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Sample records for 1h multiple quantum

  1. Thermal degradation in a trimodal PDMS network by 1H Multiple Quantum NMR

    Giuliani, J R; Gjersing, E L; Chinn, S C; Jones, T V; Wilson, T S; Alviso, C T; Herberg, J L; Pearson, M A; Maxwell, R S

    2007-06-06

    Thermal degradation of a filled, crosslinked siloxane material synthesized from PDMS chains of three different average molecular weights and with two different crosslinking species has been studied by {sup 1}H Multiple Quantum (MQ) NMR methods. Multiple domains of polymer chains were detected by MQ NMR exhibiting Residual Dipolar Coupling (<{Omega}{sub d}>) values of 200 Hz and 600 Hz, corresponding to chains with high average molecular weight between crosslinks and chains with low average molecular weight between crosslinks or near the multifunctional crosslinking sites. Characterization of the <{Omega}{sub d}> values and changes in <{Omega}{sub d}> distributions present in the material were studied as a function of time at 250 C and indicates significant time dependent degradation. For the domains with low <{Omega}{sub d}>, a broadening in the distribution was observed with aging time. For the domain with high <{Omega}{sub d}>, increases in both the mean <{Omega}{sub d}> and the width in <{Omega}{sub d}> were observed with increasing aging time. Isothermal Thermal Gravimetric Analysis (TGA) reveals a 3% decrease in weight over 20 hours of aging at 250 C. Degraded samples also were analyzed by traditional solid state {sup 1}H NMR techniques and offgassing products were identified by Solid Phase MicroExtraction followed by Gas Chromatography-Mass Spectrometry (SPME GC-MS). The results, which will be discussed here, suggest that thermal degradation proceeds by complex competition between oxidative chain scissioning and post-curing crosslinking that both contribute to embrittlement.

  2. Investigation of network heterogeneities in filled, trimodal, highly functional PDMS networks by 1H Multiple Quantum NMR

    Gjersing, E; Chinn, S; Maxwell, R S; Herberg, J; Eastwood, E; Bowen, D; Stephens, T

    2006-09-06

    The segmental order and dynamics of polymer network chains in a filled, tri-modal silicone network have been studied by static 1H Multiple Quantum (MQ) NMR methods to gain insight into the structure property relationships. The materials were synthesized with two different types of crosslinks, with functionalities of 4 and near 60. The network chains were composed of distributions of high, low, and medium molecular weight chains. Crosslinking was accomplished by standard acid catalyzed reactions. MQ NMR methods have detected domains with residual dipolar couplings (<{Omega}{sub d}>) of near 4 kRad/s and 1 kRad/s assigned to (a) the shorter polymer chains and chains near the multifunctional ({phi}=60) crosslinking sites and to (b) the longer polymer chains far from these sites. Three structural variables were systematically varied and the mechanical properties and distributions of residual dipolar couplings measured in order to gain insight in to the network structural motifs that contribute significantly to the composite properties. The partitioning of and the average values of the residual dipolar couplings for the two domains were observed to be dependent on formulation variable and provided increased insight into the mechanical properties of these materials which are unavailable from swelling and spin-echo methods. The results of this study suggest that the domains with high crosslink density contribute significantly to the high strain modulus, while the low crosslink density domains do not. This is in agreement with theories and experimental studies on silicone bimodal networks over the last 20 years. In-situ MQ-NMR of swollen sample suggests that the networks deform non-affinely, in agreement with theory. The NMR experiments shown here provide increased ability to characterize multimodal networks of typical engineering silicone materials and to gain significant insight into structure-property relationships.

  3. Investigation of network heterogeneities in filled, trimodal, highly functional PDMS networks by 1H Multiple Quantum NMR

    Maxwell, R; Gjersing, E; Chinn, S; Giuliani, J; Herberg, J; Eastwood, E; Bowen, D; Stephens, T

    2007-03-20

    The segmental order and dynamics of polymer network chains in a filled, tri-modal silicone foam network have been studied by static 1H Multiple Quantum (MQ) NMR methods to gain insight into the structure property relationships. The foam materials were synthesized with two different types of crosslinks, with functionalities, {phi}, of 4 and near 60. The network chains were composed of distributions of high, low, and medium molecular weight chains. Crosslinking was accomplished by standard acid catalyzed reactions. MQ NMR methods have detected domains with residual dipolar couplings (<{Omega}{sub d}>) of near 4 kRad/s and 1 kRad/s assigned to (a) the shorter polymer chains and chains near the multifunctional (f=60) crosslinking sites and to (b) the longer polymer chains far from these sites. Three structural variables were systematically varied and the mechanical properties via compression and distributions of residual dipolar couplings measured in order to gain insight in to the network structural motifs that contribute significantly to the composite properties. The partitioning of and the average values of the residual dipolar couplings for the two domains were observed to be dependent on formulation variable and provided increased insight into the network structure of these materials which are unavailable from swelling and spin-echo methods. The results of this study suggest that the domains with high crosslink density contribute significantly to the high strain modulus, while the low crosslink density domains do not. This is in agreement with theories and experimental studies on silicone bimodal networks over the last 20 years. In-situ MQ-NMR of swollen sample suggests that the networks deform heterogeneously and non-affinely. The heterogeneity of the deformation process was observed to depend on the amount of the high functionality crosslinking site PMHS. The NMR experiments shown here provide increased ability to characterize multimodal networks of typical

