments and base-parings are deemed to be most consistent with observed crosspeaks. The current implementation of RNA-PAIRS uses an initial peak list derived from proton-nitrogen heteronuclear multiple quantum correlation ( 1 H– 15 N 2D HMQC) and proton–proton nuclear Overhauser enhancement spectroscopy ( 1 H– 1 H 2D NOESY) experiments. We have evaluated the performance of RNA-PAIRS by using it to analyze NMR datasets from 26 previously studied RNAs, including a 111-nucleotide complex. For moderately sized RNA molecules, and over a range of comparatively complex structural motifs, the average assignment accuracy exceeds 90%, while the average base pair prediction accuracy exceeded 93%. RNA-PAIRS yielded accurate assignments and base pairings consistent with imino resonances for a

  8. RNA-PAIRS: RNA probabilistic assignment of imino resonance shifts

    Energy Technology Data Exchange (ETDEWEB)

    Bahrami, Arash; Clos, Lawrence J.; Markley, John L.; Butcher, Samuel E. [National Magnetic Resonance Facility at Madison (United States); Eghbalnia, Hamid R., E-mail: eghbalhd@uc.edu [University of Cincinnati, Department of Molecular and Cellular Physiology (United States)

    2012-04-15

    The significant biological role of RNA has further highlighted the need for improving the accuracy, efficiency and the reach of methods for investigating RNA structure and function. Nuclear magnetic resonance (NMR) spectroscopy is vital to furthering the goals of RNA structural biology because of its distinctive capabilities. However, the dispersion pattern in the NMR spectra of RNA makes automated resonance assignment, a key step in NMR investigation of biomolecules, remarkably challenging. Herein we present RNA Probabilistic Assignment of Imino Resonance Shifts (RNA-PAIRS), a method for the automated assignment of RNA imino resonances with synchronized verification and correction of predicted secondary structure. RNA-PAIRS represents an advance in modeling the assignment paradigm because it seeds the probabilistic network for assignment with experimental NMR data, and predicted RNA secondary structure, simultaneously and from the start. Subsequently, RNA-PAIRS sets in motion a dynamic network that reverberates between predictions and experimental evidence in order to reconcile and rectify resonance assignments and secondary structure information. The procedure is halted when assignments and base-parings are deemed to be most consistent with observed crosspeaks. The current implementation of RNA-PAIRS uses an initial peak list derived from proton-nitrogen heteronuclear multiple quantum correlation ({sup 1}H-{sup 15}N 2D HMQC) and proton-proton nuclear Overhauser enhancement spectroscopy ({sup 1}H-{sup 1}H 2D NOESY) experiments. We have evaluated the performance of RNA-PAIRS by using it to analyze NMR datasets from 26 previously studied RNAs, including a 111-nucleotide complex. For moderately sized RNA molecules, and over a range of comparatively complex structural motifs, the average assignment accuracy exceeds 90%, while the average base pair prediction accuracy exceeded 93%. RNA-PAIRS yielded accurate assignments and base pairings consistent with imino

  9. Photochemical deposition of NiCoO x thin films from Ni/Co heteronuclear triketonate complexes

    International Nuclear Information System (INIS)

    Buono-Core, G.E.; Tejos, M.; Cabello, G.; Guzman, N.; Hill, R.H.

    2006-01-01

    UV light irradiation of thin films of a polyketonate Ni/Co heteronuclear complex, NiCo(DBA) 2 [DBA, dibenzoylacetone)], spin coated on Si(1 0 0) substrates produced NiCoO x mixed oxides as amorphous films. On annealing at 600 deg. C under air, the mixed oxide film decomposed to NiO and CoO as indicated by XRD measurements. The morphology of the as-deposited films was examined by AFM analysis showing a smooth surface with low rms roughness values. The ratio of Ni/Co (1.08) present in the film reflects the stoichiometry in the starting compound within the experimental error, as shown by XPS analysis. The large amount of carbon (20.8%) detected on the surface of the film may be due to the presence of phenyl rings in the precursor complex

  10. Nonexistence of a universal quantum machine to examine the precision of unknown quantum states

    International Nuclear Information System (INIS)

    Pang, Shengshi; Wu, Shengjun; Chen, Zeng-Bing

    2011-01-01

    In this work, we reveal a type of impossibility discovered in our recent research which forbids comparing the closeness of multiple unknown quantum states with any nontrivial threshold in a perfect or unambiguous way. This impossibility is distinct from the existing impossibilities in that it is a ''collective'' impossibility on multiple quantum states; most other ''no-go'' theorems are concerned with only one single state each time, i.e., it is an impossibility on a nonlocal quantum operation. This impossibility may provide new insight into the nature of quantum mechanics, and it implies more limitations on quantum information tasks than the existing no-go theorems.

  11. Universal quantum computation by discontinuous quantum walk

    International Nuclear Information System (INIS)

    Underwood, Michael S.; Feder, David L.

    2010-01-01

    Quantum walks are the quantum-mechanical analog of random walks, in which a quantum ''walker'' evolves between initial and final states by traversing the edges of a graph, either in discrete steps from node to node or via continuous evolution under the Hamiltonian furnished by the adjacency matrix of the graph. We present a hybrid scheme for universal quantum computation in which a quantum walker takes discrete steps of continuous evolution. This ''discontinuous'' quantum walk employs perfect quantum-state transfer between two nodes of specific subgraphs chosen to implement a universal gate set, thereby ensuring unitary evolution without requiring the introduction of an ancillary coin space. The run time is linear in the number of simulated qubits and gates. The scheme allows multiple runs of the algorithm to be executed almost simultaneously by starting walkers one time step apart.

  12. Propagator formalism and computer simulation of restricted diffusion behaviors of inter-molecular multiple-quantum coherences

    International Nuclear Information System (INIS)

    Cai Congbo; Chen Zhong; Cai Shuhui; Zhong Jianhui

    2005-01-01

    In this paper, behaviors of single-quantum coherences and inter-molecular multiple-quantum coherences under restricted diffusion in nuclear magnetic resonance experiments were investigated. The propagator formalism based on the loss of spin phase memory during random motion was applied to describe the diffusion-induced signal attenuation. The exact expression of the signal attenuation under the short gradient pulse approximation for restricted diffusion between two parallel plates was obtained using this propagator method. For long gradient pulses, a modified formalism was proposed. The simulated signal attenuation under the effects of gradient pulses of different width based on the Monte Carlo method agrees with the theoretical predictions. The propagator formalism and computer simulation can provide convenient, intuitive and precise methods for the study of the diffusion behaviors

  13. Monolithic integration of InGaAs/InP multiple quantum wells on SOI substrates for photonic devices

    Science.gov (United States)

    Li, Zhibo; Wang, Mengqi; Fang, Xin; Li, Yajie; Zhou, Xuliang; Yu, Hongyan; Wang, Pengfei; Wang, Wei; Pan, Jiaoqing

    2018-02-01

    A direct epitaxy of III-V nanowires with InGaAs/InP multiple quantum wells on v-shaped trenches patterned silicon on insulator (SOI) substrates was realized by combining the standard semiconductor fabrication process with the aspect ratio trapping growth technique. Silicon thickness as well as the width and gap of each nanowire were carefully designed to accommodate essential optical properties and appropriate growth conditions. The III-V element ingredient, crystalline quality, and surface topography of the grown nanowires were characterized by X-ray diffraction spectroscopy, photoluminescence, and scanning electron microscope. Geometrical details and chemical information of multiple quantum wells were revealed by transmission electron microscopy and energy dispersive spectroscopy. Numerical simulations confirmed that the optical guided mode supported by one single nanowire was able to propagate 50 μm with ˜30% optical loss. This proposed integration scheme opens up an alternative pathway for future photonic integrations of III-V devices on the SOI platform at nanoscale.

  14. Quantum Darwinism

    Science.gov (United States)

    Zurek, Wojciech Hubert

    2009-03-01

    Quantum Darwinism describes the proliferation, in the environment, of multiple records of selected states of a quantum system. It explains how the quantum fragility of a state of a single quantum system can lead to the classical robustness of states in their correlated multitude; shows how effective `wave-packet collapse' arises as a result of the proliferation throughout the environment of imprints of the state of the system; and provides a framework for the derivation of Born's rule, which relates the probabilities of detecting states to their amplitudes. Taken together, these three advances mark considerable progress towards settling the quantum measurement problem.

  15. Rank-based model selection for multiple ions quantum tomography

    International Nuclear Information System (INIS)

    Guţă, Mădălin; Kypraios, Theodore; Dryden, Ian

    2012-01-01

    The statistical analysis of measurement data has become a key component of many quantum engineering experiments. As standard full state tomography becomes unfeasible for large dimensional quantum systems, one needs to exploit prior information and the ‘sparsity’ properties of the experimental state in order to reduce the dimensionality of the estimation problem. In this paper we propose model selection as a general principle for finding the simplest, or most parsimonious explanation of the data, by fitting different models and choosing the estimator with the best trade-off between likelihood fit and model complexity. We apply two well established model selection methods—the Akaike information criterion (AIC) and the Bayesian information criterion (BIC)—two models consisting of states of fixed rank and datasets such as are currently produced in multiple ions experiments. We test the performance of AIC and BIC on randomly chosen low rank states of four ions, and study the dependence of the selected rank with the number of measurement repetitions for one ion states. We then apply the methods to real data from a four ions experiment aimed at creating a Smolin state of rank 4. By applying the two methods together with the Pearson χ 2 test we conclude that the data can be suitably described with a model whose rank is between 7 and 9. Additionally we find that the mean square error of the maximum likelihood estimator for pure states is close to that of the optimal over all possible measurements. (paper)

  16. Multiple choices of time in quantum cosmology

    International Nuclear Information System (INIS)

    Małkiewicz, Przemysław

    2015-01-01

    It is often conjectured that a choice of time function merely sets up a frame for the quantum evolution of the gravitational field, meaning that all choices should be in some sense compatible. In order to explore this conjecture (and the meaning of compatibility), we develop suitable tools for determining the relation between quantum theories based on different time functions. First, we discuss how a time function fixes a canonical structure on the constraint surface. The presentation includes both the kinematical and the reduced perspective, and the relation between them. Second, we formulate twin theorems about the existence of two inequivalent maps between any two deparameterizations, a formal canonical and a coordinate one. They are used to separate the effects induced by choice of clock and other factors. We show, in an example, how the spectra of quantum observables are transformed under the change of clock and prove, via a general argument, the existence of choice-of-time-induced semiclassical effects. Finally, we study an example, in which we find that the semiclassical discrepancies can in fact be arbitrarily large for dynamical observables. We conclude that the values of critical energy density or critical volume in the bouncing scenarios of quantum cosmology cannot in general be at the Planck scale, and always need to be given with reference to a specific time function. (paper)

  17. Redshift and blueshift of GaNAs/GaAs multiple quantum wells induced by rapid thermal annealing

    Science.gov (United States)

    Sun, Yijun; Cheng, Zhiyuan; Zhou, Qiang; Sun, Ying; Sun, Jiabao; Liu, Yanhua; Wang, Meifang; Cao, Zhen; Ye, Zhi; Xu, Mingsheng; Ding, Yong; Chen, Peng; Heuken, Michael; Egawa, Takashi

    2018-02-01

    The effects of rapid thermal annealing (RTA) on the optical properties of GaNAs/GaAs multiple quantum wells (MQWs) grown by chemical beam epitaxy (CBE) are studied by photoluminescence (PL) at 77 K. The results show that the optical quality of the MQWs improves significantly after RTA. With increasing RTA temperature, PL peak energy of the MQWs redshifts below 1023 K, while it blueshifts above 1023 K. Two competitive processes which occur simultaneously during RTA result in redshift at low temperature and blueshift at high temperature. It is also found that PL peak energy shift can be explained neither by nitrogen diffusion out of quantum wells nor by nitrogen reorganization inside quantum wells. PL peak energy shift can be quantitatively explained by a modified recombination coupling model in which redshift nonradiative recombination and blueshift nonradiative recombination coexist. The results obtained have significant implication on the growth and RTA of GaNAs material for high performance optoelectronic device application.

  18. Universal quantum interfaces

    International Nuclear Information System (INIS)

    Lloyd, Seth; Landahl, Andrew J.; Slotine, Jean-Jacques E.

    2004-01-01

    To observe or control a quantum system, one must interact with it via an interface. This article exhibits simple universal quantum interfaces--quantum input/output ports consisting of a single two-state system or quantum bit that interacts with the system to be observed or controlled. It is shown that under very general conditions the ability to observe and control the quantum bit on its own implies the ability to observe and control the system itself. The interface can also be used as a quantum communication channel, and multiple quantum systems can be connected by interfaces to become an efficient universal quantum computer. Experimental realizations are proposed, and implications for controllability, observability, and quantum information processing are explored

  19. Real-Time Observation of Ultrafast Intraband Relaxation and Exciton Multiplication in PbS Quantum Dots

    KAUST Repository

    El-Ballouli, Ala’a O.

    2014-03-19

    We examine ultrafast intraconduction band relaxation and multiple-exciton generation (MEG) in PbS quantum dots (QDs) using transient absorption spectroscopy with 120 fs temporal resolution. The intraconduction band relaxation can be directly and excellently resolved spectrally and temporally by applying broadband pump-probe spectroscopy to excite and detect the wavelengths around the exciton absorption peak, which is located in the near-infrared region. The time-resolved data unambiguously demonstrate that the intraband relaxation time progressively increases as the pump-photon energy increases. Moreover, the relaxation time becomes much shorter as the size of the QDs decreases, indicating the crucial role of spatial confinement in the intraband relaxation process. Additionally, our results reveal the systematic scaling of the intraband relaxation time with both excess energy above the effective energy band gap and QD size. We also assess MEG in different sizes of the QDs. Under the condition of high-energy photon excitation, which is well above the MEG energy threshold, ultrafast bleach recovery due to the nonradiative Auger recombination of the multiple electron-hole pairs provides conclusive experimental evidence for the presence of MEG. For instance, we achieved quantum efficiencies of 159, 129 and 106% per single-absorbed photon at pump photoexcition of three times the band gap for QDs with band gaps of 880 nm (1.41 eV), 1000 nm (1.24 eV) and 1210 nm (1.0 eV), respectively. These findings demonstrate clearly that the efficiency of transferring excess photon energy to carrier multiplication is significantly increased in smaller QDs compared with larger ones. Finally, we discuss the Auger recombination dynamics of the multiple electron-hole pairs as a function of QD size.

  20. Rapid and novel discrimination and quantification of oleanolic and ursolic acids in complex plant extracts using two-dimensional nuclear magnetic resonance spectroscopy-Comparison with HPLC methods

    International Nuclear Information System (INIS)

    Kontogianni, Vassiliki G.; Exarchou, Vassiliki; Troganis, Anastassios; Gerothanassis, Ioannis P.

    2009-01-01

    A novel strategy for NMR analysis of mixtures of oleanolic and ursolic acids that occur in natural products is described. These important phytochemicals have similar structure and their discrimination and quantification is rather difficult. We report herein the combined use of proton-carbon heteronuclear single-quantum coherence ( 1 H- 13 C HSQC) and proton-carbon heteronuclear multiple-bond correlation ( 1 H- 13 C HMBC) NMR spectroscopy, in the identification and quantitation of oleanolic acid (OA) and ursolic acid (UA)in plant extracts of the Lamiaceae and Oleaceae family. The combination of 1 H- 13 C HSQC and 1 H- 13 C HMBC techniques allows the connection of the proton and carbon-13 spins across the molecular backbone resulting in the identification and, thus, discrimination of oleanolic and ursolic acid without resorting to physicochemical separation of the components. The quantitative results provided by 2D 1 H- 13 C HSQC NMR data were obtained within a short period of time (∼14 min) and are in excellent agreement with those obtained by HPLC, which support the efficiency of the suggested methodology

  1. Sesquiterpenes from the Saudi Red Sea: Litophyton arboreum with their cytotoxic and antimicrobial activities.

    Science.gov (United States)

    Abou El-Kassem, Lamia T; Hawas, Usama W; El-Desouky, Samy K; Al-Farawati, Radwan

    2018-01-26

    A new pseudoguaiane-type sesquiterpene named litopharbol (1) was isolated from the methanolic extract of the Red Sea soft coral Litophyton arboreum, along with known sesquiterpenoids alismol (2), alismorientol B (3), teuhetenone A (4), and calamusin I (5); steroid, 24-methyl-cholesta-5,24(28)-diene-3β-ol (6), alkyl glyceryl ether, chimyl alcohol (7); sphingolipid, erythro-N-dodecanoyl-docosasphinga-(4E,8E)-dienine (8); and nitrogenous bases, thymine (9) and thymidine (10). The structures were determined on the basis of nuclear magnetic resonance (NMR) spectroscopic (1D and 2D NMR data including heteronuclear single quantum coherence spectroscopy, heteronuclear multiple-bond correlation spectroscopy, and nuclear Overhauser effect spectroscopy) and mass spectrometric analyses. Compounds 1-5 were explored for antimicrobial activity and cancer cell line sensitivity tests. Compound 1 exhibited antibacterial activity against Bacillus cereus with a minimum inhibition concentration of 1.8 μg/mL, whereas compound 3 showed significant potent cytotoxic effect against MCF-7 (breast cancer cells) with IC50 4.32 μM.

  2. Further Study on Chemical Constituents of Parnassia wightiana Wall: Four New Dihydro-β-agarofuran Sesquiterpene Polyesters

    Directory of Open Access Journals (Sweden)

    Zhao-Feng Gao

    2015-04-01

    Full Text Available Four new (1–4, along with six known (5–10 dihydro-β-agarofuran sesquiterpene polyesters were isolated from the whole plants of Parnassia wightiana. The new compounds were structurally elucidated through spectroscopic analysis including UV (Ultraviolet Spectrum, IR (Infrared Spectrum, 1H-NMR (1Hydrogen-Nuclear Magnetic Resonance, 13C-NMR (13Carbon-Nuclear Magnetic Resonance, DEPT (Distortionless Enhancement by Polarization Transfer, 1H-1H COSY (1H-1H Correlation Spectroscopy, HSQC (Heteronuclear Single Quantum Coherence, HMBC (Heteronuclear Multiple Bond Correlation, NOESY (Nuclear Overhauser Enhancement Spectroscopy and HR-MS (High Resolution Mass Specttrum and their absolute configurations were proposed by comparison of NOESY spectra and specific optical rotations with those of known compounds and biosynthesis grounds. Compound 2 is the first sesquiterpene alkaloid isolated from this plant. New compounds 1–4 exhibited some cytotoxic activities against NB4, MKN-45 and MCF-7 cells at 20 μM and of which 4 showed the highest activity against NB4 and MKN-45 cells with inhibition rates of 85.6% and 30.5%, respectively.

  3. A definitive analytical spectroscopic study of Indian yellow, an ancient pigment used for dating purposes.

    Science.gov (United States)

    de Faria, Dalva L A; Edwards, Howell G M; Careaga, Valeria; Walt, Nicholas; Maier, Marta S

    2017-02-01

    The Raman spectrum of tartrazine has been mistakenly reported as being that of Indian yellow in the literature, which has serious consequences for the identification of this pigment in art works regarding their authentication. Unlike tartrazine, Indian yellow (a natural mixture of the magnesium and calcium salts of euxanthic acid) exhibits in its Raman spectrum a strong fluorescent background when visible excitation is used, however, excitation in the near infrared (1064nm) permitted the observation of the Raman bands from the raw pigment with the main features placed at 1346, 1368, 1425, 1441 and 1626cm -1 . Indian yellow identification was assured by 1 H and 13 C Nuclear Magnetic Resonance characterization and the complete assignment of the proton and carbon resonances was accomplished using heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear overhauser effect spectroscopy (NOESY) and 1 H- 1 H correlation spectroscopy (COSY). Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) analyzes were also conducted on a genuine sample of this historical pigment. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  4. Methoxyflavones from New Lingzhi Medicinal Mushroom, Ganoderma lingzhi (Agaricomycetes).

    Science.gov (United States)

    Shimizu, Kuniyoshi; Amen, Yhiya M; Kaifuchi, Satoru

    2016-01-01

    Ganoderma lingzhi is one of the most famous medicinal fungi in the world. It has been used in folk medicine, especially in East Asian countries. It is also a white-rot fungus with strong wood degradation ability, especially against lignin. Different classes of bioactive natural products have been reported in Ganoderma, including triterpenes, polysaccharides, sterols, and peptides. The triterpenes and polysaccharides are the primary bioactive compounds of Ganoderma. We report for the first time the presence of 3 methoxyflavones as minor constituents in G. linghzi. The 3 compounds were identified based on different spectroscopic techniques, including 1- and 2-dimensional nuclear magnetic resonance (1H-1H correlation spectroscopy, heteronuclear single quantum coherence, and heteronuclear multiple bond correlation) and mass spectrometry (high-resolution electrospray ionization mass spectrometry). Our report provides an approach to a possible biosynthetic pathway for biosynthetic genes in the mushrooms. Another great possibility is that these compounds may exist or be formed through degradation of the components in the woody substrate, such as lignin, and then subsequently translocate to the fruiting bodies.

  5. Multi-strategy based quantum cost reduction of linear nearest-neighbor quantum circuit

    Science.gov (United States)

    Tan, Ying-ying; Cheng, Xue-yun; Guan, Zhi-jin; Liu, Yang; Ma, Haiying

    2018-03-01

    With the development of reversible and quantum computing, study of reversible and quantum circuits has also developed rapidly. Due to physical constraints, most quantum circuits require quantum gates to interact on adjacent quantum bits. However, many existing quantum circuits nearest-neighbor have large quantum cost. Therefore, how to effectively reduce quantum cost is becoming a popular research topic. In this paper, we proposed multiple optimization strategies to reduce the quantum cost of the circuit, that is, we reduce quantum cost from MCT gates decomposition, nearest neighbor and circuit simplification, respectively. The experimental results show that the proposed strategies can effectively reduce the quantum cost, and the maximum optimization rate is 30.61% compared to the corresponding results.

  6. Quantum jumps are more quantum than quantum diffusion

    International Nuclear Information System (INIS)

    Daryanoosh, Shakib; M Wiseman, Howard

    2014-01-01

    It was recently argued (Wiseman and Gambetta 2012 Phys. Rev. Lett. 108 220402) that the stochastic dynamics (jumps or diffusion) of an open quantum system are not inherent to the system, but rather depend on the existence and nature of a distant detector. The proposed experimental tests involved homodyne detection, giving rise to quantum diffusion, and required efficiencies η of well over 50%. Here we prove that this requirement (η>0.5) is universal for diffusive-type detection, even if the system is coupled to multiple baths. However, this no-go theorem does not apply to quantum jumps, and we propose a test involving a qubit with jump-type detectors, with a threshold efficiency of only 37%. That is, quantum jumps are ‘more quantum’, and open the way to practical experimental tests. Our scheme involves a novel sort of adaptive monitoring scheme on a system coupled to two baths. (paper)

  7. Quantum correlations and light localization in disordered nanophotonic structures

    DEFF Research Database (Denmark)

    Smolka, Stephan

    This thesis reports results on quantum properties of light in multiple-scattering nano-structured materials. Spatial quantum correlations of photons are demonstrated experimentally that are induced by multiple scattering of squeezed light and of purely quantum origin. By varying the quantum state...

  8. 2 D electron transport in selectively doped Ga As/Inx Ga1-x As multiple quantum well structures

    International Nuclear Information System (INIS)

    Kulbachinskii, V.A.; Kytin, V.G.; Babushkina, T.S.; Malkina, I.G.

    1996-01-01

    Photoluminescence, temperature dependence of conductivity (0.4 x Ga 1-x As multiple quantum well (MQW) structures were investigated. The dependence of electron mobility on the width of the quantum wells and temperature were measured. It was shown that in narrow MQW structures the value of mobility is restricted by interface roughness scattering. In wider MQW structures neither interface roughness scattering nor change impurity scattering can describe the values and temperature dependence of mobility. Negative magnetoresistance was observed. From detailed comparison between theory of weak localization and experiment the relaxation time of the wave function phase τ ψ and temperature dependence of τ ψ were evaluated. Quantum Hall effect was investigated in all samples at T=0.4-4.2 K in magnetic fields up to 40 T. (author). 9 refs., 5 figs., 1 tab

  9. Excitation density dependence of the photoluminescence from CdxHg1-xTe multiple quantum wells

    International Nuclear Information System (INIS)

    Tonheim, C R; Selvig, E; Nicolas, S; Breivik, M; Haakenaasen, R; Gunnaes, A E

    2008-01-01

    A study of the photoluminescence from a four-period Cd x Hg 1-x Te multiple quantum well structure at 11 K as a function of excitation density is presented. High-resolution X-ray diffraction and transmission electron microscopy revealed that the quantum well structure is of high quality. This was supported by the narrow photoluminescence peak originating in the ground state electron - heavy hole transition, with a full width at half maximum of only 7.4 meV for an excitation density of 1.3 W/cm 2 . When the excitation density was increased from 1.3 to 23.4 W/cm 2 , the peak position was shifted toward higher energy by 2.6 meV and the full width at half maximum increased from 7.4 to 10.9 meV

  10. Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Mehnke, Frank, E-mail: mehnke@physik.tu-berlin.de; Kuhn, Christian; Guttmann, Martin; Reich, Christoph; Kolbe, Tim; Rass, Jens; Wernicke, Tim [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Kueller, Viola; Knauer, Arne; Lapeyrade, Mickael; Einfeldt, Sven; Weyers, Markus [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Kneissl, Michael [Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, EW 6-1, 10623 Berlin (Germany); Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2014-08-04

    The design and Mg-doping profile of AlN/Al{sub 0.7}Ga{sub 0.3}N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) emitting below 250 nm was investigated. By inserting an AlN electron blocking layer (EBL) into the EBH, we were able to increase the quantum well emission power and significantly reduce long wavelength parasitic luminescence. Furthermore, electron leakage was suppressed by optimizing the thickness of the AlN EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low parasitic luminescence (7% of total emission power) and external quantum efficiencies of 0.19% at 246 nm have been realized. This concept was applied to AlGaN MQW LEDs emitting between 235 nm and 263 nm with external quantum efficiencies ranging from 0.002% to 0.93%. After processing, we were able to demonstrate an UV-C LED emitting at 234 nm with 14.5 μW integrated optical output power and an external quantum efficiency of 0.012% at 18.2 A/cm{sup 2}.

  11. Efficient charge carrier injection into sub-250 nm AlGaN multiple quantum well light emitting diodes

    International Nuclear Information System (INIS)

    Mehnke, Frank; Kuhn, Christian; Guttmann, Martin; Reich, Christoph; Kolbe, Tim; Rass, Jens; Wernicke, Tim; Kueller, Viola; Knauer, Arne; Lapeyrade, Mickael; Einfeldt, Sven; Weyers, Markus; Kneissl, Michael

    2014-01-01

    The design and Mg-doping profile of AlN/Al 0.7 Ga 0.3 N electron blocking heterostructures (EBH) for AlGaN multiple quantum well (MQW) light emitting diodes (LEDs) emitting below 250 nm was investigated. By inserting an AlN electron blocking layer (EBL) into the EBH, we were able to increase the quantum well emission power and significantly reduce long wavelength parasitic luminescence. Furthermore, electron leakage was suppressed by optimizing the thickness of the AlN EBL while still maintaining sufficient hole injection. Ultraviolet (UV)-C LEDs with very low parasitic luminescence (7% of total emission power) and external quantum efficiencies of 0.19% at 246 nm have been realized. This concept was applied to AlGaN MQW LEDs emitting between 235 nm and 263 nm with external quantum efficiencies ranging from 0.002% to 0.93%. After processing, we were able to demonstrate an UV-C LED emitting at 234 nm with 14.5 μW integrated optical output power and an external quantum efficiency of 0.012% at 18.2 A/cm 2

  12. Realization of quantum gates with multiple control qubits or multiple target qubits in a cavity

    Science.gov (United States)

    Waseem, Muhammad; Irfan, Muhammad; Qamar, Shahid

    2015-06-01

    We propose a scheme to realize a three-qubit controlled phase gate and a multi-qubit controlled NOT gate of one qubit simultaneously controlling n-target qubits with a four-level quantum system in a cavity. The implementation time for multi-qubit controlled NOT gate is independent of the number of qubit. Three-qubit phase gate is generalized to n-qubit phase gate with multiple control qubits. The number of steps reduces linearly as compared to conventional gate decomposition method. Our scheme can be applied to various types of physical systems such as superconducting qubits coupled to a resonator and trapped atoms in a cavity. Our scheme does not require adjustment of level spacing during the gate implementation. We also show the implementation of Deutsch-Joza algorithm. Finally, we discuss the imperfections due to cavity decay and the possibility of physical implementation of our scheme.

  13. Simultaneous detection of multiple DNA targets by integrating dual-color graphene quantum dot nanoprobes and carbon nanotubes.

    Science.gov (United States)

    Qian, Zhaosheng; Shan, Xiaoyue; Chai, Lujing; Chen, Jianrong; Feng, Hui

    2014-12-01

    Simultaneous detection of multiple DNA targets was achieved based on a biocompatible graphene quantum dots (GQDs) and carbon nanotubes (CNTs) platform through spontaneous assembly between dual-color GQD-based probes and CNTs and subsequently self-recognition between DNA probes and targets. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Optoelectronic Performance Variations in InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes: Effects of Potential Fluctuation.

    Science.gov (United States)

    Islam, Abu Bashar Mohammad Hamidul; Shim, Jong-In; Shin, Dong-Soo

    2018-05-07

    We investigate the cause of the optoelectronic performance variations in InGaN/GaN multiple-quantum-well blue light-emitting diodes, using three different samples from an identical wafer grown on a c -plane sapphire substrate. Various macroscopic measurements have been conducted, revealing that with increasing strain in the quantum wells (QWs), the crystal quality improves with an increasing peak internal quantum efficiency while the droop becomes more severe. We propose to explain these variations using a model where the in-plane local potential fluctuation in QWs is considered. Our work is contrasted with prior works in that macroscopic measurements are utilized to find clues on the microscopic changes and their impacts on the device performances, which has been rarely attempted.

  15. Quantum light in coupled interferometers for quantum gravity tests.

    Science.gov (United States)

    Ruo Berchera, I; Degiovanni, I P; Olivares, S; Genovese, M

    2013-05-24

    In recent years quantum correlations have received a lot of attention as a key ingredient in advanced quantum metrology protocols. In this Letter we show that they provide even larger advantages when considering multiple-interferometer setups. In particular, we demonstrate that the use of quantum correlated light beams in coupled interferometers leads to substantial advantages with respect to classical light, up to a noise-free scenario for the ideal lossless case. On the one hand, our results prompt the possibility of testing quantum gravity in experimental configurations affordable in current quantum optics laboratories and strongly improve the precision in "larger size experiments" such as the Fermilab holometer; on the other hand, they pave the way for future applications to high precision measurements and quantum metrology.

  16. The Efficiency of Quantum Identity Testing of Multiple States

    OpenAIRE

    Kada, Masaru; Nishimura, Harumichi; Yamakami, Tomoyuki

    2008-01-01

    We examine two quantum operations, the Permutation Test and the Circle Test, which test the identity of n quantum states. These operations naturally extend the well-studied Swap Test on two quantum states. We first show the optimality of the Permutation Test for any input size n as well as the optimality of the Circle Test for three input states. In particular, when n=3, we present a semi-classical protocol, incorporated with the Swap Test, which approximates the Circle Test efficiently. Furt...

  17. High Field In Vivo 13C Magnetic Resonance Spectroscopy of Brain by Random Radiofrequency Heteronuclear Decoupling and Data Sampling

    Science.gov (United States)

    Li, Ningzhi; Li, Shizhe; Shen, Jun

    2017-06-01

    In vivo 13C magnetic resonance spectroscopy (MRS) is a unique and effective tool for studying dynamic human brain metabolism and the cycling of neurotransmitters. One of the major technical challenges for in vivo 13C-MRS is the high radio frequency (RF) power necessary for heteronuclear decoupling. In the common practice of in vivo 13C-MRS, alkanyl carbons are detected in the spectra range of 10-65ppm. The amplitude of decoupling pulses has to be significantly greater than the large one-bond 1H-13C scalar coupling (1JCH=125-145 Hz). Two main proton decoupling methods have been developed: broadband stochastic decoupling and coherent composite or adiabatic pulse decoupling (e.g., WALTZ); the latter is widely used because of its efficiency and superb performance under inhomogeneous B1 field. Because the RF power required for proton decoupling increases quadratically with field strength, in vivo 13C-MRS using coherent decoupling is often limited to low magnetic fields (protons via weak long-range 1H-13C scalar couplings, which can be decoupled using low RF power broadband stochastic decoupling. Recently, the carboxylic/amide 13C-MRS technique using low power random RF heteronuclear decoupling was safely applied to human brain studies at 7T. Here, we review the two major decoupling methods and the carboxylic/amide 13C-MRS with low power decoupling strategy. Further decreases in RF power deposition by frequency-domain windowing and time-domain random under-sampling are also discussed. Low RF power decoupling opens the possibility of performing in vivo 13C experiments of human brain at very high magnetic fields (such as 11.7T), where signal-to-noise ratio as well as spatial and temporal spectral resolution are more favorable than lower fields.

  18. Influence of strain relaxation on the optical properties of InGaN/GaN multiple quantum well nanorods

    International Nuclear Information System (INIS)

    Wang, Q; Bai, J; Gong, Y P; Wang, T

    2011-01-01

    Optical investigation has been carried out on InGaN/GaN nanorod structures with different indium compositions, fabricated from InGaN/GaN multiple quantum well (MQW) epitaxial wafers using a self-organized nickel nano-mask and subsequent dry etching techniques. In comparison with the as-grown InGaN/GaN MQWs, the internal quantum efficiencies of the nanorods are significantly improved, in particular, for the green InGaN/GaN nanorods with a high indium composition, the internal quantum efficiency is enhanced by a factor of 8, much larger than the enhancement factor of 3.4 for the blue InGaN/GaN nanorods. X-ray reciprocal space mapping (RSM) measurements have been performed in order to quantitatively evaluate the stain relaxation in the nanorods, demonstrating that the majority of strain in InGaN/GaN MQWs can be relaxed as a result of fabrication into nanorods. The excitation-power-dependent photoluminescence measurements have also clearly shown that a significant reduction in the strain-induced quantum confined stark effect has occurred to the nanorod structures.

  19. Hybrid quantum-classical modeling of quantum dot devices

    Science.gov (United States)

    Kantner, Markus; Mittnenzweig, Markus; Koprucki, Thomas

    2017-11-01

    The design of electrically driven quantum dot devices for quantum optical applications asks for modeling approaches combining classical device physics with quantum mechanics. We connect the well-established fields of semiclassical semiconductor transport theory and the theory of open quantum systems to meet this requirement. By coupling the van Roosbroeck system with a quantum master equation in Lindblad form, we introduce a new hybrid quantum-classical modeling approach, which provides a comprehensive description of quantum dot devices on multiple scales: it enables the calculation of quantum optical figures of merit and the spatially resolved simulation of the current flow in realistic semiconductor device geometries in a unified way. We construct the interface between both theories in such a way, that the resulting hybrid system obeys the fundamental axioms of (non)equilibrium thermodynamics. We show that our approach guarantees the conservation of charge, consistency with the thermodynamic equilibrium and the second law of thermodynamics. The feasibility of the approach is demonstrated by numerical simulations of an electrically driven single-photon source based on a single quantum dot in the stationary and transient operation regime.

  20. Multiple quantum collapse of the inflaton field and its implications on the birth of cosmic structure

    Energy Technology Data Exchange (ETDEWEB)

    Leon, Gabriel [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico DF 04510 (Mexico); De Unanue, Adolfo [C3 Centro de Ciencias de la Complejidad, Universidad Nacional Autonoma de Mexico, Torre de IngenierIa, Circuito Exterior S/N Ciudad Universitaria, Mexico DF 04510 (Mexico); Sudarsky, Daniel, E-mail: gabriel.leon@nucleares.unam.mx, E-mail: adolfo@nucleares.unam.mx, E-mail: sudarsky@nucleares.unam.mx [Instituto de AstronomIa y Fisica del Espacio (UBA-CONICET), Casilla de Correos 67, Sucursal 28, 1428 Buenos Aires (Argentina)

    2011-08-07

    The standard inflationary account for the origin of cosmic structure is, without a doubt, extremely successful. However, it is not fully satisfactory as has been argued in Perez et al (2006 Class. Quantum Grav. 23 2317). The central point is that, in the standard accounts, the inhomogeneity and anisotropy of our universe seem to emerge, unexplained, from an exactly homogeneous and isotropic initial state through processes that do not break those symmetries. The proposal made there to address this shortcoming calls for a dynamical and self-induced quantum collapse of the original homogeneous and isotropic state of the inflaton. In this paper, we consider the possibility of a multiplicity of collapses in each one of the modes of the quantum field. As we will see, the results are sensitive to a more detailed characterization of the collapse than those studied in the previous works, and in this regard two simple options will be studied. We find important constraints on the model, most remarkably on the number of possible collapses for each mode.

  1. A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

    International Nuclear Information System (INIS)

    Davies, M. J.; Hammersley, S.; Dawson, P.; Massabuau, F. C.-P.; Oliver, R. A.; Kappers, M. J.; Humphreys, C. J.

    2016-01-01

    In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with non-radiative recombination processes

  2. A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

    Energy Technology Data Exchange (ETDEWEB)

    Davies, M. J., E-mail: Matthew.Davies-2@Manchester.ac.uk; Hammersley, S.; Dawson, P. [School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Massabuau, F. C.-P.; Oliver, R. A.; Kappers, M. J.; Humphreys, C. J. [Department of Material Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)

    2016-02-07

    In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of the quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with non-radiative recombination processes.

  3. Perfect tuning of spin-polarization in a ring-shaped multiple-quantum-dot nanostructure in the presence of Rashba spin–orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Eslami, L., E-mail: Leslami@iust.ac.ir; Chaghari, Z.; Faizabadi, E.

    2013-09-02

    Spin-dependent electronic transport through an open multiple-quantum-dot ring threaded by a magnetic flux is theoretically investigated by using the single particle Green's function method. By introducing local Rashba spin–orbit interaction on an individual quantum dot and local magnetic moments on two of other quantum dots, we calculate the spin-polarization in the output lead. We find the spin-polarization can be tuned by manipulating magnetic moments, adjusting magnetic flux and setting the Rashba spin–orbit strength. It is also shown the system can operate as an efficient spin-inverter when the structure is adjusted properly. The analysis can be utilized in designing optimized nanodevices.

  4. Kowalevski top in quantum mechanics

    International Nuclear Information System (INIS)

    Matsuyama, A.