  4. Nitrogen-15 labeled 5S RNA. Identification of uridine base pairs in Escherichia coli 5S RNA by 1H-15N multiple quantum NMR

    Escherichia coli 5S RNA labeled with 15N at N3 of the uridines was isolated from the Sφ-187 uracil auxotroph grown on a minimal medium supplemented with [3-15N]uracil. 1H-15N multiple quantum filtered and 2D chemical shift correlated spectra gave resonances for the uridine imino 1H-15N units whose protons were exchanging slowly with solvent. Peaks with 1H/15N shifts at 11.6/154.8, 11.7/155.0, 11.8/155.5, 12.1/155.0, and 12.2/155.0 ppm were assigned to GU interactions. Two labile high-field AU resonances at 12.6/156.8 and 12.8/157.3 ppm typical of Au pairs in a shielded environment at the end of a helix were seen. Intense AU signals were also found at 13.4/158.5 and 13.6/159.2 ppm where 1H-15N units in normal Watson-Crick pairs resonate. 1H resonances at 10.6 and 13.8 ppm were too weak, presumably because of exchange with water, to give peaks in chemical shift correlated spectra. 1H chemical shifts suggest that the resonance at 13.8 ppm represents a labile AU pair, while the resonance at 10.6 ppm is typical of a tertiary interaction between U and a tightly bound water or a phosphate residue. The NMR data are consistent with proposed secondary structures for 5S RNA

  5. Localized double-quantum-filtered 1H NMR spectroscopy

    Thomas, M. A.; Hetherington, H. P.; Meyerhoff, D. J.; Twieg, D. B.

    The image-guided in vivo spectroscopic (ISIS) pulse sequence has been combined with a double-quantum-filter scheme in order to obtain localized and water-suppressed 1H NMR spectra of J-coupled metabolites. The coherence-transfer efficiency associated with the DQ filter for AX and A 3X spin systems is described. Phantom results of carnosine, alanine, and ethanol in aqueous solution are presented. For comparison, the 1H NMR spectrum of alanine in aqueous solution with the binomial (1331, 2662) spin-echo sequence is also shown.

  6. Quantum Optical Multiple Scattering

    Ott, Johan Raunkjær

    for the dipoles while treating them as quantum two-level systems and using the Born–Markov and rotating-wave approximations. Postponing the rotating-wave approximation to the very end of the formal calculations allows us to identify the different physical parameters of the dipole evolution in terms of...... 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...

  7. Probabilities of multiple quantum teleportation

    Woesler, Richard

    2002-01-01

    Using quantum teleportation a quantum state can be teleported with a certain probability. Here the probabilities for multiple teleportation are derived, i. e. for the case that a teleported quantum state is teleported again or even more than two times, for the two-dimensional case, e. g., for the two orthogonal direcations of the polarization of photons. It is shown that the probability for an exact teleportation, except for an irrelevant phase factor, is 25 %, i. e., surprisingly, this resul...

  8. Quantum Multiple Access Channel

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  9. Quantum Interference of Multiple Beams Induced by Multiple Scattering

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

    2011-01-01

    We report on quantum interference induced by the transmission of quantized light through a multiple-scattering medium. We show that entangled states can be created by multiple-scattering and that quantum interference survives disorder averaging.......We report on quantum interference induced by the transmission of quantized light through a multiple-scattering medium. We show that entangled states can be created by multiple-scattering and that quantum interference survives disorder averaging....

  10. Scattering Induced Quantum Interference of Multiple Quantum Optical States

    Ott, Johan Raunkjær; Wubs, Martijn; Mortensen, N. Asger;

    2011-01-01

    Using a discrete mode theory for propagation of quantum optical states, we investigate the consequences of multiple scattering on the degree of quadrature entanglement and quantum interference. We report that entangled states can be created by multiple-scattering. We furthermore show that quantum...

  11. Quantum internet using code division multiple access

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

    2013-07-01

    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.

  12. Longitudinal monitoring of metabolic alterations in cuprizone mouse model of multiple sclerosis using 1H-magnetic resonance spectroscopy.

    Orije, Jasmien; Kara, Firat; Guglielmetti, Caroline; Praet, Jelle; Linden, van der, M.; Ponsaerts, Peter; Verhoye, Marleen

    2015-01-01

    Non-invasive measures of well-known pathological hallmarks of multiple sclerosis (MS) such as demyelination, inflammation and axonal injury would serve as useful markers to monitor disease progression and evaluate potential therapies. To this end, in vivo localized proton magnetic resonance spectroscopy ((1)H-MRS) provides a powerful means to monitor metabolic changes in the brain and may be sensitive to these pathological hallmarks. In our study, we used the cuprizone mouse model to study pa...

  13. Multiple-Access Quantum-Classical Networks

    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.

  14. 1H MR spectroscopy of the lumbar spine in bone demineralization of patients suffering from diffuse multiple myeloma or osteoporosis

    Purpose: To evaluate the role of in vivo 1H MR spectroscopic determination of relaxation times and of fat and water content to differentiate between infiltration of multiple myeloma or osteoporosis in patients with roentgenologic nuclear demineralization of the lumbar spine. Results: There were highly significant differences in T2 values and fat content between patients with osteoporosis and multiple myeloma. T2 values were decreased in osteoporosis (37 ms and 59 ms vs. 44 ms and 70 ms in plasmocytoma) and fat content was decreased in multiple myeloma (20% vs 31% and 34% in volunteers and osteoporosis). Between volunteers and patients with osteoporosis the differences in the T2 of the fat component was significantly different. Conclusions: In our preliminary experience MRS is helpful in the differential diagnosis of bony demineralization. It enables a differentiation between osteoporosis and diffuse multiple myeloma. T2 value measurements may be helpful in the diagnostic trial of osteoporosis. (orig./AJ)

  15. Electronic structure of (1e,1h) states of carbon nanotube quantum dots

    Osika, E. N.; B. Szafran

    2016-01-01

    We provide an atomistic tight-binding description of a few carriers confined in ambipolar (n-p) double quantum dots defined in a semiconducting carbon nanotube. We focus our attention on the charge state of the system in which Pauli blockade of the current flow is observed [F. Pei et al., Nat. Nanotechnol. 7, 630 (2012); E. A. Laird et al., ibid 8, 565 (2013)] with a single excess electron in the n-dot and a single hole in the p-dot. We use the configuration interaction approach to determine ...

  16. Quantum teleportation of multiple properties of a single quantum particle

    Wang, Xi-Lin; Su, Zu-En; Chen, Ming-Cheng; Wu, Dian; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei

    2014-01-01

    Quantum teleportation provides a "disembodied" way to transfer quantum states of an object over arbitrarily long distance, without physical travelling of the object itself. A single quantum particle can possess various degrees of freedom-internal and external-and with coherent coupling among them. Yet, all the previous experiments were limited to teleportation of a single degree of freedom only. A fundamental open challenge is to simultaneously teleport multiple degrees of freedom which is necessary to fully describe an object, thereby truly teleporting it intactly. Here, we demonstrate the first quantum teleportation of both spin and orbital angular momentum of a single photon, in the form of spin-orbit hybrid entangled states. We use spin-orbit hyper-entangled photon pairs as quantum channel, and develop a new technique to discriminate hyper-entangled Bell state exploiting quantum non-demolition measurement. This work demonstrates an enhanced capability for quantum communications, and moves a step toward co...

  17. Electronic structure of (1e,1h) states of carbon nanotube quantum dots

    Osika, E. N.; Szafran, B.

    2016-04-01

    We provide an atomistic tight-binding description of a few carriers confined in ambipolar (n -p ) double quantum dots defined in a semiconducting carbon nanotube. We focus our attention on the charge configuration in which Pauli blockade of the current flow is observed [F. Pei et al., Nat. Nanotechnol. 7, 630 (2012), 10.1038/nnano.2012.160; E. A. Laird et al., Nat. Nanotechnol. 8, 565 (2013), 10.1038/nnano.2013.140] with a single excess electron in the n dot and a single hole in the p dot. We use the configuration interaction approach to determine the spin-valley structure of the states near the neutrality point and discuss its consequences for the interdot exchange interaction, the degeneracy of the energy spectrum, and the symmetry of the confined states. We calculate the transition energies lifting the Pauli blockade and analyze their dependence on the magnetic field vector. Furthermore, we introduce bending of the nanotube and demonstrate its influence on the transition energy spectra. The best qualitative agreement with the experimental data is observed for nanotubes deflected in the gated areas in which the carrier confinement is induced.

  18. (1)H NMR z-spectra of acetate methyl in stretched hydrogels: quantum-mechanical description and Markov chain Monte Carlo relaxation-parameter estimation.

    Shishmarev, Dmitry; Chapman, Bogdan E; Naumann, Christoph; Mamone, Salvatore; Kuchel, Philip W

    2015-01-01

    The (1)H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm. PMID:25486634

  19. Time-domain multiple-quantum NMR

    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

  20. Quantum hyperparallel algorithm for matrix multiplication.

    Zhang, Xin-Ding; Zhang, Xiao-Ming; Xue, Zheng-Yuan

    2016-01-01

    Hyperentangled states, entangled states with more than one degree of freedom, are considered as promising resource in quantum computation. Here we present a hyperparallel quantum algorithm for matrix multiplication with time complexity O(N(2)), which is better than the best known classical algorithm. In our scheme, an N dimensional vector is mapped to the state of a single source, which is separated to N paths. With the assistance of hyperentangled states, the inner product of two vectors can be calculated with a time complexity independent of dimension N. Our algorithm shows that hyperparallel quantum computation may provide a useful tool in quantum machine learning and "big data" analysis. PMID:27125586

  1. 15N and 1H NMR evidence for multiple conformations of the complex of dihydrofolate reductase with its substrate, folate

    The binding of folate to Lactobacillus casei dihydrofolate reductase in the presence and absence of NADP+ has been studied by 15N NMR, using [5-15N]folate. In the presence of NADP+, three separate signals were observed for the single 15N atom, in agreement with our earlier evidence from 1H and 13C NMR for multiple conformations of this complex. The 15N spectra of the binary enzyme-folate complex provide evidence for the first time that this complex also exists in at least two conformational states. This is confirmed by the observation of two separate resonances for the 7-proton of bound folate, located by two-dimensional exchange spectroscopy. 15 refs.; 3 figs.; 1 table

  2. Quantum internet using code division multiple access

    Zhang, Jing; Ozdemir, Sahin Kaya; Wu, Re-Bing; Wang, Xiang-Bin; Nori, Franco

    2012-01-01

    Code division multiple access (CDMA) is a spread-spectrum technology, in which a code is used to spread the spectral content of information to achieve larger network capacity. It has been widely used in classical communication and wireless networks. Here, we extend CDMA to the quantum case, where many pairs of nodes can transmit quantum information through a shared channel. This can be achieved by chaotic encoding of quantum information to spread its spectral content and by chaos synchronization, to separate different sender-receiver pairs. The proposed method is robust to low-frequency noise, and achieves faithful transmission with fidelities of up to 0.99.