    2013-01-01

    The quantum mechanical Kowalevski top is studied by the direct diagonalization of the Hamiltonian. The spectra show different behaviors depending on the region divided by the bifurcation sets of the classical invariant tori. Some of these spectra are nearly degenerate due to the multiplicity of the invariant tori. The Kowalevski top has several symmetries and symmetry quantum numbers can be assigned to the eigenstates. We have also carried out the semiclassical quantization of the Kowalevski top by the EBK formulation. It is found that the semiclassical spectra are close to the exact values, thus the eigenstates can be also labeled by the integer quantum numbers. The symmetries of the system are shown to have close relations with the semiclassical quantum numbers and the near-degeneracy of the spectra. -- Highlights: •Quantum spectra of the Kowalevski top are calculated. •Semiclassical quantization is carried out by the EBK formulation. •Quantum states are labeled by the semiclassical integer quantum numbers. •Multiplicity of the classical torus makes the spectra nearly degenerate. •Symmetries, quantum numbers and near-degenerate spectra are closely related

  5. A programmable quantum current standard from the Josephson and the quantum Hall effects

    Energy Technology Data Exchange (ETDEWEB)

    Poirier, W., E-mail: wilfrid.poirier@lne.fr; Lafont, F.; Djordjevic, S.; Schopfer, F.; Devoille, L. [Quantum metrology group, Laboratoire National de métrologie et d' Essais, 29 avenue Roger Hennequin, 78197 Trappes (France)

    2014-01-28

    We propose a way to realize a programmable quantum current standard (PQCS) from the Josephson voltage standard and the quantum Hall resistance standard (QHR) exploiting the multiple connection technique provided by the quantum Hall effect (QHE) and the exactness of the cryogenic current comparator. The PQCS could lead to breakthroughs in electrical metrology like the realization of a programmable quantum current source, a quantum ampere-meter, and a simplified closure of the quantum metrological triangle. Moreover, very accurate universality tests of the QHE could be performed by comparing PQCS based on different QHRs.

  6. Ultrafast conductivity dynamics in optically excited InGaN/GaN multiple quantum wells, observed by transient THz spectroscopy

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Porte, Henrik; Cooke, David

    2010-01-01

    We investigate ultrafast carrier dynamics in photoexcited InGaN/GaN multiple quantum wells by time-resolved terahertz spectroscopy. The initially very strong built-in piezoelectric field is screened upon photoexcitation by the polarized carriers, and is gradually restored as the carriers recombine...

  7. Optically controlled reflection modulator using GaAs-AlGaAs n-i-p-i/multiple-quantum-well structures

    Science.gov (United States)

    Law, K.-K.; Simes, R. J.; Coldren, L. A.; Gossard, A. C.; Maserjian, J.

    1989-01-01

    An optically controlled reflection modulator has been demonstrated that consists of a combination of a GaAs-AlGaAs n-i-p-i doping structure with a multiple-quantum-well structures on top of a distributed Bragg reflector, all grown by MBE. A modulation of approximately 60 percent is obtained on the test structure, corresponding to a differential change of absorption coefficient in the quantum wells of approximately 7500/cm. Changes in reflectance can be observed with a control beam power as low as 1.5 microW. This device structure has the potential of being developed as an optically addressed spatial light modulator for optical information processing.

  8. Photoreflectance Spectroscopy Characterization of Ge/Si0.16Ge0.84 Multiple Quantum Wells on Ge Virtual Substrate

    Directory of Open Access Journals (Sweden)

    Hung-Pin Hsu

    2013-01-01

    Full Text Available We report a detailed characterization of a Ge/Si0.16Ge0.84 multiple quantum well (MQW structure on Ge-on-Si virtual substrate (VS grown by ultrahigh vacuum chemical vapor deposition by using temperature-dependent photoreflectance (PR in the temperature range from 10 to 300 K. The PR spectra revealed a wide range of optical transitions from the MQW region as well as transitions corresponding to the light-hole and heavy-hole splitting energies of Ge-on-Si VS. A detailed comparison of PR spectral line shape fits and theoretical calculation led to the identification of various quantum-confined interband transitions. The temperature-dependent PR spectra of Ge/Si0.16Ge0.84 MQW were analyzed using Varshni and Bose-Einstein expressions. The parameters that describe the temperature variations of various quantum-confined interband transition energies were evaluated and discussed.

  9. Evaluation of field emission properties from multiple-stacked Si quantum dots

    International Nuclear Information System (INIS)

    Takeuchi, Daichi; Makihara, Katsunori; Ohta, Akio; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2016-01-01

    Multiple-stacked Si quantum dots (QDs) with ultrathin SiO 2 interlayers were formed on ultrathin SiO 2 layers by repeating a process sequence consisting of the formation of Si-QDs by low pressure chemical vapor deposition using a SiH 4 gas and the surface oxidation and subsequent surface modification by remote hydrogen and oxygen plasmas, respectively. To clarify the electron emission mechanism from multiple-stacked Si-QDs covered with an ultrathin Au top electrode, the energy distribution of the emitted electrons and its electric field dependence was measured using a hemispherical electron energy analyzer in an X-ray photoelectron spectroscopy system under DC bias application to the multiple-stacked Si-QD structure. At − 6 V and over, the energy distributions reached a peak at ~ 2.5 eV with a tail toward the higher energy side. While the electron emission intensity was increased exponentially with an increase in the applied DC bias, there was no significant increase in the emission peak energy. The observed emission characteristics can be interpreted in terms of field emissions from the second and/or third topmost Si-QDs resulting from the electric concentration there. - Highlights: • Electron field emission from 6-fold stack of Si-QDs has been evaluated. • AFM measurements show the local electron emission from individual Si-QDs. • Impact of applied bias on the electron emission energy distribution was investigated.

  10. Terahertz study of ultrafast carrier dynamics in InGa/GaN multiple quantum wells

    DEFF Research Database (Denmark)

    Porte, Henrik; Turchinovich, Dmitry; Cooke, David

    2009-01-01

    Ultrafast carrier dynamics in InGaN/GaN multiple quantum wells is measured by time-resolved terahertz spectroscopy. The built-in piezoelectric field is initially screened by photoexcited, polarized carriers, and is gradullay restored as the carriers recombine. We observe a nonexponential decay...... of the carrier density. Time-integrated photoluminescence spectra have shown a complete screening of the built-in piezoelectric field at high excitation fluences. We also observe that the terahertz conductivity spectra differs from simple Drude conductivity, describing the response of free carriers, and are well...

  11. Microscopic theory of multiple-phonon-mediated dephasing and relaxation of quantum dots near a photonic band gap

    Science.gov (United States)

    Roy, Chiranjeeb; John, Sajeev

    2010-02-01

    We derive a quantum theory of the role of acoustic and optical phonons in modifying the optical absorption line shape, polarization dynamics, and population dynamics of a two-level atom (quantum dot) in the “colored” electromagnetic vacuum of a photonic band-gap (PBG) material. This is based on a microscopic Hamiltonian describing both radiative and vibrational processes quantum mechanically. We elucidate the extent to which phonon-assisted decay limits the lifetime of a single photon-atom bound state and derive the modified spontaneous emission dynamics due to coupling to various phonon baths. We demonstrate that coherent interaction with undamped phonons can lead to an enhanced lifetime of a photon-atom bound state in a PBG. This results in reduction of the steady-state atomic polarization but an increase in the fractionalized upper state population in the photon-atom bound state. We demonstrate, on the other hand, that the lifetime of the photon-atom bound state in a PBG is limited by the lifetime of phonons due to lattice anharmonicities (breakup of phonons into lower energy phonons) and purely nonradiative decay. We also derive the modified polarization decay and dephasing rates in the presence of such damping. This leads to a microscopic, quantum theory of the optical absorption line shapes. Our model and formalism provide a starting point for describing dephasing and relaxation in the presence of external coherent fields and multiple quantum dot interactions in electromagnetic reservoirs with radiative memory effects.

  12. Microscopic theory of multiple-phonon-mediated dephasing and relaxation of quantum dots near a photonic band gap

    International Nuclear Information System (INIS)

    Roy, Chiranjeeb; John, Sajeev

    2010-01-01

    We derive a quantum theory of the role of acoustic and optical phonons in modifying the optical absorption line shape, polarization dynamics, and population dynamics of a two-level atom (quantum dot) in the ''colored'' electromagnetic vacuum of a photonic band-gap (PBG) material. This is based on a microscopic Hamiltonian describing both radiative and vibrational processes quantum mechanically. We elucidate the extent to which phonon-assisted decay limits the lifetime of a single photon-atom bound state and derive the modified spontaneous emission dynamics due to coupling to various phonon baths. We demonstrate that coherent interaction with undamped phonons can lead to an enhanced lifetime of a photon-atom bound state in a PBG. This results in reduction of the steady-state atomic polarization but an increase in the fractionalized upper state population in the photon-atom bound state. We demonstrate, on the other hand, that the lifetime of the photon-atom bound state in a PBG is limited by the lifetime of phonons due to lattice anharmonicities (breakup of phonons into lower energy phonons) and purely nonradiative decay. We also derive the modified polarization decay and dephasing rates in the presence of such damping. This leads to a microscopic, quantum theory of the optical absorption line shapes. Our model and formalism provide a starting point for describing dephasing and relaxation in the presence of external coherent fields and multiple quantum dot interactions in electromagnetic reservoirs with radiative memory effects.

  13. Recent progress in heteronuclear long-range NMR of complex carbohydrates: 3D H2BC and clean HMBC

    DEFF Research Database (Denmark)

    Meier, Sebastian; Petersen, Bent O.; Duus, Jens Øllgaard

    2009-01-01

    carbohydrates whose structure has been determined by NMR, not least due to the enhanced resolution offered by the third dimension in 3D H2BC and the improved spectral quality due to artifact suppression in clean HMBC. Hence these new experiments set the scene to take advantage of the sensitivity boost achieved...... by the latest generation of cold probes for NMR structure determination of even larger and more complex carbohydrates in solution.......The new NMR experiments 3D H2BC and clean HMBC are explored for challenging applications to a complex carbohydrate at natural abundance of 13C. The 3D H2BC experiment is crucial for sequential assignment as it yields heteronuclear one- and two-bond together with COSY correlations for the 1H spins...

  14. Synthesis and investigation of new heteronuclear [Zn-La] coordination compounds based on unsaturated lanthanum complex with N,N'-tetraethyl-N''-trichloacetylphosphortriamide

    International Nuclear Information System (INIS)

    Amyirkhanov, O.V.; Sliva, T.Yu.; Moroz, O.V.; Trush, Je.A.; Frits'kij, Yi.O.

    2011-01-01

    New heteronuclear [Zn-La] coordination compounds, perspective luminescent materials, with general formulas [Zn(Ve)La(X) 2 (Ac)] ({Zn-La;Ve;X}) and [Zn(Vp)La(X) 2 (Ac)] ({Zn-La;Vp;X}) have been synthesized HX=CCl 3 C(O)NHP(O)[N(C 2 H 5 ) 2 ] 2 - N,N'-tetraethyl-N''-trichloracetylphosphortriamide, H 2 Ve and H 2 Vp are products of the condensation of 1,2-diaminoethane and 1,3-diaminopropane with o-vanillin, respectively). The composition of [Zn-La] complexes has been determined, and the coordination mode of a phosphorylated ligand has been suggested by element analysis, IR- and 1 H, 31 P NMR-spectroscopy.

  15. Universal core model for multiple-gate field-effect transistors with short channel and quantum mechanical effects

    Science.gov (United States)

    Shin, Yong Hyeon; Bae, Min Soo; Park, Chuntaek; Park, Joung Won; Park, Hyunwoo; Lee, Yong Ju; Yun, Ilgu

    2018-06-01

    A universal core model for multiple-gate (MG) field-effect transistors (FETs) with short channel effects (SCEs) and quantum mechanical effects (QMEs) is proposed. By using a Young’s approximation based solution for one-dimensional Poisson’s equations the total inversion charge density (Q inv ) in the channel is modeled for double-gate (DG) and surrounding-gate SG (SG) FETs, following which a universal charge model is derived based on the similarity of the solutions, including for quadruple-gate (QG) FETs. For triple-gate (TG) FETs, the average of DG and QG FETs are used. A SCEs model is also proposed considering the potential difference between the channel’s surface and center. Finally, a QMEs model for MG FETs is developed using the quantum correction compact model. The proposed universal core model is validated on commercially available three-dimensional ATLAS numerical simulations.

  16. Symmetries of quantum spaces. Subgroups and quotient spaces of quantum SU(2) and SO(3) groups

    International Nuclear Information System (INIS)

    Podles, P.

    1995-01-01

    We prove that each action of a compact matrix quantum group on a compact quantum space can be decomposed into irreducible representations of the group. We give the formula for the corresponding multiplicities in the case of the quotient quantum spaces. We describe the subgroups and the quotient spaces of quantum SU(2) and SO(3) groups. (orig.)

  17. Frequency up-conversion in nonpolar a-plane GaN/AlGaN based multiple quantum wells optimized for applications with silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Radosavljević, S.; Radovanović, J., E-mail: radovanovic@etf.bg.ac.rs; Milanović, V. [School of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11200 Belgrade (Serbia); Tomić, S. [Joule Physics Laboratory, School of Computing, Science and Engineering, University of Salford, Manchester M5 4WT (United Kingdom)

    2014-07-21

    We have described a method for structural parameters optimization of GaN/AlGaN multiple quantum well based up-converter for silicon solar cells. It involves a systematic tuning of individual step quantum wells by use of the genetic algorithm for global optimization. In quantum well structures, the up-conversion process can be achieved by utilizing nonlinear optical effects based on intersubband transitions. Both single and double step quantum wells have been tested in order to maximize the second order susceptibility derived from the density matrix formalism. The results obtained for single step wells proved slightly better and have been further pursued to obtain a more complex design, optimized for conversion of an entire range of incident photon energies.

  18. Efficient dipolar double quantum filtering under magic angle spinning without a (1)H decoupling field.

    Science.gov (United States)

    Courtney, Joseph M; Rienstra, Chad M

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Harsh photovoltaics using InGaN/GaN multiple quantum well schemes

    KAUST Repository

    Lien, Derhsien

    2015-01-01

    Harvesting solar energy at extremely harsh environments is of practical interest for building a self-powered harsh electronic system. However, working at high temperature and radiative environments adversely affects the performance of conventional solar cells. To improve the performance, GaN-based multiple quantum wells (MQWs) are introduced into the solar cells. The implementation of MQWs enables improved efficiency (+0.52%/K) and fill factor (+0.35%/K) with elevated temperature and shows excellent reliability under high-temperature operation. In addition, the GaN-based solar cell exhibits superior radiation robustness (lifetime >30 years under solar storm proton irradiation) due to their strong atomic bonding and direct-bandgap characteristics. This solar cell employing MQW nanostructures provides valuable routes for future developments in self-powered harsh electronics.

  20. Performance improvement of InGaN/GaN light-emitting diodes with triangular- shaped multiple quantum wells

    International Nuclear Information System (INIS)

    Zhu, Li-Hong; Zheng, Qing-Hong; Liu, Bao-Lin

    2009-01-01

    Triangular-shaped InGaN/GaN multiple quantum wells (MQWs) grown on a sapphire substrate were adopted as an active layer of light-emitting diodes (LEDs). The temperature dependence of the normalized integrated photoluminescence (PL) intensity showed that the internal quantum efficiency (IQE) of the LEDs with triangular-shaped MQW is much higher than that of the LEDs with conventional rectangular MQW structures. The electroluminescence (EL) spectra of the two series devices have been comparatively studied as functions of injection current. It was found that the device with the triangular-shaped MQW structure exhibited a stronger intensity and a narrower linewidth. Furthermore, the peak energy is nearly independent of the injection current, indicating that the triangular MQW LEDs are more efficient and stable than the rectangular ones

  1. Atom-dimer scattering in a heteronuclear mixture with a finite intraspecies scattering length

    Science.gov (United States)

    Gao, Chao; Zhang, Peng

    2018-04-01

    We study the three-body problem of two ultracold identical bosonic atoms (denoted by B ) and one extra atom (denoted by X ), where the scattering length aB X between each bosonic atom and atom X is resonantly large and positive. We calculate the scattering length aad between one bosonic atom and the shallow dimer formed by the other bosonic atom and atom X , and investigate the effect induced by the interaction between the two bosonic atoms. We find that even if this interaction is weak (i.e., the corresponding scattering length aB B is of the same order of the van der Waals length rvdW or even smaller), it can still induce a significant effect for the atom-dimer scattering length aad. Explicitly, an atom-dimer scattering resonance can always occur when the value of aB B varies in the region with | aB B|≲ rvdW . As a result, both the sign and the absolute value of aad, as well as the behavior of the aad-aB X function, depends sensitively on the exact value of aB B. Our results show that, for a good quantitative theory, the intraspecies interaction is required to be taken into account for this heteronuclear system, even if this interaction is weak.

  2. Trace Oxygen Sensitive Material Based on Two Porphyrin Derivatives in a Heterodimeric Complex

    Directory of Open Access Journals (Sweden)

    Eugenia Fagadar-Cosma

    2017-10-01

    Full Text Available The successful preparation of a novel dimer complex formed between 5,10,15,20-tetrakis(3,4-dimethoxyphenyl-porphyrin Fe(III chloride and (5,10,15,20-tetraphenylporphinato dichlorophosphorus(V chloride using the well-known reactivity of the P–X bond is reported. The obtained complex was characterized by UV-vis, Fourier transform infrared spectroscopy (FT-IR, fluorescence, 1H-NMR, 13C-NMR, and 31P-NMR spectroscopic techniques and also by additional Heteronuclear Single Quantum Coherence (HSQC and Heteronuclear Multiple Bond Correlation (HMBC experiments in order to correctly assign the NMR signals. Scanning electron microscopy (SEM and EDX quantifications completed the characterizations. This novel porphyrin dimer complex demonstrated fluorescence sensing of H2O2 in water for low oxygen concentrations in the range of 40–90 µM proving medical relevance for early diagnosis of diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and even cancer because higher concentrations of H2O2 than 50 μM are consideredcytotoxic for life. Due to its optical properties, this novel metalloporphyrin–porphyrin based complex is expected to show PDT and bactericidal activity under visible-light irradiation.

  3. An Improved Quantum-Behaved Particle Swarm Optimization Method for Economic Dispatch Problems with Multiple Fuel Options and Valve-Points Effects

    Directory of Open Access Journals (Sweden)

    Hong-Yun Zhang

    2012-09-01

    Full Text Available Quantum-behaved particle swarm optimization (QPSO is an efficient and powerful population-based optimization technique, which is inspired by the conventional particle swarm optimization (PSO and quantum mechanics theories. In this paper, an improved QPSO named SQPSO is proposed, which combines QPSO with a selective probability operator to solve the economic dispatch (ED problems with valve-point effects and multiple fuel options. To show the performance of the proposed SQPSO, it is tested on five standard benchmark functions and two ED benchmark problems, including a 40-unit ED problem with valve-point effects and a 10-unit ED problem with multiple fuel options. The results are compared with differential evolution (DE, particle swarm optimization (PSO and basic QPSO, as well as a number of other methods reported in the literature in terms of solution quality, convergence speed and robustness. The simulation results confirm that the proposed SQPSO is effective and reliable for both function optimization and ED problems.

  4. Ab initio multiple cloning algorithm for quantum nonadiabatic molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Makhov, Dmitry V.; Shalashilin, Dmitrii V. [Department of Chemistry, University of Leeds, Leeds LS2 9JT (United Kingdom); Glover, William J.; Martinez, Todd J. [Department of Chemistry and The PULSE Institute, Stanford University, Stanford, California 94305, USA and SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2014-08-07

    We present a new algorithm for ab initio quantum nonadiabatic molecular dynamics that combines the best features of ab initio Multiple Spawning (AIMS) and Multiconfigurational Ehrenfest (MCE) methods. In this new method, ab initio multiple cloning (AIMC), the individual trajectory basis functions (TBFs) follow Ehrenfest equations of motion (as in MCE). However, the basis set is expanded (as in AIMS) when these TBFs become sufficiently mixed, preventing prolonged evolution on an averaged potential energy surface. We refer to the expansion of the basis set as “cloning,” in analogy to the “spawning” procedure in AIMS. This synthesis of AIMS and MCE allows us to leverage the benefits of mean-field evolution during periods of strong nonadiabatic coupling while simultaneously avoiding mean-field artifacts in Ehrenfest dynamics. We explore the use of time-displaced basis sets, “trains,” as a means of expanding the basis set for little cost. We also introduce a new bra-ket averaged Taylor expansion (BAT) to approximate the necessary potential energy and nonadiabatic coupling matrix elements. The BAT approximation avoids the necessity of computing electronic structure information at intermediate points between TBFs, as is usually done in saddle-point approximations used in AIMS. The efficiency of AIMC is demonstrated on the nonradiative decay of the first excited state of ethylene. The AIMC method has been implemented within the AIMS-MOLPRO package, which was extended to include Ehrenfest basis functions.

  5. Analysis and investigation of temperature and hydrostatic pressure effects on optical characteristics of multiple quantum well slow light devices.

    Science.gov (United States)

    Abdolhosseini, Saeed; Kohandani, Reza; Kaatuzian, Hassan

    2017-09-10

    This paper represents the influences of temperature and hydrostatic pressure variations on GaAs/AlGaAs multiple quantum well slow light systems based on coherence population oscillations. An analytical model in non-integer dimension space is used to study the considerable effects of these parameters on optical properties of the slow light apparatus. Exciton oscillator strength and fractional dimension constants have special roles on the analytical model in fractional dimension. Hence, the impacts of hydrostatic pressure and temperature on exciton oscillator strength and fractional dimension quantity are investigated theoretically in this paper. Based on the achieved results, temperature and hydrostatic pressure play key roles on optical parameters of the slow light systems, such as the slow down factor and central energy of the device. It is found that the slope and value of the refractive index real part change with alterations of temperature and hydrostatic pressure in the range of 5-40 deg of Kelvin and 1 bar to 2 kbar, respectively. Thus, the peak value of the slow down factor can be adjusted by altering these parameters. Moreover, the central energy of the device shifts when the hydrostatic pressure is applied to the slow light device or temperature is varied. In comparison with previous reported experimental results, our simulations follow them successfully. It is shown that the maximum value of the slow down factor is estimated close to 5.5×10 4 with a fine adjustment of temperature and hydrostatic pressure. Meanwhile, the central energy shift of the slow light device rises up to 27 meV, which provides an appropriate basis for different optical devices in which multiple quantum well slow light is one of their essential subsections. This multiple quantum well slow light device has potential applications for use as a tunable optical buffer and pressure/temperature sensors.

  6. Time-resolved photoluminescence of Ga(NAsP) multiple quantum wells grown on Si substrate: Effects of rapid thermal annealing

    Energy Technology Data Exchange (ETDEWEB)

    Woscholski, R., E-mail: ronja.woscholski@physik.uni-marburg.de; Shakfa, M.K.; Gies, S.; Wiemer, M.; Rahimi-Iman, A.; Zimprich, M.; Reinhard, S.; Jandieri, K.; Baranovskii, S.D.; Heimbrodt, W.; Volz, K.; Stolz, W.; Koch, M.

    2016-08-31

    Time-resolved photoluminescence (TR-PL) spectroscopy has been used to study the impact of rapid thermal annealing (RTA) on the optical properties and carrier dynamics in Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates. TR-PL measurements reveal an enhancement in the PL efficiency when the RTA temperature is increased up to 925 °C. Then, the PL intensity dramatically decreases with the annealing temperature. This behavior is explained by the variation of the disorder degree in the studied structures. The analysis of the low-temperature emission-energy-dependent PL decay time enables us to characterize the disorder in the Ga(NAsP) MQWHs. The theoretically extracted energy-scales of disorder confirm the experimental observations. - Highlights: • Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates • Impact of rapid thermal annealing on the optical properties and carrier dynamics • Time resolved photoluminescence spectroscopy was applied. • PL transients became continuously faster with increasing annealing temperature. • Enhancement in the PL efficiency with increasing annealing temperature up to 925 °C.

  7. Time-resolved photoluminescence of Ga(NAsP) multiple quantum wells grown on Si substrate: Effects of rapid thermal annealing

    International Nuclear Information System (INIS)

    Woscholski, R.; Shakfa, M.K.; Gies, S.; Wiemer, M.; Rahimi-Iman, A.; Zimprich, M.; Reinhard, S.; Jandieri, K.; Baranovskii, S.D.; Heimbrodt, W.; Volz, K.; Stolz, W.; Koch, M.

    2016-01-01

    Time-resolved photoluminescence (TR-PL) spectroscopy has been used to study the impact of rapid thermal annealing (RTA) on the optical properties and carrier dynamics in Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates. TR-PL measurements reveal an enhancement in the PL efficiency when the RTA temperature is increased up to 925 °C. Then, the PL intensity dramatically decreases with the annealing temperature. This behavior is explained by the variation of the disorder degree in the studied structures. The analysis of the low-temperature emission-energy-dependent PL decay time enables us to characterize the disorder in the Ga(NAsP) MQWHs. The theoretically extracted energy-scales of disorder confirm the experimental observations. - Highlights: • Ga(NAsP) multiple quantum well heterostructures (MQWHs) grown on silicon substrates • Impact of rapid thermal annealing on the optical properties and carrier dynamics • Time resolved photoluminescence spectroscopy was applied. • PL transients became continuously faster with increasing annealing temperature. • Enhancement in the PL efficiency with increasing annealing temperature up to 925 °C

  8. Acousto-optic modulation of III-V semiconductor multiple quantum wells

    International Nuclear Information System (INIS)

    Smith, D.L.; Kogan, S.M.; Ruden, P.P.; Mailhiot, C.

    1996-01-01

    We present an analysis of the effect of surface acoustic waves (SAW close-quote s) on the optical properties of III-V semiconductor multiple quantum wells (MQW close-quote s). Modulation spectra at the fundamental and second harmonic of the SAW frequency are presented. The SAW modulates the optical properties of the MQW primarily by changing optical transition energies. The SAW generates both strains, which modulate the transition energies by deformation potential effects, and electric fields, which modulate the transition energies by the quantum confined Stark effect. We find that modulation of the transition energies by strain effects is usually more important than by electric-field effects. If large static electric fields occur in the MQW, the SAW-generated electric field can mix with the static field to give optical modulation, which is comparable in magnitude to modulation from the deformation potential effect. If there are no large static electric fields, modulation by the SAW-generated fields is negligible. A large static electric field distributes oscillator strength among the various optical transitions so that no single transition is as strong as the primary allowed transitions without a static electric field. To achieve the maximum modulation for fixed SAW parameters, it is best to modulate a strong optical transition. Thus optimum modulation occurs when there are no large static electric fields present and that modulation is primarily from deformation potential effects. We specifically consider Ga x In 1-x As/Ga x Al 1-x As MQW close-quote s grown on (100) and (111) oriented substrates, but our general conclusions apply to other type I MQW close-quote s fabricated from III-V semiconductors. copyright 1996 The American Physical Society

  9. Effects of InGaN barriers with low indium content on internal quantum efficiency of blue InGaN multiple quantum wells

    International Nuclear Information System (INIS)

    Lai, Wang; Jia-Xing, Wang; Wei, Zhao; Xiang, Zou; Yi, Luo

    2010-01-01

    Blue In 0.2 Ga 0.8 N multiple quantum wells (MQWs) with In x Ga 1–x N (x = 0.01–0.04) barriers are grown by metal organic vapour phase epitaxy. The internal quantum efficiencies (IQEs) of these MQWs are studied in a way of temperature-dependent photoluminescence spectra. Furthermore, a 2-channel Arrhenius model is used to analyse the nonradiative recombination centres (NRCs). It is found that by adopting the InGaN barrier beneath the lowest well, it is possible to reduce the strain hence the NRCs in InGaN MQWs. By optimizing the thickness and the indium content of the InGaN barriers, the IQEs of InGaN/InGaN MQWs can be increased by about 2.5 times compared with conventional InGaN/GaN MQWs. On the other hand, the incorporation of indium atoms into the intermediate barriers between adjacent wells does not improve IQE obviously. In addition, the indium content of the intermediate barriers should match with that of the lowest barrier to avoid relaxation. (condensed matter: structure, thermal and mechanical properties)

  10. An improved synthesis of α-13C glycine and heteronuclear NMR studies of its incorporation into thioredoxin

    International Nuclear Information System (INIS)

    Wishart, D.S.; Sykes, B.D.; Richards, F.M.

    1992-01-01

    We present an improved method to easily prepare gram quantities of α- 13 C glycine beginning from K 13 CN. The four step synthesis involves the production of an N, N-diphenyl-cyanoformamidine intermediate through the coupling of cyanide to N, N-diphenylcarbodiimide. Subsequent reduction by LiAlH 4 and hydrolysis of the resulting amidine produces fully enriched α- 13 C labelled glycine with a 45-50% yield. This relatively fast and simple synthesis uses only commonly available compounds and requires no special equipment, making the process easy to perform in any well equipped biochemistry laboratory. We further demonstrate that the product may be used, without extensive purification, to specifically label bacterially expressed proteins (E. coli thioredoxin) through standard biosynthetic procedures. We also show that the 13 C glycine-labelled protein may be readily analyzed using commonly available heteronuclear NMR techniques. Complete assignments for all 9 glycines of native E. coli thoredoxin are presented. (Author)

  11. Quantum control of vibrational excitations in a heteronuclear ...

    Indian Academy of Sciences (India)

    WINTEC

    Optimal control theory is applied to obtain infrared laser pulses for selective vibrational exci- tation in a ... introduced in the field prior to evaluation of the cost functional for better field shape. Conjugate ... focused greater attention on optimal control of quan- tum states ... from the ground state to the first excited state in a.

  12. Young Quantum Meetings

    CERN Document Server

    Aerts, Sven; Ronde, Christian de; Probing the Meaning of Quantum Mechanics : Physical, Philosophical, and Logical Perspectives

    2014-01-01

    This book provides a new original perspective on one of the most fascinating and important open questions in science: What is quantum mechanics talking about? Quantum theory is perhaps our best confirmed physical theory. However, in spite of its great empirical effectiveness and the subsequent technological developments that it gave rise to in the 20th century, from the interpretation of the periodic table of elements to CD players, holograms and quantum state teleportation, it stands even today without a universally accepted interpretation. The novelty of the book comes from the multiple view

  13. Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer

    Directory of Open Access Journals (Sweden)

    Yang XF

    2010-01-01

    Full Text Available Abstract We investigate quantum interference effects in a double-Aharonov-Bohm (AB interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green’s function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2π to π by controlling the difference of the magnetic fluxes threading the two quantum rings.

  14. Quantum entanglement and the dissociation process of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Rodolfo O; Molina-Espiritu, Moyocoyani [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340-Mexico DF (Mexico); Flores-Gallegos, Nelson [Unidad Profesional Interdisciplinaria de IngenierIa, Campus Guanajuato del Instituto Politecnico Nacional, 36275-Guanajuato (Mexico); Plastino, A R; Angulo, Juan Carlos; Dehesa, Jesus S [Instituto Carlos I de Fisica Teorica y Computacional, and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Antolin, Juan, E-mail: esquivel@xanum.uam.mx, E-mail: arplastino@ugr.es [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2011-09-14

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  15. Solution structure of human intestinal fatty acid binding protein: Implications for ligand entry and exit

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Fengli [Boston University School of Medicine, Department of Biophysics (United States); Luecke, Christian [Johann Wolfgang Goethe-Universitaet (Germany); Baier, Leslie J. [NIDDK, NIH, Phoenix Epidemiology and Clinical Research Branch (United States); Sacchettini, James C. [Texas A and M University, Department of Biochemistry and Biophysics (United States); Hamilton, James A. [Boston University School of Medicine, Department of Biophysics (United States)

    1997-04-15

    The human intestinal fatty acid binding protein (I-FABP) is a small (131 amino acids) protein which binds dietary long-chain fatty acids in the cytosol of enterocytes. Recently, an alanine to threonine substitution at position 54 in I-FABP has been identified which affects fatty acid binding and transport, and is associated with the development of insulin resistance in several populations including Mexican-Americans and Pima Indians. To investigate the molecular basis of the binding properties of I-FABP, the 3D solution structure of the more common form of human I-FABP (Ala54) was studied by multidimensional NMR spectroscopy.Recombinant I-FABP was expressed from E. coli in the presence and absence of 15N-enriched media. The sequential assignments for non-delipidated I-FABP were completed by using 2D homonuclear spectra (COSY, TOCSY and NOESY) and 3D heteronuclear spectra(NOESY-HMQC and TOCSY-HMQC). The tertiary structure of human I-FABP was calculated by using the distance geometry program DIANA based on 2519 distance constraints obtained from the NMR data. Subsequent energy minimization was carried out by using the program SYBYL in the presence of distance constraints. The conformation of human I-FABP consists of 10 antiparallel {beta}-strands which form two nearly orthogonal {beta}-sheets of five strands each, and two short {alpha}-helices that connect the {beta}-strands A and B. The interior of the protein consists of a water-filled cavity between the two {beta}-sheets. The NMR solution structure of human I-FABP is similar to the crystal structure of rat I-FABP.The NMR results show significant conformational variability of certain backbone segments around the postulated portal region for the entry and exit of fatty acid ligand.

  16. Solution structure of human intestinal fatty acid binding protein: Implications for ligand entry and exit

    International Nuclear Information System (INIS)

    Zhang Fengli; Luecke, Christian; Baier, Leslie J.; Sacchettini, James C.; Hamilton, James A.

    1997-01-01

    The human intestinal fatty acid binding protein (I-FABP) is a small (131 amino acids) protein which binds dietary long-chain fatty acids in the cytosol of enterocytes. Recently, an alanine to threonine substitution at position 54 in I-FABP has been identified which affects fatty acid binding and transport, and is associated with the development of insulin resistance in several populations including Mexican-Americans and Pima Indians. To investigate the molecular basis of the binding properties of I-FABP, the 3D solution structure of the more common form of human I-FABP (Ala54) was studied by multidimensional NMR spectroscopy.Recombinant I-FABP was expressed from E. coli in the presence and absence of 15N-enriched media. The sequential assignments for non-delipidated I-FABP were completed by using 2D homonuclear spectra (COSY, TOCSY and NOESY) and 3D heteronuclear spectra(NOESY-HMQC and TOCSY-HMQC). The tertiary structure of human I-FABP was calculated by using the distance geometry program DIANA based on 2519 distance constraints obtained from the NMR data. Subsequent energy minimization was carried out by using the program SYBYL in the presence of distance constraints. The conformation of human I-FABP consists of 10 antiparallel β-strands which form two nearly orthogonal β-sheets of five strands each, and two short α-helices that connect the β-strands A and B. The interior of the protein consists of a water-filled cavity between the two β-sheets. The NMR solution structure of human I-FABP is similar to the crystal structure of rat I-FABP.The NMR results show significant conformational variability of certain backbone segments around the postulated portal region for the entry and exit of fatty acid ligand

  17. Interfacial sharpness and intermixing in a Ge-SiGe multiple quantum well structure

    Science.gov (United States)

    Bashir, A.; Gallacher, K.; Millar, R. W.; Paul, D. J.; Ballabio, A.; Frigerio, J.; Isella, G.; Kriegner, D.; Ortolani, M.; Barthel, J.; MacLaren, I.

    2018-01-01

    A Ge-SiGe multiple quantum well structure created by low energy plasma enhanced chemical vapour deposition, with nominal well thickness of 5.4 nm separated by 3.6 nm SiGe spacers, is analysed quantitatively using scanning transmission electron microscopy. Both high angle annular dark field imaging and electron energy loss spectroscopy show that the interfaces are not completely sharp, suggesting that there is some intermixing of Si and Ge at each interface. Two methods are compared for the quantification of the spectroscopy datasets: a self-consistent approach that calculates binary substitutional trends without requiring experimental or computational k-factors from elsewhere and a standards-based cross sectional calculation. Whilst the cross section approach is shown to be ultimately more reliable, the self-consistent approach provides surprisingly good results. It is found that the Ge quantum wells are actually about 95% Ge and that the spacers, whilst apparently peaking at about 35% Si, contain significant interdiffused Ge at each side. This result is shown to be not just an artefact of electron beam spreading in the sample, but mostly arising from a real chemical interdiffusion resulting from the growth. Similar results are found by use of X-ray diffraction from a similar area of the sample. Putting the results together suggests a real interdiffusion with a standard deviation of about 0.87 nm, or put another way—a true width defined from 10%-90% of the compositional gradient of about 2.9 nm. This suggests an intrinsic limit on how sharp such interfaces can be grown by this method and, whilst 95% Ge quantum wells (QWs) still behave well enough to have good properties, any attempt to grow thinner QWs would require modifications to the growth procedure to reduce this interdiffusion, in order to maintain a composition of ≥95% Ge.

  18. Multi-dimensional photonic states from a quantum dot

    Science.gov (United States)

    Lee, J. P.; Bennett, A. J.; Stevenson, R. M.; Ellis, D. J. P.; Farrer, I.; Ritchie, D. A.; Shields, A. J.

    2018-04-01

    Quantum states superposed across multiple particles or degrees of freedom offer an advantage in the development of quantum technologies. Creating these states deterministically and with high efficiency is an ongoing challenge. A promising approach is the repeated excitation of multi-level quantum emitters, which have been shown to naturally generate light with quantum statistics. Here we describe how to create one class of higher dimensional quantum state, a so called W-state, which is superposed across multiple time bins. We do this by repeated Raman scattering of photons from a charged quantum dot in a pillar microcavity. We show this method can be scaled to larger dimensions with no reduction in coherence or single-photon character. We explain how to extend this work to enable the deterministic creation of arbitrary time-bin encoded qudits.

  19. Quantum memory Quantum memory

    Science.gov (United States)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  20. Fabrication of GaAs concentric multiple quantum rings by droplet epitaxy

    International Nuclear Information System (INIS)

    Somaschini, C; Bietti, S; Sanguinetti, S; Koguchi, N; Fedorov, A; Abbarchi, M; Gurioli, M

    2009-01-01

    We present the fabrication of a novel quantum nanostructure, constituted by three concentric quantum rings by droplet epitaxy. Atomic Force Microscopy and photoluminescence characterization of these nanostructures is reported.

  1. Mathematics and quantum mechanics

    International Nuclear Information System (INIS)

    Santander, M.

    2000-01-01

    Several episodes in the relation between Mathematics and Quantum Mechanics are discussed; and the emphasis is put in the existence of multiple and sometimes unexpected connections between ideas originating in Mathematics and in Quantum Physics. The question of the unresasonable effectiveness of Mathematics in Physics is also presented in the same light. (Author) 3 refs

  2. Effects of Hydrostatic Pressure and Electric Field on the Electron-Related Optical Properties in GaAs Multiple Quantum Well.

    Science.gov (United States)

    Ospina, D A; Mora-Ramos, M E; Duque, C A

    2017-02-01

    The properties of the electronic structure of a finite-barrier semiconductor multiple quantum well are investigated taking into account the effects of the application of a static electric field and hydrostatic pressure. With the information of the allowed quasi-stationary energy states, the coefficients of linear and nonlinear optical absorption and of the relative refractive index change associated to transitions between allowed subbands are calculated with the use of a two-level scheme for the density matrix equation of motion and the rotating wave approximation. It is noticed that the hydrostatic pressure enhances the amplitude of the nonlinear contribution to the optical response of the multiple quantum well, whilst the linear one becomes reduced. Besides, the calculated coefficients are blueshifted due to the increasing of the applied electric field, and shows systematically dependence upon the hydrostatic pressure. The comparison of these results with those related with the consideration of a stationary spectrum of states in the heterostructure-obtained by placing infinite confining barriers at a conveniently far distance-shows essential differences in the pressure-induced effects in the sense of resonant frequency shifting as well as in the variation of the amplitudes of the optical responses.

  3. Quantum-Well Thermophotovoltaic Cells

    Science.gov (United States)

    Freudlich, Alex; Ignatiev, Alex

    2009-01-01

    Thermophotovoltaic cells containing multiple quantum wells have been invented as improved means of conversion of thermal to electrical energy. The semiconductor bandgaps of the quantum wells can be tailored to be narrower than those of prior thermophotovoltaic cells, thereby enabling the cells to convert energy from longer-wavelength photons that dominate the infrared-rich spectra of typical thermal sources with which these cells would be used. Moreover, in comparison with a conventional single-junction thermophotovoltaic cell, a cell containing multiple narrow-bandgap quantum wells according to the invention can convert energy from a wider range of wavelengths. Hence, the invention increases the achievable thermal-to-electrical energy-conversion efficiency. These thermophotovoltaic cells are expected to be especially useful for extracting electrical energy from combustion, waste-heat, and nuclear sources having temperatures in the approximate range from 1,000 to 1,500 C.

  4. Femtosecond coherent control of absorption and free induction decay in a GaAs multiple quantum well

    CERN Document Server

    Yee, D S

    2000-01-01

    Excitonic polarizations are coherently excited using two phase-locked pulses. By probing the linear propagation of the pulses through a GaAs/AlGaAs multiple quantum well sample, we directly demonstrate the intriguing interaction between the coherent exciton polarizations and the controlling pulses. It is shown that the second pulse can be either strongly amplified by taking up energy gained from the destruction of the exciton polarization or drastically decreased by giving up all its energy to excitons. The temporal signatures of the transmitted pulse shapes agree well with model calculations.

  5. Quantum Secure Group Communication.

    Science.gov (United States)

    Li, Zheng-Hong; Zubairy, M Suhail; Al-Amri, M

    2018-03-01

    We propose a quantum secure group communication protocol for the purpose of sharing the same message among multiple authorized users. Our protocol can remove the need for key management that is needed for the quantum network built on quantum key distribution. Comparing with the secure quantum network based on BB84, we show our protocol is more efficient and securer. Particularly, in the security analysis, we introduce a new way of attack, i.e., the counterfactual quantum attack, which can steal information by "invisible" photons. This invisible photon can reveal a single-photon detector in the photon path without triggering the detector. Moreover, the photon can identify phase operations applied to itself, thereby stealing information. To defeat this counterfactual quantum attack, we propose a quantum multi-user authorization system. It allows us to precisely control the communication time so that the attack can not be completed in time.

  6. Block-free optical quantum Banyan network based on quantum state fusion and fission

    International Nuclear Information System (INIS)

    Zhu Chang-Hua; Meng Yan-Hong; Quan Dong-Xiao; Zhao Nan; Pei Chang-Xing

    2014-01-01

    Optical switch fabric plays an important role in building multiple-user optical quantum communication networks. Owing to its self-routing property and low complexity, a banyan network is widely used for building switch fabric. While, there is no efficient way to remove internal blocking in a banyan network in a classical way, quantum state fusion, by which the two-dimensional internal quantum states of two photons could be combined into a four-dimensional internal state of a single photon, makes it possible to solve this problem. In this paper, we convert the output mode of quantum state fusion from spatial-polarization mode into time-polarization mode. By combining modified quantum state fusion and quantum state fission with quantum Fredkin gate, we propose a practical scheme to build an optical quantum switch unit which is block free. The scheme can be extended to building more complex units, four of which are shown in this paper. (general)

  7. Excitation density dependence of the photoluminescence from Cd{sub x}Hg{sub 1-x}Te multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Tonheim, C R; Selvig, E; Nicolas, S; Breivik, M; Haakenaasen, R [Norwegian Defence Research Establishment, PO Box 25, N-2027 Kjeller (Norway); Gunnaes, A E [Department of Physics, University of Oslo, Boks 1048 Blindern, N-0316 Oslo (Norway)], E-mail: celin.tonheim@ffi.no

    2008-03-15

    A study of the photoluminescence from a four-period Cd{sub x}Hg{sub 1-x}Te multiple quantum well structure at 11 K as a function of excitation density is presented. High-resolution X-ray diffraction and transmission electron microscopy revealed that the quantum well structure is of high quality. This was supported by the narrow photoluminescence peak originating in the ground state electron - heavy hole transition, with a full width at half maximum of only 7.4 meV for an excitation density of 1.3 W/cm{sup 2}. When the excitation density was increased from 1.3 to 23.4 W/cm{sup 2}, the peak position was shifted toward higher energy by 2.6 meV and the full width at half maximum increased from 7.4 to 10.9 meV.

  8. Infrared photoluminescence of high In-content InN/InGaN multiple-quantum-wells

    Energy Technology Data Exchange (ETDEWEB)

    Valdueza-Felip, Sirona; Naranjo, Fernando B.; Gonzalez-Herraez, Miguel [Electronics Department, University of Alcala, Alcala de Henares (Spain); Rigutti, Lorenzo; Julien, Francois H. [Institut d' Electronique Fondamentale, University of Paris Sud XI, UMR 8622 CNRS, Orsay (France); Lacroix, Bertrand; Ruterana, Pierre [Centre de Recherche sur les Ions les Materiaux et la Photonique (CIMAP), UMR 6252, CNRS, ENSICAEN, CEA, UCBN, Caen (France); Fernandez, Susana [Departamento de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Madrid (Spain); Monroy, Eva [CEA Grenoble, INAC/SP2M, Grenoble (France)

    2012-01-15

    We report on the thermal evolution of the photoluminescence (PL) from high In-content InN/In{sub 0.9}Ga{sub 0.1}N multiple-quantum wells (MQWs) synthesized by plasma-assisted molecular-beam epitaxy on GaN-on-sapphire templates. The structural quality and the well/barrier thickness uniformity in the MQW structure are assessed by X-ray diffraction and transmission electron microscopy measurements. PL results are compared with the luminescence from a 1-{mu}m-thick InN reference sample. In both cases, the dominant low-temperature (5 K) PL emission peaks at {proportional_to}0.73 eV with a full width at half maximum of {proportional_to}86 meV. The InN layer displays an S-shape evolution of the emission peak energy with temperaure, explained in terms of carrier localization. A carrier localization energy of {proportional_to}12 meV is estimated for the InN layer, in good agreement with the expected carrier concentration. In the case of the MQW structure, an enhancement of the carrier localization associated to the piezoelectric field results in an improved thermal stability of the PL intensity, reaching an internal quantum efficiency of {proportional_to}16%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Infrared photoluminescence of high In-content InN/InGaN multiple-quantum-wells

    International Nuclear Information System (INIS)

    Valdueza-Felip, Sirona; Naranjo, Fernando B.; Gonzalez-Herraez, Miguel; Rigutti, Lorenzo; Julien, Francois H.; Lacroix, Bertrand; Ruterana, Pierre; Fernandez, Susana; Monroy, Eva

    2012-01-01

    We report on the thermal evolution of the photoluminescence (PL) from high In-content InN/In 0.9 Ga 0.1 N multiple-quantum wells (MQWs) synthesized by plasma-assisted molecular-beam epitaxy on GaN-on-sapphire templates. The structural quality and the well/barrier thickness uniformity in the MQW structure are assessed by X-ray diffraction and transmission electron microscopy measurements. PL results are compared with the luminescence from a 1-μm-thick InN reference sample. In both cases, the dominant low-temperature (5 K) PL emission peaks at ∝0.73 eV with a full width at half maximum of ∝86 meV. The InN layer displays an S-shape evolution of the emission peak energy with temperature, explained in terms of carrier localization. A carrier localization energy of ∝12 meV is estimated for the InN layer, in good agreement with the expected carrier concentration. In the case of the MQW structure, an enhancement of the carrier localization associated to the piezoelectric field results in an improved thermal stability of the PL intensity, reaching an internal quantum efficiency of ∝16%. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Feng; Ikeda, Masao, E-mail: mikeda2013@sinano.ac.cn; Liu, Jianping; Zhang, Shuming [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Zhou, Kun; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Institute of Semiconductors (CAS), Beijing 100083 (China); Liu, Zongshun [Institute of Semiconductors (CAS), Beijing 100083 (China)

    2015-07-21

    Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.

  11. A quantum extended Kalman filter

    International Nuclear Information System (INIS)

    Emzir, Muhammad F; Woolley, Matthew J; Petersen, Ian R

    2017-01-01

    In quantum physics, a stochastic master equation (SME) estimates the state (density operator) of a quantum system in the Schrödinger picture based on a record of measurements made on the system. In the Heisenberg picture, the SME is a quantum filter. For a linear quantum system subject to linear measurements and Gaussian noise, the dynamics may be described by quantum stochastic differential equations (QSDEs), also known as quantum Langevin equations, and the quantum filter reduces to a so-called quantum Kalman filter. In this article, we introduce a quantum extended Kalman filter (quantum EKF), which applies a commutative approximation and a time-varying linearization to systems of nonlinear QSDEs. We will show that there are conditions under which a filter similar to a classical EKF can be implemented for quantum systems. The boundedness of estimation errors and the filtering problem with ‘state-dependent’ covariances for process and measurement noises are also discussed. We demonstrate the effectiveness of the quantum EKF by applying it to systems that involve multiple modes, nonlinear Hamiltonians, and simultaneous jump-diffusive measurements. (paper)

  12. A quantum extended Kalman filter

    Science.gov (United States)

    Emzir, Muhammad F.; Woolley, Matthew J.; Petersen, Ian R.

    2017-06-01

    In quantum physics, a stochastic master equation (SME) estimates the state (density operator) of a quantum system in the Schrödinger picture based on a record of measurements made on the system. In the Heisenberg picture, the SME is a quantum filter. For a linear quantum system subject to linear measurements and Gaussian noise, the dynamics may be described by quantum stochastic differential equations (QSDEs), also known as quantum Langevin equations, and the quantum filter reduces to a so-called quantum Kalman filter. In this article, we introduce a quantum extended Kalman filter (quantum EKF), which applies a commutative approximation and a time-varying linearization to systems of nonlinear QSDEs. We will show that there are conditions under which a filter similar to a classical EKF can be implemented for quantum systems. The boundedness of estimation errors and the filtering problem with ‘state-dependent’ covariances for process and measurement noises are also discussed. We demonstrate the effectiveness of the quantum EKF by applying it to systems that involve multiple modes, nonlinear Hamiltonians, and simultaneous jump-diffusive measurements.

  13. Enhancement of coherent acoustic phonons in InGaN multiple quantum wells

    Science.gov (United States)

    Hafiz, Shopan D.; Zhang, Fan; Monavarian, Morteza; Avrutin, Vitaliy; Morkoç, Hadis; Özgür, Ümit

    2015-03-01

    Enhancement of coherent zone folded longitudinal acoustic phonon (ZFLAP) oscillations at terahertz frequencies was demonstrated in InGaN multiple quantum wells (MQWs) by using wavelength degenerate time resolved differential transmission spectroscopy. Screening of the piezoelectric field in InGaN MQWs by photogenerated carriers upon femtosecond pulse excitation gave rise to terahertz ZFLAPs, which were monitored at the Brillouin zone center in the transmission geometry. MQWs composed of 10 pairs InxGa1-xN wells and In0.03Ga0.97N barriers provided coherent phonon frequencies of 0.69-0.80 THz depending on the period of MQWs. Dependences of ZFLAP amplitude on excitation density and wavelength were also investigated. Possibility of achieving phonon cavity, incorporating a MQW placed between two AlN/GaN phonon mirrors designed to exhibit large acoustic gaps at the zone center, was also explored.

  14. Applications of one-dimensional or two-dimensional nuclear magnetic resonance to the structural and conformational study of oligosaccharides. Design and adjustment of new techniques

    International Nuclear Information System (INIS)

    Berthault, Patrick

    1988-01-01

    Oligosaccharides are natural compounds of huge importance as they intervene in all metabolic processes of cell life. Before the determination of structure-activity relationships, a precise knowledge of their chemical nature is therefore required. Thus, this research thesis aims at describing various experiments of high resolution nuclear magnetic resonance (NMR), and at demonstrating their applications on four oligosaccharides. After a brief description of NMR principles by using a conventional description and also a formalism derived from quantum mechanics, the author outlines the weaknesses of old NMR techniques, and introduces new techniques by using scalar couplings, by processing magnetization transfers with one-dimensional hetero-nuclear experiments. General principles of two-dimensional experiments are then presented and developed in terms of simple correlations, multiple correlations, correlations via double quantum coherencies. Experiments with light water are then described, and different experiments are performed to determine the structure and conformation of each unit. Bipolar interactions are then addressed to highlight proximities between atoms [fr

  15. Exact synthesis of three-qubit quantum circuits from non-binary quantum gates

    Science.gov (United States)

    Yang, Guowu; Hung, William N. N.; Song, Xiaoyu; Perkowski, Marek A.

    2010-04-01

    Because of recent nano-technological advances, nano-structured systems have become highly ordered, making it quantum computing schemas possible. We propose an approach to optimally synthesise quantum circuits from non-permutative quantum gates such as controlled-square-root-of-not (i.e., controlled-V). Our approach reduces the synthesis problem to multiple-valued optimisation and uses group theory. We devise a novel technique that transforms the quantum logic synthesis problem from a multi-valued constrained optimisation problem to a permutable representation. The transformation enables us to use group theory to exploit the symmetric properties of the synthesis problem. Assuming a cost of one for each two-qubit gate, we found all reversible circuits with quantum costs of 4, 5, 6, etc., and give another algorithm to realise these reversible circuits with quantum gates. The approach can be used for both binary permutative deterministic circuits and probabilistic circuits such as controlled random-number generators and hidden Markov models.

  16. Enhanced Solar Cell Conversion Efficiency of InGaN/GaN Multiple Quantum Wells by Piezo-Phototronic Effect.

    Science.gov (United States)

    Jiang, Chunyan; Jing, Liang; Huang, Xin; Liu, Mengmeng; Du, Chunhua; Liu, Ting; Pu, Xiong; Hu, Weiguo; Wang, Zhong Lin

    2017-09-26

    The piezo-phototronic effect is the tuning of piezoelectric polarization charges at the interface to largely enhance the efficiency of optoelectronic processes related to carrier separation or recombination. Here, we demonstrated the enhanced short-circuit current density and the conversion efficiency of InGaN/GaN multiple quantum well solar cells with an external stress applied on the device. The external-stress-induced piezoelectric charges generated at the interfaces of InGaN and GaN compensate the piezoelectric charges induced by lattice mismatch stress in the InGaN wells. The energy band realignment is calculated with a self-consistent numerical model to clarify the enhancement mechanism of optical-generated carriers. This research not only theoretically and experimentally proves the piezo-phototronic effect modulated the quantum photovoltaic device but also provides a great promise to maximize the use of solar energy in the current energy revolution.

  17. A New Benzoyl Compound Isolated from the Endophytic Fungi of Kandis Gajah (Garcinia griffithii and Asam Kandis (Garcinia cowa

    Directory of Open Access Journals (Sweden)

    Elfita Elfita

    2016-12-01

    Full Text Available Garcinia griffithii and Garcinia cowa belong to the genus Garcinia. The genus Garcinia has been known to be a rich source of secondary metabolites, such as xanthones, benzophenones, flavonoids, steroids, terpenoids, and other phenolic derivatives. Previous investigations of endophytic fungi from G. griffithii revealed the presence of three compounds not found in the host. In order to the continue the phytochemical work on endophytic fungi of G. griffithii, the constituent of the endophytic fungi of G. griffithii was re-examined. In this study, a benzoyl compound similar to that found in the endophytic fungus of G. cowa was observed. The same benzoyl compound was also isolated from the endophytic fungus Acremonium sp of G. griffithii and Aspergillus sp of G. cowa with cultivation of eight weeks in static conditions at room temperature. The culture medium was partitioned using ethyl acetate and evaporated to obtain the concentrated extract. Isolation of compounds was performed using the chromatography method. The chemical structure was proposed on the basis of spectroscopic data, including ultraviolet (UV, infrared (IR, mass spectrometry (MS, proton nuclear magnetic resonance (1H-NMR, carbon nuclear magnetic resonance (13C-NMR, heteronuclear single-quantum correlation spectroscopy (HSQC, heteronuclear multiple-bond correlation spectroscopy (HMBC, and correlation spectroscopy (COSY.

  18. Aptamer/quantum dot-based simultaneous electrochemical detection of multiple small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Haixia [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Jiang Bingying [School of Chemistry and Chemical Engineering, Chongqing University of Technology, Chongqing 400040 (China); Xiang Yun, E-mail: yunatswu@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zhang Yuyong; Chai Yaqin [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Yuan Ruo, E-mail: yuanruo@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2011-03-04

    A novel strategy for 'signal on' and sensitive one-spot simultaneous detection of multiple small molecular analytes based on electrochemically encoded barcode quantum dot (QD) tags is described. The target analytes, adenosine triphosphate (ATP) and cocaine, respectively, are sandwiched between the corresponding set of surface-immobilized primary binding aptamers and the secondary binding aptamer/QD bioconjugates. The captured QDs yield distinct electrochemical signatures after acid dissolution, whose position and size reflect the identity and level, respectively, of the corresponding target analytes. Due to the inherent amplification feature of the QD labels and the 'signal on' detection scheme, as well as the sensitive monitoring of the metal ions released upon acid dissolution of the QD labels, low detection limits of 30 nM and 50 nM were obtained for ATP and cocaine, respectively, in our assays. Our multi-analyte sensing system also shows high specificity to target analytes and promising applicability to complex sample matrix, which makes the proposed assay protocol an attractive route for screening of small molecules in clinical diagnosis.

  19. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning

    Energy Technology Data Exchange (ETDEWEB)

    Shmyreva, Anna A. [Center for Magnetic Resonance, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Safdari, Majid; Furó, István [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Dvinskikh, Sergey V., E-mail: sergeid@kth.se [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg 199034 (Russian Federation)

    2016-06-14

    Orders of magnitude decrease of {sup 207}Pb and {sup 199}Hg NMR longitudinal relaxation times T{sub 1} upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX{sub 2} (Me = Pb, Hg and X = Cl, Br, I). In lead(II) halides, the most dramatic decrease of T{sub 1} relative to that in a static sample is in PbI{sub 2}, while it is smaller but still significant in PbBr{sub 2}, and not detectable in PbCl{sub 2}. The effect is magnetic-field dependent but independent of the spinning speed in the range 200–15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  20. Barrier potential design criteria in multiple-quantum-well-based solar-cell structures

    Science.gov (United States)

    Mohaidat, Jihad M.; Shum, Kai; Wang, W. B.; Alfano, R. R.

    1994-01-01

    The barrier potential design criteria in multiple-quantum-well (MQW)-based solar-cell structures is reported for the purpose of achieving maximum efficiency. The time-dependent short-circuit current density at the collector side of various MQW solar-cell structures under resonant condition was numerically calculated using the time-dependent Schroedinger equation. The energy efficiency of solar cells based on the InAs/Ga(y)In(1-y)As and GaAs/Al(x)Ga(1-x)As MQW structues were compared when carriers are excited at a particular solar-energy band. Using InAs/Ga(y)In(1-y)As MQW structures it is found that a maximum energy efficiency can be achieved if the structure is designed with barrier potential of about 450 meV. The efficiency is found to decline linearly as the barrier potential increases for GaAs/Al(x)Ga(1-x)As MQW-structure-based solar cells.

  1. Continuous quantum measurement and the quantum to classical transition

    International Nuclear Information System (INIS)

    Bhattacharya, Tanmoy; Habib, Salman; Jacobs, Kurt

    2003-01-01

    While ultimately they are described by quantum mechanics, macroscopic mechanical systems are nevertheless observed to follow the trajectories predicted by classical mechanics. Hence, in the regime defining macroscopic physics, the trajectories of the correct classical motion must emerge from quantum mechanics, a process referred to as the quantum to classical transition. Extending previous work [Bhattacharya, Habib, and Jacobs, Phys. Rev. Lett. 85, 4852 (2000)], here we elucidate this transition in some detail, showing that once the measurement processes that affect all macroscopic systems are taken into account, quantum mechanics indeed predicts the emergence of classical motion. We derive inequalities that describe the parameter regime in which classical motion is obtained, and provide numerical examples. We also demonstrate two further important properties of the classical limit: first, that multiple observers all agree on the motion of an object, and second, that classical statistical inference may be used to correctly track the classical motion

  2. Biotransformation of bergapten and xanthotoxin by Glomerella cingulata.

    Science.gov (United States)

    Marumoto, Shinsuke; Miyazawa, Mitsuo

    2010-07-14

    The biotransformation of bergapten (1) by the fungus Glomerella cingulata gave the corresponding reduced acid, 6,7-furano-5-methoxy hydrocoumaric acid (2), a new compound. Xanthotoxin (3) was also converted to the corresponding reduced acid cnidiol b (4) and demethylated metabolite xanthotoxol (5) by G. cingulata. The structure of the new compound 2 was elucidated by high-resolution mass spectrometry, extensive NMR techniques, including (1)H NMR and (13)C NMR, (1)H-(1)H correlation spectroscopy, heteronuclear multiple quantum coherence, and heteonuclear multiple bond coherence. The methyl ester or methyl ether or methyl ester and ether derivatives of 2 and 4 were synthesized. All compounds were tested for the beta-secretase (BACE1) inhibitory activity in vitro. The methyl ester and ether derivative 8 was shown to possess BACE1 inhibitory activity, and a IC(50) value was 0.64 +/- 0.04 mM.

  3. Quantum A∞-structures for open-closed topological strings

    International Nuclear Information System (INIS)

    Herbst, M.

    2006-02-01

    We study factorizations of topological string amplitudes on higher genus Riemann surfaces with multiple boundary components and find quantum A ∞ -relations, which are the higher genus analog of the (classical) A ∞ -relations on the disk. For topological strings with c=3 the quantum A ∞ -relations are trivially satisfied on a single D-brane, whereas in a multiple D-brane configuration they may be used to compute open higher genus amplitudes recursively from disk amplitudes. This can be helpful in open Gromov-Witten theory in order to determine open string higher genus instanton corrections. Finally, we find that the quantum A ∞ -structure cannot quite be recast into a quantum master equation on the open string moduli space. (orig.)

  4. Experimental characterization of quantum correlated triple beams generated by cascaded four-wave mixing processes

    Science.gov (United States)

    Qin, Zhongzhong; Cao, Leiming; Jing, Jietai

    2015-05-01

    Quantum correlations and entanglement shared among multiple modes are fundamental ingredients of most continuous-variable quantum technologies. Recently, a method used to generate multiple quantum correlated beams using cascaded four-wave mixing (FWM) processes was theoretically proposed and experimentally realized by our group [Z. Qin et al., Phys. Rev. Lett. 113, 023602 (2014)]. Our study of triple-beam quantum correlation paves the way to showing the tripartite entanglement in our system. Our system also promises to find applications in quantum information and precision measurement such as the controlled quantum communications, the generation of multiple quantum correlated images, and the realization of a multiport nonlinear interferometer. For its applications, the degree of quantum correlation is a crucial figure of merit. In this letter, we experimentally study how various parameters, such as the cell temperatures, one-photon, and two-photon detunings, influence the degree of quantum correlation between the triple beams generated from the cascaded two-FWM configuration.

  5. Quantum Stratonovich calculus and the quantum Wong-Zakai theorem

    International Nuclear Information System (INIS)

    Gough, John

    2006-01-01

    We extend the Ito(bar sign)-to-Stratonovich analysis or quantum stochastic differential equations, introduced by Gardiner and Collett for emission (creation), absorption (annihilation) processes, to include scattering (conservation) processes. Working within the framework of quantum stochastic calculus, we define Stratonovich calculus as an algebraic modification of the Ito(bar sign) one and give conditions for the existence of Stratonovich time-ordered exponentials. We show that conversion formula for the coefficients has a striking resemblance to Green's function formulas from standard perturbation theory. We show that the calculus conveniently describes the Markov limit of regular open quantum dynamical systems in much the same way as in the Wong-Zakai approximation theorems of classical stochastic analysis. We extend previous limit results to multiple-dimensions with a proof that makes use of diagrammatic conventions

  6. HN-NCA heteronuclear TOCSY-NH experiment for {sup 1}H{sup N} and {sup 15}N sequential correlations in ({sup 13}C, {sup 15}N) labelled intrinsically disordered proteins

    Energy Technology Data Exchange (ETDEWEB)

    Wiedemann, Christoph; Goradia, Nishit; Häfner, Sabine [Leibniz Institute for Age Research, Fritz Lipmann Institute, Research Group Biomolecular NMR Spectroscopy (Germany); Herbst, Christian [Ubon Ratchathani University, Department of Physics, Faculty of Science (Thailand); Görlach, Matthias; Ohlenschläger, Oliver; Ramachandran, Ramadurai, E-mail: raman@fli-leibniz.de [Leibniz Institute for Age Research, Fritz Lipmann Institute, Research Group Biomolecular NMR Spectroscopy (Germany)

    2015-10-15

    A simple triple resonance NMR experiment that leads to the correlation of the backbone amide resonances of each amino acid residue ‘i’ with that of residues ‘i−1’ and ‘i+1’ in ({sup 13}C, {sup 15}N) labelled intrinsically disordered proteins (IDPs) is presented. The experimental scheme, {HN-NCA heteronuclear TOCSY-NH}, exploits the favourable relaxation properties of IDPs and the presence of {sup 1}J{sub CαN} and {sup 2}J{sub CαN} couplings to transfer the {sup 15}N{sub x} magnetisation from amino acid residue ‘i’ to adjacent residues via the application of a band-selective {sup 15}N–{sup 13}C{sup α} heteronuclear cross-polarisation sequence of ∼100 ms duration. Employing non-uniform sampling in the indirect dimensions, the efficacy of the approach has been demonstrated by the acquisition of 3D HNN chemical shift correlation spectra of α-synuclein. The experimental performance of the RF pulse sequence has been compared with that of the conventional INEPT-based HN(CA)NH pulse scheme. As the availability of data from both the HCCNH and HNN experiments will make it possible to use the information extracted from one experiment to simplify the analysis of the data of the other and lead to a robust approach for unambiguous backbone and side-chain resonance assignments, a time-saving strategy for the simultaneous collection of HCCNH and HNN data is also described.

  7. Efficient Multiple Exciton Generation Observed in Colloidal PbSe Quantum Dots with Temporally and Spectrally Resolved Intraband Excitation

    KAUST Repository

    Ji, Minbiao

    2009-03-11

    We have spectrally resolved the intraband transient absorption of photogenerated excitons to quantify the exciton population dynamics in colloidal PbSe quantum dots (QDs). These measurements demonstrate that the spectral distribution, as well as the amplitude, of the transient spectrum depends on the number of excitons excited in a QD. To accurately quantify the average number of excitons per QD, the transient spectrum must be spectrally integrated. With spectral integration, we observe efficient multiple exciton generation In colloidal PbSe QDs. © 2009 American Chemical Society.

  8. Efficient Multiple Exciton Generation Observed in Colloidal PbSe Quantum Dots with Temporally and Spectrally Resolved Intraband Excitation

    KAUST Repository

    Ji, Minbiao; Park, Sungnam; Connor, Stephen T.; Mokari, Taleb; Cui, Yi; Gaffney, Kelly J.

    2009-01-01

    We have spectrally resolved the intraband transient absorption of photogenerated excitons to quantify the exciton population dynamics in colloidal PbSe quantum dots (QDs). These measurements demonstrate that the spectral distribution, as well as the amplitude, of the transient spectrum depends on the number of excitons excited in a QD. To accurately quantify the average number of excitons per QD, the transient spectrum must be spectrally integrated. With spectral integration, we observe efficient multiple exciton generation In colloidal PbSe QDs. © 2009 American Chemical Society.

  9. High-fidelity quantum gates on quantum-dot-confined electron spins in low-Q optical microcavities

    Science.gov (United States)

    Li, Tao; Gao, Jian-Cun; Deng, Fu-Guo; Long, Gui-Lu

    2018-04-01

    We propose some high-fidelity quantum circuits for quantum computing on electron spins of quantum dots (QD) embedded in low-Q optical microcavities, including the two-qubit controlled-NOT gate and the multiple-target-qubit controlled-NOT gate. The fidelities of both quantum gates can, in principle, be robust to imperfections involved in a practical input-output process of a single photon by converting the infidelity into a heralded error. Furthermore, the influence of two different decay channels is detailed. By decreasing the quality factor of the present microcavity, we can largely increase the efficiencies of these quantum gates while their high fidelities remain unaffected. This proposal also has another advantage regarding its experimental feasibility, in that both quantum gates can work faithfully even when the QD-cavity systems are non-identical, which is of particular importance in current semiconductor QD technology.

  10. Electronic and optical properties of GaAs/AlGaAs Fibonacci ordered multiple quantum well systems

    Science.gov (United States)

    Amini, M.; Soleimani, M.; Ehsani, M. H.

    2017-12-01

    We numerically investigated the optical rectification coefficients (ORCs), transmission coefficient, energy levels and corresponding eigen-functions of GaAs/AlGaAs Fibonacci ordered multiple quantum well systems (FO-MQWs) in the presence of an external electric field. In our calculations, two different methods, including transfer matrix and finite-difference have been used. It has been illustrated that with three types of the FO-MQWs, presented here, localization of the wave-function in any position of the structure is possible. Therefore, managing the electron distribution within the system is easier now. Finally, using the presented structures we could tune the position and amplitude of the ORCs.

  11. Hydrogen cluster/network in tobermorite as studied by multiple-quantum spin counting {sup 1}H NMR

    Energy Technology Data Exchange (ETDEWEB)

    Mogami, Yuuki [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Yamazaki, Satoru; Matsuno, Shinya [Analysis and Simulation Center, Asahi Kasei Corporation, Fuji, Shizuoka 416-8501 (Japan); Matsui, Kunio [Products and Marketing Development Dept., Asahi Kasei Construction Materials Corporation, Sakai-machi, Ibaraki 306-0493 (Japan); Noda, Yasuto [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Takegoshi, K., E-mail: takeyan@kuchem.kyoto-u.ac.jp [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2014-12-15

    Proton multiple-quantum (MQ) spin-counting experiment has been employed to study arrangement of hydrogen atoms in 9 Å/11 Å natural/synthetic tobermorites. Even though all tobermorite samples give similar characterless, broad static-powder {sup 1}H NMR spectra, their MQ spin-counting spectra are markedly different; higher quanta in 11 Å tobermorite do not grow with the MQ excitation time, while those in 9 Å one do. A statistical analysis of the MQ results recently proposed [26] is applied to show that hydrogens align in 9 Å tobermorite one dimensionally, while in 11 Å tobermorite they exist as a cluster of 5–8 hydrogen atoms.

  12. The Misapplication of Probability Theory in Quantum Mechanics

    Science.gov (United States)

    Racicot, Ronald

    2014-03-01

    This article is a revision of two papers submitted to the APS in the past two and a half years. In these papers, arguments and proofs are summarized for the following: (1) The wrong conclusion by EPR that Quantum Mechanics is incomplete, perhaps requiring the addition of ``hidden variables'' for completion. Theorems that assume such ``hidden variables,'' such as Bell's theorem, are also wrong. (2) Quantum entanglement is not a realizable physical phenomenon and is based entirely on assuming a probability superposition model for quantum spin. Such a model directly violates conservation of angular momentum. (3) Simultaneous multiple-paths followed by a quantum particle traveling through space also cannot possibly exist. Besides violating Noether's theorem, the multiple-paths theory is based solely on probability calculations. Probability calculations by themselves cannot possibly represent simultaneous physically real events. None of the reviews of the submitted papers actually refuted the arguments and evidence that was presented. These analyses should therefore be carefully evaluated since the conclusions reached have such important impact in quantum mechanics and quantum information theory.

  13. Classical system boundaries cannot be determined within quantum Darwinism

    Science.gov (United States)

    Fields, Chris

    Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.

  14. On-chip photonic system using suspended p-n junction InGaN/GaN multiple quantum wells device and multiple waveguides

    International Nuclear Information System (INIS)

    Wang, Yongjin; Zhu, Guixia; Gao, Xumin; Yang, Yongchao; Yuan, Jialei; Shi, Zheng; Zhu, Hongbo; Cai, Wei

    2016-01-01

    We propose, fabricate, and characterize the on-chip integration of suspended p-n junction InGaN/GaN multiple quantum wells (MQWs) device and multiple waveguides on the same GaN-on-silicon platform. The integrated devices are fabricated via a wafer-level process and exhibit selectable functionalities for diverse applications. As the suspended p-n junction InGaN/GaN MQWs device operates under a light emitting diode (LED) mode, part of the light emission is confined and guided by the suspended waveguides. The in-plane propagation along the suspended waveguides is measured by a micro-transmittance setup. The on-chip data transmission is demonstrated for the proof-of-concept photonic integration. As the suspended p-n junction InGaN/GaN MQWs device operates under photodiode mode, the light is illuminated on the suspended waveguides with the aid of the micro-transmittance setup and, thus, coupled into the suspended waveguides. The guided light is finally sensed by the photodiode, and the induced photocurrent trace shows a distinct on/off switching performance. These experimental results indicate that the on-chip photonic integration is promising for the development of sophisticated integrated photonic circuits in the visible wavelength region.

  15. Thick-shell nanocrystal quantum dots

    Science.gov (United States)

    Hollingsworth, Jennifer A [Los Alamos, NM; Chen, Yongfen [Eugene, OR; Klimov, Victor I [Los Alamos, NM; Htoon, Han [Los Alamos, NM; Vela, Javier [Los Alamos, NM

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  16. Broadband cross-polarization-based heteronuclear dipolar recoupling for structural and dynamic NMR studies of rigid and soft solids

    International Nuclear Information System (INIS)

    Kharkov, B. B.; Chizhik, V. I.; Dvinskikh, S. V.

    2016-01-01

    Dipolar recoupling is an essential part of current solid-state NMR methodology for probing atomic-resolution structure and dynamics in solids and soft matter. Recently described magic-echo amplitude- and phase-modulated cross-polarization heteronuclear recoupling strategy aims at efficient and robust recoupling in the entire range of coupling constants both in rigid and highly dynamic molecules. In the present study, the properties of this recoupling technique are investigated by theoretical analysis, spin-dynamics simulation, and experimentally. The resonance conditions and the efficiency of suppressing the rf field errors are examined and compared to those for other recoupling sequences based on similar principles. The experimental data obtained in a variety of rigid and soft solids illustrate the scope of the method and corroborate the results of analytical and numerical calculations. The technique benefits from the dipolar resolution over a wider range of coupling constants compared to that in other state-of-the-art methods and thus is advantageous in studies of complex solids with a broad range of dynamic processes and molecular mobility degrees

  17. Steering of quantum waves: Demonstration of Y-junction transistors using InAs quantum wires

    Science.gov (United States)

    Jones, Gregory M.; Qin, Jie; Yang, Chia-Hung; Yang, Ming-Jey

    2005-06-01

    In this paper we demonstrate using an InAs quantum wire Y-branch switch that the electron wave can be switched to exit from the two drains by a lateral gate bias. The gating modifies the electron wave functions as well as their interference pattern, causing the anti-correlated, oscillatory transconductances. Our result suggests a new transistor function in a multiple-lead ballistic quantum wire system.

  18. Modeling techniques for quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Jirauschek, Christian [Institute for Nanoelectronics, Technische Universität München, D-80333 Munich (Germany); Kubis, Tillmann [Network for Computational Nanotechnology, Purdue University, 207 S Martin Jischke Drive, West Lafayette, Indiana 47907 (United States)

    2014-03-15

    Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.

  19. Modeling techniques for quantum cascade lasers

    Science.gov (United States)

    Jirauschek, Christian; Kubis, Tillmann

    2014-03-01

    Quantum cascade lasers are unipolar semiconductor lasers covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement of quantum cascade lasers with respect to operating temperature, efficiency, and spectral range requires detailed modeling of the underlying physical processes in these structures. Moreover, the quantum cascade laser constitutes a versatile model device for the development and improvement of simulation techniques in nano- and optoelectronics. This review provides a comprehensive survey and discussion of the modeling techniques used for the simulation of quantum cascade lasers. The main focus is on the modeling of carrier transport in the nanostructured gain medium, while the simulation of the optical cavity is covered at a more basic level. Specifically, the transfer matrix and finite difference methods for solving the one-dimensional Schrödinger equation and Schrödinger-Poisson system are discussed, providing the quantized states in the multiple-quantum-well active region. The modeling of the optical cavity is covered with a focus on basic waveguide resonator structures. Furthermore, various carrier transport simulation methods are discussed, ranging from basic empirical approaches to advanced self-consistent techniques. The methods include empirical rate equation and related Maxwell-Bloch equation approaches, self-consistent rate equation and ensemble Monte Carlo methods, as well as quantum transport approaches, in particular the density matrix and non-equilibrium Green's function formalism. The derived scattering rates and self-energies are generally valid for n-type devices based on one-dimensional quantum confinement, such as quantum well structures.

  20. Quantum game application to spectrum scarcity problems

    Science.gov (United States)

    Zabaleta, O. G.; Barrangú, J. P.; Arizmendi, C. M.