  3. Quantum hyperparallel algorithm for matrix multiplication

    Zhang, Xin-Ding; Zhang, Xiao-Ming; Xue, Zheng-Yuan

    2016-01-01

    Hyperentangled states, entangled states with more than one degree of freedom, are considered as promising resource in quantum computation. Here we present a hyperparallel quantum algorithm for matrix multiplication with time complexity O(N2), which is better than the best known classical algorithm. In our scheme, an N dimensional vector is mapped to the state of a single source, which is separated to N paths. With the assistance of hyperentangled states, the inner product of two vectors can be calculated with a time complexity independent of dimension N. Our algorithm shows that hyperparallel quantum computation may provide a useful tool in quantum machine learning and “big data” analysis. PMID:27125586

  4. Multiple exciton generation effect in quantum dots

    Full text: Recently among various investigations in the field of nanophysics a great intensification in studying of multiple exciton generation (MEG) effect in quantum dots at absorption of photons with the energy several times higher than the gap in electronic spectra (hν>>Eg) has been made [1-2]. There have been proposed four theoretical approaches to explain the MEG effect. However, the statistic approach basing on the Fermi theory of multiple pi-mesons generation (1950) is the most adequate related to others. In this work: 1. the results of statistic approach have been generalized; 2. the microscopic mechanism basing on theory of electronic 'shaking' has been proposed; 3. the problem of deviation of mean multiplicity of MEG effect from the Poisson law of fluctuations has been investigated that is a evidence of strong non-linear and non-equilibrium character of exciton generation process; 4. the role of interface electronic states of quantum dot and ligand has been considered by means of perturbation theory of closed states related to surface Tamm electronic states of quantum dot and legend; 5. the problem of size optimization of quantum dot to receive the maximum multiplicity has been studied; 6. the efficiency of MEG effect for the third generation of solar cells has been calculated on the basis of proposed theory. (authors)

  5. Selectivity in multiple quantum nuclear magnetic resonance

    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

  6. Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors.

    Zhang, Ming-Liang; Yue, Deng-Feng; Wang, Zhen-Hua; Luo, Yuan; Xu, Xiao-Ying; Zhang, Xiao-Mei; Yuan, Wei-Cheng

    2016-01-01

    For the first time, a catalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones was achieved with a chiral bifunctional amine-thiourea as a catalyst possessing multiple hydrogen-bond donors. With this developed method, a range of 3-hydroxy-3-nitromethyl-1H-pyrrol-2(3H)-ones bearing quaternary stereocenters were obtained in acceptable yield (up to 75%) and enantioselectivity (up to 73% ee). PMID:26977188

  7. Spatial Quantum Correlations Induced by Multiple Scattering of Light

    Lodahl, Peter; Lagendijk, Ad

    2006-01-01

    It is experimentally demonstrated how quantum noise of light is transported through a multiple scattering random medium. We predict the existence of novel spatial quantum correlations that are induced by multiple scattering.......It is experimentally demonstrated how quantum noise of light is transported through a multiple scattering random medium. We predict the existence of novel spatial quantum correlations that are induced by multiple scattering....

  8. Spin-orbit interaction in multiple quantum wells

    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.

  9. Multiple-Access Quantum Key Distribution Networks

    Razavi, Mohsen

    2011-01-01

    This paper addresses multi-user quantum key distribution networks, in which any two users can mutually exchange a secret key without trusting any other nodes. The same network also supports conventional classical communications by assigning two different wavelength bands to quantum and classical signals. Time and code division multiple access (CDMA) techniques, within a passive star network, are considered. In the case of CDMA, it turns out that the optimal performance is achieved at a unity code weight. A listen-before-send protocol is then proposed to improve secret key generation rates in this case. Finally, a hybrid setup with wavelength routers and passive optical networks, which can support a large number of users, is considered and analyzed.

  10. Quantum optics in multiple scattering random media

    Lodahl, Peter

    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...... correla-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...

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

    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...... results suggest that multiple scattering provides a promising way of coherently interfering many independent quantum states of light of potential use in quantum information processing....

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

    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.

  13. Quantum Cosmological Perturbations of Multiple Fluids

    Peter, Patrick; Vitenti, Sandro Dias Pinto

    2015-01-01

    The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described. We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations. The final Hamiltonian is obtained without assuming any equations of motions for the background variables. This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history. Quantization is achieved using an adiabatic expansion of the basis functions. This allows for an unambiguous definition of a vacuum state up to the given adiabatic order. Using this basis, we show that particle creation is well defined for a suitable choice of vacuum and canonical variables, so that the time evolution of the corresponding quantum fields is unitary. This provides constraints for setting initial conditions for an a...