    2017-01-01

    Recent spectrum-sharing research has produced a strategy to address spectrum scarcity problems. This novel idea, named cognitive radio, considers that secondary users can opportunistically exploit spectrum holes left temporarily unused by primary users. This presents a competitive scenario among cognitive users, making it suitable for game theory treatment. In this work, we show that the spectrum-sharing benefits of cognitive radio can be increased by designing a medium access control based on quantum game theory. In this context, we propose a model to manage spectrum fairly and effectively, based on a multiple-users multiple-choice quantum minority game. By taking advantage of quantum entanglement and quantum interference, it is possible to reduce the probability of collision problems commonly associated with classic algorithms. Collision avoidance is an essential property for classic and quantum communications systems. In our model, two different scenarios are considered, to meet the requirements of different user strategies. The first considers sensor networks where the rational use of energy is a cornerstone; the second focuses on installations where the quality of service of the entire network is a priority.

  1. Formalization of Quantum Protocols using Coq

    Directory of Open Access Journals (Sweden)

    Jaap Boender

    2015-11-01

    Full Text Available Quantum Information Processing, which is an exciting area of research at the intersection of physics and computer science, has great potential for influencing the future development of information processing systems. The building of practical, general purpose Quantum Computers may be some years into the future. However, Quantum Communication and Quantum Cryptography are well developed. Commercial Quantum Key Distribution systems are easily available and several QKD networks have been built in various parts of the world. The security of the protocols used in these implementations rely on information-theoretic proofs, which may or may not reflect actual system behaviour. Moreover, testing of implementations cannot guarantee the absence of bugs and errors. This paper presents a novel framework for modelling and verifying quantum protocols and their implementations using the proof assistant Coq. We provide a Coq library for quantum bits (qubits, quantum gates, and quantum measurement. As a step towards verifying practical quantum communication and security protocols such as Quantum Key Distribution, we support multiple qubits, communication and entanglement. We illustrate these concepts by modelling the Quantum Teleportation Protocol, which communicates the state of an unknown quantum bit using only a classical channel.

  2. Heteronuclear multidimensional NMR and homology modelling studies of the C-terminal nucleotide-binding domain of the human mitochondrial ABC transporter ABCB6

    Energy Technology Data Exchange (ETDEWEB)

    Kurashima-Ito, Kaori [RIKEN, Cellular and Molecular Biology Laboratory (Japan); Ikeya, Teppei [National Institute of Advanced Industrial Science and Technology (AIST), (Japan); Senbongi, Hiroshi [Mitochondrial Diseases Group, MRC Dunn Human NutritionUnit (United Kingdom); Tochio, Hidehito [International Graduate School of Arts and Sciences, Supramolecular Biology, Yokohama City University, Molecular Biophysics Laboratory (Japan); Mikawa, Tsutomu [RIKEN, Cellular and Molecular Biology Laboratory (Japan); Shibata, Takehiko [RIKEN, Shibata Distinguished Senior Scientist Laboratory (Japan); Ito, Yutaka [RIKEN, Cellular and Molecular Biology Laboratory (Japan)], E-mail: ito-yutaka@center.tmu.ac.jp

    2006-05-15

    Human ATP-binding cassette, sub-family B, member 6 (ABCB6) is a mitochondrial ABC transporter, and presumably contributes to iron homeostasis. Aimed at understanding the structural basis for the conformational changes accompanying the substrate-transportation cycle, we have studied the C-terminal nucleotide-binding domain of ABCB6 (ABCB6-C) in both the nucleotide-free and ADP-bound states by heteronuclear multidimensional NMR and homology modelling. A non-linear sampling scheme was utilised for indirectly acquired {sup 13}C and {sup 15}N dimensions of all 3D triple-resonance NMR experiments, in order to overcome the instability and the low solubility of ABCB6-C. The backbone resonances for approximately 25% of non-proline residues, which are mostly distributed around the functionally important loops and in the Helical domain, were not observed for nucleotide-free form of ABCB6-C. From the pH, temperature and magnetic field strength dependencies of the resonance intensities, we concluded that this incompleteness in the assignments is mainly due to the exchange between multiple conformations at an intermediate rate on the NMR timescale. These localised conformational dynamics remained in ADP-bound ABCB6-C except for the loops responsible for adenine base and {alpha}/{beta}-phosphate binding. These results revealed that the localised dynamic cooperativity, which was recently proposed for a prokaryotic ABC MJ1267, also exists in a higher eukaryotic ABC, and is presumably shared by all members of the ABC family. Since the Helical domain is the putative interface to the transmembrane domain, this cooperativity may explain the coupled functions between domains in the substrate-transportation cycle.

  3. Photoreflectance Spectroscopy Characterization of Ge/Si0.16Ge0.84 Multiple Quantum Wells on Ge Virtual Substrate

    OpenAIRE

    Hsu, Hung-Pin; Yang, Pong-Hong; Huang, Jeng-Kuang; Wu, Po-Hung; Huang, Ying-Sheng; Li, Cheng; Huang, Shi-Hao; Tiong, Kwong-Kau

    2013-01-01

    We report a detailed characterization of a Ge/Si0.16Ge0.84 multiple quantum well (MQW) structure on Ge-on-Si virtual substrate (VS) grown by ultrahigh vacuum chemical vapor deposition by using temperature-dependent photoreflectance (PR) in the temperature range from 10 to 300 K. The PR spectra revealed a wide range of optical transitions from the MQW region as well as transitions corresponding to the light-hole and heavy-hole splitting energies of Ge-on-Si VS. A detailed comparison of PR spec...

  4. Picture this: The value of multiple visual representations for student learning of quantum concepts in general chemistry

    Science.gov (United States)

    Allen, Emily Christine

    Mental models for scientific learning are often defined as, "cognitive tools situated between experiments and theories" (Duschl & Grandy, 2012). In learning, these cognitive tools are used to not only take in new information, but to help problem solve in new contexts. Nancy Nersessian (2008) describes a mental model as being "[loosely] characterized as a representation of a system with interactive parts with representations of those interactions. Models can be qualitative, quantitative, and/or simulative (mental, physical, computational)" (p. 63). If conceptual parts used by the students in science education are inaccurate, then the resulting model will not be useful. Students in college general chemistry courses are presented with multiple abstract topics and often struggle to fit these parts into complete models. This is especially true for topics that are founded on quantum concepts, such as atomic structure and molecular bonding taught in college general chemistry. The objectives of this study were focused on how students use visual tools introduced during instruction to reason with atomic and molecular structure, what misconceptions may be associated with these visual tools, and how visual modeling skills may be taught to support students' use of visual tools for reasoning. The research questions for this study follow from Gilbert's (2008) theory that experts use multiple representations when reasoning and modeling a system, and Kozma and Russell's (2005) theory of representational competence levels. This study finds that as students developed greater command of their understanding of abstract quantum concepts, they spontaneously provided additional representations to describe their more sophisticated models of atomic and molecular structure during interviews. This suggests that when visual modeling with multiple representations is taught, along with the limitations of the representations, it can assist students in the development of models for reasoning about

  5. Advances in acrylic-alkyd hybrid synthesis and characterization

    Science.gov (United States)

    Dziczkowski, Jamie

    2008-10-01

    In situ graft acrylic-alkyd hybrid resins were formed by polymerizing acrylic and acrylic-mixed monomers in the presence of alkyds by introduction of a free radical initiator to promote graft formation. Two-dimensional NMR, specifically gradient heteronuclear multiple quantum coherence (gHMQC), was used to clarify specific graft sites of the hybrid materials. Both individual and mixed-monomer systems were produced to determine any individual monomer preferences and to model current acrylic-alkyd systems. Different classes of initiators were used to determine any initiator effects on graft location. The 2D-NMR results confirm grafting at doubly allylic hydrogens located on the fatty acid chains and the polyol segment of the alkyd backbone. The gHMQC spectra show no evidence of grafting across double bonds on either pendant fatty acid groups or THPA unsaturation sites for any of the monomer or mixed monomer systems. It was also determined that choice of initiator has no effect on graft location. In addition, a design of experiments using response surface methodology was utilized to obtain a better understanding of this commercially available class of materials and relate both the chemical and physical properties to one another. A Box-Behnkin design was used, varying the oil length of the alkyd phase, the degree of unsaturation in the polyester backbone, and acrylic to alkyd ratio. Acrylic-alkyd hybrid resins were reduced with an amine/water mixture. Hydrolytic stability was tested and viscoelastic properties were obtained to determine crosslink density. Cured films were prepared and basic coatings properties were evaluated. It was found that the oil length of the alkyd is the most dominant factor for final coatings properties of the resins. Acrylic to alkyd ratio mainly influences the resin properties such as acid number, average molecular weight, and hydrolytic stability. The degree of unsaturation in the alkyd backbone has minimal effects on resin and film

  6. Nuclear magnetic resonance spectroscopy in the structure elucidation and biosynthesis of natural products

    International Nuclear Information System (INIS)

    Meksuriyen, D.

    1988-01-01

    Examination of a chloroform extract of Dracaena loureiri Gagnep (Agavaceae), a Thia medicinal plant possessing antibacterial activity, has led to the isolation of fifteen flavenoids. The biogenic relationships among these flavenoids isolated were briefly discussed. Definition of the skeleton and the unambiguous assignment of all of the protons of the isolates was achieved through extensive 2D-homonuclear chemical shift correlation, nuclear Overhauser effect (NOE) difference spectroscopy and 2D-NOE experiments. The 1 H and 13 C NMR spectra of staurosporine, a potent biologically active agent from Streptomyces staurosporeus, were unambiguously assigned by using 2D homonuclear chemical shift correlation, NOE, 1 H-detected heteronuclear multiple-quantum coherence via direct coupling and via multiple-bond coupling for resonance assignments of protonated and nonprotonated carbons, respectively. S. Staurosporeus was found to utilize endogenous and exogenous D- and L-isomers of trytophan in the production of staurosporine. The biosynthesis of staurosporine was examined by employing carbon-14, tritium, and carbon-13 labeled precursors

  7. InAs0.45P0.55/InP strained multiple quantum wells intermixed by inductively coupled plasma etching

    International Nuclear Information System (INIS)

    Cao, Meng; Wu, Hui-Zhen; Lao, Yan-Feng; Cao, Chun-Fang; Liu, Cheng

    2009-01-01

    The intermixing effect on InAs 0.45 P 0.55 /InP strained multiple quantum wells (SMQWs) by inductively coupled plasma (ICP) etching and rapid thermal annealing (RTA) is investigated. Experiments show that the process of ICP etching followed RTA induces the blue shift of low temperature photoluminescence (PL) peaks of QWs. With increasing etching depth, the PL intensities are firstly enhanced and then diminished. This phenomenon is attributed to the variation of surface roughness and microstructure transformation inside the QW structure during ICP processing.

  8. Analysis of mode-hopping effect in Fabry–Pérot multiple-quantum well laser diodes via low frequency noise investigation

    DEFF Research Database (Denmark)

    Pralgauskaitė, Sandra; Palenskis, Vilius; Matukas, Jonas

    2013-01-01

    Comprehensive investigation of noise characteristics and radiation spectrum with special attention to the mode-hopping effect of Fabry–Pérot (FP) multiple quantum well laser diodes (LDs) have been carried out: laser radiation spectra, optical and electrical fluctuations and cross-correlation factor...... between them have been measured under stable and mode-hopping operation. At the mode-hopping that occurs at particular operation conditions (injection current and temperature) LD radiation spectrum is unstable in time, very intensive and highly correlated Lorentzian-type optical and electrical...

  9. A review on quantum search algorithms

    Science.gov (United States)

    Giri, Pulak Ranjan; Korepin, Vladimir E.

    2017-12-01

    The use of superposition of states in quantum computation, known as quantum parallelism, has significant advantage in terms of speed over the classical computation. It is evident from the early invented quantum algorithms such as Deutsch's algorithm, Deutsch-Jozsa algorithm and its variation as Bernstein-Vazirani algorithm, Simon algorithm, Shor's algorithms, etc. Quantum parallelism also significantly speeds up the database search algorithm, which is important in computer science because it comes as a subroutine in many important algorithms. Quantum database search of Grover achieves the task of finding the target element in an unsorted database in a time quadratically faster than the classical computer. We review Grover's quantum search algorithms for a singe and multiple target elements in a database. The partial search algorithm of Grover and Radhakrishnan and its optimization by Korepin called GRK algorithm are also discussed.

  10. Quantum engineering. Confining the state of light to a quantum manifold by engineered two-photon loss.

    Science.gov (United States)

    Leghtas, Z; Touzard, S; Pop, I M; Kou, A; Vlastakis, B; Petrenko, A; Sliwa, K M; Narla, A; Shankar, S; Hatridge, M J; Reagor, M; Frunzio, L; Schoelkopf, R J; Mirrahimi, M; Devoret, M H

    2015-02-20

    Physical systems usually exhibit quantum behavior, such as superpositions and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. This notion can be generalized to the confinement of a system into a manifold of quantum states, consisting of all coherent superpositions of multiple stable steady states. We have confined the state of a superconducting resonator to the quantum manifold spanned by two coherent states of opposite phases and have observed a Schrödinger cat state spontaneously squeeze out of vacuum before decaying into a classical mixture. This experiment points toward robustly encoding quantum information in multidimensional steady-state manifolds. Copyright © 2015, American Association for the Advancement of Science.

  11. Quantum-enhanced sensing from hyperentanglement

    Science.gov (United States)

    Walborn, S. P.; Pimentel, A. H.; Davidovich, L.; de Matos Filho, R. L.

    2018-01-01

    Hyperentanglement—simultaneous entanglement between multiple degrees of freedom of two or more systems—has been used to enhance quantum information tasks such as quantum communication and photonic quantum computing. Here we show that hyperentanglement can lead to increased quantum advantage in metrology, with contributions from the entanglement in each degree of freedom, allowing for Heisenberg scaling in the precision of parameter estimation. Our experiment employs photon pairs entangled in polarization and spatial degrees of freedom to estimate a small tilt angle of a mirror. Precision limits beyond shot noise are saturated through a simple binary measurement of the polarization state. The dynamics considered here have broad applicability, implying that similar strategies based on hyperentanglement can offer improvement in a wide variety of physical scenarios and metrological tasks.

  12. Multiple environment single system quantum mechanical/molecular mechanical (MESS-QM/MM) calculations. 1. Estimation of polarization energies.

    Science.gov (United States)

    Sodt, Alexander J; Mei, Ye; König, Gerhard; Tao, Peng; Steele, Ryan P; Brooks, Bernard R; Shao, Yihan

    2015-03-05

    In combined quantum mechanical/molecular mechanical (QM/MM) free energy calculations, it is often advantageous to have a frozen geometry for the quantum mechanical (QM) region. For such multiple-environment single-system (MESS) cases, two schemes are proposed here for estimating the polarization energy: the first scheme, termed MESS-E, involves a Roothaan step extrapolation of the self-consistent field (SCF) energy; whereas the other scheme, termed MESS-H, employs a Newton-Raphson correction using an approximate inverse electronic Hessian of the QM region (which is constructed only once). Both schemes are extremely efficient, because the expensive Fock updates and SCF iterations in standard QM/MM calculations are completely avoided at each configuration. They produce reasonably accurate QM/MM polarization energies: MESS-E can predict the polarization energy within 0.25 kcal/mol in terms of the mean signed error for two of our test cases, solvated methanol and solvated β-alanine, using the M06-2X or ωB97X-D functionals; MESS-H can reproduce the polarization energy within 0.2 kcal/mol for these two cases and for the oxyluciferin-luciferase complex, if the approximate inverse electronic Hessians are constructed with sufficient accuracy.

  13. Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

    International Nuclear Information System (INIS)

    Khalil, H.M.; Mazzucato, S.; Ardali, S.; Celik, O.; Mutlu, S.; Royall, B.; Tiras, E.; Balkan, N.; Puustinen, J.; Korpijärvi, V.-M.; Guina, M.

    2012-01-01

    Highlights: ► We studied p-i-n GaInNAs MQW devices as function of temperature and magnetic field. ► Observed oscillations in the sample current–voltage curves at low temperature. ► Shift in oscillation position with magnetic field described by Landau level split. ► Resonant tunnelling and thermionic emission used to describe oscillations. - Abstract: The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current–voltage I–V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I–V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission. Magnetic fields up to B = 11 T were applied parallel to the planes of the QWs. A small voltage shift in the position of the oscillations was observed, proportional to the magnetic field intensity and dependent upon the temperature. Calculation of the Landau level energy separation (16 meV) agrees with the observed experimental data. Magneto-tunnelling spectroscopy probes in detail the nature of band- or impurity-like states responsible for resonances in first and second subbands, observing the I–V plot in dark condition and under illumination. The field-dependence of the amplitude of the oscillation peaks in I–V has the characteristic form of a quantum mechanical admixing effect. This enhancement is also probably due to the hole recombination with majority electrons tunnelling in the N-related states of the quantum wells.

  14. Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, H.M., E-mail: hkhalia@essex.ac.uk [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Mazzucato, S. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Ardali, S.; Celik, O.; Mutlu, S. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Royall, B. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Tiras, E. [Anadolu University, Faculty of Science, Department of Physics, Yunus Emre Campus 26470, Eskisehir (Turkey); Balkan, N. [School of Computer Science and Electronic Engineering, University of Essex, CO4 3SQ, Colchester (United Kingdom); Puustinen, J.; Korpijaervi, V.-M.; Guina, M. [Optoelectronics Research Centre, Tampere University of Technology, Korkeakoulunkatu 10, FI-33720 Tampere (Finland)

    2012-06-05

    Highlights: Black-Right-Pointing-Pointer We studied p-i-n GaInNAs MQW devices as function of temperature and magnetic field. Black-Right-Pointing-Pointer Observed oscillations in the sample current-voltage curves at low temperature. Black-Right-Pointing-Pointer Shift in oscillation position with magnetic field described by Landau level split. Black-Right-Pointing-Pointer Resonant tunnelling and thermionic emission used to describe oscillations. - Abstract: The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current-voltage I-V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I-V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission. Magnetic fields up to B = 11 T were applied parallel to the planes of the QWs. A small voltage shift in the position of the oscillations was observed, proportional to the magnetic field intensity and dependent upon the temperature. Calculation of the Landau level energy separation (16 meV) agrees with the observed experimental data. Magneto-tunnelling spectroscopy probes in detail the nature of band- or impurity-like states responsible for resonances in first and second subbands, observing the I-V plot in dark condition and under illumination. The field-dependence of the amplitude of the oscillation peaks in I-V has the characteristic form of a quantum mechanical admixing effect. This enhancement is also probably due to the hole recombination with majority electrons tunnelling in the N-related states of the quantum wells.

  15. Computationally Efficient Nonlinear Bell Inequalities for Quantum Networks

    Science.gov (United States)

    Luo, Ming-Xing

    2018-04-01

    The correlations in quantum networks have attracted strong interest with new types of violations of the locality. The standard Bell inequalities cannot characterize the multipartite correlations that are generated by multiple sources. The main problem is that no computationally efficient method is available for constructing useful Bell inequalities for general quantum networks. In this work, we show a significant improvement by presenting new, explicit Bell-type inequalities for general networks including cyclic networks. These nonlinear inequalities are related to the matching problem of an equivalent unweighted bipartite graph that allows constructing a polynomial-time algorithm. For the quantum resources consisting of bipartite entangled pure states and generalized Greenberger-Horne-Zeilinger (GHZ) states, we prove the generic nonmultilocality of quantum networks with multiple independent observers using new Bell inequalities. The violations are maximal with respect to the presented Tsirelson's bound for Einstein-Podolsky-Rosen states and GHZ states. Moreover, these violations hold for Werner states or some general noisy states. Our results suggest that the presented Bell inequalities can be used to characterize experimental quantum networks.

  16. Heteronuclear Adiabatic Relaxation Dispersion (HARD) for quantitative analysis of conformational dynamics in proteins.

    Science.gov (United States)

    Traaseth, Nathaniel J; Chao, Fa-An; Masterson, Larry R; Mangia, Silvia; Garwood, Michael; Michaeli, Shalom; Seelig, Burckhard; Veglia, Gianluigi

    2012-06-01

    NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R(1ρ) and Carr-Purcell-Meiboom-Gill (CPMG) R(2) experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R(1ρ) and transverse R(2ρ)) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (k(ex)∼10(4)-10(5) s(-1)). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R(1ρ) and R(2ρ) relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R(1ρ) and R(2ρ) that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R(1ρ) experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Hopping mixed hybrid excitations in multiple composite quantum wire structures

    International Nuclear Information System (INIS)

    Nguyen Ba An; Tran Thai Hoa

    1995-10-01

    A structure consisting of N pairs of inorganic semiconductor and organic quantum wires is considered theoretically. In such an isolated pair of wires, while the intrawire coupling forms Wannier-Mott exciton in an inorganic semiconductor quantum wire and Frenkel exciton in an organic one, the interwire coupling gives rise to hybrid excitons residing within the pair. When N pairs of wires are packed together 2N new mixed hybrid modes appear that are the true elementary excitations and can hop throughout the whole structure. Energies and wave functions of such hopping mixed hybrid excitations are derived analytically in detail accounting for the global interwire coupling and the different polarization configurations. (author). 19 refs

  18. An elementary quantum network using robust nuclear spin qubits in diamond

    Science.gov (United States)

    Kalb, Norbert; Reiserer, Andreas; Humphreys, Peter; Blok, Machiel; van Bemmelen, Koen; Twitchen, Daniel; Markham, Matthew; Taminiau, Tim; Hanson, Ronald

    Quantum registers containing multiple robust qubits can form the nodes of future quantum networks for computation and communication. Information storage within such nodes must be resilient to any type of local operation. Here we demonstrate multiple robust memories by employing five nuclear spins adjacent to a nitrogen-vacancy defect centre in diamond. We characterize the storage of quantum superpositions and their resilience to entangling attempts with the electron spin of the defect centre. The storage fidelity is found to be limited by the probabilistic electron spin reset after failed entangling attempts. Control over multiple memories is then utilized to encode states in decoherence protected subspaces with increased robustness. Furthermore we demonstrate memory control in two optically linked network nodes and characterize the storage capabilities of both memories in terms of the process fidelity with the identity. These results pave the way towards multi-qubit quantum algorithms in a remote network setting.

  19. Theoretical analysis of multiple quantum-well, slow-light devices under applied external fields using a fully analytical model in fractional dimension

    Energy Technology Data Exchange (ETDEWEB)

    Kohandani, R; Kaatuzian, H [Photonics Research Laboratory, Electrical Engineering Department, AmirKabir University of Technology, Hafez Ave., Tehran (Iran, Islamic Republic of)

    2015-01-31

    We report a theoretical study of optical properties of AlGaAs/GaAs multiple quantum-well (MQW), slow-light devices based on excitonic population oscillations under applied external magnetic and electric fields using an analytical model for complex dielectric constant of Wannier excitons in fractional dimension. The results are shown for quantum wells (QWs) of different width. The significant characteristics of the exciton in QWs such as exciton energy and exciton oscillator strength (EOS) can be varied by application of external magnetic and electric fields. It is found that a higher bandwidth and an appropriate slow-down factor (SDF) can be achieved by changing the QW width during the fabrication process and by applying magnetic and electric fields during device functioning, respectively. It is shown that a SDF of 10{sup 5} is obtained at best. (slowing of light)

  20. Chemical Constituents and Antibacterial Properties of Indocalamus latifolius McClure Leaves, the Packaging Material for “Zongzi”

    Directory of Open Access Journals (Sweden)

    Jia Sun

    2015-08-01

    Full Text Available The glutinous rice dumpling named “Zongzi” in Chinese is a type of traditional food that is popular in East Asian countries. “Zongzi” is made of glutinous rice and wrapped in the leaves of Indocalamus latifolius McClure as the packaging material. Four new compounds, latifoliusine A (2, (7S,8R syringylglycerol-8-O-4′-sinapyl ether 4-O-β-d-glucopyranoside (7, (7S,8S syringylglycerol-8-O-4′-sinapyl ether 7-O-β-d-glucopyranoside (8, and (7R,8S syringylglycerol-8-O-4′-sinapyl ether 7-O-β-d-glucopyranoside (10, along with six known compounds (1, 3–6 and 9 were isolated from I. latifolius McClure leaves. The structures and relative configurations of the compounds were determined by detailed spectroscopic analysis, high-resolution electrospray ionization mass spectroscopy (HRESIMS, heteronuclear single quantum correlation (HSQC, heteronuclear multiple bond correlation (HMBC, nuclear overhauser enhancement (NOE and circular dichroism (CD. All of the isolated compounds were screened for their antibacterial activities in vitro. The results indicated that apigenin 6-C-α-l-arabinopyranosyl-8-C-β-d-glucopyranoside (5 and apigenin 7-O,8-C-di-glucopyranoside (6 have antibacterial activities against four bacterial strains (Staphylococcus aureus, Bacillus thuringiensis, Escherichia coli and Pseudomonas solanacearum.

  1. Use of 15N reverse gradient two-dimensional nuclear magnetic resonance spectroscopy to follow metabolic activity in Nicotiana plumbaginifolia cell-suspension cultures.

    Science.gov (United States)

    Mesnard, F; Azaroual, N; Marty, D; Fliniaux, M A; Robins, R J; Vermeersch, G; Monti, J P

    2000-02-01

    Nitrogen metabolism was monitored in suspension cultured cells of Nicotiana plumbaginifolia Viv. using nuclear magnetic resonance (NMR) spectroscopy following the feeding of (15NH4)2SO4 and K15NO3. By using two-dimensional 15N-1H NMR with heteronuclear single-quantum-coherence spectroscopy and heteronuclear multiple-bond-coherence spectroscopy sequences, an enhanced resolution of the incorporation of 15N label into a range of compounds could be detected. Thus, in addition to the amino acids normally observed in one-dimensional 15N NMR (glutamine, aspartate, alanine), several other amino acids could be resolved, notably serine, glycine and proline. Furthermore, it was found that the peak normally assigned to the non-protein amino-acid gamma-aminobutyric acid in the one-dimensional 15N NMR spectrum was resolved into a several components. A peak of N-acetylated compounds was resolved, probably composed of the intermediates in arginine biosynthesis, N-acetylglutamate and N-acetylornithine and, possibly, the intermediate of putrescine degradation into gamma-aminobutyric acid, N-acetylputrescine. The occurrence of 15N-label in agmatine and the low detection of labelled putrescine indicate that crucial intermediates of the pathway from glutamate to polyamines and/or the tobacco alkaloids could be monitored. For the first time, labelling of the peptide glutathione and of the nucleotide uridine could be seen.

  2. Performance analysis of quantum access network using code division multiple access model

    Science.gov (United States)

    Hu, Linxi; Yang, Can; He, Guangqiang

    2017-06-01

    Not Available Project supported by the National Natural Science Foundation of China (Grant Nos. 61475099 and 61102053), the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices (Grant No. KF201405), the Open Fund of IPOC (BUPT) (Grant No. IPOC2015B004), and the Program of State Key Laboratory of Information Security (Grant No. 2016-MS-05).

  3. Sufficient condition for a quantum state to be genuinely quantum non-Gaussian

    Science.gov (United States)

    Happ, L.; Efremov, M. A.; Nha, H.; Schleich, W. P.

    2018-02-01

    We show that the expectation value of the operator \\hat{{ \\mathcal O }}\\equiv \\exp (-c{\\hat{x}}2)+\\exp (-c{\\hat{p}}2) defined by the position and momentum operators \\hat{x} and \\hat{p} with a positive parameter c can serve as a tool to identify quantum non-Gaussian states, that is states that cannot be represented as a mixture of Gaussian states. Our condition can be readily tested employing a highly efficient homodyne detection which unlike quantum-state tomography requires the measurements of only two orthogonal quadratures. We demonstrate that our method is even able to detect quantum non-Gaussian states with positive–definite Wigner functions. This situation cannot be addressed in terms of the negativity of the phase-space distribution. Moreover, we demonstrate that our condition can characterize quantum non-Gaussianity for the class of superposition states consisting of a vacuum and integer multiples of four photons under more than 50 % signal attenuation.

  4. Quantum ergodicity and a quantum measure algebra

    International Nuclear Information System (INIS)

    Stechel, E.B.

    1985-01-01

    A quantum ergodic theory for finite systems (such as isolated molecules) is developed by introducing the concept of a quantum measure algebra. The basic concept in classical ergodic theory is that of a measure space. A measure space is a set M, together with a specified sigma algebra of subsets in M and a measure defined on that algebra. A sigma algebra is closed under the formation of intersections and symmetric differences. A measure is a nonnegative and countably additive set function. For this to be further classified as a dynamical system, a measurable transformation is introduced. A measurable transformation is a mapping from a measure space into a measure space, such that the inverse image of every measurable set is measurable. In conservative dynamical systems, a measurable transformation is measure preserving, which is to say that the inverse image of every measurable set has the same measure as the original set. Once the measure space and the measurable transformation are defined, ergodic theory can be investigated on three levels: describable as analytic, geometric and algebraic. The analytic level studies linear operators induced by a transformation. The geometric level is concerned directly with transformations on a measure space and the algebraic treatments substitute a measure algebra for the measure space and basically equate sets that differ only by sets of measure zero. It is this latter approach that is most directly paralleled here. A measure algebra for a quantum dynamical system is defined within which stochastic concepts in quantum mechanics can be investigated. The quantum measure algebra differs from a normal measure algebra only in that multiplication is noncommutative and addition is nonassociative. Nonetheless, the quantum measure algebra preserves the essence of a normal measure algebra

  5. Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire.

    Science.gov (United States)

    Li, Qiang; Pan, Deng; Wei, Hong; Xu, Hongxing

    2018-03-14

    Hybrid systems composed of multiple quantum emitters coupled with plasmonic waveguides are promising building blocks for future integrated quantum nanophotonic circuits. The techniques that can super-resolve and selectively excite contiguous quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the single plasmon generation and propagation in plasmonic circuits. Here we show that multiple quantum dots coupled with a silver nanowire can be controllably excited by tuning the interference field of surface plasmons on the nanowire. Because of the period of the interference pattern is much smaller than the diffraction limit, we demonstrate the selective excitation of two quantum dots separated by a distance as short as 100 nm. We also numerically demonstrate a new kind of super-resolution imaging method that combines the tunable surface plasmon interference pattern on the NW with the structured illumination microscopy technique. Our work provides a novel high-resolution optical excitation and imaging method for the coupled systems of multiple quantum emitters and plasmonic waveguides, which adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

  6. Quantum state sharing against the controller's cheating

    Science.gov (United States)

    Shi, Run-hua; Zhong, Hong; Huang, Liu-sheng

    2013-08-01

    Most existing QSTS schemes are equivalent to the controlled teleportation, in which a designated agent (i.e., the recoverer) can recover the teleported state with the help of the controllers. However, the controller may attempt to cheat the recoverer during the phase of recovering the secret state. How can we detect this cheating? In this paper, we considered the problem of detecting the controller's cheating in Quantum State Sharing, and further proposed an effective Quantum State Sharing scheme against the controller's cheating. We cleverly use Quantum Secret Sharing, Multiple Quantum States Sharing and decoy-particle techniques. In our scheme, via a previously shared entanglement state Alice can teleport multiple arbitrary multi-qubit states to Bob with the help of Charlie. Furthermore, by the classical information shared previously, Alice and Bob can check whether there is any cheating of Charlie. In addition, our scheme only needs to perform Bell-state and single-particle measurements, and to apply C-NOT gate and other single-particle unitary operations. With the present techniques, it is feasible to implement these necessary measurements and operations.

  7. Role of controllability in optimizing quantum dynamics

    International Nuclear Information System (INIS)

    Wu Rebing; Hsieh, Michael A.; Rabitz, Herschel

    2011-01-01

    This paper reveals an important role that controllability plays in the complexity of optimizing quantum control dynamics. We show that the loss of controllability generally leads to multiple locally suboptimal controls when gate fidelity in a quantum control system is maximized, which does not happen if the system is controllable. Such local suboptimal controls may attract an optimization algorithm into a local trap when a global optimal solution is sought, even if the target gate can be perfectly realized. This conclusion results from an analysis of the critical topology of the corresponding quantum control landscape, which refers to the gate fidelity objective as a functional of the control fields. For uncontrollable systems, due to SU(2) and SU(3) dynamical symmetries, the control landscape corresponding to an implementable target gate is proven to possess multiple locally optimal critical points, and its ruggedness can be further increased if the target gate is not realizable. These results imply that the optimization of quantum dynamics can be seriously impeded when operating with local search algorithms under these conditions, and thus full controllability is demanded.

  8. Compact representations for the design of quantum logic

    CERN Document Server

    Niemann, Philipp

    2017-01-01

    This book discusses modern approaches and challenges of computer-aided design (CAD) of quantum circuits with a view to providing compact representations of quantum functionality. Focusing on the issue of quantum functionality, it presents Quantum Multiple-Valued Decision Diagrams (QMDDs – a means of compactly and efficiently representing and manipulating quantum logic. For future quantum computers, going well beyond the size of present-day prototypes, the manual design of quantum circuits that realize a given (quantum) functionality on these devices is no longer an option. In order to keep up with the technological advances, methods need to be provided which, similar to the design and synthesis of conventional circuits, automatically generate a circuit description of the desired functionality. To this end, an efficient representation of the desired quantum functionality is of the essence. While straightforward representations are restricted due to their (exponentially) large matrix descriptions and other de...

  9. Activation and thermodynamic parameter study of the heteronuclear C=O···H-N hydrogen bonding of diphenylurethane isomeric structures by FT-IR spectroscopy using the regularized inversion of an eigenvalue problem.

    Science.gov (United States)

    Spegazzini, Nicolas; Siesler, Heinz W; Ozaki, Yukihiro

    2012-08-02

    The doublet of the ν(C=O) carbonyl band in isomeric urethane systems has been extensively discussed in qualitative terms on the basis of FT-IR spectroscopy of the macromolecular structures. Recently, a reaction extent model was proposed as an inverse kinetic problem for the synthesis of diphenylurethane for which hydrogen-bonded and non-hydrogen-bonded C=O functionalities were identified. In this article, the heteronuclear C=O···H-N hydrogen bonding in the isomeric structure of diphenylurethane synthesized from phenylisocyanate and phenol was investigated via FT-IR spectroscopy, using a methodology of regularization for the inverse reaction extent model through an eigenvalue problem. The kinetic and thermodynamic parameters of this system were derived directly from the spectroscopic data. The activation and thermodynamic parameters of the isomeric structures of diphenylurethane linked through a hydrogen bonding equilibrium were studied. The study determined the enthalpy (ΔH = 15.25 kJ/mol), entropy (TΔS = 14.61 kJ/mol), and free energy (ΔG = 0.6 kJ/mol) of heteronuclear C=O···H-N hydrogen bonding by FT-IR spectroscopy through direct calculation from the differences in the kinetic parameters (δΔ(‡)H, -TδΔ(‡)S, and δΔ(‡)G) at equilibrium in the chemical reaction system. The parameters obtained in this study may contribute toward a better understanding of the properties of, and interactions in, supramolecular systems, such as the switching behavior of hydrogen bonding.

  10. Traffic Flow Optimization Using a Quantum Annealer

    Directory of Open Access Journals (Sweden)

    Florian Neukart

    2017-12-01

    Full Text Available Quantum annealing algorithms belong to the class of metaheuristic tools, applicable for solving binary optimization problems. Hardware implementations of quantum annealing, such as the quantum processing units (QPUs produced by D-Wave Systems, have been subject to multiple analyses in research, with the aim of characterizing the technology’s usefulness for optimization and sampling tasks. In this paper, we present a real-world application that uses quantum technologies. Specifically, we show how to map certain parts of a real-world traffic flow optimization problem to be suitable for quantum annealing. We show that time-critical optimization tasks, such as continuous redistribution of position data for cars in dense road networks, are suitable candidates for quantum computing. Due to the limited size and connectivity of current-generation D-Wave QPUs, we use a hybrid quantum and classical approach to solve the traffic flow problem.

  11. Single-shot secure quantum network coding on butterfly network with free public communication

    Science.gov (United States)

    Owari, Masaki; Kato, Go; Hayashi, Masahito

    2018-01-01

    Quantum network coding on the butterfly network has been studied as a typical example of quantum multiple cast network. We propose a secure quantum network code for the butterfly network with free public classical communication in the multiple unicast setting under restricted eavesdropper’s power. This protocol certainly transmits quantum states when there is no attack. We also show the secrecy with shared randomness as additional resource when the eavesdropper wiretaps one of the channels in the butterfly network and also derives the information sending through public classical communication. Our protocol does not require verification process, which ensures single-shot security.

  12. Quasi quantum group covariant q-oscillators

    International Nuclear Information System (INIS)

    Schomerus, V.

    1992-05-01

    If q is a p-th root of unity there exists a quasi-co-associative truncated quantum group algebra U T q (sl 2 ) whose indecomposable representations are the physical representations of U q (sl 2 ), whose co-product yields the truneated tensor product of physical representations of U q (sl 2 ), and whose R-matrix satisfies quasi Yang Baxter equations. For primitive p-th roots q, we consider a 2-dimensional q-oscillator which admits U T q (sl 2 ) as a symmetry algebra. Its wave functions lie in a space F T q of 'functions on the truncated quantum plane', i.e. of polynomials in noncommuting complex coordinate functions z a , on which multiplication operators Z a and the elements of U T q (sl 2 ) can act. This illustrates the concept of quasi quantum planes. Due to the truncation, the Hilbert space of states is finite dimensional. The subspaces F T(n) of monomials in x a of n-th degree vanish for n ≥ p-1, and F T(n) carries the 2J+1 dimensional irreducible representation of U T q (sl 2 ) if n=2J, J=0, 1/2, ... 1/2(p-2). Partial derivatives δ a are introduced. We find a *-operation on the algebra of multiplication operators Z i and derivatives δ b such that the adjoints Z * a act as differentiation on the truncated quantum plane. Multiplication operators Z a ('creation operators') and their adjoints ('annihilation operators') obey q -1/2 -commutation relations. The *-operation is used to determine a positive definite scalar product on the truncated quantum plane F T q . Some natural candidates of Hamiltonians for the q-oscillators are determined. (orig./HSI)

  13. The symmetric extendibility of quantum states

    International Nuclear Information System (INIS)

    Nowakowski, Marcin L

    2016-01-01

    Studies on the symmetric extendibility of quantum states have become particularly important in the context of the analysis of one-way quantum measures of entanglement, and the distillability and security of quantum protocols. In this paper we analyze composite systems containing a symmetric extendible part, with particular attention devoted to the one-way security of such systems. Further, we introduce a new one-way entanglement monotone based on the best symmetric approximation of a quantum state and the extendible number of a quantum state. We underpin these results with geometric observations about the structures of multi-party settings which posses substantial symmetric extendible components in their subspaces. The impossibility of reducing the maximal symmetric extendibility by means of the one-way local operations and classical communication method is pointed out on multiple copies. Finally, we state a conjecture linking symmetric extendibility with the one-way distillability and security of all quantum states, analyzing the behavior of a private key in the neighborhood of symmetric extendible states. (paper)

  14. Frustration and quantum criticality

    Science.gov (United States)

    Vojta, Matthias

    2018-06-01

    This review article is devoted to the interplay between frustrated magnetism and quantum critical phenomena, covering both theoretical concepts and ideas as well as recent experimental developments in correlated-electron materials. The first part deals with local-moment magnetism in Mott insulators and the second part with frustration in metallic systems. In both cases, frustration can either induce exotic phases accompanied by exotic quantum critical points or lead to conventional ordering with unconventional crossover phenomena. In addition, the competition of multiple phases inherent to frustrated systems can lead to multi-criticality.