  14. On Multiplicative Linear Logic, Modality and Quantum Circuits

    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.

  15. Experimental demonstration of spatial quantum correlations in multiple scattering media

    Smolka, Stephan; Huck, Alexander; Andersen, Ulrik Lund; Lagendijk, Ad; Lodahl, Peter

    We demonstrate that spatial quantum correlations are induced by multiple scattering of squeezed light. The correlation relates multiple scattered photons at different spatial positions, and is tunable by varying photon fluctuations of the illuminating beam.......We demonstrate that spatial quantum correlations are induced by multiple scattering of squeezed light. The correlation relates multiple scattered photons at different spatial positions, and is tunable by varying photon fluctuations of the illuminating beam....

  16. Study of correlations in molecular motion by multiple quantum NMR

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH3 and CD3) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed

  17. Quantum broadcasting multiple blind signature with constant size

    Xiao, Min; Li, Zhenli

    2016-06-01

    Using quantum homomorphic signature in quantum network, we propose a quantum broadcasting multiple blind signature scheme. Different from classical signature and current quantum signature schemes, the multi-signature proposed in our scheme is not generated by simply putting the individual signatures together, but by aggregating the individual signatures based on homomorphic property. Therefore, the size of the multi-signature is constant. Furthermore, based on a wide range of investigation for the security of existing quantum signature protocols, our protocol is designed to resist possible forgery attacks against signature and message from the various attack sources and disavowal attacks from participants.

  18. Multiple Quantum NMR Investigations of Structure- Property Relationships in Synthetic and Aged Silicone Elastomers

    Maxwell, R; Gjersing, E; Chinn, S; Herberg, J; Eastwood, E; Bowen, D; Stephens, T

    2006-09-27

    Complex engineering elastomeric materials are often characterized by a complex network structure obtained by crosslinking network chains with multiple chain lengths. Further, these networks are commonly filled with thixotropic reinforcing agents such as SiO{sub 2} or carbon black. Degradation of such materials often occurs via mechanisms that alter the fundamental network structure. In order to understand the effects of modifications of network structure and filler-polymer interaction on component performance, a series of model compounds have been studied by {sup 1}H multiple quantum NMR analysis and traditional mechanical property assessments. The {sup 1}H NMR data provides insight into the distribution of segmental dynamics that reveals insight into the changes in mechanical properties.

  19. Secure Multiparty Quantum Computation for Summation and Multiplication.

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

    2016-01-01

    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. PMID:26792197

  20. Quantum filtering for multiple diffusive and Poissonian measurements

    We provide a rigorous derivation of a quantum filter for the case of multiple measurements being made on a quantum system. We consider a class of measurement processes which are functions of bosonic field operators, including combinations of diffusive and Poissonian processes. This covers the standard cases from quantum optics, where homodyne detection may be described as a diffusive process and photon counting may be described as a Poissonian process. We obtain a necessary and sufficient condition for any pair of such measurements taken at different output channels to satisfy a commutation relationship. Then, we derive a general, multiple-measurement quantum filter as an extension of a single-measurement quantum filter. As an application we explicitly obtain the quantum filter corresponding to homodyne detection and photon counting at the output ports of a beam splitter. (paper)

  1. Multiplicity-free Quantum 6 j-Symbols for

    Nawata, Satoshi; Pichai, Ramadevi; Zodinmawia

    2013-12-01

    We conjecture a closed form expression for the simplest class of multiplicity-free quantum 6 j-symbols for . The expression is a natural generalization of the quantum 6 j-symbols for obtained by Kirillov and Reshetikhin. Our conjectured form enables computation of colored HOMFLY polynomials for various knots and links carrying arbitrary symmetric representations.

  2. Multiple-server Flexible Blind Quantum Computation in Networks

    Kong, Xiaoqin; Li, Qin; Wu, Chunhui; Yu, Fang; He, Jinjun; Sun, Zhiyuan

    2016-06-01

    Blind quantum computation (BQC) can allow a client with limited quantum power to delegate his quantum computation to a powerful server and still keep his own data private. In this paper, we present a multiple-server flexible BQC protocol, where a client who only needs the ability of accessing qua ntum channels can delegate the computational task to a number of servers. Especially, the client's quantum computation also can be achieved even when one or more delegated quantum servers break down in networks. In other words, when connections to certain quantum servers are lost, clients can adjust flexibly and delegate their quantum computation to other servers. Obviously it is trivial that the computation will be unsuccessful if all servers are interrupted.

  3. Study of correlations in molecular motion by multiple quantum NMR

    Tang, J.H.

    1981-11-01

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH/sub 3/ and CD/sub 3/) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed.

  4. Computer studies of multiple-quantum spin dynamics

    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

  5. Frequency domain quantum optimal control under multiple constraints

    Shu, Chuan-Cun; Ho, Tak-San; Xing, Xi; Rabitz, Herschel

    2016-03-01

    Optimal control of quantum systems with complex constrained external fields is one of the longstanding theoretical and numerical challenges at the frontier of quantum control research. Here, we present a theoretical method that can be utilized to optimize the control fields subject to multiple constraints while guaranteeing monotonic convergence towards desired physical objectives. This optimization method is formulated in the frequency domain in line with the current ultrafast pulse shaping technique, providing the possibility for performing quantum optimal control simulations and experiments in a unified fashion. For illustrations, this method is successfully employed to perform multiple constraint spectral-phase-only optimization for maximizing resonant multiphoton transitions with desired pulses.