  15. Intensity dependent absorption bleaching of high subband excitons in GaAs/AlGaAs multiple quantum wells

    CERN Document Server

    Shin, S H; Lee, E H; Chae, K M; Park, S H; Kim, U

    1998-01-01

    We have investigated the influence of carrier generation on the absorption bleaching of the n=2 and n=3 excitons in GaAs/AlGaAs multiple quantum wells (MQWs). With the excitation near the resonance of the n=1 exciton absorption, the long range coulomb screening and collision broadening had significant effects on the exciton bleaching. At low excitation intensity, the absorption bleaching of the n=2 exciton in 75 A-thick MQWs and that of the n=3 exciton in 150 A-thick MQWs were due to linewidth broadening by the collision broadening effect only. At high excitation intensity, however, the reduction of oscillator strength due to the long range coulomb screening contributed dominantly to absorption bleaching.

  16. Quantum fields and processes a combinatorial approach

    CERN Document Server

    Gough, John

    2018-01-01

    Wick ordering of creation and annihilation operators is of fundamental importance for computing averages and correlations in quantum field theory and, by extension, in the Hudson-Parthasarathy theory of quantum stochastic processes, quantum mechanics, stochastic processes, and probability. This book develops the unified combinatorial framework behind these examples, starting with the simplest mathematically, and working up to the Fock space setting for quantum fields. Emphasizing ideas from combinatorics such as the role of lattice of partitions for multiple stochastic integrals by Wallstrom-Rota and combinatorial species by Joyal, it presents insights coming from quantum probability. It also introduces a 'field calculus' which acts as a succinct alternative to standard Feynman diagrams and formulates quantum field theory (cumulant moments, Dyson-Schwinger equation, tree expansions, 1-particle irreducibility) in this language. Featuring many worked examples, the book is aimed at mathematical physicists, quant...

  17. Quantum fields and processes a combinatorial approach

    CERN Document Server

    Gough, John

    2018-01-01

    Wick ordering of creation and annihilation operators is of fundamental importance for computing averages and correlations in quantum field theory and, by extension, in the Hudson–Parthasarathy theory of quantum stochastic processes, quantum mechanics, stochastic processes, and probability. This book develops the unified combinatorial framework behind these examples, starting with the simplest mathematically, and working up to the Fock space setting for quantum fields. Emphasizing ideas from combinatorics such as the role of lattice of partitions for multiple stochastic integrals by Wallstrom–Rota and combinatorial species by Joyal, it presents insights coming from quantum probability. It also introduces a 'field calculus' which acts as a succinct alternative to standard Feynman diagrams and formulates quantum field theory (cumulant moments, Dyson–Schwinger equation, tree expansions, 1-particle irreducibility) in this language. Featuring many worked examples, the book is aimed at mathematical physicists,...

  18. Algebraic Topology Foundations of Supersymmetry and Symmetry Breaking in Quantum Field Theory and Quantum Gravity: A Review

    Directory of Open Access Journals (Sweden)

    Ion C. Baianu

    2009-04-01

    Full Text Available A novel algebraic topology approach to supersymmetry (SUSY and symmetry breaking in quantum field and quantum gravity theories is presented with a view to developing a wide range of physical applications. These include: controlled nuclear fusion and other nuclear reaction studies in quantum chromodynamics, nonlinear physics at high energy densities, dynamic Jahn-Teller effects, superfluidity, high temperature superconductors, multiple scattering by molecular systems, molecular or atomic paracrystal structures, nanomaterials, ferromagnetism in glassy materials, spin glasses, quantum phase transitions and supergravity. This approach requires a unified conceptual framework that utilizes extended symmetries and quantum groupoid, algebroid and functorial representations of non-Abelian higher dimensional structures pertinent to quantized spacetime topology and state space geometry of quantum operator algebras. Fourier transforms, generalized Fourier-Stieltjes transforms, and duality relations link, respectively, the quantum groups and quantum groupoids with their dual algebraic structures; quantum double constructions are also discussed in this context in relation to quasi-triangular, quasi-Hopf algebras, bialgebroids, Grassmann-Hopf algebras and higher dimensional algebra. On the one hand, this quantum algebraic approach is known to provide solutions to the quantum Yang-Baxter equation. On the other hand, our novel approach to extended quantum symmetries and their associated representations is shown to be relevant to locally covariant general relativity theories that are consistent with either nonlocal quantum field theories or local bosonic (spin models with the extended quantum symmetry of entangled, 'string-net condensed' (ground states.

  19. Subcarrier multiplexing optical quantum key distribution

    International Nuclear Information System (INIS)

    Ortigosa-Blanch, A.; Capmany, J.

    2006-01-01

    We present the physical principles of a quantum key distribution system that opens the possibility of parallel quantum key distribution and, therefore, of a substantial improvement in the bit rate of such systems. Quantum mechanics allows for multiple measurements at different frequencies and thus we exploit this concept by extending the concept of frequency coding to the case where more than one radio-frequency subcarrier is used for independently encoding the bits onto an optical carrier. Taking advantage of subcarrier multiplexing techniques we demonstrate that the bit rate can be greatly improved as parallel key distribution is enabled

  20. Investigating non-Markovian dynamics of quantum open systems

    Science.gov (United States)

    Chen, Yusui

    Quantum open system coupled to a non-Markovian environment has recently attracted widespread interest for its important applications in quantum information processing and quantum dissipative systems. New phenomena induced by the non-Markovian environment have been discovered in variety of research areas ranging from quantum optics, quantum decoherence to condensed matter physics. However, the study of the non-Markovian quantum open system is known a difficult problem due to its technical complexity in deriving the fundamental equation of motion and elusive conceptual issues involving non-equilibrium dynamics for a strong coupled environment. The main purpose of this thesis is to introduce several new techniques of solving the quantum open systems including a systematic approach to dealing with non-Markovian master equations from a generic quantum-state diffusion (QSD) equation. In the first part of this thesis, we briefly introduce the non-Markovian quantum-state diffusion approach, and illustrate some pronounced non-Markovian quantum effects through numerical investigation on a cavity-QED model. Then we extend the non-Markovian QSD theory to an interesting model where the environment has a hierarchical structure, and find out the exact non-Markovian QSD equation of this model system. We observe the generation of quantum entanglement due to the interplay between the non-Markovian environment and the cavity. In the second part, we show an innovative method to obtain the exact non-Markovian master equations for a set of generic quantum open systems based on the corresponding non-Markovian QSD equations. Multiple-qubit systems and multilevel systems are discussed in details as two typical examples. Particularly, we derive the exact master equation for a model consisting of a three-level atom coupled to an optical cavity and controlled by an external laser field. Additionally, we discuss in more general context the mathematical similarity between the multiple

  1. 2D 1H -13C Heteronuclear Shift Correlation Of 2a - Hydroxy Aiantolactone From Pulicaria Undulata C.A. Mey

    Directory of Open Access Journals (Sweden)

    A. Rustaiyan

    1992-07-01

    Full Text Available We have reported recently the isolation and characterization of several sesquiterpene lactones from Pulicaria undulata (1."nThe lactones were isolated from an Et20 - Petrol (1:3 fraction by different chromatographic techniques including HPLC (RP 8, MeOH - H2O, 13:7."nIn this way three eudesmanolides 1 - 3, a guaianolide 4, a nor -guaianolide 5, as well as the pseudoguaianolide 6 and the xanthanolide 7 were isolated. One of the eudesmanolides (2a - hydroxy aiantolactone, 1, was present as the main component."nSuch lactones being known as biologically active substances, we have decided to describe for the first time a detailed interpretation of proton, 1H -NMR, 13C - NMR and 2D lH -13C - heteronuclear shift correlation spectra of 2a - hydroxy aiantolactone. The stereochemistry of C - 2 , C - 7 and C - 8 was determined by the NOESY experiments, H - 7 and H - 8 are in the a configuration and H - 2 is in the b configuration.

  2. Uniqueness of Nash equilibria in a quantum Cournot duopoly game

    International Nuclear Information System (INIS)

    Sekiguchi, Yohei; Sakahara, Kiri; Sato, Takashi

    2010-01-01

    A quantum Cournot game whose classical form game has multiple Nash equilibria is examined. Although the classical equilibria fail to be Pareto optimal, the quantum equilibrium exhibits the following two properties: (i) if the measurement of entanglement between strategic variables chosen by the competing firms is sufficiently large, the multiplicity of equilibria vanishes, and (ii) the more strongly the strategic variables are entangled, the more closely the unique equilibrium approaches to the optimal one.

  3. The quantum structure of matter grand challenge project: Large-scale 3-D solutions in relativistic quantum dynamics

    International Nuclear Information System (INIS)

    Wells, J.C.; Oberacker, V.E.; Umar, A.S.

    1993-01-01

    We describe the numerical methods used to solve the time-dependent Dirac equation on a three-dimensional Cartesian lattice. Efficient algorithms are required for computationally intensive studies of nonperturbative relativistic quantum dynamics. Discretization is achieved through the lattice basis-spline collocation method, in which quantum-state vectors and coordinate-space operators are expressed in terms of basis-spline functions on a spatial lattice. All numerical procedures reduce to a series of matrix-vector operations which we perform on the Intel iPSC/860 hypercube, making full use of parallelism. We discuss our solutions to the problems of limited node memory and node-to-node communication overhead inherent in using distributed-memory, multiple-instruction, multiple-data stream parallel computers

  4. A quantum-classical simulation of a multi-surface multi-mode ...

    Indian Academy of Sciences (India)

    Multi surface multi mode quantum dynamics; parallelized quantum classical approach; TDDVR method. 1. ... cal simulation on molecular system is a great cha- llenge for ..... on a multiple core cluster with shared memory using. OpenMP based ...

  5. Quantum Information: Opportunities and Challenges

    Energy Technology Data Exchange (ETDEWEB)

    Bennink, Ryan S [ORNL

    2008-01-01

    Modern society is shaped by the ability to transmit, manipulate, and store large amounts of information. Although we tend to think of information as abstract, information is physical, and computing is a physical process. How then should we understand information in a quantum world, in which physical systems may exist in multiple states at once and are altered by the very act of observation? This question has evolved into an exciting new field of research called Quantum Information (QI). QI challenges many accepted rules and practices in computer science. For example, a quantum computer would turn certain hard problems into soft problems, and would render common computationally-secure encryption methods (such as RSA) insecure. At the same time, quantum communication would provide an unprecedented kind of intrinsic information security at the level of the smallest physical objects used to store or transmit the information. This talk provides a general introduction to the subject of quantum information and its relevance to cyber security. In the first part, two of the stranger aspects of quantum physics namely, superposition and uncertainty are explained, along with their relation to the concept of information. These ideas are illustrated with a few examples: quantum ID cards, quantum key distribution, and Grover s quantum search algorithm. The state-of-the-art in quantum computing and communication hardware is then discussed, along with the daunting technological challenges that must be overcome. Relevant experimental and theoretical efforts at ORNL are highlighted. The talk concludes with speculations on the short- and long-term impact of quantum information on cyber security.

  6. Two-dimensional quantum repeaters

    Science.gov (United States)

    Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.

    2016-11-01

    The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.

  7. Spectroscopy of Charged Quantum Dot Molecules

    Science.gov (United States)

    Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.; Korenev, V. L.

    2006-03-01

    Spins of single charges in quantum dots are attractive for many quantum information and spintronic proposals. Scalable quantum information applications require the ability to entangle and operate on multiple spins in coupled quantum dots (CQDs). To further the understanding of these systems, we present detailed spectroscopic studies of InAs CQDs with control of the discrete electron or hole charging of the system. The optical spectrum reveals a pattern of energy anticrossings and crossings in the photoluminescence as a function of applied electric field. These features can be understood as a superposition of charge and spin configurations of the two dots and represent clear signatures of quantum mechanical coupling. The molecular resonance leading to these anticrossings is achieved at different electric fields for the optically excited (trion) states and the ground (hole) states allowing for the possibility of using the excited states for optically induced coupling of the qubits.

  8. Radiative recombination mechanism of carriers in InGaN/AlInGaN multiple quantum wells with varying aluminum content

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tong [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Jiao, Shujie, E-mail: shujiejiao@gmail.com [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory for Photonic and Electric Bandgap Materials, Ministry of Education, Harbin Normal University, Harbin 150001 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Wang, Dongbo [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Gao, Shiyong, E-mail: gaoshiyong@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Yang, Tianpeng [EpiTop Optoelectronic Co., Ltd., Pingxiang 337000 (China); Liang, Hongwei [School of Physics and Optoelectronic Engineering, Dalian University of Technology, Dalian 116024 (China); Zhao, Liancheng [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-02-05

    Highlights: • Structural and optical properties of In GaN/Al{sub x}In{sub y}Ga{sub 1−x−y}N MQWs were investigated. • The existence of In-rich clusters has been verified by Raman spectra. • The degree of localization effect increase with increasing Al content in barriers. • The origin of the deep localized states could be assigned to the larger QCSE. • Recombination mechanism of carriers with increasing temperature has been proposed. - Abstract: The structural and optical properties of In{sub 0.20}Ga{sub 0.80}N/Al{sub x}In{sub y}Ga{sub 1−x−y}N multiple quantum wells samples with varying Al content in barrier layers grown on sapphire substrates by metalorganic chemical vapor deposition have been investigated by means of high-resolution X-ray diffraction, Raman scattering measurements and temperature-dependent photoluminescence. Raman measurements verified the existence of In-rich clusters in ternary and quaternary layers. At 10 K and 300 K, the PL spectrum of each sample is dominated by a sharp emission peak arising from In{sub 0.20}Ga{sub 0.80}N well layers. The anomalous temperature-dependent S-shaped behaviors of emission energies have been observed, indicating the presence of localized states induced by the potential fluctuations in the quantum wells due to the inhomogeneous distribution of In-rich clusters. The degree of the localization effect and the transition temperatures between different temperature regions can be enhanced by increasing Al content in barrier layers. The improvement of the localized states emission has been observed at the lower energy side of band gap emission of quantum wells with increasing Al content. The origin of the deep localized states could be attributed to the larger quantum-confined Stark effect in the quantum wells with higher Al content. The recombination mechanism of carriers between band edge and localized states was proposed for interpreting of the emission characteristics.

  9. Efficient quantum computing using coherent photon conversion.

    Science.gov (United States)

    Langford, N K; Ramelow, S; Prevedel, R; Munro, W J; Milburn, G J; Zeilinger, A

    2011-10-12

    Single photons are excellent quantum information carriers: they were used in the earliest demonstrations of entanglement and in the production of the highest-quality entanglement reported so far. However, current schemes for preparing, processing and measuring them are inefficient. For example, down-conversion provides heralded, but randomly timed, single photons, and linear optics gates are inherently probabilistic. Here we introduce a deterministic process--coherent photon conversion (CPC)--that provides a new way to generate and process complex, multiquanta states for photonic quantum information applications. The technique uses classically pumped nonlinearities to induce coherent oscillations between orthogonal states of multiple quantum excitations. One example of CPC, based on a pumped four-wave-mixing interaction, is shown to yield a single, versatile process that provides a full set of photonic quantum processing tools. This set satisfies the DiVincenzo criteria for a scalable quantum computing architecture, including deterministic multiqubit entanglement gates (based on a novel form of photon-photon interaction), high-quality heralded single- and multiphoton states free from higher-order imperfections, and robust, high-efficiency detection. It can also be used to produce heralded multiphoton entanglement, create optically switchable quantum circuits and implement an improved form of down-conversion with reduced higher-order effects. Such tools are valuable building blocks for many quantum-enabled technologies. Finally, using photonic crystal fibres we experimentally demonstrate quantum correlations arising from a four-colour nonlinear process suitable for CPC and use these measurements to study the feasibility of reaching the deterministic regime with current technology. Our scheme, which is based on interacting bosonic fields, is not restricted to optical systems but could also be implemented in optomechanical, electromechanical and superconducting

  10. Hybrid Toffoli gate on photons and quantum spins.

    Science.gov (United States)

    Luo, Ming-Xing; Ma, Song-Ya; Chen, Xiu-Bo; Wang, Xiaojun

    2015-11-16

    Quantum computation offers potential advantages in solving a number of interesting and difficult problems. Several controlled logic gates, the elemental building blocks of quantum computer, have been realized with various physical systems. A general technique was recently proposed that significantly reduces the realization complexity of multiple-control logic gates by harnessing multi-level information carriers. We present implementations of a key quantum circuit: the three-qubit Toffoli gate. By exploring the optical selection rules of one-sided optical microcavities, a Toffoli gate may be realized on all combinations of photon and quantum spins in the QD-cavity. The three general controlled-NOT gates are involved using an auxiliary photon with two degrees of freedom. Our results show that photons and quantum spins may be used alternatively in quantum information processing.

  11. Designing Novel Quaternary Quantum Reversible Subtractor Circuits

    Science.gov (United States)

    Haghparast, Majid; Monfared, Asma Taheri

    2018-01-01

    Reversible logic synthesis is an important area of current research because of its ability to reduce energy dissipation. In recent years, multiple valued logic has received great attention due to its ability to reduce the width of the reversible circuit which is a main requirement in quantum technology. Subtractor circuits are between major components used in quantum computers. In this paper, we will discuss the design of a quaternary quantum reversible half subtractor circuit using quaternary 1-qudit, 2-qudit Muthukrishnan-Stroud and 3-qudit controlled gates and a 2-qudit Generalized quaternary gate. Then a design of a quaternary quantum reversible full subtractor circuit based on the quaternary half subtractor will be presenting. The designs shall then be evaluated in terms of quantum cost, constant input, garbage output, and hardware complexity. The proposed quaternary quantum reversible circuits are the first attempt in the designing of the aforementioned subtractor.

  12. Mathematics and quantum mechanics; Matematicas y mecanica cuantica

    Energy Technology Data Exchange (ETDEWEB)

    Santander, M.

    2000-07-01

    Several episodes in the relation between Mathematics and Quantum Mechanics are discussed; and the emphasis is put in the existence of multiple and sometimes unexpected connections between ideas originating in Mathematics and in Quantum Physics. The question of the unresasonable effectiveness of Mathematics in Physics is also presented in the same light. (Author) 3 refs.

  13. The quantum handshake entanglement, nonlocality and transactions

    CERN Document Server

    Cramer, John G

    2016-01-01

    This book shines bright light into the dim recesses of quantum theory, where the mysteries of entanglement, nonlocality, and wave collapse have motivated some to conjure up multiple universes, and others to adopt a "shut up and calculate" mentality. After an extensive and accessible introduction to quantum mechanics and its history, the author turns attention to his transactional model. Using a quantum handshake between normal and time-reversed waves, this model provides a clear visual picture explaining the baffling experimental results that flow daily from the quantum physics laboratories of the world. To demonstrate its powerful simplicity, the transactional model is applied to a collection of counter-intuitive experiments and conceptual problems.

  14. Sensitivity enhancement by multiple-contact cross-polarization under magic-angle spinning.

    Science.gov (United States)

    Raya, J; Hirschinger, J

    2017-08-01

    Multiple-contact cross-polarization (MC-CP) is applied to powder samples of ferrocene and l-alanine under magic-angle spinning (MAS) conditions. The method is described analytically through the density matrix formalism. The combination of a two-step memory function approach and the Anderson-Weiss approximation is found to be particularly useful to derive approximate analytical solutions for single-contact Hartmann-Hahn CP (HHCP) and MC-CP dynamics under MAS. We show that the MC-CP sequence requiring no pulse-shape optimization yields higher polarizations at short contact times than optimized adiabatic passage through the HH condition CP (APHH-CP) when the MAS frequency is comparable to the heteronuclear dipolar coupling, i.e., when APHH-CP through a single sideband matching condition is impossible or difficult to perform. It is also shown that the MC-CP sideband HH conditions are generally much broader than for single-contact HHCP and that efficient polarization transfer at the centerband HH condition can be reintroduced by rotor-asynchronous multiple equilibrations-re-equilibrations with the proton spin bath. Boundary conditions for the successful use of the MC-CP experiment when relying on spin-lattice relaxation for repolarization are also examined. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Quantum Computers and Quantum Computer Languages: Quantum Assembly Language and Quantum C

    OpenAIRE

    Blaha, Stephen

    2002-01-01

    We show a representation of Quantum Computers defines Quantum Turing Machines with associated Quantum Grammars. We then create examples of Quantum Grammars. Lastly we develop an algebraic approach to high level Quantum Languages using Quantum Assembly language and Quantum C language as examples.

  16. Frustration and quantum criticality.

    Science.gov (United States)

    Vojta, Matthias

    2018-03-15

    This review article is devoted to the interplay between frustrated magnetism and quantum critical phenomena, covering both theoretical concepts and ideas as well as recent experimental developments in correlated-electron materials. The first part deals with local-moment magnetism in Mott insulators and the second part with frustration in metallic systems. In both cases, frustration can either induce exotic phases accompanied by exotic quantum critical points or lead to conventional ordering with unconventional crossover phenomena. In addition, the competition of multiple phases inherent to frustrated systems can lead to multi-criticality. © 2018 IOP Publishing Ltd.

  17. Quantum and classical mechanics in the phase space representation

    International Nuclear Information System (INIS)

    Shirokov, Yu.M.

    1979-01-01

    The theory of the hamiltonian mechanical systems has been formulated in terms of only such physical and mathematical concepts which are meaningful in both mechanics. For instance the observables in both mechanics are represented as c-number functions of coordinates and momenta. The operations of the usual multiplication of observables as well as Poisson bracket (also treated as a sort of multiplication) are singled out as separate objects which can possess their own structure including h-dependence. This leads to the conclusion that the only primary distinction between classical and quantum mechanics is reduced to the distinction in the form of the algebraic identity for the multiplication operations. All other distinctions are proved to be of the secondary origin. The formalism developed in the paper is especially useful for quantizations and for the transitions (including partial ones) to the classical limits. The transitions in both directions are transparent and accessible for analysis for any quantity at any step of calculations. The unified quantum-classical scattering theory is constructed. The integral quantum Lippman-Schwinder type equation is derived where the free solution term is replaced by the solution of the corresponding classical problem. The iteration of this equation gives the quantum corrections to the classical solution

  18. Quantum-dot cluster-state computing with encoded qubits

    International Nuclear Information System (INIS)

    Weinstein, Yaakov S.; Hellberg, C. Stephen; Levy, Jeremy

    2005-01-01

    A class of architectures is advanced for cluster-state quantum computation using quantum dots. These architectures include using single and multiple dots as logical qubits. Special attention is given to supercoherent qubits introduced by Bacon et al. [Phys. Rev. Lett. 87, 247902 (2001)] for which we discuss the effects of various errors and present a means of error protection

  19. Unified quantum no-go theorems and transforming of quantum pure states in a restricted set

    Science.gov (United States)

    Luo, Ming-Xing; Li, Hui-Ran; Lai, Hong; Wang, Xiaojun

    2017-12-01

    The linear superposition principle in quantum mechanics is essential for several no-go theorems such as the no-cloning theorem, the no-deleting theorem and the no-superposing theorem. In this paper, we investigate general quantum transformations forbidden or permitted by the superposition principle for various goals. First, we prove a no-encoding theorem that forbids linearly superposing of an unknown pure state and a fixed pure state in Hilbert space of a finite dimension. The new theorem is further extended for multiple copies of an unknown state as input states. These generalized results of the no-encoding theorem include the no-cloning theorem, the no-deleting theorem and the no-superposing theorem as special cases. Second, we provide a unified scheme for presenting perfect and imperfect quantum tasks (cloning and deleting) in a one-shot manner. This scheme may lead to fruitful results that are completely characterized with the linear independence of the representative vectors of input pure states. The upper bounds of the efficiency are also proved. Third, we generalize a recent superposing scheme of unknown states with a fixed overlap into new schemes when multiple copies of an unknown state are as input states.

  20. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems.

    Science.gov (United States)

    Baranowski, M; Woźniak-Braszak, A; Jurga, K

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2MHz and 28.411MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins (1)H are polarized in the magnetic field B0 while fluorine spins (19)F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Design of a Super-Pixel-Based Quantum Secure Authentication Demonstrator

    NARCIS (Netherlands)

    Toebes, Chris; Tentrup, Tristan B.H.; Pinkse, Pepijn W.H.

    2017-01-01

    Quantum Secure Authentication (QSA) is a method recently developed to authenticate a multiple-scattering key [1]. Previous implementations only showed proof-of-principle setups. We present a design of a compact and robust demonstration device for Quantum Secure Authentication. The challenge and

  2. Superposing pure quantum states with partial prior information

    Science.gov (United States)

    Dogra, Shruti; Thomas, George; Ghosh, Sibasish; Suter, Dieter

    2018-05-01

    The principle of superposition is an intriguing feature of quantum mechanics, which is regularly exploited in many different circumstances. A recent work [M. Oszmaniec et al., Phys. Rev. Lett. 116, 110403 (2016), 10.1103/PhysRevLett.116.110403] shows that the fundamentals of quantum mechanics restrict the process of superimposing two unknown pure states, even though it is possible to superimpose two quantum states with partial prior knowledge. The prior knowledge imposes geometrical constraints on the choice of input states. We discuss an experimentally feasible protocol to superimpose multiple pure states of a d -dimensional quantum system and carry out an explicit experimental realization for two single-qubit pure states with partial prior information on a two-qubit NMR quantum information processor.

  3. Quantum states and their marginals. From multipartite entanglement to quantum error-correcting codes

    International Nuclear Information System (INIS)

    Huber, Felix Michael

    2017-01-01

    At the heart of the curious phenomenon of quantum entanglement lies the relation between the whole and its parts. In my thesis, I explore different aspects of this theme in the multipartite setting by drawing connections to concepts from statistics, graph theory, and quantum error-correcting codes: first, I address the case when joint quantum states are determined by their few-body parts and by Jaynes' maximum entropy principle. This can be seen as an extension of the notion of entanglement, with less complex states already being determined by their few-body marginals. Second, I address the conditions for certain highly entangled multipartite states to exist. In particular, I present the solution of a long-standing open problem concerning the existence of an absolutely maximally entangled state on seven qubits. This sheds light on the algebraic properties of pure quantum states, and on the conditions that constrain the sharing of entanglement amongst multiple particles. Third, I investigate Ulam's graph reconstruction problems in the quantum setting, and obtain legitimacy conditions of a set of states to be the reductions of a joint graph state. Lastly, I apply and extend the weight enumerator machinery from quantum error correction to investigate the existence of codes and highly entangled states in higher dimensions. This clarifies the physical interpretation of the weight enumerators and of the quantum MacWilliams identity, leading to novel applications in multipartite entanglement.

  4. Corrigendum to "Multiple-quantum spin counting in magic-angle-spinning NMR via low-power symmetry-based dipolar recoupling" [J. Magn. Reson. 236 (2013) 31-40

    Science.gov (United States)

    Teymoori, Gholamhasan; Pahari, Bholanath; Viswanathan, Elumalai; Edén, Mattias

    2017-03-01

    The authors regret that an inappropriate NMR data processing, not known to all authors at the time of publication, was used to produce the multiple-quantum coherence (MQC) spin counting data presented in our article: this lead to artificially enhanced results, particularly concerning those obtained at long MQC excitation intervals (τexc). Here we reproduce Figs. 4-7 with correctly processed data.

  5. Students' Conceptual Difficulties in Quantum Mechanics: Potential Well Problems

    Science.gov (United States)

    Ozcan, Ozgur; Didis, Nilufer; Tasar, Mehmet Fatih

    2009-01-01

    In this study, students' conceptual difficulties about some basic concepts in quantum mechanics like one-dimensional potential well problems and probability density of tunneling particles were identified. For this aim, a multiple choice instrument named Quantum Mechanics Conceptual Test has been developed by one of the researchers of this study…

  6. Instantaneous Non-Local Computation of Low T-Depth Quantum Circuits

    DEFF Research Database (Denmark)

    Speelman, Florian

    2016-01-01

    -depth of a quantum circuit, able to perform non-local computation of quantum circuits with a (poly-)logarithmic number of layers of T gates with quasi-polynomial entanglement. Our proofs combine ideas from blind and delegated quantum computation with the garden-hose model, a combinatorial model of communication......Instantaneous non-local quantum computation requires multiple parties to jointly perform a quantum operation, using pre-shared entanglement and a single round of simultaneous communication. We study this task for its close connection to position-based quantum cryptography, but it also has natural...... applications in the context of foundations of quantum physics and in distributed computing. The best known general construction for instantaneous non-local quantum computation requires a pre-shared state which is exponentially large in the number of qubits involved in the operation, while efficient...

  7. Engineered valley-orbit splittings in quantum-confined nanostructures in silicon

    NARCIS (Netherlands)

    Rahman, R.; Verduijn, J.; Kharche, N.; Lansbergen, G.P.; Klimeck, G.; Hollenberg, L.C.L.; Rogge, S.

    2011-01-01

    An important challenge in silicon quantum electronics in the few electron regime is the potentially small energy gap between the ground and excited orbital states in 3D quantum confined nanostructures due to the multiple valley degeneracies of the conduction band present in silicon. Understanding

  8. Preparation of Greenberger-Horne-Zeilinger entangled states with multiple superconducting quantum-interference device qubits or atoms in cavity QED

    International Nuclear Information System (INIS)

    Yang Chuiping; Han Siyuan

    2004-01-01

    A scheme is proposed for generating Greenberger-Horne-Zeilinger (GHZ) entangled states of multiple superconducting quantum-interference device (SQUID) qubits by the use of a microwave cavity. The scheme operates essentially by creating a single photon through an auxiliary SQUID built in the cavity and performing a joint multiqubit phase shift with assistance of the cavity photon. It is shown that entanglement can be generated using this method, deterministic and independent of the number of SQUID qubits. In addition, we show that the present method can be applied to preparing many atoms in a GHZ entangled state, with tolerance to energy relaxation during the operation

  9. Quantum Computers and Quantum Computer Languages: Quantum Assembly Language and Quantum C Language

    OpenAIRE

    Blaha, Stephen

    2002-01-01

    We show a representation of Quantum Computers defines Quantum Turing Machines with associated Quantum Grammars. We then create examples of Quantum Grammars. Lastly we develop an algebraic approach to high level Quantum Languages using Quantum Assembly language and Quantum C language as examples.

  10. Quantum chi-squared and goodness of fit testing

    Energy Technology Data Exchange (ETDEWEB)

    Temme, Kristan [IQIM, California Institute of Technology, Pasadena, California 91125 (United States); Verstraete, Frank [Fakultät für Physik, Universität Wien, Boltzmanngasse 5, 1090 Wien, Austria and Faculty of Science, Ghent University, B-9000 Ghent (Belgium)

    2015-01-15

    A quantum mechanical hypothesis test is presented for the hypothesis that a certain setup produces a given quantum state. Although the classical and the quantum problems are very much related to each other, the quantum problem is much richer due to the additional optimization over the measurement basis. A goodness of fit test for i.i.d quantum states is developed and a max-min characterization for the optimal measurement is introduced. We find the quantum measurement which leads both to the maximal Pitman and Bahadur efficiencies, and determine the associated divergence rates. We discuss the relationship of the quantum goodness of fit test to the problem of estimating multiple parameters from a density matrix. These problems are found to be closely related and we show that the largest error of an optimal strategy, determined by the smallest eigenvalue of the Fisher information matrix, is given by the divergence rate of the goodness of fit test.

  11. Quantum Bio-Informatics II From Quantum Information to Bio-Informatics

    Science.gov (United States)

    Accardi, L.; Freudenberg, Wolfgang; Ohya, Masanori

    2009-02-01

    The problem of quantum-like representation in economy cognitive science, and genetics / L. Accardi, A. Khrennikov and M. Ohya -- Chaotic behavior observed in linea dynamics / M. Asano, T. Yamamoto and Y. Togawa -- Complete m-level quantum teleportation based on Kossakowski-Ohya scheme / M. Asano, M. Ohya and Y. Tanaka -- Towards quantum cybernetics: optimal feedback control in quantum bio informatics / V. P. Belavkin -- Quantum entanglement and circulant states / D. Chruściński -- The compound Fock space and its application in brain models / K. -H. Fichtner and W. Freudenberg -- Characterisation of beam splitters / L. Fichtner and M. Gäbler -- Application of entropic chaos degree to a combined quantum baker's map / K. Inoue, M. Ohya and I. V. Volovich -- On quantum algorithm for multiple alignment of amino acid sequences / S. Iriyama and M. Ohya --Quantum-like models for decision making in psychology and cognitive science / A. Khrennikov -- On completely positive non-Markovian evolution of a d-level system / A. Kossakowski and R. Rebolledo -- Measures of entanglement - a Hilbert space approach / W. A. Majewski -- Some characterizations of PPT states and their relation / T. Matsuoka -- On the dynamics of entanglement and characterization ofentangling properties of quantum evolutions / M. Michalski -- Perspective from micro-macro duality - towards non-perturbative renormalization scheme / I. Ojima -- A simple symmetric algorithm using a likeness with Introns behavior in RNA sequences / M. Regoli -- Some aspects of quadratic generalized white noise functionals / Si Si and T. Hida -- Analysis of several social mobility data using measure of departure from symmetry / K. Tahata ... [et al.] -- Time in physics and life science / I. V. Volovich -- Note on entropies in quantum processes / N. Watanabe -- Basics of molecular simulation and its application to biomolecules / T. Ando and I. Yamato -- Theory of proton-induced superionic conduction in hydrogen-bonded systems

  12. Quantum walks, quantum gates, and quantum computers

    International Nuclear Information System (INIS)

    Hines, Andrew P.; Stamp, P. C. E.

    2007-01-01

    The physics of quantum walks on graphs is formulated in Hamiltonian language, both for simple quantum walks and for composite walks, where extra discrete degrees of freedom live at each node of the graph. It is shown how to map between quantum walk Hamiltonians and Hamiltonians for qubit systems and quantum circuits; this is done for both single-excitation and multiexcitation encodings. Specific examples of spin chains, as well as static and dynamic systems of qubits, are mapped to quantum walks, and walks on hyperlattices and hypercubes are mapped to various gate systems. We also show how to map a quantum circuit performing the quantum Fourier transform, the key element of Shor's algorithm, to a quantum walk system doing the same. The results herein are an essential preliminary to a Hamiltonian formulation of quantum walks in which coupling to a dynamic quantum environment is included

  13. Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices.

    Science.gov (United States)

    Sapienza, Luca; Liu, Jin; Song, Jin Dong; Fält, Stefan; Wegscheider, Werner; Badolato, Antonio; Srinivasan, Kartik

    2017-07-24

    We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots. The motivation of this work is to determine an approach that allows to assess single quantum dots as candidates for quantum nanophotonic devices. By combining optical and scanning probe characterization techniques, we find that single quantum dots often appear in the vicinity of comparatively large topographic features. Despite this, the quantum dots generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions, and this behavior is observed across multiple wafers produced in different growth chambers. Such large surface features are nevertheless a detriment to applications in which single quantum dots are embedded within nanofabricated photonic devices: they are likely to cause large spectral shifts in the wavelength of cavity modes designed to resonantly enhance the quantum dot emission, thereby resulting in a nominally perfectly-fabricated single quantum dot device failing to behave in accordance with design. We anticipate that the approach of screening quantum dots not only based on their optical properties, but also their surrounding surface topographies, will be necessary to improve the yield of single quantum dot nanophotonic devices.

  14. Investigation of silicon/silicon germanium multiple quantum well layers in silicon avalanche photodiodes

    International Nuclear Information System (INIS)

    Loudon, A.Y.

    2002-01-01

    Silicon single photon avalanche diodes (SPADs) are currently utilised in many single photon counting systems due to their high efficiency, fast response times, low voltage operation and potentially low cost. For fibre based applications however (at wavelengths 1.3 and 1.55μm) and eye-safe wavelength applications (>1.4μm), Si devices are not suitable due to their 1.1μm absorption edge and hence greatly reduced absorption above this wavelength. InGaAs/InP or Ge SPADs absorb at these longer wavelengths, but both require cryogenic cooling for low noise operation and III-V integration with conventional Si circuitry is difficult. Si/SiGe is currently attracting great interest for optoelectronic applications and attempts to combine Si avalanche photodiodes with Si/SiGe multiple quantum well absorbing layers have been successful. Here, an effort to utilise this material system has shown an improvement in photon counting efficiency above 1.1μm of more than 30 times compared to an all-Si control device. In addition to its longer wavelength response, this Si/SiGe device has room temperature operation, low cost fabrication and is compatible with conventional Si circuitry. (author)

  15. Stereoselective and stereospecific effects in the formation of heteronuclear tartrate complexes of 3d- and 4f-elements from proton magnetic relaxation data

    International Nuclear Information System (INIS)

    Sal'nikov, Yu.I.; Chevela, V.V.

    1987-01-01

    A new approach to identification of stereoselective and stereospecific effects in the formation of heteronuclear tartrate complexes of 3d- and 4f-elements according to proton magnetic relaxation data is developed. At the first stage comparison of experimental dependences of the property measured (relaxation efficiency coefficient, Bjerrum function etc.) on the consentrational parameters is conducted. Their different course in systems with dH 4 L (d-tartaric acid) and dlH 4 L (dl-tartaric acid) points out to the presence of stereoeffects. Then, using mathematical simulation the most true stoichiometry of complex particles is determined as well as optimized values of their stability constants and intensity factors. The method is used when investigating the following systems: Fe 3+ -dH 4 L(dlH 4 L), Ln 3+ -dH 4 L(dlH 4 L), Fe 3+ -Ln 3+ -dH 4 L(dlH 4 L)(Ln 3+ -Gd 3+ , Ho 3+ , Er 3+ , Tm 3+ )

  16. Critical parameters for the molecular beam epitaxial growth of 1.55 μm (Ga,In)(N,As) multiple quantum wells

    International Nuclear Information System (INIS)

    Ishikawa, Fumitaro; Luna, Esperanza; Trampert, Achim; Ploog, Klaus H.

    2006-01-01

    The authors discuss the effect of substrate temperature and As beam equivalent pressure (BEP) on the molecular beam epitaxial growth of (Ga,In)(N,As) multiple quantum wells (MQWs). Transmission electron microscopy studies reveal that a low substrate temperature essentially prevents composition modulations. Secondary ion mass spectrometry results indicate that a low As BEP reduces the incorporation competition of group V elements. The low substrate temperature and low As BEP growth condition leads to (Ga,In)(N,As) MQWs containing more than 4% N preserving good structural and optical properties, and hence demonstrating 1.55 μm photoluminescence emission at room temperature

  17. Coherent states for quantum compact groups

    CERN Document Server

    Jurco, B

    1996-01-01

    Coherent states are introduced and their properties are discussed for all simple quantum compact groups. The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit and interpret the coherent state as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R--matrix formulation (generalizing this way the q--deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel--Weil construction) are described using the concept of coherent state. The relation between representation theory and non--commutative differential geometry is suggested.}

  18. Quantum strongly secure ramp secret sharing

    DEFF Research Database (Denmark)

    Zhang, Paul; Matsumoto, Rytaro Yamashita

    2015-01-01

    Quantum secret sharing is a scheme for encoding a quantum state (the secret) into multiple shares and distributing them among several participants. If a sufficient number of shares are put together, then the secret can be fully reconstructed. If an insufficient number of shares are put together...... however, no information about the secret can be revealed. In quantum ramp secret sharing, partial information about the secret is allowed to leak to a set of participants, called an unqualified set, that cannot fully reconstruct the secret. By allowing this, the size of a share can be drastically reduced....... This paper introduces a quantum analog of classical strong security in ramp secret sharing schemes. While the ramp secret sharing scheme still leaks partial information about the secret to unqualified sets of participants, the strong security condition ensures that qudits with critical information can...

  19. Simultaneous dual-functioning InGaN/GaN multiple-quantum-well diode for transferrable optoelectronics

    Science.gov (United States)

    Shi, Zheng; Yuan, Jialei; Zhang, Shuai; Liu, Yuhuai; Wang, Yongjin

    2017-10-01

    We propose a wafer-level procedure for the fabrication of 1.5-mm-diameter dual functioning InGaN/GaN multiple-quantum-well (MQW) diodes on a GaN-on-silicon platform for transferrable optoelectronics. Nitride semiconductor materials are grown on (111) silicon substrates with intermediate Al-composition step-graded buffer layers, and membrane-type MQW-diode architectures are obtained by a combination of silicon removal and III-nitride film backside thinning. Suspended MQW-diodes are directly transferred from silicon to foreign substrates such as metal, glass and polyethylene terephthalate by mechanically breaking the support beams. The transferred MQW-diodes display strong electroluminescence under current injection and photodetection under light irradiation. Interestingly, they demonstrate a simultaneous light-emitting light-detecting function, endowing the 1.5-mm-diameter MQW-diode with the capability of producing transferrable optoelectronics for adjustable displays, wearable optical sensors, multifunctional energy harvesting, flexible light communication and monolithic photonic circuit.

  20. Dynamics of quantum Fisher information in a two-level system coupled to multiple bosonic reservoirs

    Science.gov (United States)

    Wang, Guo-You; Guo, You-Neng; Zeng, Ke

    2015-11-01

    We consider the optimal parameter estimation for a two-level system coupled to multiple bosonic reservoirs. By using quantum Fisher information (QFI), we investigate the effect of the Markovian reservoirs’ number N on QFI in both weak and strong coupling regimes for a two-level system surrounded by N zero-temperature reservoirs of field modes initially in the vacua. The results show that the dynamics of QFI non-monotonically decays to zero with revival oscillations at some time in the weak coupling regime depending on the reservoirs’ parameters. Furthermore, we also present the relations between the QFI flow, the flows of energy and information, and the sign of the decay rate to gain insight into the physical processes characterizing the dynamics. Project supported by the Hunan Provincial Innovation Foundation for Postgraduate, China (Grant No. CX2014B194) and the Scientific Research Foundation of Hunan Provincial Education Department, China (Grant No. 13C039).

  1. Anomalous disorder-related phenomena in InGaN/GaN multiple quantum well heterosystems

    International Nuclear Information System (INIS)

    Hu, Y.-J.; Huang, Y.-W.; Fang, C.-H.; Wang, J.-C.; Chen, Y.-F.; Nee, T.-E.

    2010-01-01

    The influences of InGaN/GaN multiple quantum well (MQW) heterostructures with InGaN/GaN and GaN barriers on carrier confinement were investigated. The degree of disordering over a broad range of temperatures from 20 to 300 K was considered. The optical and electrical properties were strongly influenced by structural and compositional disordering of the InGaN/GaN MQW heterostructures. To compare the degree of disordering we examined the temperature dependence of the luminescence spectra and electrical conductance contingent on the Berthelot-type mechanisms in the InGaN/GaN MQW heterostructures. We further considered carrier transport in the InGaN/GaN disordered systems, probability of carrier tunneling, and activation energy of the transport mechanism for devices with InGaN/GaN and GaN barriers. The optical properties of InGaN/GaN disordered heterosystems can be interpreted from the features of the absorption spectra. The anomalous temperature-dependent characteristics of the disordered InGaN/GaN MQW structures were attributable to the enhancement of the exciton confinement.

  2. Multiple multicontrol unitary operations: Implementation and applications

    Science.gov (United States)

    Lin, Qing

    2018-04-01

    The efficient implementation of computational tasks is critical to quantum computations. In quantum circuits, multicontrol unitary operations are important components. Here, we present an extremely efficient and direct approach to multiple multicontrol unitary operations without decomposition to CNOT and single-photon gates. With the proposed approach, the necessary two-photon operations could be reduced from O( n 3) with the traditional decomposition approach to O( n), which will greatly relax the requirements and make large-scale quantum computation feasible. Moreover, we propose the potential application to the ( n- k)-uniform hypergraph state.

  3. Adiabatic Quantum Computing

    Science.gov (United States)

    Landahl, Andrew

    2012-10-01

    Quantum computers promise to exploit counterintuitive quantum physics principles like superposition, entanglement, and uncertainty to solve problems using fundamentally fewer steps than any conventional computer ever could. The mere possibility of such a device has sharpened our understanding of quantum coherent information, just as lasers did for our understanding of coherent light. The chief obstacle to developing quantum computer technology is decoherence--one of the fastest phenomena in all of physics. In principle, decoherence can be overcome by using clever entangled redundancies in a process called fault-tolerant quantum error correction. However, the quality and scale of technology required to realize this solution appears distant. An exciting alternative is a proposal called ``adiabatic'' quantum computing (AQC), in which adiabatic quantum physics keeps the computer in its lowest-energy configuration throughout its operation, rendering it immune to many decoherence sources. The Adiabatic Quantum Architectures In Ultracold Systems (AQUARIUS) Grand Challenge Project at Sandia seeks to demonstrate this robustness in the laboratory and point a path forward for future hardware development. We are building devices in AQUARIUS that realize the AQC architecture on up to three quantum bits (``qubits'') in two platforms: Cs atoms laser-cooled to below 5 microkelvin and Si quantum dots cryo-cooled to below 100 millikelvin. We are also expanding theoretical frontiers by developing methods for scalable universal AQC in these platforms. We have successfully demonstrated operational qubits in both platforms and have even run modest one-qubit calculations using our Cs device. In the course of reaching our primary proof-of-principle demonstrations, we have developed multiple spinoff technologies including nanofabricated diffractive optical elements that define optical-tweezer trap arrays and atomic-scale Si lithography commensurate with placing individual donor atoms with

  4. Silicon CMOS architecture for a spin-based quantum computer.

    Science.gov (United States)

    Veldhorst, M; Eenink, H G J; Yang, C H; Dzurak, A S

    2017-12-15

    Recent advances in quantum error correction codes for fault-tolerant quantum computing and physical realizations of high-fidelity qubits in multiple platforms give promise for the construction of a quantum computer based on millions of interacting qubits. However, the classical-quantum interface remains a nascent field of exploration. Here, we propose an architecture for a silicon-based quantum computer processor based on complementary metal-oxide-semiconductor (CMOS) technology. We show how a transistor-based control circuit together with charge-storage electrodes can be used to operate a dense and scalable two-dimensional qubit system. The qubits are defined by the spin state of a single electron confined in quantum dots, coupled via exchange interactions, controlled using a microwave cavity, and measured via gate-based dispersive readout. We implement a spin qubit surface code, showing the prospects for universal quantum computation. We discuss the challenges and focus areas that need to be addressed, providing a path for large-scale quantum computing.

  5. TG/DTG, FT-ICR Mass Spectrometry, and NMR Spectroscopy Study of Heavy Fuel Oil

    KAUST Repository

    Elbaz, Ayman M.; Abdul Jameel, Abdul Gani; Hourani, Nadim; Emwas, Abdul-Hamid M.; Sarathy, Mani; Roberts, William L.

    2015-01-01

    infusion atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry (APCI-FTICR MS), high resolution 1H nuclear magnetic resonance (NMR), 13C NMR, and two-dimensional heteronuclear multiple bond correlation (HMBC

  6. Strategies in a symmetric quantum Kolkata restaurant problem

    Science.gov (United States)

    Sharif, Puya; Heydari, Hoshang

    2012-12-01

    The Quantum Kolkata restaurant problem is a multiple-choice version of the quantum minority game, where a set of n non-communicating players have to chose between one of m choices. A payoff is granted to the players that make a unique choice. It has previously been shown that shared entanglement and quantum operations can aid the players to coordinate their actions and acquire higher payoffs than is possible with classical randomization. In this paper the initial quantum state is expanded to a family of GHZ-type states and strategies are discussed in terms of possible final outcomes. It is shown that the players individually seek outcomes that maximize the collective good.

  7. Multi-functional quantum router using hybrid opto-electromechanics

    Science.gov (United States)

    Ma, Peng-Cheng; Yan, Lei-Lei; Chen, Gui-Bin; Li, Xiao-Wei; Liu, Shu-Jing; Zhan, You-Bang

    2018-03-01

    Quantum routers engineered with multiple frequency bands play a key role in quantum networks. We propose an experimentally accessible scheme for a multi-functional quantum router, using photon-phonon conversion in a hybrid opto-electromechanical system. Our proposed device functions as a bidirectional, tunable multi-channel quantum router, and demonstrates the possibility to route single optical photons bidirectionally and simultaneously to three different output ports, by adjusting the microwave power. Further, the device also behaves as an interswitching unit for microwave and optical photons, yielding probabilistic routing of microwave (optical) signals to optical (microwave) outports. With respect to potential application, we verify the insignificant influence from vacuum and thermal noises in the performance of the router under cryogenic conditions.

  8. GaSb quantum rings in GaAs/Al{sub x}Ga{sub 1−x}As quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Hodgson, P. D., E-mail: pdhodgson@hotmail.co.uk; Hayne, M.; Robson, A. J.; Zhuang, Q. D. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Danos, L. [Department of Chemistry, Lancaster University, Lancaster LA1 4YB (United Kingdom)

    2016-01-28

    We report the results of continuous and time-resolved photoluminescence measurements on type-II GaSb quantum rings embedded within GaAs/Al{sub x}Ga{sub 1−x}As quantum wells. A range of samples were grown with different well widths, compensation-doping concentrations within the wells, and number of quantum-ring layers. We find that each of these variants have no discernible effect on the radiative recombination, except for the very narrowest (5 nm) quantum well. In contrast, single-particle numerical simulations of the sample predict changes in photoluminescence energy of up to 200 meV. This remarkable difference is explained by the strong Coulomb binding of electrons to rings that are multiply charged with holes. The resilience of the emission to compensation doping indicates that multiple hole occupancy of the quantum rings is required for efficient carrier recombination, regardless of whether these holes come from doping or excitation.

  9. Unconditional polarization qubit quantum memory at room temperature

    Science.gov (United States)

    Namazi, Mehdi; Kupchak, Connor; Jordaan, Bertus; Shahrokhshahi, Reihaneh; Figueroa, Eden

    2016-05-01

    The creation of global quantum key distribution and quantum communication networks requires multiple operational quantum memories. Achieving a considerable reduction in experimental and cost overhead in these implementations is thus a major challenge. Here we present a polarization qubit quantum memory fully-operational at 330K, an unheard frontier in the development of useful qubit quantum technology. This result is achieved through extensive study of how optical response of cold atomic medium is transformed by the motion of atoms at room temperature leading to an optimal characterization of room temperature quantum light-matter interfaces. Our quantum memory shows an average fidelity of 86.6 +/- 0.6% for optical pulses containing on average 1 photon per pulse, thereby defeating any classical strategy exploiting the non-unitary character of the memory efficiency. Our system significantly decreases the technological overhead required to achieve quantum memory operation and will serve as a building block for scalable and technologically simpler many-memory quantum machines. The work was supported by the US-Navy Office of Naval Research, Grant Number N00141410801 and the Simons Foundation, Grant Number SBF241180. B. J. acknowledges financial assistance of the National Research Foundation (NRF) of South Africa.

  10. One-dimensional multiple-well oscillators: A time-dependent

    Indian Academy of Sciences (India)

    ... quantum mechanical multiple-well oscillators. An imaginary-time evolution technique, coupled with the minimization of energy expectation value to reach a global minimum, subject to orthogonality constraint (for excited states) has been employed. Pseudodegeneracy in symmetric, deep multiple-well potentials, probability ...

  11. Trade-off between bandwidth and efficiency in semipolar (20 2 ¯ 1 ¯) InGaN/GaN single- and multiple-quantum-well light-emitting diodes

    Science.gov (United States)

    Monavarian, M.; Rashidi, A.; Aragon, A. A.; Nami, M.; Oh, S. H.; DenBaars, S. P.; Feezell, D.

    2018-05-01

    InGaN/GaN light-emitting diodes (LEDs) with large modulation bandwidths are desirable for visible-light communication. Along with modulation speed, the consideration of the internal quantum efficiency (IQE) under operating conditions is also important. Here, we report the modulation characteristics of semipolar (20 2 ¯ 1 ¯ ) InGaN/GaN (LEDs) with single-quantum well (SQW) and multiple-quantum-well (MQW) active regions grown on free-standing semipolar GaN substrates with peak internal quantum efficiencies (IQEs) of 0.93 and 0.73, respectively. The MQW LEDs exhibit on average about 40-80% higher modulation bandwidth, reaching 1.5 GHz at 13 kA/cm2, but about 27% lower peak IQE than the SQW LEDs. We extract the differential carrier lifetimes (DLTs), RC parasitics, and carrier escape lifetimes and discuss their role in the bandwidth and IQE characteristics. A coulomb-enhanced capture process is shown to rapidly reduce the DLT of the MQW LED at high current densities. Auger recombination is also shown to play little role in increasing the speed of the LEDs. Finally, we investigate the trade-offs between the bandwidth and efficiency and introduce the bandwidth-IQE product as a potential figure of merit for optimizing speed and efficiency in InGaN/GaN LEDs.

  12. Coherent states for quantum compact groups

    International Nuclear Information System (INIS)

    Jurco, B.; Stovicek, P.; CTU, Prague

    1996-01-01

    Coherent states are introduced and their properties are discussed for simple quantum compact groups A l , B l , C l and D l . The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit. The coherent state is interpreted as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R-matrix formulation (generalizing this way the q-deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel-Weil construction) is described using the concept of coherent state. The relation between representation theory and non-commutative differential geometry is suggested. (orig.)

  13. Imagery, intuition and imagination in quantum physics education

    Science.gov (United States)

    Stapleton, Andrew J.

    2018-03-01

    In response to the authors, I demonstrate how threshold concepts offer a means to both contextualise teaching and learning of quantum physics and help transform students into the culture of physics, and as a way to identify particularly troublesome concepts within quantum physics. By drawing parallels from my own doctoral research in another area of contemporary physics—special relativity—I highlight concepts that require an ontological change, namely a shift beyond the reality of everyday Newtonian experience such as time dilation and length contraction, as being troublesome concepts that can present barriers to learning with students often asking "is it real?". Similarly, the domain of quantum physics requires students to move beyond "common sense" perception as it brings into sharp focus the difference between what is experienced via the sense perceptions and the mental abstraction of phenomena. And it's this issue that highlights the important role imagery and creativity have both in quantum physics and in the evolution of physics more generally, and lies in stark contrast to the apparent mathematical focus and lack of opportunity for students to explore ontological issues evident in the authors' research. By reflecting on the authors' observations of a focus on mathematical formalisms and problem solving at the expense of alternative approaches, I explore the dialectic between Heisenberg's highly mathematical approach and Schrödinger's mechanical wave view of the atom, together with its conceptual imagery, at the heart of the evolution of quantum mechanics. In turn, I highlight the significance of imagery, imagination and intuition in quantum physics, together with the importance of adopting an epistemological pluralism—multiple ways of knowing and thinking—in physics education. Again drawing parallels with the authors' work and my own, I identify the role thought experiments have in both quantum physics education and in physics more generally. By

  14. Avoiding bias effects in NMR experiments for heteronuclear dipole-dipole coupling determinations: principles and application to organic semiconductor materials.

    Science.gov (United States)

    Kurz, Ricardo; Cobo, Marcio Fernando; de Azevedo, Eduardo Ribeiro; Sommer, Michael; Wicklein, André; Thelakkat, Mukundan; Hempel, Günter; Saalwächter, Kay

    2013-09-16

    Carbon-proton dipole-dipole couplings between bonded atoms represent a popular probe of molecular dynamics in soft materials or biomolecules. Their site-resolved determination, for example, by using the popular DIPSHIFT experiment, can be challenged by spectral overlap with nonbonded carbon atoms. The problem can be solved by using very short cross-polarization (CP) contact times, however, the measured modulation curves then deviate strongly from the theoretically predicted shape, which is caused by the dependence of the CP efficiency on the orientation of the CH vector, leading to an anisotropic magnetization distribution even for isotropic samples. Herein, we present a detailed demonstration and explanation of this problem, as well as providing a solution. We combine DIPSHIFT experiments with the rotor-directed exchange of orientations (RODEO) method, and modifications of it, to redistribute the magnetization and obtain undistorted modulation curves. Our strategy is general in that it can also be applied to other types of experiments for heteronuclear dipole-dipole coupling determinations that rely on dipolar polarization transfer. It is demonstrated with perylene-bisimide-based organic semiconductor materials, as an example, in which measurements of dynamic order parameters reveal correlations of the molecular dynamics with the phase structure and functional properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Parrondo's game using a discrete-time quantum walk

    International Nuclear Information System (INIS)

    Chandrashekar, C.M.; Banerjee, Subhashish

    2011-01-01

    We present a new form of a Parrondo game using discrete-time quantum walk on a line. The two players A and B with different quantum coins operators, individually losing the game can develop a strategy to emerge as joint winners by using their coins alternatively, or in combination for each step of the quantum walk evolution. We also present a strategy for a player A (B) to have a winning probability more than player B (A). Significance of the game strategy in information theory and physical applications are also discussed. - Highlights: → Novel form of Parrondo's game on a single particle discrete-time quantum walk. → Strategies for players to emerge as individual winners or as joint winners. → General framework for controlling and using quantum walk with multiple coins. → Strategies can be used in algorithms and situations involving directed motion.

  16. Quantum Strategies and Local Operations

    Science.gov (United States)

    Gutoski, Gus

    2010-02-01

    This thesis is divided into two parts. In Part I we introduce a new formalism for quantum strategies, which specify the actions of one party in any multi-party interaction involving the exchange of multiple quantum messages among the parties. This formalism associates with each strategy a single positive semidefinite operator acting only upon the tensor product of the input and output message spaces for the strategy. We establish three fundamental properties of this new representation for quantum strategies and we list several applications, including a quantum version of von Neumann's celebrated 1928 Min-Max Theorem for zero-sum games and an efficient algorithm for computing the value of such a game. In Part II we establish several properties of a class of quantum operations that can be implemented locally with shared quantum entanglement or classical randomness. In particular, we establish the existence of a ball of local operations with shared randomness lying within the space spanned by the no-signaling operations and centred at the completely noisy channel. The existence of this ball is employed to prove that the weak membership problem for local operations with shared entanglement is strongly NP-hard. We also provide characterizations of local operations in terms of linear functionals that are positive and "completely" positive on a certain cone of Hermitian operators, under a natural notion of complete positivity appropriate to that cone. We end the thesis with a discussion of the properties of no-signaling quantum operations.

  17. A numerical study of the quantum oscillations in multiple dangling rings

    International Nuclear Information System (INIS)

    Gu, B.Y.; Basu, C.

    1994-12-01

    We present the quantum mechanical calculations on magnetoconductance of the quantum waveguide topology containing multiply connected dangling mesoscopic rings with the transfer matrix approach. The profiles of the conductance as functions of the Fermi wave number of electrons and of the magnetic flux depend on the number of rings as also on the geometric configuration of the system. The conductance spectrum of this system for disordered lengths in the ring circumferences, dangling links, ballistic leads connecting consecutive dangling rings and disordered magnetic flux is examined in details. We find that there exist two kinds of mini-bands, one originating from the eigenstates of the rings, i.e. the intrinsic mini-bands, and the extra mini-bands. Some of these extra minibands are associated with the dangling links connecting the rings to the main quantum wire, while others are from the standing wave modes associated with the ballistic leads connecting adjacent dangling rings. These different kinds of mini-bands have completely different properties and responds differently to the geometric parameter fluctuations. Unlike the system of potential scatterers, this system of geometric scatterers shows complete band formations at all energies even for finite number of scatterers present. There is a preferential decay of the energy states, depending upon the type of disorder introduced. By controlling the geometric parameters, the conductance band structure of such a model can be artificially tailored and thus may guide the design of better mesoscopic switching devices. (author). 19 refs, 7 figs

  18. Development and validation of an achievement test in introductory quantum mechanics: The Quantum Mechanics Visualization Instrument (QMVI)

    Science.gov (United States)

    Cataloglu, Erdat

    The purpose of this study was to construct a valid and reliable multiple-choice achievement test to assess students' understanding of core concepts of introductory quantum mechanics. Development of the Quantum Mechanics Visualization Instrument (QMVI) occurred across four successive semesters in 1999--2001. During this time 213 undergraduate and graduate students attending the Pennsylvania State University (PSU) at University Park and Arizona State University (ASU) participated in this development and validation study. Participating students were enrolled in four distinct groups of courses: Modern Physics, Undergraduate Quantum Mechanics, Graduate Quantum Mechanics, and Chemistry Quantum Mechanics. Expert panels of professors of physics experienced in teaching quantum mechanics courses and graduate students in physics and science education established the core content and assisted in the validating of successive versions of the 24-question QMVI. Instrument development was guided by procedures outlined in the Standards for Educational and Psychological Testing (AERA-APA-NCME, 1999). Data gathered in this study provided information used in the development of successive versions of the QMVI. Data gathered in the final phase of administration of the QMVI also provided evidence that the intended score interpretation of the QMVI achievement test is valid and reliable. A moderate positive correlation coefficient of 0.49 was observed between the students' QMVI scores and their confidence levels. Analyses of variance indicated that students' scores in Graduate Quantum Mechanics and Undergraduate Quantum Mechanics courses were significantly higher than the mean scores of students in Modern Physics and Chemistry Quantum Mechanics courses (p important factor for students in acquiring a successful understanding of quantum mechanics.

  19. I, Quantum Robot: Quantum Mind control on a Quantum Computer

    OpenAIRE

    Zizzi, Paola

    2008-01-01

    The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.

  20. Structural studies of the activation of the two component receiver domain NTRC by multidimensional heteronuclear NMR

    Energy Technology Data Exchange (ETDEWEB)

    Nohaile, Michael James [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1996-05-01

    Multidimensional heteronuclear NMR spectroscopy was used to investigate the N-terminal domain of the transcriptional enhancer NTRC (NiTrogen Regulatory protein C). This domain belongs to the family of receiver domains of two-component regulatory systems involved in signal transduction. Phosphorylation of NTRC at D54 leads to an activated form of the molecule which stimulates transcription of genes involved in nitrogen regulation. Three and four dimensional NMR techniques were used to determine an intermediate resolution structure of the unphosphorylated, inactive form of the N-terminal domain of NTRC. The structure is comprised of five α-helices and a five-stranded β-sheet in a (β/α)5 topology. Analysis of the backbone dynamics of NTRC indicate that helix 4 and strand 5 are significantly more flexible than the rest of the secondary structure of the protein and that the loops making up the active site are flexible. The short lifetime of phospho-NTRC hampers the study of this form. However, conditions for determining the resonance assignments and, possibly, the three dimensional structure of phosphorylated NTRC have been obtained. Tentative assignments of the phosphorylated form indicate that the majority of the changes that NTRC experiences upon phosphorylation occur in helix 3, strand 4, helix 4, strand 5, and the loop between strand 5 and helix 5 (the 3445 face of NTRC) as well as near the site of phosphorylation. In order to examine a stable, activated form of the protein, constitutively active mutants of NTRC were investigated.

  1. Control of Multiple Exciton Generation and Electron-Phonon Coupling by Interior Nanospace in Hyperstructured Quantum Dot Superlattice.

    Science.gov (United States)

    Chang, I-Ya; Kim, DaeGwi; Hyeon-Deuk, Kim

    2017-09-20

    The possibility of precisely manipulating interior nanospace, which can be adjusted by ligand-attaching down to the subnanometer regime, in a hyperstructured quantum dot (QD) superlattice (QDSL) induces a new kind of collective resonant coupling among QDs and opens up new opportunities for developing advanced optoelectric and photovoltaic devices. Here, we report the first real-time dynamics simulations of the multiple exciton generation (MEG) in one-, two-, and three-dimensional (1D, 2D, and 3D) hyperstructured H-passivated Si QDSLs, accounting for thermally fluctuating band energies and phonon dynamics obtained by finite-temperature ab initio molecular dynamics simulations. We computationally demonstrated that the MEG was significantly accelerated, especially in the 3D QDSL compared to the 1D and 2D QDSLs. The MEG acceleration in the 3D QDSL was almost 1.9 times the isolated QD case. The dimension-dependent MEG acceleration was attributed not only to the static density of states but also to the dynamical electron-phonon couplings depending on the dimensionality of the hyperstructured QDSL, which is effectively controlled by the interior nanospace. Such dimension-dependent modifications originated from the short-range quantum resonance among component QDs and were intrinsic to the hyperstructured QDSL. We propose that photoexcited dynamics including the MEG process can be effectively controlled by only manipulating the interior nanospace of the hyperstructured QDSL without changing component QD size, shape, compositions, ligand, etc.

  2. Self-organized template formation for quantum dot ordering

    International Nuclear Information System (INIS)

    Noetzel, Richard; Mano, Takaaki; Wolter, Joachim H.

    2004-01-01

    Ordered arrays of quantum dots (QDs) are created by self-organized anisotropic strain engineering of (In,Ga)As/GaAs quantum wire (QWR) superlattice (SL) templates on exactly oriented GaAs (100) substrates by molecular beam epitaxy (MBE). The well-defined one-dimensional arrays of (In,Ga)As QDs formed on top of these templates due to local strain recognition are of excellent structural and optical quality up to room temperature. The QD arrays thus allow for fundamental studies and device operation principles based on single- and multiple carrier- and photon-, and coherent quantum interference effects

  3. Construction of a quantum repeater with linear optics

    International Nuclear Information System (INIS)

    Kok, Pieter; Williams, Colin P.; Dowling, Jonathan P.

    2003-01-01

    We study the mechanism and complexity of an efficient quantum repeater, employing double-photon guns, for long-distance optical quantum communication. The guns create polarization-entangled photon pairs on demand. One such source might be a semiconducter quantum dot, which has the distinct advantage over parametric down-conversion that the probability of creating a photon pair is close to 1, while the probability of creating multiple pairs vanishes. The swapping and purifying components are implemented by polarizing beam splitters and probabilistic optical controlled-NOT gates. We also show that the bottleneck in the efficiency of this repeater is due to detector losses

  4. Dirac fields in loop quantum gravity and big bang nucleosynthesis

    International Nuclear Information System (INIS)

    Bojowald, Martin; Das, Rupam; Scherrer, Robert J.

    2008-01-01

    Big bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of big bang nucleosynthesis, to place bounds on these corrections and especially the patch size of discrete quantum gravity states.

  5. Toward structural dynamics: protein motions viewed by chemical shift modulations and direct detection of C'N multiple-quantum relaxation.

    Science.gov (United States)

    Mori, Mirko; Kateb, Fatiha; Bodenhausen, Geoffrey; Piccioli, Mario; Abergel, Daniel

    2010-03-17

    Multiple quantum relaxation in proteins reveals unexpected relationships between correlated or anti-correlated conformational backbone dynamics in alpha-helices or beta-sheets. The contributions of conformational exchange to the relaxation rates of C'N coherences (i.e., double- and zero-quantum coherences involving backbone carbonyl (13)C' and neighboring amide (15)N nuclei) depend on the kinetics of slow exchange processes, as well as on the populations of the conformations and chemical shift differences of (13)C' and (15)N nuclei. The relaxation rates of C'N coherences, which reflect concerted fluctuations due to slow chemical shift modulations (CSMs), were determined by direct (13)C detection in diamagnetic and paramagnetic proteins. In well-folded proteins such as lanthanide-substituted calbindin (CaLnCb), copper,zinc superoxide dismutase (Cu,Zn SOD), and matrix metalloproteinase (MMP12), slow conformational exchange occurs along the entire backbone. Our observations demonstrate that relaxation rates of C'N coherences arising from slow backbone dynamics have positive signs (characteristic of correlated fluctuations) in beta-sheets and negative signs (characteristic of anti-correlated fluctuations) in alpha-helices. This extends the prospects of structure-dynamics relationships to slow time scales that are relevant for protein function and enzymatic activity.

  6. Multiple stable states of a periodically driven electron spin in a quantum dot using circularly polarized light

    Science.gov (United States)

    Korenev, V. L.

    2011-06-01

    The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. The same physics underlie the frequency-locking effect for two-color and mode-locked excitations. However, the pulsed excitation with mode-locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than 100 stable channels.

  7. Potential-controlled filtering in quantum star graphs

    International Nuclear Information System (INIS)

    Turek, Ondřej; Cheon, Taksu

    2013-01-01

    We study the scattering in a quantum star graph with a Fülöp–Tsutsui coupling in its vertex and with external potentials on the lines. We find certain special couplings for which the probability of the transmission between two given lines of the graph is strongly influenced by the potential applied on another line. On the basis of this phenomenon we design a tunable quantum band-pass spectral filter. The transmission from the input to the output line is governed by a potential added on the controlling line. The strength of the potential directly determines the passband position, which allows to control the filter in a macroscopic manner. Generalization of this concept to quantum devices with multiple controlling lines proves possible. It enables the construction of spectral filters with more controllable parameters or with more operation modes. In particular, we design a band-pass filter with independently adjustable multiple passbands. We also address the problem of the physical realization of Fülöp–Tsutsui couplings and demonstrate that the couplings needed for the construction of the proposed quantum devices can be approximated by simple graphs carrying only δ potentials. - Highlights: ► Spectral filtering devices based on quantum graphs are designed theoretically. ► The passband is controlled by the application of macroscopic potentials on lines. ► The filters are built upon special Fulop–Tsutsui type couplings at graph vertices. ► A method of construction of Fulop–Tsutsui vertices from delta potentials is devised.

  8. Quantum Cybernetics and Complex Quantum Systems Science - A Quantum Connectionist Exploration

    OpenAIRE

    Gonçalves, Carlos Pedro

    2014-01-01

    Quantum cybernetics and its connections to complex quantum systems science is addressed from the perspective of complex quantum computing systems. In this way, the notion of an autonomous quantum computing system is introduced in regards to quantum artificial intelligence, and applied to quantum artificial neural networks, considered as autonomous quantum computing systems, which leads to a quantum connectionist framework within quantum cybernetics for complex quantum computing systems. Sever...

  9. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    Energy Technology Data Exchange (ETDEWEB)

    Baart, T. A.; Vandersypen, L. M. K. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Eendebak, P. T. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 155, 2600 AD Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)

    2016-05-23

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  10. Coherent states for quantum compact groups

    Energy Technology Data Exchange (ETDEWEB)

    Jurco, B. [European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Stovicek, P. [Ceske Vysoke Uceni Technicke, Prague (Czech Republic). Dept. of Mathematics]|[CTU, Prague (Czech Republic). Doppler Inst.

    1996-12-01

    Coherent states are introduced and their properties are discussed for simple quantum compact groups A{sub l}, B{sub l}, C{sub l} and D{sub l}. The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit. The coherent state is interpreted as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R-matrix formulation (generalizing this way the q-deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel-Weil construction) is described using the concept of coherent state. The relation between representation theory and non-commutative differential geometry is suggested. (orig.)

  11. J-holomorphic curves and quantum cohomology

    CERN Document Server

    McDuff, Dusa

    1994-01-01

    J-holomorphic curves revolutionized the study of symplectic geometry when Gromov first introduced them in 1985. Through quantum cohomology, these curves are now linked to many of the most exciting new ideas in mathematical physics. This book presents the first coherent and full account of the theory of J-holomorphic curves, the details of which are presently scattered in various research papers. The first half of the book is an expository account of the field, explaining the main technical aspects. McDuff and Salamon give complete proofs of Gromov's compactness theorem for spheres and of the existence of the Gromov-Witten invariants. The second half of the book focuses on the definition of quantum cohomology. The authors establish that this multiplication exists, and give a new proof of the Ruan-Tian result that is associative on appropriate manifolds. They then describe the Givental-Kim calculation of the quantum cohomology of flag manifolds, leading to quantum Chern classes and Witten's calculation for Gras...

  12. Emulating weak localization using a solid-state quantum circuit.

    Science.gov (United States)

    Chen, Yu; Roushan, P; Sank, D; Neill, C; Lucero, Erik; Mariantoni, Matteo; Barends, R; Chiaro, B; Kelly, J; Megrant, A; Mutus, J Y; O'Malley, P J J; Vainsencher, A; Wenner, J; White, T C; Yin, Yi; Cleland, A N; Martinis, John M

    2014-10-14

    Quantum interference is one of the most fundamental physical effects found in nature. Recent advances in quantum computing now employ interference as a fundamental resource for computation and control. Quantum interference also lies at the heart of sophisticated condensed matter phenomena such as Anderson localization, phenomena that are difficult to reproduce in numerical simulations. Here, employing a multiple-element superconducting quantum circuit, with which we manipulate a single microwave photon, we demonstrate that we can emulate the basic effects of weak localization. By engineering the control sequence, we are able to reproduce the well-known negative magnetoresistance of weak localization as well as its temperature dependence. Furthermore, we can use our circuit to continuously tune the level of disorder, a parameter that is not readily accessible in mesoscopic systems. Demonstrating a high level of control, our experiment shows the potential for employing superconducting quantum circuits as emulators for complex quantum phenomena.

  13. Novel multi-dimensional heteronuclear NMR techniques for the study of 13C-O-acetylated oligosaccharides: Expanding the dimensions for carbohydrate structures

    Energy Technology Data Exchange (ETDEWEB)

    Jones, David N.M. [University of Colorado Health Sciences Center, Departments of Pharmacology (United States); Bendiak, Brad [University of Colorado Health Sciences Center, Departments of Cellular and Structural Biology (United States)

    1999-10-15

    Complex carbohydrates have critical roles in a wide variety of biological processes. An understanding of the molecular mechanisms that underlie these processes is essential in the development of novel oligosaccharide-based therapeutic strategies. Unfortunately, obtaining detailed structural information for larger oligosaccharides (>10 residues) can be exceedingly difficult, especially where the amount of sample available is limited. Here we demonstrate the application of {sup 13} C O-acetylation in combination with novel NMR experiments to obtain much of the information required to characterize the primary structure of oligosaccharides. (H)C{sub Me}COH-HEHAHA and H(C{sub Me})COH-HEHAHA experiments are presented that use heteronuclear Hartmann-Hahn transfer to correlate the acetyl groups with sugar ring protons in peracetylated oligosaccharides. The in-phase, pure absorption nature of the correlation peaks in these experiments allows measurement of both chemical shifts and, importantly, {sup 1}H-{sup 1}H coupling constants that are used to define the stereochemistry of the sugar ring. The (HC{sub Me})COH and (HC{sub Me})COH-RELAY experiments provide additional methods for obtaining chemical shift assignments for larger oligosaccharides to define the sites of glycosidic linkages from the patterns of acetylation.

  14. Growth of InGaN multiple quantum wells and GaN eplilayer on GaN substrate

    International Nuclear Information System (INIS)

    Lee, Sung-Nam; Paek, H.S.; Son, J.K.; Sakong, T.; Yoon, E.; Nam, O.H.; Park, Y.

    2006-01-01

    We investigated that the surface morphology of GaN epilayers was significantly affected by the surface tilt orientation of GaN substrate. Surface morphologies of GaN epilayers on GaN substrates show three types: mirror, wavy, and hillock. These surface morphologies are dependent on the surface orientation of GaN substrates. It is found that the hillock morphology of GaN epilayer was formed on the GaN substrate with surface tilt orientation less than 0.1 o . As the surface tilt angle increased to 0.35 o , the surface morphology varied from hillock to wavy morphology. Above a surface tilt angle of 0.4 o , surface morphology changed to the mirror-like type morphology. Additionally, these three types of GaN surface morphology also affected the optical quality of GaN epilayers as well as InGaN multiple quantum wells on GaN substrates by non-uniform In incorporation on the different surface morphologies of GaN epilayers

  15. High resolution kinetic beam schemes in generalized coordinates for ideal quantum gas dynamics

    International Nuclear Information System (INIS)

    Shi, Yu-Hsin; Huang, J.C.; Yang, J.Y.

    2007-01-01

    A class of high resolution kinetic beam schemes in multiple space dimensions in general coordinates system for the ideal quantum gas is presented for the computation of quantum gas dynamical flows. The kinetic Boltzmann equation approach is adopted and the local equilibrium quantum statistics distribution is assumed. High-order accurate methods using essentially non-oscillatory interpolation concept are constructed. Computations of shock wave diffraction by a circular cylinder in an ideal quantum gas are conducted to illustrate the present method. The present method provides a viable means to explore various practical ideal quantum gas flows

  16. Designs for a quantum electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kruit, P., E-mail: p.kruit@tudelft.nl [Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628CJ Delft (Netherlands); Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hammer, J.; Thomas, S.; Weber, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Hommelhoff, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Berggren, K.K. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-05-15

    One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

  17. Designs for a quantum electron microscope

    International Nuclear Information System (INIS)

    Kruit, P.; Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R.; Hammer, J.; Thomas, S.; Weber, P.; Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A.; Hommelhoff, P.; Berggren, K.K.