  6. Computer studies of multiple-quantum spin dynamics

    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.

  7. Transferring Quantum Information through the Quantum Channel using Synchronous Multiplexing for Multiple users

    H.R.Sumathi

    2015-03-01

    Full Text Available Transmission of information in the form of qubits much faster than the speed of light is the important aspects of quantum information theory. Quantum information processing exploits the quantum nature of information that needs to be stored, encoded, transmit, receive and decode the information in the form of qubits. Bosonic channels appear to be very attractive for the physical implementation of quantum communication. This paper does the study of quantum channels and how best it can be implemented with the existing infrastructure that is the classical communication. Multiple access to the quantum network is the requirement where multiple users want to transmit their quantum information simultaneously without interfering with each others.

  8. 31 P and two-dimensional 31 P-1 H NMR analysis of brain extracts in animal models of multiple sclerosis

    We report here the study of the brain phospholipid content of normal and myelin deficient (md) rats, which develop a physiological impairment at about 15-20 days, and die at 20-25 days of age. The aim is to gain insights into the lipid composition of developing brain, and also to reveal of there exist some early event in the phospholipid metabolism that produces a pathological condition similar to the formation of demyelination plaques in multiple sclerosis. 31 P NMR allows one to detect phospholipids selectively out of a complex lipid mixture in crude extracts. Two-dimensional (2D) 31 P-1H NMR with isotropic proton mixing seems to be a superior technique for assignment of phospholipid 31 P resonances. (author)

  9. Multiple choices of time in quantum cosmology

    Malkiewicz, Przemyslaw

    2014-01-01

    It is often conjectured that a choice of time function merely sets up a frame for the quantum evolution of 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 {\\it formal canonical} and a {\\it coordinate} one. They are used to separate the effect of choice of clock from other effects. 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....

  10. On Quantum Algorithm for Multiple Alignment of Amino Acid Sequences

    Iriyama, Satoshi; Ohya, Masanori

    2009-02-01

    The alignment of genome sequences or amino acid sequences is one of fundamental operations for the study of life. Usual computational complexity for the multiple alignment of N sequences with common length L by dynamic programming is O(LN). This alignment is considered as one of the NP problems, so that it is desirable to find a nice algorithm of the multiple alignment. Thus in this paper we propose the quantum algorithm for the multiple alignment based on the works12,1,2 in which the NP complete problem was shown to be the P problem by means of quantum algorithm and chaos information dynamics.

  11. A Hybrid Quantum Search Engine: A Fast Quantum Algorithm for Multiple Matches

    Younes, A; Miller, J; Younes, Ahmed; Rowe, Jon; Miller, Julian

    2003-01-01

    In this paper we will present a quantum algorithm which works very efficiently in case of multiple matches within the search space and in the case of few matches, the algorithm performs classically. This allows us to propose a hybrid quantum search engine that integrates Grover's algorithm and the proposed algorithm here to have general performance better that any pure classical or quantum search algorithm.

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

    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....

  13. Multiplicity-free Quantum 6j-Symbols for

    Nawata, Satoshi; Ramadevi, P.; Zodinmawia

    2013-01-01

    We conjecture a closed form expression for the simplest class of multiplicity-free quantum 6j-symbols for U_q(sl_N). The expression is a natural generalization of the quantum 6j-symbols for U_q(sl_2) obtained by Kirillov and Reshetikhin. Our conjectured form enables computation of colored HOMFLY polynomials for various knots and links carrying arbitrary symmetric representations.

  14. Multiple Scattering of Quantum Optical States

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

    2011-01-01

    Wave propagation through multiple scattering media has been an active research field since the discovery of Anderson localization [1]. This interest has amongst other resulted in the discovery of classical wave phenomena such as enhanced coherent back scattering [2] and universal conductance...

  15. Perfect transfer of multiple excitations in quantum networks

    Brougham, T; Jex, I; 10.1103/PhysRevA.83.022323

    2011-01-01

    We present a general formalism to the problem of perfect state-transfer (PST), where the state involves multiple excitations of the quantum network. A key feature of our formalism is that it allows for inclusion of nontrivial interactions between the excitations. Hence, it is perfectly suited to addressing the problem of PST in the context of various types of physical realizations. The general formalism is also flexible enough to account for situations where multiple excitations are "focused" onto the same site.

  16. Optimum testing of multiple hypotheses in quantum detection theory

    Yuen, H. P.; Kennedy, R. S.; Lax, M.

    1975-01-01

    The problem of specifying the optimum quantum detector in multiple hypotheses testing is considered for application to optical communications. The quantum digital detection problem is formulated as a linear programming problem on an infinite-dimensional space. A necessary and sufficient condition is derived by the application of a general duality theorem specifying the optimum detector in terms of a set of linear operator equations and inequalities. Existence of the optimum quantum detector is also established. The optimality of commuting detection operators is discussed in some examples. The structure and performance of the optimal receiver are derived for the quantum detection of narrow-band coherent orthogonal and simplex signals. It is shown that modal photon counting is asymptotically optimum in the limit of a large signaling alphabet and that the capacity goes to infinity in the absence of a bandwidth limitation.