    2016-01-01

    One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

  18. Strain compensation in InGaN-based multiple quantum wells using AlGaN interlayers

    Directory of Open Access Journals (Sweden)

    Syed Ahmed Al Muyeed

    2017-10-01

    Full Text Available Data are presented on strain compensation in InGaN-based multiple quantum wells (MQW using AlGaN interlayers (ILs. The MQWs consist of five periods of InxGa1-xN/AlyGa1-yN/GaN emitting in the green (λ ∼ 535 nm ± 15 nm, and the AlyGa1-yN IL has an Al composition of y = 0.42. The IL is varied from 0 - 2.1 nm, and the relaxation of the MQW with respect to the GaN template layer varies with IL thickness as determined by reciprocal space mapping about the (202¯5 reflection. The minimum in the relaxation occurs at an interlayer thickness of 1 nm, and the MQW is nearly pseudomorphic to GaN. Both thinner and thicker ILs display increased relaxation. Photoluminescence data shows enhanced spectral intensity and narrower full width at half maximum for the MQW with 1 nm thick ILs, which is a product of pseudomorphic layers with lower defect density and non-radiative recombination.

  19. Quantum Erasure: Quantum Interference Revisited

    OpenAIRE

    Walborn, Stephen P.; Cunha, Marcelo O. Terra; Pádua, Sebastião; Monken, Carlos H.

    2005-01-01

    Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.

  20. Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs

    Directory of Open Access Journals (Sweden)

    Caspani Lucia

    2016-06-01

    Full Text Available Recent developments in quantum photonics have initiated the process of bringing photonic-quantumbased systems out-of-the-lab and into real-world applications. As an example, devices to enable the exchange of a cryptographic key secured by the laws of quantum mechanics are already commercially available. In order to further boost this process, the next step is to transfer the results achieved by means of bulky and expensive setups into miniaturized and affordable devices. Integrated quantum photonics is exactly addressing this issue. In this paper, we briefly review the most recent advancements in the generation of quantum states of light on-chip. In particular, we focus on optical microcavities, as they can offer a solution to the problem of low efficiency that is characteristic of the materials typically used in integrated platforms. In addition, we show that specifically designed microcavities can also offer further advantages, such as compatibility with telecom standards (for exploiting existing fibre networks and quantum memories (necessary to extend the communication distance, as well as giving a longitudinal multimode character for larger information transfer and processing. This last property (i.e., the increased dimensionality of the photon quantum state is achieved through the ability to generate multiple photon pairs on a frequency comb, corresponding to the microcavity resonances. Further achievements include the possibility of fully exploiting the polarization degree of freedom, even for integrated devices. These results pave the way for the generation of integrated quantum frequency combs that, in turn, may find important applications toward the realization of a compact quantum-computing platform.

  1. Single-photon three-qubit quantum logic using spatial light modulators.

    Science.gov (United States)

    Kagalwala, Kumel H; Di Giuseppe, Giovanni; Abouraddy, Ayman F; Saleh, Bahaa E A

    2017-09-29

    The information-carrying capacity of a single photon can be vastly expanded by exploiting its multiple degrees of freedom: spatial, temporal, and polarization. Although multiple qubits can be encoded per photon, to date only two-qubit single-photon quantum operations have been realized. Here, we report an experimental demonstration of three-qubit single-photon, linear, deterministic quantum gates that exploit photon polarization and the two-dimensional spatial-parity-symmetry of the transverse single-photon field. These gates are implemented using a polarization-sensitive spatial light modulator that provides a robust, non-interferometric, versatile platform for implementing controlled unitary gates. Polarization here represents the control qubit for either separable or entangling unitary operations on the two spatial-parity target qubits. Such gates help generate maximally entangled three-qubit Greenberger-Horne-Zeilinger and W states, which is confirmed by tomographical reconstruction of single-photon density matrices. This strategy provides access to a wide range of three-qubit states and operations for use in few-qubit quantum information processing protocols.Photons are essential for quantum information processing, but to date only two-qubit single-photon operations have been realized. Here the authors demonstrate experimentally a three-qubit single-photon linear deterministic quantum gate by exploiting polarization along with spatial-parity symmetry.

  2. Quantum Monte Carlo tunneling from quantum chemistry to quantum annealing

    Science.gov (United States)

    Mazzola, Guglielmo; Smelyanskiy, Vadim N.; Troyer, Matthias

    2017-10-01

    Quantum tunneling is ubiquitous across different fields, from quantum chemical reactions and magnetic materials to quantum simulators and quantum computers. While simulating the real-time quantum dynamics of tunneling is infeasible for high-dimensional systems, quantum tunneling also shows up in quantum Monte Carlo (QMC) simulations, which aim to simulate quantum statistics with resources growing only polynomially with the system size. Here we extend the recent results obtained for quantum spin models [Phys. Rev. Lett. 117, 180402 (2016), 10.1103/PhysRevLett.117.180402], and we study continuous-variable models for proton transfer reactions. We demonstrate that QMC simulations efficiently recover the scaling of ground-state tunneling rates due to the existence of an instanton path, which always connects the reactant state with the product. We discuss the implications of our results in the context of quantum chemical reactions and quantum annealing, where quantum tunneling is expected to be a valuable resource for solving combinatorial optimization problems.

  3. Transport properties of a Kondo dot with a larger side-coupled noninteracting quantum dot

    International Nuclear Information System (INIS)

    Liu, Y S; Fan, X H; Xia, Y J; Yang, X F

    2008-01-01

    We investigate theoretically linear and nonlinear quantum transport through a smaller quantum dot in a Kondo regime connected to two leads in the presence of a larger side-coupled noninteracting quantum dot, without tunneling coupling to the leads. To do this we employ the slave boson mean field theory with the help of the Keldysh Green's function at zero temperature. The numerical results show that the Kondo conductance peak may develop multiple resonance peaks and multiple zero points in the conductance spectrum owing to constructive and destructive quantum interference effects when the energy levels of the large side-coupled noninteracting dot are located in the vicinity of the Fermi level in the leads. As the coupling strength between two quantum dots increases, the tunneling current through the quantum device as a function of gate voltage applied across the two leads is suppressed. The spin-dependent transport properties of two parallel coupled quantum dots connected to two ferromagnetic leads are also investigated. The numerical results show that, for the parallel configuration, the spin current or linear spin differential conductance are enhanced when the polarization strength in the two leads is increased

  4. Strain-compensated (Ga,In)N/(Al,Ga)N/GaN multiple quantum wells for improved yellow/amber light emission

    Energy Technology Data Exchange (ETDEWEB)

    Lekhal, K.; Damilano, B., E-mail: bd@crhea.cnrs.fr; De Mierry, P.; Vennéguès, P. [CRHEA-CNRS, Centre de Recherche sur l' Hétéro-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, Valbonne 06560 (France); Ngo, H. T.; Rosales, D.; Gil, B. [Laboratoire Charles Coulomb, CNRS-INP-UMR 5221, Université Montpellier 2, F-34095 Montpellier (France); Hussain, S. [CRHEA-CNRS, Centre de Recherche sur l' Hétéro-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, Valbonne 06560 (France); Université de Nice Sophia Antipolis, Parc Valrose, 28 av. Valrose, 06108 Nice cedex 2 (France)

    2015-04-06

    Yellow/amber (570–600 nm) emitting In{sub x}Ga{sub 1−x}N/Al{sub y}Ga{sub 1−y}N/GaN multiple quantum wells (QWs) have been grown by metal organic chemical vapor deposition on GaN-on- sapphire templates. When the (Al,Ga)N thickness of the barrier increases, the room temperature photoluminescence is red-shifted while its yield increases. This is attributed to an increase of the QW internal electric field and an improvement of the material quality due to the compensation of the compressive strain of the In{sub x}Ga{sub 1−x}N QWs by the Al{sub y}Ga{sub 1−y}N layers, respectively.

  5. Growth of InGaAs/GaAsP multiple quantum well solar cells on mis-orientated GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sodabanlu, Hassanet, E-mail: sodabanlu@hotaka.t.u-tokyo.ac.jp; Wang, Yunpeng; Watanabe, Kentaroh [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8904 (Japan); Sugiyama, Masakazu [Department of Electrical Engineering and Information System, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Institute of Engineering Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Nakano, Yoshiaki [Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8904 (Japan); Department of Electrical Engineering and Information System, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

    2014-06-21

    The effects of growth temperature on the properties of InGaAs/GaAsP multiple quantum well (MQW) solar cells on various mis-orientated GaAs substrates were studied using metalorganic vapor phase epitaxy. Thickness modulation effect caused by mismatch strain of InGaAs/GaAsP could be suppressed by low growth temperature. Consequently, abrupt MQWs with strong light absorption could be deposited on mis-oriented substrates. However, degradation in crystal quality and impurity incorporation are the main drawbacks with low temperature growth because they tend to strongly degraded carrier transport and collection efficiency. MQW solar cells grown at optimized temperature showed the better conversion efficiency. The further investigation should focus on improvement of crystal quality and background impurities.

  6. Experimental two-dimensional quantum walk on a photonic chip.

    Science.gov (United States)

    Tang, Hao; Lin, Xiao-Feng; Feng, Zhen; Chen, Jing-Yuan; Gao, Jun; Sun, Ke; Wang, Chao-Yue; Lai, Peng-Cheng; Xu, Xiao-Yun; Wang, Yao; Qiao, Lu-Feng; Yang, Ai-Lin; Jin, Xian-Min

    2018-05-01

    Quantum walks, in virtue of the coherent superposition and quantum interference, have exponential superiority over their classical counterpart in applications of quantum searching and quantum simulation. The quantum-enhanced power is highly related to the state space of quantum walks, which can be expanded by enlarging the photon number and/or the dimensions of the evolution network, but the former is considerably challenging due to probabilistic generation of single photons and multiplicative loss. We demonstrate a two-dimensional continuous-time quantum walk by using the external geometry of photonic waveguide arrays, rather than the inner degree of freedoms of photons. Using femtosecond laser direct writing, we construct a large-scale three-dimensional structure that forms a two-dimensional lattice with up to 49 × 49 nodes on a photonic chip. We demonstrate spatial two-dimensional quantum walks using heralded single photons and single photon-level imaging. We analyze the quantum transport properties via observing the ballistic evolution pattern and the variance profile, which agree well with simulation results. We further reveal the transient nature that is the unique feature for quantum walks of beyond one dimension. An architecture that allows a quantum walk to freely evolve in all directions and at a large scale, combining with defect and disorder control, may bring up powerful and versatile quantum walk machines for classically intractable problems.

  7. Mesoscopic effects in the quantum Hall regime

    Indian Academy of Sciences (India)

    . When band mixing between multiple Landau levels is present, mesoscopic effects cause a crossover from a sequence of quantum Hall transitions for weak disorder to classical behavior for strong disorder. This behavior may be of relevance ...

  8. Quantum games as quantum types

    Science.gov (United States)

    Delbecque, Yannick

    In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer [DH02]: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. [DKP07]. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other

  9. Surface Passivation by Quantum Exclusion Using Multiple Layers

    Science.gov (United States)

    Hoenk, Michael E. (Inventor)

    2015-01-01

    A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes at least two doped layers fabricated using MBE methods. The dopant sheet densities in the doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. The electrically active dopant sheet densities are quite high, reaching more than 1.times.10.sup.14 cm.sup.-2, and locally exceeding 10.sup.22 per cubic centimeter. It has been found that silicon detector devices that have two or more such dopant layers exhibit improved resistance to degradation by UV radiation, at least at wavelengths of 193 nm, as compared to conventional silicon p-on-n devices.

  10. Resonance fluorescence and quantum jumps in single atoms: Testing the randomness of quantum mechanics

    International Nuclear Information System (INIS)

    Erber, T.; Hammerling, P.; Hockney, G.; Porrati, M.; Putterman, S.; La Jolla Institute, La Jolla, California 92037; Department of Physics, University of California, Los Angeles, California 90024)

    1989-01-01

    When a single trapped 198 Hg + ion is illuminated by two lasers, each tuned to an approximate transition, the resulting fluorescence switches on and off in a series of pulses resembling a bistable telegraph. This intermittent fluorescence can also be obtained by optical pumping with a single laser. Quantum jumps between successive atomic levels may be traced directly with multiple-resonance fluorescence. Atomic transition rates and photon antibunching distributions can be inferred from the pulse statistics and compared with quantum theory. Stochastic tests also indicate that the quantum telegraphs are good random number generators. During periods when the fluorescence is switched off, the radiationless atomic currents that generate the telegraph signals can be adjusted by varying the laser illumination: if this coherent evolution of the wave functions is sustained over sufficiently long time intervals, novel interactive precision measurements, near the limits of the time-energy uncertainty relations, are possible. Copyright 1989 Academic Press, Inc

  11. Cathodoluminescence studies of chevron features in semi-polar (11 2 ¯ 2 ) InGaN/GaN multiple quantum well structures

    Science.gov (United States)

    Brasser, C.; Bruckbauer, J.; Gong, Y.; Jiu, L.; Bai, J.; Warzecha, M.; Edwards, P. R.; Wang, T.; Martin, R. W.

    2018-05-01

    Epitaxial overgrowth of semi-polar III-nitride layers and devices often leads to arrowhead-shaped surface features, referred to as chevrons. We report on a study into the optical, structural, and electrical properties of these features occurring in two very different semi-polar structures, a blue-emitting multiple quantum well structure, and an amber-emitting light-emitting diode. Cathodoluminescence (CL) hyperspectral imaging has highlighted shifts in their emission energy, occurring in the region of the chevron. These variations are due to different semi-polar planes introduced in the chevron arms resulting in a lack of uniformity in the InN incorporation across samples, and the disruption of the structure which could cause a narrowing of the quantum wells (QWs) in this region. Atomic force microscopy has revealed that chevrons can penetrate over 150 nm into the sample and quench light emission from the active layers. The dominance of non-radiative recombination in the chevron region was exposed by simultaneous measurement of CL and the electron beam-induced current. Overall, these results provide an overview of the nature and impact of chevrons on the luminescence of semi-polar devices.

  12. Semiconductor Quantum Dash Broadband Emitters: Modeling and Experiments

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2013-10-01

    Broadband light emitters operation, which covers multiple wavelengths of the electromagnetic spectrum, has been established as an indispensable element to the human kind, continuously advancing the living standard by serving as sources in important multi-disciplinary field applications such as biomedical imaging and sensing, general lighting and internet and mobile phone connectivity. In general, most commercial broadband light sources relies on complex systems for broadband light generation which are bulky, and energy hungry. \\tRecent demonstration of ultra-broadband emission from semiconductor light sources in the form of superluminescent light emitting diodes (SLDs) has paved way in realization of broadband emitters on a completely novel platform, which offered compactness, cost effectiveness, and comparatively energy efficient, and are already serving as a key component in medical imaging systems. The low power-bandwidth product is inherent in SLDs operating in the amplified spontaneous emission regime. A quantum leap in the advancement of broadband emitters, in which high power and large bandwidth (in tens of nm) are in demand. Recently, the birth of a new class of broadband semiconductor laser diode (LDs) producing multiple wavelength light in stimulated emission regime was demonstrated. This very recent manifestation of a high power-bandwidth-product semiconductor broadband LDs relies on interband optical transitions via quantum confined dot/dash nanostructures and exploiting the natural inhomogeneity of the self-assembled growth technology. This concept is highly interesting and extending the broad spectrum of stimulated emission by novel device design forms the central focus of this dissertation. \\tIn this work, a simple rate equation numerical technique for modeling InAs/InP quantum dash laser incorporating the properties of inhomogeneous broadening effect on lasing spectra was developed and discussed, followed by a comprehensive experimental analysis

  13. Computational physics simulation of classical and quantum systems

    CERN Document Server

    Scherer, Philipp O J

    2017-01-01

    This textbook presents basic numerical methods and applies them to a large variety of physical models in multiple computer experiments. Classical algorithms and more recent methods are explained. Partial differential equations are treated generally comparing important methods, and equations of motion are solved by a large number of simple as well as more sophisticated methods. Several modern algorithms for quantum wavepacket motion are compared. The first part of the book discusses the basic numerical methods, while the second part simulates classical and quantum systems. Simple but non-trivial examples from a broad range of physical topics offer readers insights into the numerical treatment but also the simulated problems. Rotational motion is studied in detail, as are simple quantum systems. A two-level system in an external field demonstrates elementary principles from quantum optics and simulation of a quantum bit. Principles of molecular dynamics are shown. Modern bounda ry element methods are presented ...

  14. Aspergillus fumigatus CY018, an endophytic fungus in Cynodon dactylon as a versatile producer of new and bioactive metabolites.

    Science.gov (United States)

    Liu, J Y; Song, Y C; Zhang, Z; Wang, L; Guo, Z J; Zou, W X; Tan, R X

    2004-11-09

    Aspergillus fumigatus CY018 was recognized as an endophytic fungus for the first time in the leaf of Cynodon dactylon. By bioassay-guided fractionation, the EtOAc extract of a solid-matrix steady culture of this fungus afforded two new metabolites, named asperfumoid (1) and asperfumin (2), together with six known bioactive compounds including monomethylsulochrin, fumigaclavine C, fumitremorgin C, physcion, helvolic acid and 5alpha,8alpha-epidioxy-ergosta-6,22-diene-3beta-ol as well as other four known compounds ergosta-4,22-diene-3beta-ol, ergosterol, cyclo(Ala-Leu) and cyclo(Ala-Ile). Through detailed spectroscopic analyses including HRESI-MS, homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC), the structures of asperfumoid and asperfumin were established to be spiro-(3-hydroxyl-2,6-dimethoxyl-2,5-diene-4-cyclohexone-(1,3')-5'-methoxyl-7'-methyl-(1'H, 2'H, 4'H)-quinoline-2',4'-dione) and 5-hydroxyl-2-(6-hydroxyl-2-methoxyl-4-methylbenzoyl)-3,6-dimethoxyl-benzoic methyl ester, respectively. All of the 12 isolates were subjected to in vitro bioactive assays against three human pathogenic fungi Candida albicans, Tricophyton rubrum and Aspergillus niger. As a result, asperfumoid, fumigaclavine C, fumitremorgin C, physcion and helvolic acid were shown to inhibit C. albicans with MICs of 75.0, 31.5, 62.5, 125.0 and 31.5 microg/mL, respectively.

  15. Dependence of the photovoltaic performance of pseudomorphic InGaN/GaN multiple-quantum-well solar cells on the active region thickness

    Energy Technology Data Exchange (ETDEWEB)

    Mukhtarova, Anna; Valdueza-Felip, Sirona; Redaelli, Luca; Durand, Christophe; Monroy, Eva; Eymery, Joël, E-mail: joel.eymery@cea.fr [Université Grenoble Alpes, 38000 Grenoble (France); CEA-CNRS group “Nanophysique et semiconducteurs”, CEA-INAC-PHELIQS, 17 av. des Martyrs, 38054 Grenoble (France); Bougerol, Catherine [Université Grenoble Alpes, 38000 Grenoble (France); CEA-CNRS group “Nanophysique et semiconducteurs”, Institut Néel-CNRS, 25 av. des Martyrs, 38042 Grenoble (France)

    2016-04-18

    We investigate the photovoltaic performance of pseudomorphic In{sub 0.1}Ga{sub 0.9}N/GaN multiple-quantum well (MQW) solar cells as a function of the total active region thickness. An increase in the number of wells from 5 to 40 improves the short-circuit current and the open-circuit voltage, resulting in a 10-fold enhancement of the overall conversion efficiency. Further increasing the number of wells leads to carrier collection losses due to an incomplete depletion of the active region. Capacitance-voltage measurements point to a hole diffusion length of 48 nm in the MQW region.

  16. Efficient charge-carrier extraction from Ag₂S quantum dots prepared by the SILAR method for utilization of multiple exciton generation.

    Science.gov (United States)

    Zhang, Xiaoliang; Liu, Jianhua; Johansson, Erik M J

    2015-01-28

    The utilization of electron-hole pairs (EHPs) generated from multiple excitons in quantum dots (QDs) is of great interest toward efficient photovoltaic devices and other optoelectronic devices; however, extraction of charge carriers remains difficult. Herein, we extract photocharges from Ag2S QDs and investigate the dependence of the electric field on the extraction of charges from multiple exciton generation (MEG). Low toxic Ag2S QDs are directly grown on TiO2 mesoporous substrates by employing the successive ionic layer adsorption and reaction (SILAR) method. The contact between QDs is important for the initial charge separation after MEG and for the carrier transport, and the space between neighbor QDs decreases with more SILAR cycles, resulting in better charge extraction. At the optimal electric field for extraction of photocharges, the results suggest that the threshold energy (hνth) for MEG is 2.41Eg. The results reveal that Ag2S QD is a promising material for efficient extraction of charges from MEG and that QDs prepared by SILAR have an advantageous electrical contact facilitating charge separation and extraction.

  17. Sensitivity to Heavy-Metal Ions of Unfolded Fullerene Quantum Dots

    Directory of Open Access Journals (Sweden)

    Erica Ciotta

    2017-11-01

    Full Text Available A novel type of graphene-like quantum dots, synthesized by oxidation and cage-opening of C60 buckminsterfullerene, has been studied as a fluorescent and absorptive probe for heavy-metal ions. The lattice structure of such unfolded fullerene quantum dots (UFQDs is distinct from that of graphene since it includes both carbon hexagons and pentagons. The basic optical properties, however, are similar to those of regular graphene oxide quantum dots. On the other hand, UFQDs behave quite differently in the presence of heavy-metal ions, in that multiple sensitivity to Cu2+, Pb2+ and As(III was observed through comparable quenching of the fluorescent emission and different variations of the transmittance spectrum. By dynamic light scattering measurements and transmission electron microscope (TEM images we confirmed, for the first time in metal sensing, that this response is due to multiple complexation and subsequent aggregation of UFQDs. Nonetheless, the explanation of the distinct behaviour of transmittance in the presence of As(III and the formation of precipitate with Pb2+ require further studies. These differences, however, also make it possible to discriminate between the three metal ions in view of the implementation of a selective multiple sensor.

  18. Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics.

    Science.gov (United States)

    Kockum, Anton Frisk; Johansson, Göran; Nori, Franco

    2018-04-06

    In quantum-optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation with which they interact. However, superconducting qubits coupled to a meandering transmission line, or to surface acoustic waves, can realize "giant artificial atoms" that couple to a bosonic field at several points which are wavelengths apart. Here, we study setups with multiple giant atoms coupled at multiple points to a one-dimensional (1D) waveguide. We show that the giant atoms can be protected from decohering through the waveguide, but still have exchange interactions mediated by the waveguide. Unlike in decoherence-free subspaces, here the entire multiatom Hilbert space (2^{N} states for N atoms) is protected from decoherence. This is not possible with "small" atoms. We further show how this decoherence-free interaction can be designed in setups with multiple atoms to implement, e.g., a 1D chain of atoms with nearest-neighbor couplings or a collection of atoms with all-to-all connectivity. This may have important applications in quantum simulation and quantum computing.

  19. Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics

    Science.gov (United States)

    Kockum, Anton Frisk; Johansson, Göran; Nori, Franco

    2018-04-01

    In quantum-optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation with which they interact. However, superconducting qubits coupled to a meandering transmission line, or to surface acoustic waves, can realize "giant artificial atoms" that couple to a bosonic field at several points which are wavelengths apart. Here, we study setups with multiple giant atoms coupled at multiple points to a one-dimensional (1D) waveguide. We show that the giant atoms can be protected from decohering through the waveguide, but still have exchange interactions mediated by the waveguide. Unlike in decoherence-free subspaces, here the entire multiatom Hilbert space (2N states for N atoms) is protected from decoherence. This is not possible with "small" atoms. We further show how this decoherence-free interaction can be designed in setups with multiple atoms to implement, e.g., a 1D chain of atoms with nearest-neighbor couplings or a collection of atoms with all-to-all connectivity. This may have important applications in quantum simulation and quantum computing.

  20. Quantum information. Teleporation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Breuer, Reinhard

    2010-01-01

    The following topics are dealt with: Reality in the test house, quantum teleportation, 100 years of quantum theory, the reality of quanta, interactionless quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view into the future of quantum optics. (HSI)

  1. Multiple Quantum Coherences (MQ) NMR and Entanglement Dynamics in the Mixed-Three-Spin XXX Heisenberg Model with Single-Ion Anisotropy

    Science.gov (United States)

    Hamid, Arian Zad

    2016-12-01

    We analytically investigate Multiple Quantum (MQ) NMR dynamics in a mixed-three-spin (1/2,1,1/2) system with XXX Heisenberg model at the front of an external homogeneous magnetic field B. A single-ion anisotropy property ζ is considered for the spin-1. The intensities dependence of MQ NMR coherences on their orders (zeroth and second orders) for two pairs of spins (1,1/2) and (1/2,1/2) of the favorite tripartite system are obtained. It is also investigated dynamics of the pairwise quantum entanglement for the bipartite (sub)systems (1,1/2) and (1/2,1/2) permanently coupled by, respectively, coupling constants J}1 and J}2, by means of concurrence and fidelity. Then, some straightforward comparisons are done between these quantities and the intensities of MQ NMR coherences and ultimately some interesting results are reported. We also show that the time evolution of MQ coherences based on the reduced density matrix of the pair spins (1,1/2) is closely connected with the dynamics of the pairwise entanglement. Finally, we prove that one can introduce MQ coherence of the zeroth order corresponds to the pair spins (1,1/2) as an entanglement witness at some special time intervals.

  2. Toward protocols for quantum-ensured privacy and secure voting

    International Nuclear Information System (INIS)

    Bonanome, Marianna; Buzek, Vladimir; Ziman, Mario; Hillery, Mark

    2011-01-01

    We present a number of schemes that use quantum mechanics to preserve privacy, in particular, we show that entangled quantum states can be useful in maintaining privacy. We further develop our original proposal [see M. Hillery, M. Ziman, V. Buzek, and M. Bielikova, Phys. Lett. A 349, 75 (2006)] for protecting privacy in voting, and examine its security under certain types of attacks, in particular dishonest voters and external eavesdroppers. A variation of these quantum-based schemes can be used for multiparty function evaluation. We consider functions corresponding to group multiplication of N group elements, with each element chosen by a different party. We show how quantum mechanics can be useful in maintaining the privacy of the choices group elements.

  3. Toward protocols for quantum-ensured privacy and secure voting

    Energy Technology Data Exchange (ETDEWEB)

    Bonanome, Marianna [Department of Applied Mathematics and Computer Science, New York City College of Technology, 300 Jay Street, Brooklyn, New York 11201 (United States); Buzek, Vladimir; Ziman, Mario [Research Center for Quantum Information, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Faculty of Informatics, Masaryk University, Botanicka 68a, 602 00 Brno (Czech Republic); Hillery, Mark [Department of Physics, Hunter College of CUNY, 695 Park Avenue, New York, New York 10021 (United States)

    2011-08-15

    We present a number of schemes that use quantum mechanics to preserve privacy, in particular, we show that entangled quantum states can be useful in maintaining privacy. We further develop our original proposal [see M. Hillery, M. Ziman, V. Buzek, and M. Bielikova, Phys. Lett. A 349, 75 (2006)] for protecting privacy in voting, and examine its security under certain types of attacks, in particular dishonest voters and external eavesdroppers. A variation of these quantum-based schemes can be used for multiparty function evaluation. We consider functions corresponding to group multiplication of N group elements, with each element chosen by a different party. We show how quantum mechanics can be useful in maintaining the privacy of the choices group elements.

  4. Toward Designing a Quantum Key Distribution Network Simulation Model

    OpenAIRE

    Miralem Mehic; Peppino Fazio; Miroslav Voznak; Erik Chromy

    2016-01-01

    As research in quantum key distribution network technologies grows larger and more complex, the need for highly accurate and scalable simulation technologies becomes important to assess the practical feasibility and foresee difficulties in the practical implementation of theoretical achievements. In this paper, we described the design of simplified simulation environment of the quantum key distribution network with multiple links and nodes. In such simulation environment, we analyzed several ...

  5. Trapped modes in linear quantum stochastic networks with delays

    Energy Technology Data Exchange (ETDEWEB)

    Tabak, Gil [Stanford University, Department of Applied Physics, Stanford, CA (United States); Mabuchi, Hideo

    2016-12-15

    Networks of open quantum systems with feedback have become an active area of research for applications such as quantum control, quantum communication and coherent information processing. A canonical formalism for the interconnection of open quantum systems using quantum stochastic differential equations (QSDEs) has been developed by Gough, James and co-workers and has been used to develop practical modeling approaches for complex quantum optical, microwave and optomechanical circuits/networks. In this paper we fill a significant gap in existing methodology by showing how trapped modes resulting from feedback via coupled channels with finite propagation delays can be identified systematically in a given passive linear network. Our method is based on the Blaschke-Potapov multiplicative factorization theorem for inner matrix-valued functions, which has been applied in the past to analog electronic networks. Our results provide a basis for extending the Quantum Hardware Description Language (QHDL) framework for automated quantum network model construction (Tezak et al. in Philos. Trans. R. Soc. A, Math. Phys. Eng. Sci. 370(1979):5270-5290, 2012) to efficiently treat scenarios in which each interconnection of components has an associated signal propagation time delay. (orig.)

  6. Design analysis of phosphor-free monolithic white light-emitting-diodes with InGaN/ InGaN multiple quantum wells on ternary InGaN substrates

    Directory of Open Access Journals (Sweden)

    Yu Kee Ooi

    2015-05-01

    Full Text Available Phosphor-free monolithic white light emitting diodes (LEDs based on InGaN/ InGaN multiple quantum wells (MQWs on ternary InGaN substrates are proposed and analyzed in this study. Simulation studies show that LED devices composed of multi-color-emitting InGaN/ InGaN quantum wells (QWs employing ternary InGaN substrate with engineered active region exhibit stable white color illumination with large output power (∼ 170 mW and high external quantum efficiency (EQE (∼ 50%. The chromaticity coordinate for the investigated monolithic white LED devices are located at (0.30, 0.28 with correlated color temperature (CCT of ∼ 8200 K at J = 50 A/cm2. A reference LED device without any nanostructure engineering exhibits green color emission shows that proper engineered structure is essential to achieve white color illumination. This proof-of-concept study demonstrates that high-efficiency and cost-effective phosphor-free monolithic white LED is feasible by the use of InGaN/ InGaN MQWs on ternary InGaN substrate combined with nanostructure engineering, which would be of great impact for solid state lighting.

  7. Design analysis of phosphor-free monolithic white light-emitting-diodes with InGaN/ InGaN multiple quantum wells on ternary InGaN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ooi, Yu Kee, E-mail: Yu.Kee.Ooi@rit.edu; Zhang, Jing, E-mail: Jing.Zhang@rit.edu [Department of Electrical and Microelectronics Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)

    2015-05-15

    Phosphor-free monolithic white light emitting diodes (LEDs) based on InGaN/ InGaN multiple quantum wells (MQWs) on ternary InGaN substrates are proposed and analyzed in this study. Simulation studies show that LED devices composed of multi-color-emitting InGaN/ InGaN quantum wells (QWs) employing ternary InGaN substrate with engineered active region exhibit stable white color illumination with large output power (∼ 170 mW) and high external quantum efficiency (EQE) (∼ 50%). The chromaticity coordinate for the investigated monolithic white LED devices are located at (0.30, 0.28) with correlated color temperature (CCT) of ∼ 8200 K at J = 50 A/cm{sup 2}. A reference LED device without any nanostructure engineering exhibits green color emission shows that proper engineered structure is essential to achieve white color illumination. This proof-of-concept study demonstrates that high-efficiency and cost-effective phosphor-free monolithic white LED is feasible by the use of InGaN/ InGaN MQWs on ternary InGaN substrate combined with nanostructure engineering, which would be of great impact for solid state lighting.

  8. Quantum space and quantum completeness

    Science.gov (United States)

    Jurić, Tajron

    2018-05-01

    Motivated by the question whether quantum gravity can "smear out" the classical singularity we analyze a certain quantum space and its quantum-mechanical completeness. Classical singularity is understood as a geodesic incompleteness, while quantum completeness requires a unique unitary time evolution for test fields propagating on an underlying background. Here the crucial point is that quantum completeness renders the Hamiltonian (or spatial part of the wave operator) to be essentially self-adjoint in order to generate a unique time evolution. We examine a model of quantum space which consists of a noncommutative BTZ black hole probed by a test scalar field. We show that the quantum gravity (noncommutative) effect is to enlarge the domain of BTZ parameters for which the relevant wave operator is essentially self-adjoint. This means that the corresponding quantum space is quantum complete for a larger range of BTZ parameters rendering the conclusion that in the quantum space one observes the effect of "smearing out" the singularity.

  9. Quantum correlations in multipartite quantum systems

    Science.gov (United States)

    Jafarizadeh, M. A.; Heshmati, A.; Karimi, N.; Yahyavi, M.

    2018-03-01

    Quantum entanglement is the most famous type of quantum correlation between elements of a quantum system that has a basic role in quantum communication protocols like quantum cryptography, teleportation and Bell inequality detection. However, it has already been shown that various applications in quantum information theory do not require entanglement. Quantum discord as a new kind of quantum correlations beyond entanglement, is the most popular candidate for general quantum correlations. In this paper, first we find the entanglement witness in a particular multipartite quantum system which consists of a N-partite system in 2 n -dimensional space. Then we give an exact analytical formula for the quantum discord of this system. At the end of the paper, we investigate the additivity relation of the quantum correlation and show that this relation is satisfied for a N-partite system with 2 n -dimensional space.

  10. Renormalisation in Quantum Mechanics, Quantum Instantons and Quantum Chaos

    OpenAIRE

    Jirari, H.; Kröger, H.; Luo, X. Q.; Moriarty, K. J. M.

    2001-01-01

    We suggest how to construct non-perturbatively a renormalized action in quantum mechanics. We discuss similarties and differences with the standard effective action. We propose that the new quantum action is suitable to define and compute quantum instantons and quantum chaos.

  11. Nonlinear Dynamics In Quantum Physics -- Quantum Chaos and Quantum Instantons

    OpenAIRE

    Kröger, H.

    2003-01-01

    We discuss the recently proposed quantum action - its interpretation, its motivation, its mathematical properties and its use in physics: quantum mechanical tunneling, quantum instantons and quantum chaos.

  12. Complete {sup 1}H and {sup 13}C NMR structural assignments for a group of four goyazensolide-type furanoheliangolides

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Ana Carolina Ferreira; Silva, Aline Nazare; Matos, Priscilla Mendonca; Silva, Eder Henrique da; Heleno, Vladimir Constantino Gomes [Universidade de Franca, Franca, SP (Brazil). Nucleo de Pesquisas em Ciencias Exatas e Tecnologicas; Lopes, Norberto Peporine; Lopes, Joao Luis Callegari [Universidade de Sao Paulo (FCFRP/USP), Ribeirao Preto, SP (Brazil). Fac. de Ciencias Farmaceuticas de Ribeirao Preto. Dept. de Quimica e Fisica; Sass, Daiane Cristina, E-mail: vheleno_05@yahoo.com.br [Universidade de Sao Paulo (FFCLRP/USP), Ribeirao Preto, SP (Brazil). Fac. de Filosofia, Ciencias e Letras de Ribeirao Preto. Dept. de Quimica

    2012-07-01

    Four goyazensolide-type sesquiterpene lactones - lychnofolide, centratherin, goyazensolide and goyazensolide acetate - were thoroughly studied by NMR experimental techniques. {sup 1}H NMR, {sup 13}C NMR {l_brace}{sup 1}H{r_brace}, COSY, HMQC, HMBC, J-res. and NOE experiments were performed to provide the needed structural information. Complete and unequivocal assignment, including the determination of all multiplicities, was obtained for each structure and the data collections are presented in tables (author)

  13. Quantum dynamics of quantum bits

    International Nuclear Information System (INIS)

    Nguyen, Bich Ha

    2011-01-01

    The theory of coherent oscillations of the matrix elements of the density matrix of the two-state system as a quantum bit is presented. Different calculation methods are elaborated in the case of a free quantum bit. Then the most appropriate methods are applied to the study of the density matrices of the quantum bits interacting with a classical pumping radiation field as well as with the quantum electromagnetic field in a single-mode microcavity. The theory of decoherence of a quantum bit in Markovian approximation is presented. The decoherence of a quantum bit interacting with monoenergetic photons in a microcavity is also discussed. The content of the present work can be considered as an introduction to the study of the quantum dynamics of quantum bits. (review)

  14. Entangled trajectories Hamiltonian dynamics for treating quantum nuclear effects

    Science.gov (United States)

    Smith, Brendan; Akimov, Alexey V.

    2018-04-01

    A simple and robust methodology, dubbed Entangled Trajectories Hamiltonian Dynamics (ETHD), is developed to capture quantum nuclear effects such as tunneling and zero-point energy through the coupling of multiple classical trajectories. The approach reformulates the classically mapped second-order Quantized Hamiltonian Dynamics (QHD-2) in terms of coupled classical trajectories. The method partially enforces the uncertainty principle and facilitates tunneling. The applicability of the method is demonstrated by studying the dynamics in symmetric double well and cubic metastable state potentials. The methodology is validated using exact quantum simulations and is compared to QHD-2. We illustrate its relationship to the rigorous Bohmian quantum potential approach, from which ETHD can be derived. Our simulations show a remarkable agreement of the ETHD calculation with the quantum results, suggesting that ETHD may be a simple and inexpensive way of including quantum nuclear effects in molecular dynamics simulations.

  15. Fibred Coalgebraic Logic and Quantum Protocols

    Directory of Open Access Journals (Sweden)

    Daniel Marsden

    2014-12-01

    Full Text Available Motivated by applications in modelling quantum systems using coalgebraic techniques, we introduce a fibred coalgebraic logic. Our approach extends the conventional predicate lifting semantics with additional modalities relating conditions on different fibres. As this fibred setting will typically involve multiple signature functors, the logic incorporates a calculus of modalities enabling the construction of new modalities using various composition operations. We extend the semantics of coalgebraic logic to this setting, and prove that this extension respects behavioural equivalence. We show how properties of the semantics of modalities are preserved under composition operations, and then apply the calculational aspect of our logic to produce an expressive set of modalities for reasoning about quantum systems, building these modalities up from simpler components. We then demonstrate how these modalities can describe some standard quantum protocols. The novel features of our logic are shown to allow for a uniform description of unitary evolution, and support local reasoning such as "Alice's qubit satisfies condition" as is common when discussing quantum protocols.

  16. Quantum symmetry in quantum theory

    International Nuclear Information System (INIS)

    Schomerus, V.