  17. Multiple Nuclear Polarization States in a Double Quantum Dot

    Danon, J.; Vink, I.T.; Koppens, F.H.L.; Nowack, K.C.; Vandersypen, L.M.K.; Nazarov, Y.V.

    2009-01-01

    We observe multiple stable states of nuclear polarization and nuclear self-tuning over a large range of fields in a double quantum dot under conditions of electron spin resonance. The observations can be understood within an elaborated theoretical rate equation model for the polarization in each of

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

    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.

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

    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

  20. Formal power series arising from multiplication of quantum integers

    Nathanson, Melvyn B.

    2003-01-01

    For the quantum integer [n]_q = 1+q+q^2+... + q^{n-1} there is a natural polynomial multiplication such that [mn]_q = [m]_q \\otimes_q [n]_q. This multiplication is given by the functional equation f_{mn}(q) = f_m(q) f_n(q^m), defined on a sequence {f_n(q)} of polynomials such that f_n(0)=1 for all n. It is proved that if {f_n(q)} is a solution of this functional equation, then the sequence {f_n(q)} converges to a formal power series F(q). Quantum mulitplication also leads to the functional eq...

  1. Quantum teleportation scheme by selecting one of multiple output ports

    Ishizaka, Satoshi; Hiroshima, Tohya

    2009-01-01

    The scheme of quantum teleportation, where Bob has multiple (N) output ports and obtains the teleported state by simply selecting one of the N ports, is thoroughly studied. We consider both deterministic version and probabilistic version of the teleportation scheme aiming to teleport an unknown state of a qubit. Moreover, we consider two cases for each version: (i) the state employed for the teleportation is fixed to a maximally entangled state, and (ii) the state is also optimized as well as...

  2. Multiple Quantum Well AlGaAs Nanowires

    Chen, C.; Braidy, N.; Couteau, C.; Fradin, C.; Weihs, G.; LaPierre, R.

    2008-01-01

    This letter reports on the growth, structure and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy performed on individual NWs are consistent with a configuration composed of conical segments stacked al...

  3. Lecture notes on Gaussian multiplicative chaos and Liouville Quantum Gravity

    Rhodes, Rémi; Vargas, Vincent

    2016-01-01

    The purpose of these notes, based on a course given by the second author at Les Houches summer school, is to explain the probabilistic construction of Polyakov's Liouville quantum gravity using the theory of Gaussian multiplicative chaos. In particular, these notes contain a detailed description of the so-called Liouville measures of the theory and their conjectured relation to the scaling limit of large planar maps properly embedded in the sphere. These notes are rather short and require no ...

  4. A functional equation arising from multiplication of quantum integers

    Nathanson, Melvyn B.

    2002-01-01

    For the quantum integer $[n]_q = 1+q+...+q^{n-1}$ there is a natural polynomial multiplication $*_q$ such that $[m]_q *_q [n]_q = [mn]_q$. This multiplication leads to the functional equation $f_{mn}(q) = f_m(q)f_n(q^m),$ defined on a given sequence $\\mathcal(F)=\\{f_n(q)\\}_{n=1}^{\\infty}$ of polynomials. This paper contains various results concerning the classification and construction of polynomial sequences that satisfy the functional equation, as well as a list of open problems that arise ...

  5. Quantum superposition of multiple clones and the novel cloning machine

    Pati, Arun Kumar

    1999-01-01

    we envisage a novel quantum cloning machine, which takes an input state and produces an output state whose success branch can exist in a linear superposition of multiple copies of the input state and the failure branch exist in a superposition of composite state independent of the input state. We prove that unknown non-orthogonal states chosen from a set $\\cal S$ can evolve into a linear superposition of multiple clones by a unitary process if and only if the states are linearly independent. ...

  6. Controllable multiple-quantum transitions in a T-shaped small quantum dot-ring system

    Chen, Xiongwen; Chen, Baoju; Song, Kehui; Zhou, Guanghui

    2016-05-01

    Based on the tight-binding model and the slave boson mean field approximation, we investigate the electron transport properties in a small quantum dot (QD)-ring system. Namely, a strongly correlated QD not only attaches directly to two normal metallic electrodes, but also forms a magnetic control Aharonov-Bohm quantum ring with a few noninteracting QDs. We show that the parity effect, the Kondo effect, and the multiple Fano effects coexist in our system. Moreover, the parities, defined by the odd- and even-numbered energy levels in this system, can be switched by adjusting magnetic flux phase ϕ located at the center of the quantum ring, which induces multiple controllable Fano-interference energy pathways. Therefore, the constructive and destructive multi-Fano interference transition, the Kondo and Fano resonance transition at the Fermi level, the Fano resonance and ani-resonance transition are realized in the even parity system. They can also be observed in the odd parity system when one adjusts the phase ϕ and the gate voltage Vg applied to the noninteracting QDs. The multi-quantum transitions determine some interesting transport properties such as the current switch and its multi-flatsteps, the differential conductance switch at zero bias voltage and its oscillation or quantization at the low bias voltage. These results may be useful for the observation of multiple quantum effect interplays experimentally and the design of controllable QD-based device.