    1993-02-01

    Symmetry concepts have always been of great importance for physical problems like explicit calculations, classification or model building. More recently, new 'quantum symmetries' ((quasi) quantum groups) attracted much interest in quantum theory. It is shown that all these quantum symmetries permit a conventional formulation as symmetry in quantum mechanics. Symmetry transformations can act on the Hilbert space H of physical states such that the ground state is invariant and field operators transform covariantly. Models show that one must allow for 'truncation' in the tensor product of representations of a quantum symmetry. This means that the dimension of the tensor product of two representations of dimension σ 1 and σ 2 may be strictly smaller than σ 1 σ 2 . Consistency of the transformation law of field operators local braid relations leads us to expect, that (weak) quasi quantum groups are the most general symmetries in local quantum theory. The elements of the R-matrix which appears in these local braid relations turn out to be operators on H in general. It will be explained in detail how examples of field algebras with weak quasi quantum group symmetry can be obtained. Given a set of observable field with a finite number of superselection sectors, a quantum symmetry together with a complete set of covariant field operators which obey local braid relations are constructed. A covariant transformation law for adjoint fields is not automatic but will follow when the existence of an appropriate antipode is assumed. At the example of the chiral critical Ising model, non-uniqueness of the quantum symmetry will be demonstrated. Generalized quantum symmetries yield examples of gauge symmetries in non-commutative geometry. Quasi-quantum planes are introduced as the simplest examples of quasi-associative differential geometry. (Weak) quasi quantum groups can act on them by generalized derivations much as quantum groups do in non-commutative (differential-) geometry

  17. Quantum information. Teleportation - cryptography - quantum computer

    International Nuclear Information System (INIS)

    Koenneker, Carsten

    2012-01-01

    The following topics are dealt with: Reality in the test facility, quantum teleportation, the reality of quanta, interaction-free quantum measurement, rules for quantum computers, quantum computers with ions, spintronics with diamond, the limits of the quantum computers, a view in the future of quantum optics. (HSI)

  18. Quantum field theory and the standard model

    CERN Document Server

    Schwartz, Matthew D

    2014-01-01

    Providing a comprehensive introduction to quantum field theory, this textbook covers the development of particle physics from its foundations to the discovery of the Higgs boson. Its combination of clear physical explanations, with direct connections to experimental data, and mathematical rigor make the subject accessible to students with a wide variety of backgrounds and interests. Assuming only an undergraduate-level understanding of quantum mechanics, the book steadily develops the Standard Model and state-of-the-art calculation techniques. It includes multiple derivations of many important results, with modern methods such as effective field theory and the renormalization group playing a prominent role. Numerous worked examples and end-of-chapter problems enable students to reproduce classic results and to master quantum field theory as it is used today. Based on a course taught by the author over many years, this book is ideal for an introductory to advanced quantum field theory sequence or for independe...

  19. Quantumness-generating capability of quantum dynamics

    Science.gov (United States)

    Li, Nan; Luo, Shunlong; Mao, Yuanyuan

    2018-04-01

    We study quantumness-generating capability of quantum dynamics, where quantumness refers to the noncommutativity between the initial state and the evolving state. In terms of the commutator of the square roots of the initial state and the evolving state, we define a measure to quantify the quantumness-generating capability of quantum dynamics with respect to initial states. Quantumness-generating capability is absent in classical dynamics and hence is a fundamental characteristic of quantum dynamics. For qubit systems, we present an analytical form for this measure, by virtue of which we analyze several prototypical dynamics such as unitary dynamics, phase damping dynamics, amplitude damping dynamics, and random unitary dynamics (Pauli channels). Necessary and sufficient conditions for the monotonicity of quantumness-generating capability are also identified. Finally, we compare these conditions for the monotonicity of quantumness-generating capability with those for various Markovianities and illustrate that quantumness-generating capability and quantum Markovianity are closely related, although they capture different aspects of quantum dynamics.

  20. A surface code quantum computer in silicon

    Science.gov (United States)

    Hill, Charles D.; Peretz, Eldad; Hile, Samuel J.; House, Matthew G.; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y.; Hollenberg, Lloyd C. L.

    2015-01-01

    The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel—posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited. PMID:26601310

  1. A surface code quantum computer in silicon.

    Science.gov (United States)

    Hill, Charles D; Peretz, Eldad; Hile, Samuel J; House, Matthew G; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y; Hollenberg, Lloyd C L

    2015-10-01

    The exceptionally long quantum coherence times of phosphorus donor nuclear spin qubits in silicon, coupled with the proven scalability of silicon-based nano-electronics, make them attractive candidates for large-scale quantum computing. However, the high threshold of topological quantum error correction can only be captured in a two-dimensional array of qubits operating synchronously and in parallel-posing formidable fabrication and control challenges. We present an architecture that addresses these problems through a novel shared-control paradigm that is particularly suited to the natural uniformity of the phosphorus donor nuclear spin qubit states and electronic confinement. The architecture comprises a two-dimensional lattice of donor qubits sandwiched between two vertically separated control layers forming a mutually perpendicular crisscross gate array. Shared-control lines facilitate loading/unloading of single electrons to specific donors, thereby activating multiple qubits in parallel across the array on which the required operations for surface code quantum error correction are carried out by global spin control. The complexities of independent qubit control, wave function engineering, and ad hoc quantum interconnects are explicitly avoided. With many of the basic elements of fabrication and control based on demonstrated techniques and with simulated quantum operation below the surface code error threshold, the architecture represents a new pathway for large-scale quantum information processing in silicon and potentially in other qubit systems where uniformity can be exploited.

  2. Cytotoxicity of Labruscol, a New Resveratrol Dimer Produced by Grapevine Cell Suspensions, on Human Skin Melanoma Cancer Cell Line HT-144

    Directory of Open Access Journals (Sweden)

    Laetitia Nivelle

    2017-11-01

    Full Text Available A new resveratrol dimer (1 called labruscol, has been purified by centrifugal partition chromatography of a crude ethyl acetate stilbene extract obtained from elicited grapevine cell suspensions of Vitis labrusca L. cultured in a 14-liter stirred bioreactor. One dimensional (1D and two dimensional (2D nuclear magnetic resonance (NMR analyses including 1H, 13C, heteronuclear single-quantum correlation (HSQC, heteronuclear multiple bond correlation (HMBC, and correlation spectroscopy (COSY as well as high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS were used to characterize this compound and to unambiguously identify it as a new stilbene dimer, though its relative stereochemistry remained unsolved. Labruscol was recovered as a pure compound (>93% in sufficient amounts (41 mg to allow assessment of its biological activity (cell viability, cell invasion and apoptotic activity on two different cell lines, including one human skin melanoma cancer cell line HT-144 and a healthy human dermal fibroblast (HDF line. This compound induced almost 100% of cell viability inhibition in the cancer line at a dose of 100 μM within 72 h of treatment. However, at all tested concentrations and treatment times, resveratrol displayed an inhibition of the cancer line viability higher than that of labruscol in the presence of fetal bovine serum. Both compounds also showed differential activities on healthy and cancer cell lines. Finally, labruscol at a concentration of 1.2 μM was shown to reduce cell invasion by 40%, although no similar activity was observed with resveratrol. The cytotoxic activity of this newly-identified dimer is discussed.

  3. Investigating and Improving Student Understanding of Key Ideas in Quantum Mechanics throughout Instruction

    Science.gov (United States)

    Emigh, Paul Jeffrey

    This dissertation describes research on student understanding of quantum mechanics across multiple levels of instruction. The primary focus has been to identify patterns in student reasoning related to key concepts in quantum mechanics. The specific topics include quantum measurements, time dependence, vector spaces, and angular momentum. The research has spanned a variety of different quantum courses intended for introductory physics students, upper-division physics majors, and graduate students in physics. The results of this research have been used to develop a set of curriculum, Tutorials in Physics: Quantum Mechanics, for addressing the most persistent student difficulties. We document both the development of this curriculum and how it has impacted and improved student understanding of quantum mechanics.

  4. The microcanonical ensemble of the ideal relativistic quantum gas with angular momentum conservation

    International Nuclear Information System (INIS)

    Becattini, F.; Ferroni, L.

    2007-01-01

    We derive the microcanonical partition function of the ideal relativistic quantum gas with fixed intrinsic angular momentum as an expansion over fixed multiplicities. We developed a group theoretical approach by generalizing known projection techniques to the Poincare group. Our calculation is carried out in a quantum field framework and applies to particles with any spin. It extends known results in the literature in that it does not introduce any large volume approximation, and it takes particle spin fully into account. We provide expressions of the microcanonical partition function at fixed multiplicities in the limiting classical case of large volumes and large angular momenta and in the grand-canonical ensemble. We also derive the microcanonical partition function of the ideal relativistic quantum gas with fixed parity. (orig.)

  5. Single-shot quantum nondemolition measurement of a quantum-dot electron spin using cavity exciton-polaritons

    Science.gov (United States)

    Puri, Shruti; McMahon, Peter L.; Yamamoto, Yoshihisa

    2014-10-01

    We propose a scheme to perform single-shot quantum nondemolition (QND) readout of the spin of an electron trapped in a semiconductor quantum dot (QD). Our proposal relies on the interaction of the QD electron spin with optically excited, quantum well (QW) microcavity exciton-polaritons. The spin-dependent Coulomb exchange interaction between the QD electron and cavity polaritons causes the phase and intensity response of left circularly polarized light to be different than that of right circularly polarized light, in such a way that the QD electron's spin can be inferred from the response to a linearly polarized probe reflected or transmitted from the cavity. We show that with careful device design it is possible to essentially eliminate spin-flip Raman transitions. Thus a QND measurement of the QD electron spin can be performed within a few tens of nanoseconds with fidelity ˜99.95%. This improves upon current optical QD spin readout techniques across multiple metrics, including speed and scalability.

  6. Probabilistic programmable quantum processors with multiple copies of program states

    International Nuclear Information System (INIS)

    Brazier, Adam; Buzek, Vladimir; Knight, Peter L.

    2005-01-01

    We examine the execution of general U(1) transformations on programmable quantum processors. We show that, with only the minimal assumption of availability of copies of the 1-qubit program state, the apparent advantage of existing schemes proposed by G. Vidal et al. [Phys. Rev. Lett. 88, 047905 (2002)] and M. Hillery et al. [Phys. Rev. A 65, 022301 (2003)] to execute a general U(1) transformation with greater probability using complex program states appears not to hold

  7. Quantum entanglement and quantum teleportation

    International Nuclear Information System (INIS)

    Shih, Y.H.

    2001-01-01

    One of the most surprising consequences of quantum mechanics is the entanglement of two or more distance particles. The ''ghost'' interference and the ''ghost'' image experiments demonstrated the astonishing nonlocal behavior of an entangled photon pair. Even though we still have questions in regard to fundamental issues of the entangled quantum systems, quantum entanglement has started to play important roles in quantum information and quantum computation. Quantum teleportation is one of the hot topics. We have demonstrated a quantum teleportation experiment recently. The experimental results proved the working principle of irreversibly teleporting an unknown arbitrary quantum state from one system to another distant system by disassembling into and then later reconstructing from purely classical information and nonclassical EPR correlations. The distinct feature of this experiment is that the complete set of Bell states can be distinguished in the Bell state measurement. Teleportation of a quantum state can thus occur with certainty in principle. (orig.)

  8. Quantum ensembles of quantum classifiers.

    Science.gov (United States)

    Schuld, Maria; Petruccione, Francesco

    2018-02-09

    Quantum machine learning witnesses an increasing amount of quantum algorithms for data-driven decision making, a problem with potential applications ranging from automated image recognition to medical diagnosis. Many of those algorithms are implementations of quantum classifiers, or models for the classification of data inputs with a quantum computer. Following the success of collective decision making with ensembles in classical machine learning, this paper introduces the concept of quantum ensembles of quantum classifiers. Creating the ensemble corresponds to a state preparation routine, after which the quantum classifiers are evaluated in parallel and their combined decision is accessed by a single-qubit measurement. This framework naturally allows for exponentially large ensembles in which - similar to Bayesian learning - the individual classifiers do not have to be trained. As an example, we analyse an exponentially large quantum ensemble in which each classifier is weighed according to its performance in classifying the training data, leading to new results for quantum as well as classical machine learning.

  9. Quantum computer games: quantum minesweeper

    Science.gov (United States)

    Gordon, Michal; Gordon, Goren

    2010-07-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.

  10. Proceedings of quantum field theory, quantum mechanics, and quantum optics

    International Nuclear Information System (INIS)

    Dodonov, V.V.; Man; ko, V.I.

    1991-01-01

    This book contains papers presented at the XVIII International Colloquium on Group Theoretical Methods in Physics held in Moscow on June 4-9, 1990. Topics covered include; applications of algebraic methods in quantum field theory, quantum mechanics, quantum optics, spectrum generating groups, quantum algebras, symmetries of equations, quantum physics, coherent states, group representations and space groups

  11. Quantum control limited by quantum decoherence

    International Nuclear Information System (INIS)

    Xue, Fei; Sun, C. P.; Yu, S. X.

    2006-01-01

    We describe quantum controllability under the influences of the quantum decoherence induced by the quantum control itself. It is shown that, when the controller is considered as a quantum system, it will entangle with its controlled system and then cause quantum decoherence in the controlled system. In competition with this induced decoherence, the controllability will be limited by some uncertainty relation in a well-armed quantum control process. In association with the phase uncertainty and the standard quantum limit, a general model is studied to demonstrate the possibility of realizing a decoherence-free quantum control with a finite energy within a finite time. It is also shown that if the operations of quantum control are to be determined by the initial state of the controller, then due to the decoherence which results from the quantum control itself, there exists a low bound for quantum controllability

  12. Dynamic analysis of optical soliton pair and four-wave mixing via Fano interference in multiple quantum wells

    International Nuclear Information System (INIS)

    Yan, Wei; Qu, Junle; Niu, H B

    2014-01-01

    We perform a time-dependent analysis of the formation and stable propagation of an ultraslow optical soliton pair, and four-wave mixing (FWM) via tunable Fano interference in double-cascade type semiconductor multiple quantum wells (SMQWs). By using the probability amplitude method to describe the interaction of the system, we demonstrate that the electromagnetically induced transparency (EIT) can be controlled by Fano interference in the linear case and the strength of Fano interference has an important effect on the group velocity and amplitude of the soliton pair in the nonlinear case. Then, when the signal field is removed, the dynamic FWM process is analyzed in detail, and we find that the strength of Fano interference also has an important effect on the FWM’s efficiency: the maximum FWM efficiency is ∼28% in appropriate conditions. The investigations are promising for practical applications in optical devices and optical information processing for solid systems. (paper)

  13. Quantum electrodynamics of the internal source x-ray holographies: Bremsstrahlung, fluorescence, and multiple-energy x-ray holography

    International Nuclear Information System (INIS)

    Miller, G.A.; Sorensen, L.B.

    1997-01-01

    Quantum electrodynamics (QED) is used to derive the differential cross sections measured in the three new experimental internal source ensemble x-ray holographies: bremsstrahlung (BXH), fluorescence (XFH), and multiple-energy (MEXH) x-ray holography. The polarization dependence of the BXH cross section is also obtained. For BXH, we study analytically and numerically the possible effects of the virtual photons and electrons which enter QED calculations in summing over the intermediate states. For the low photon and electron energies used in the current experiments, we show that the virtual intermediate states produce only very small effects. This is because the uncertainty principle limits the distance that the virtual particles can propagate to be much shorter than the separation between the regions of high electron density in the adjacent atoms. We also find that using the asymptotic form of the scattering wave function causes about a 5 10% error for near forward scattering. copyright 1997 The American Physical Society

  14. From quantum coherence to quantum correlations

    Science.gov (United States)

    Sun, Yuan; Mao, Yuanyuan; Luo, Shunlong

    2017-06-01

    In quantum mechanics, quantum coherence of a state relative to a quantum measurement can be identified with the quantumness that has to be destroyed by the measurement. In particular, quantum coherence of a bipartite state relative to a local quantum measurement encodes quantum correlations in the state. If one takes minimization with respect to the local measurements, then one is led to quantifiers which capture quantum correlations from the perspective of coherence. In this vein, quantum discord, which quantifies the minimal correlations that have to be destroyed by quantum measurements, can be identified as the minimal coherence, with the coherence measured by the relative entropy of coherence. To advocate and formulate this idea in a general context, we first review coherence relative to Lüders measurements which extends the notion of coherence relative to von Neumann measurements (or equivalently, orthonomal bases), and highlight the observation that quantum discord arises as minimal coherence through two prototypical examples. Then, we introduce some novel measures of quantum correlations in terms of coherence, illustrate them through examples, investigate their fundamental properties and implications, and indicate their applications to quantum metrology.

  15. Quantum dot conjugates in a sub-micrometer fluidic channel

    Science.gov (United States)

    Stavis, Samuel M.; Edel, Joshua B.; Samiee, Kevan T.; Craighead, Harold G.

    2010-04-13

    A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.

  16. Quantum dot conjugates in a sub-micrometer fluidic channel

    Science.gov (United States)

    Stavis, Samuel M [Ithaca, NY; Edel, Joshua B [Brookline, MA; Samiee, Kevan T [Ithaca, NY; Craighead, Harold G [Ithaca, NY

    2008-07-29

    A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.

  17. Quantum Hilbert Hotel.

    Science.gov (United States)

    Potoček, Václav; Miatto, Filippo M; Mirhosseini, Mohammad; Magaña-Loaiza, Omar S; Liapis, Andreas C; Oi, Daniel K L; Boyd, Robert W; Jeffers, John

    2015-10-16

    In 1924 David Hilbert conceived a paradoxical tale involving a hotel with an infinite number of rooms to illustrate some aspects of the mathematical notion of "infinity." In continuous-variable quantum mechanics we routinely make use of infinite state spaces: here we show that such a theoretical apparatus can accommodate an analog of Hilbert's hotel paradox. We devise a protocol that, mimicking what happens to the guests of the hotel, maps the amplitudes of an infinite eigenbasis to twice their original quantum number in a coherent and deterministic manner, producing infinitely many unoccupied levels in the process. We demonstrate the feasibility of the protocol by experimentally realizing it on the orbital angular momentum of a paraxial field. This new non-Gaussian operation may be exploited, for example, for enhancing the sensitivity of NOON states, for increasing the capacity of a channel, or for multiplexing multiple channels into a single one.

  18. Quantum Instantons and Quantum Chaos

    OpenAIRE

    Jirari, H.; Kröger, H.; Luo, X. Q.; Moriarty, K. J. M.; Rubin, S. G.

    1999-01-01

    Based on a closed form expression for the path integral of quantum transition amplitudes, we suggest rigorous definitions of both, quantum instantons and quantum chaos. As an example we compute the quantum instanton of the double well potential.

  19. Duality Quantum Information and Duality Quantum Communication

    International Nuclear Information System (INIS)

    Li, C. Y.; Wang, W. Y.; Wang, C.; Song, S. Y.; Long, G. L.

    2011-01-01

    Quantum mechanical systems exhibit particle wave duality property. This duality property has been exploited for information processing. A duality quantum computer is a quantum computer on the move and passing through a multi-slits. It offers quantum wave divider and quantum wave combiner operations in addition to those allowed in an ordinary quantum computer. It has been shown that all linear bounded operators can be realized in a duality quantum computer, and a duality quantum computer with n qubits and d-slits can be realized in an ordinary quantum computer with n qubits and a qudit in the so-called duality quantum computing mode. The quantum particle-wave duality can be used in providing secure communication. In this paper, we will review duality quantum computing and duality quantum key distribution.

  20. Quantum computers and quantum computations

    International Nuclear Information System (INIS)

    Valiev, Kamil' A

    2005-01-01

    This review outlines the principles of operation of quantum computers and their elements. The theory of ideal computers that do not interact with the environment and are immune to quantum decohering processes is presented. Decohering processes in quantum computers are investigated. The review considers methods for correcting quantum computing errors arising from the decoherence of the state of the quantum computer, as well as possible methods for the suppression of the decohering processes. A brief enumeration of proposed quantum computer realizations concludes the review. (reviews of topical problems)

  1. III–V quantum light source and cavity-QED on Silicon

    Science.gov (United States)

    Luxmoore, I. J.; Toro, R.; Pozo-Zamudio, O. Del; Wasley, N. A.; Chekhovich, E. A.; Sanchez, A. M.; Beanland, R.; Fox, A. M.; Skolnick, M. S.; Liu, H. Y.; Tartakovskii, A. I.

    2013-01-01

    Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers of quantum information and can be exploited for linear optics quantum information processing. Scale-up requires miniaturisation of the waveguide circuit and multiple single photon sources. Silicon photonics, driven by the incentive of optical interconnects is a highly promising platform for the passive optical components, but integrated light sources are limited by silicon's indirect band-gap. III–V semiconductor quantum-dots, on the other hand, are proven quantum emitters. Here we demonstrate single-photon emission from quantum-dots coupled to photonic crystal nanocavities fabricated from III–V material grown directly on silicon substrates. The high quality of the III–V material and photonic structures is emphasized by observation of the strong-coupling regime. This work opens-up the advantages of silicon photonics to the integration and scale-up of solid-state quantum optical systems. PMID:23393621

  2. III-V quantum light source and cavity-QED on silicon.

    Science.gov (United States)

    Luxmoore, I J; Toro, R; Del Pozo-Zamudio, O; Wasley, N A; Chekhovich, E A; Sanchez, A M; Beanland, R; Fox, A M; Skolnick, M S; Liu, H Y; Tartakovskii, A I

    2013-01-01

    Non-classical light sources offer a myriad of possibilities in both fundamental science and commercial applications. Single photons are the most robust carriers of quantum information and can be exploited for linear optics quantum information processing. Scale-up requires miniaturisation of the waveguide circuit and multiple single photon sources. Silicon photonics, driven by the incentive of optical interconnects is a highly promising platform for the passive optical components, but integrated light sources are limited by silicon's indirect band-gap. III-V semiconductor quantum-dots, on the other hand, are proven quantum emitters. Here we demonstrate single-photon emission from quantum-dots coupled to photonic crystal nanocavities fabricated from III-V material grown directly on silicon substrates. The high quality of the III-V material and photonic structures is emphasized by observation of the strong-coupling regime. This work opens-up the advantages of silicon photonics to the integration and scale-up of solid-state quantum optical systems.

  3. Achieving Uniform Carriers Distribution in MBE Grown Compositionally Graded InGaN Multiple-Quantum-Well LEDs

    KAUST Repository

    Mishra, Pawan; Janjua, Bilal; Ng, Tien Khee; Shen, Chao; Salhi, Abdelmajid; Alyamani, Ahmed; El-Desouki, Munir; Ooi, Boon S.

    2015-01-01

    We investigated the design and growth of compositionally-graded InGaN multiple quantum wells (MQW) based light-emitting diode (LED) without an electron-blocking layer (EBL). Numerical investigation showed uniform carrier distribution in the active region, and higher radiative recombination rate for the optimized graded-MQW design, i.e. In0→xGa1→(1-x)N / InxGa(1-x)N / Inx→0Ga(1-x)→1N, as compared to the conventional stepped-MQW-LED. The composition-grading schemes, such as linear, parabolic, and Fermi-function profiles were numerically investigated for comparison. The stepped- and graded-MQW-LED were then grown using plasma assisted molecular beam epitaxy (PAMBE) through surface-stoichiometry optimization based on reflection high-energy electron-diffraction (RHEED) in-situ observations. Stepped- and graded-MQW-LED showed efficiency roll over at 160 A/cm2 and 275 A/cm2, respectively. The extended threshold current density roll-over (droop) in graded-MQW-LED is due to the improvement in carrier uniformity and radiative recombination rate, consistent with the numerical simulation.

  4. VLS growth of alternating InAsP/InP heterostructure nanowires for multiple-quantum-dot structures.

    Science.gov (United States)

    Tateno, Kouta; Zhang, Guoqiang; Gotoh, Hideki; Sogawa, Tetsuomi

    2012-06-13

    We investigated the Au-assisted growth of alternating InAsP/InP heterostructures in wurtzite InP nanowires on InP(111)B substrates for constructing multiple-quantum-dot structures. Vertical InP nanowires without stacking faults were obtained at a high PH(3)/TMIn mole flow ratio of 300-1000. We found that the growth rate changed largely when approximately 40 min passed. Ten InAsP layers were inserted in the InP nanowire, and it was found that both the InP growth rate and the background As level increased after the As supply. We also grew the same structure using TBAs/TBP and could reduce the As level in the InP segments. A simulation using a finite-difference time-domain method suggests that the nanowire growth was dominated by the diffusion of the reaction species with long residence time on the surface. For TBAs/TBP, when the source gases were changed, the formed surface species showed a short diffusion length so as to reduce the As background after the InAsP growth.

  5. Achieving Uniform Carriers Distribution in MBE Grown Compositionally Graded InGaN Multiple-Quantum-Well LEDs

    KAUST Repository

    Mishra, Pawan

    2015-05-06

    We investigated the design and growth of compositionally-graded InGaN multiple quantum wells (MQW) based light-emitting diode (LED) without an electron-blocking layer (EBL). Numerical investigation showed uniform carrier distribution in the active region, and higher radiative recombination rate for the optimized graded-MQW design, i.e. In0→xGa1→(1-x)N / InxGa(1-x)N / Inx→0Ga(1-x)→1N, as compared to the conventional stepped-MQW-LED. The composition-grading schemes, such as linear, parabolic, and Fermi-function profiles were numerically investigated for comparison. The stepped- and graded-MQW-LED were then grown using plasma assisted molecular beam epitaxy (PAMBE) through surface-stoichiometry optimization based on reflection high-energy electron-diffraction (RHEED) in-situ observations. Stepped- and graded-MQW-LED showed efficiency roll over at 160 A/cm2 and 275 A/cm2, respectively. The extended threshold current density roll-over (droop) in graded-MQW-LED is due to the improvement in carrier uniformity and radiative recombination rate, consistent with the numerical simulation.

  6. Space-Time Quantum Imaging

    Directory of Open Access Journals (Sweden)

    Ronald E. Meyers

    2015-03-01

    Full Text Available We report on an experimental and theoretical investigation of quantum imaging where the images are stored in both space and time. Ghost images of remote objects are produced with either one or two beams of chaotic laser light generated by a rotating ground glass and two sensors measuring the reference field and bucket field at different space-time points. We further observe that the ghost images translate depending on the time delay between the sensor measurements. The ghost imaging experiments are performed both with and without turbulence. A discussion of the physics of the space-time imaging is presented in terms of quantum nonlocal two-photon analysis to support the experimental results. The theoretical model includes certain phase factors of the rotating ground glass. These experiments demonstrated a means to investigate the time and space aspects of ghost imaging and showed that ghost imaging contains more information per measured photon than was previously recognized where multiple ghost images are stored within the same ghost imaging data sets. This suggests new pathways to explore quantum information stored not only in multi-photon coincidence information but also in time delayed multi-photon interference. The research is applicable to making enhanced space-time quantum images and videos of moving objects where the images are stored in both space and time.

  7. Quantum Computation and Quantum Spin Dynamics

    NARCIS (Netherlands)

    Raedt, Hans De; Michielsen, Kristel; Hams, Anthony; Miyashita, Seiji; Saito, Keiji

    2001-01-01

    We analyze the stability of quantum computations on physically realizable quantum computers by simulating quantum spin models representing quantum computer hardware. Examples of logically identical implementations of the controlled-NOT operation are used to demonstrate that the results of a quantum

  8. Multiple reflection Michelson interferometer with picometer resolution.

    Science.gov (United States)

    Pisani, Marco

    2008-12-22

    A Michelson interferometer based on an optical set-up allowing multiple reflection between two plane mirrors performs the multiplication of the optical path by a factor N, proportionally increasing the resolution of the measurement. A multiplication factor of almost two orders of magnitude has been demonstrated with a simple set-up. The technique can be applied to any interferometric measurement where the classical interferometer limits due to fringe nonlinearities and quantum noise are an issue. Applications in precision engineering, vibration analysis, nanometrology, and spectroscopy are foreseen.

  9. Piezo-Phototronic Effect in a Quantum Well Structure.

    Science.gov (United States)

    Huang, Xin; Du, Chunhua; Zhou, Yongli; Jiang, Chunyan; Pu, Xiong; Liu, Wei; Hu, Weiguo; Chen, Hong; Wang, Zhong Lin

    2016-05-24

    With enhancements in the performance of optoelectronic devices, the field of piezo-phototronics has attracted much attention, and several theoretical works have been reported based on semiclassical models. At present, the feature size of optoelectronic devices are rapidly shrinking toward several tens of nanometers, which results in the quantum confinement effect. Starting from the basic piezoelectricity equation, Schrödinger equation, Poisson equation, and Fermi's golden rule, a self-consistent theoretical model is proposed to study the piezo-phototronic effect in the framework of perturbation theory in quantum mechanics. The validity and universality of this model are well-proven with photoluminescence measurements in a single GaN/InGaN quantum well and multiple GaN/InGaN quantum wells. This study provides important insight into the working principle of nanoscale piezo-phototronic devices as well as guidance for the future device design.

  10. Wigner tomography of multispin quantum states

    Science.gov (United States)

    Leiner, David; Zeier, Robert; Glaser, Steffen J.

    2017-12-01

    We study the tomography of multispin quantum states in the context of finite-dimensional Wigner representations. An arbitrary operator can be completely characterized and visualized using multiple shapes assembled from linear combinations of spherical harmonics [A. Garon, R. Zeier, and S. J. Glaser, Phys. Rev. A 91, 042122 (2015), 10.1103/PhysRevA.91.042122]. We develop a general methodology to experimentally recover these shapes by measuring expectation values of rotated axial spherical tensor operators and provide an interpretation in terms of fictitious multipole potentials. Our approach is experimentally demonstrated for quantum systems consisting of up to three spins using nuclear magnetic resonance spectroscopy.

  11. What is quantum in quantum randomness?

    Science.gov (United States)

    Grangier, P; Auffèves, A

    2018-07-13

    It is often said that quantum and classical randomness are of different nature, the former being ontological and the latter epistemological. However, so far the question of 'What is quantum in quantum randomness?', i.e. what is the impact of quantization and discreteness on the nature of randomness, remains to be answered. In a first part, we make explicit the differences between quantum and classical randomness within a recently proposed ontology for quantum mechanics based on contextual objectivity. In this view, quantum randomness is the result of contextuality and quantization. We show that this approach strongly impacts the purposes of quantum theory as well as its areas of application. In particular, it challenges current programmes inspired by classical reductionism, aiming at the emergence of the classical world from a large number of quantum systems. In a second part, we analyse quantum physics and thermodynamics as theories of randomness, unveiling their mutual influences. We finally consider new technological applications of quantum randomness that have opened up in the emerging field of quantum thermodynamics.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).

  12. Assembly of CdS Quantum Dots onto Hierarchical TiO2 Structure for Quantum Dots Sensitized Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Syed Mansoor Ali

    2015-05-01

    Full Text Available Quantum dot (QD sensitized solar cells based on Hierarchical TiO2 structure (HTS consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate is fabricated. The hierarchical TiO2 structure consisting of spherical nano-urchins on transparent conductive fluorine doped tin oxide glass substrate synthesized by hydrothermal route. The CdS quantum dots were grown by the successive ionic layer adsorption and reaction deposition method. The quantum dot sensitized solar cell based on the hierarchical TiO2 structure shows a current density JSC = 1.44 mA, VOC = 0.46 V, FF = 0.42 and η = 0.27%. The QD provide a high surface area and nano-urchins offer a highway for fast charge collection and multiple scattering centers within the photoelectrode.

  13. Planar quantum squeezing and atom interferometry

    Energy Technology Data Exchange (ETDEWEB)

    He, Q. Y.; Drummond, P. D.; Reid, M. D. [ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122 (Australia); Peng Shiguo [Department of Physics, Tsinghua University, Beijing 100084 (China)

    2011-08-15

    We obtain a lower bound on the sum of two orthogonal spin component variances in a plane. This gives a planar uncertainty relation which holds even when the Heisenberg relation is not useful. We investigate the asymptotic, large-J limit and derive the properties of the planar quantum squeezed states that saturate this uncertainty relation. These states extend the concept of spin squeezing to any two conjugate spin directions. We show that planar quantum squeezing can be achieved experimentally as the ground state of a Bose-Einstein condensate in two coupled potential wells with a critical attractive interaction. These states reduce interferometric phase noise at all phase angles simultaneously. This is useful for one-shot interferometric phase measurements where the measured phase is completely unknown. Our results can also be used to derive entanglement criteria for multiple spins J at separated sites, with applications in quantum information.

  14. Long-distance multipartite quantum communication

    International Nuclear Information System (INIS)

    Herbst, T.

    2014-01-01

    entangled four photons in a GHZ-state with one of the recipients being separated by 143 km. Entanglement swapping and multi-photon entanglement such as GHZ-states lay the foundation for the distribution of entanglement over large distances and for entangling multiple nodes with each other. Our findings prove the feasibility of these protocols in future satellite-based quantum-communication applications, furthering the vision of quantum networks on a global scale. (author) [de

  15. An Early Quantum Computing Proposal

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Stephen Russell [Los Alamos National Laboratory; Alexander, Francis Joseph [Los Alamos National Laboratory; Barros, Kipton Marcos [Los Alamos National Laboratory; Daniels, Marcus G. [Los Alamos National Laboratory; Gattiker, James R. [Los Alamos National Laboratory; Hamada, Michael Scott [Los Alamos National Laboratory; Howse, James Walter [Los Alamos National Laboratory; Loncaric, Josip [Los Alamos National Laboratory; Pakin, Scott D. [Los Alamos National Laboratory; Somma, Rolando Diego [Los Alamos National Laboratory; Vernon, Louis James [Los Alamos National Laboratory

    2016-04-04

    The D-Wave 2X is the third generation of quantum processing created by D-Wave. NASA (with Google and USRA) and Lockheed Martin (with USC), both own D-Wave systems. Los Alamos National Laboratory (LANL) purchased a D-Wave 2X in November 2015. The D-Wave 2X processor contains (nominally) 1152 quantum bits (or qubits) and is designed to specifically perform quantum annealing, which is a well-known method for finding a global minimum of an optimization problem. This methodology is based on direct execution of a quantum evolution in experimental quantum hardware. While this can be a powerful method for solving particular kinds of problems, it also means that the D-Wave 2X processor is not a general computing processor and cannot be programmed to perform a wide variety of tasks. It is a highly specialized processor, well beyond what NNSA currently thinks of as an “advanced architecture.”A D-Wave is best described as a quantum optimizer. That is, it uses quantum superposition to find the lowest energy state of a system by repeated doses of power and settling stages. The D-Wave produces multiple solutions to any suitably formulated problem, one of which is the lowest energy state solution (global minimum). Mapping problems onto the D-Wave requires defining an objective function to be minimized and then encoding that function in the Hamiltonian of the D-Wave system. The quantum annealing method is then used to find the lowest energy configuration of the Hamiltonian using the current D-Wave Two, two-level, quantum processor. This is not always an easy thing to do, and the D-Wave Two has significant limitations that restrict problem sizes that can be run and algorithmic choices that can be made. Furthermore, as more people are exploring this technology, it has become clear that it is very difficult to come up with general approaches to optimization that can both utilize the D-Wave and that can do better than highly developed algorithms on conventional computers for

  16. Noninvasive detection of temozolomide in brain tumor xenografts by magnetic resonance spectroscopy

    DEFF Research Database (Denmark)

    Kato, Y.; Holm, David Alberg; Okollie, B.

    2010-01-01

    demonstrate partial breakdown of the BBB/BTB and good vascularization in U87MG xenografts. A [C-13] TMZ peak was detected at 3.9 ppm by HMQC from a selected volume of about 0.15 cm(3) within the brain tumor with HMQC pulse sequences. This study clearly demonstrates the noninvasive detection of [C-13]TMZ...

  17. Quantum robots and quantum computers

    Energy Technology Data Exchange (ETDEWEB)

    Benioff, P.

    1998-07-01

    Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.

  18. Nontrivial transition of transmission in a highly open quantum point contact in the quantum Hall regime

    Science.gov (United States)

    Hong, Changki; Park, Jinhong; Chung, Yunchul; Choi, Hyungkook; Umansky, Vladimir

    2017-11-01

    Transmission through a quantum point contact (QPC) in the quantum Hall regime usually exhibits multiple resonances as a function of gate voltage and high nonlinearity in bias. Such behavior is unpredictable and changes sample by sample. Here, we report the observation of a sharp transition of the transmission through an open QPC at finite bias, which was observed consistently for all the tested QPCs. It is found that the bias dependence of the transition can be fitted to the Fermi-Dirac distribution function through universal scaling. The fitted temperature matches quite nicely to the electron temperature measured via shot-noise thermometry. While the origin of the transition is unclear, we propose a phenomenological model based on our experimental results that may help to understand such a sharp transition. Similar transitions are observed in the fractional quantum Hall regime, and it is found that the temperature of the system can be measured by rescaling the quasiparticle energy with the effective charge (e*=e /3 ). We believe that the observed phenomena can be exploited as a tool for measuring the electron temperature of the system and for studying the quasiparticle charges of the fractional quantum Hall states.

  19. Local Gate Control of a Carbon Nanotube Double Quantum Dot

    Science.gov (United States)

    2016-04-04

    describ- ing the levitation . Quantitative comparisons are made difficult by the complicated aniso- tropy of the nematic’s viscoelasticity (21). However...director fields. For example, as a straightforward extension of the levitation , a liquid crystal that twists through many periods (such as a cholesteric...Nanotube Double Quantum Dot N. Mason,*† M. J. Biercuk,* C. M. Marcus† We have measured carbon nanotube quantum dots with multiple electro- static gates and

  20. Quantum relativity theory and quantum space-time

    International Nuclear Information System (INIS)

    Banai, M.

    1984-01-01

    A quantum relativity theory formulated in terms of Davis' quantum relativity principle is outlined. The first task in this theory as in classical relativity theory is to model space-time, the arena of natural processes. It is shown that the quantum space-time models of Banai introduced in another paper is formulated in terms of Davis's quantum relativity. The recently proposed classical relativistic quantum theory of Prugovecki and his corresponding classical relativistic quantum model of space-time open the way to introduce, in a consistent way, the quantum space-time model (the quantum substitute of Minkowski space) of Banai proposed in the paper mentioned. The goal of quantum mechanics of quantum relativistic particles living in this model of space-time is to predict the rest mass system properties of classically relativistic (massive) quantum particles (''elementary particles''). The main new aspect of this quantum mechanics is that it provides a true mass eigenvalue problem, and that the excited mass states of quantum relativistic particles can be interpreted as elementary particles. The question of field theory over quantum relativistic model of space-time is also discussed. Finally it is suggested that ''quarks'' should be considered as quantum relativistic particles. (author)