  7. Improvement of a quantum broadcasting multiple blind signature scheme based on quantum teleportation

    Zhang, Wei; Qiu, Daowen; Zou, Xiangfu

    2016-03-01

    Recently, a broadcasting multiple blind signature scheme based on quantum teleportation has been proposed for the first time. It is claimed to have unconditional security and properties of quantum multiple signature and quantum blind signature. In this paper, we analyze the security of the protocol and show that each signatory can learn the signed message by a single-particle measurement and the signed message can be modified at random by any attacker according to the scheme. Furthermore, there are some participant attacks and external attacks existing in the scheme. Finally, we present an improved scheme and show that it can resist all of the mentioned attacks. Additionally, the secret keys can be used again and again, making it more efficient and practical.

  8. Improvement of a quantum broadcasting multiple blind signature scheme based on quantum teleportation

    Zhang, Wei; Qiu, Daowen; Zou, Xiangfu

    2016-06-01

    Recently, a broadcasting multiple blind signature scheme based on quantum teleportation has been proposed for the first time. It is claimed to have unconditional security and properties of quantum multiple signature and quantum blind signature. In this paper, we analyze the security of the protocol and show that each signatory can learn the signed message by a single-particle measurement and the signed message can be modified at random by any attacker according to the scheme. Furthermore, there are some participant attacks and external attacks existing in the scheme. Finally, we present an improved scheme and show that it can resist all of the mentioned attacks. Additionally, the secret keys can be used again and again, making it more efficient and practical.

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

    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, t1, is of a non-decaying constant-time nature for a duration that depends on the length of t2, and vice versa, prior to the onset of conventional exponential decay. Line shape simulations for the 1H-15N PARE indicate that this strategy significantly enhances both sensitivity and resolution in the indirect 1H 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 HN-HN NOEs in KcsA in SDS micelles at 50oC was found to increase the experimental sensitivity by a factor of 1.7±0.3 with a concomitant resolution increase in the indirectly detected 1H dimension. The method is also demonstrated for a situation in which homonuclear 13C-13C decoupling is required while measuring weak H3'-2'OH NOEs in an RNA oligomer

  10. A QUANTUM MULTIPLE ACCESS COMMUNICATIONS SCHEME USING ORBITAL ANGULAR MOMENTUM

    Dong Xiaoliang; Zhao Shengmei; Zheng Baoyu

    2013-01-01

    We propose a quantum multiple access communications scheme using Orbital Angular Momentum (OAM) sector states in the paper.In the scheme,each user has an individual modified Poincare Bloch sphere and encodes his information with his own corresponding sector OAM states.A prepared entangled photon pairs are separated at transmitter and receiver.At the transmitter,each user encodes his information with the sector OAM states on the photons and the superposition of the different sector OAM states is carried by the photons.Then the photons are transmitted through quantum noiseless channel to the receiver.At the receiver,each user could retrieve his information by coincidently measuring the transmitted photons with the receiver side photons which are modulated by a special prepared measurement basis.The theoretical analysis and the numerical simulations show that each user could get his information from the superposition state without error.It seems that this scheme provides a novel method for quantum multiple users communications.

  11. Robust Multiple-Range Coherent Quantum State Transfer

    Chen, Bing; Peng, Yan-Dong; Li, Yong; Qian, Xiao-Feng

    2016-07-01

    We propose a multiple-range quantum communication channel to realize coherent two-way quantum state transport with high fidelity. In our scheme, an information carrier (a qubit) and its remote partner are both adiabatically coupled to the same data bus, i.e., an N-site tight-binding chain that has a single defect at the center. At the weak interaction regime, our system is effectively equivalent to a three level system of which a coherent superposition of the two carrier states constitutes a dark state. The adiabatic coupling allows a well controllable information exchange timing via the dark state between the two carriers. Numerical results show that our scheme is robust and efficient under practically inevitable perturbative defects of the data bus as well as environmental dephasing noise.

  12. Thermodynamics of quantum systems with multiple conserved quantities.

    Guryanova, Yelena; Popescu, Sandu; Short, Anthony J; Silva, Ralph; Skrzypczyk, Paul

    2016-01-01

    Recently, there has been much progress in understanding the thermodynamics of quantum systems, even for small individual systems. Most of this work has focused on the standard case where energy is the only conserved quantity. Here we consider a generalization of this work to deal with multiple conserved quantities. Each conserved quantity, which, importantly, need not commute with the rest, can be extracted and stored in its own battery. Unlike the standard case, in which the amount of extractable energy is constrained, here there is no limit on how much of any individual conserved quantity can be extracted. However, other conserved quantities must be supplied, and the second law constrains the combination of extractable quantities and the trade-offs between them. We present explicit protocols that allow us to perform arbitrarily good trade-offs and extract arbitrarily good combinations of conserved quantities from individual quantum systems. PMID:27384384

  13. Multiple Energy Exciton Shelves in Quantum-Dot-DNA Nanobioelectronics.

    Goodman, Samuel M; Singh, Vivek; Ribot, Josep Casamada; Chatterjee, Anushree; Nagpal, Prashant

    2014-11-01

    Quantum dots (QDs) are semiconductor nanocrystallites with multiple size-dependent quantum-confined states that are being explored for utilizing broadband radiation. While DNA has been used for the self-assembly of nanocrystals, it has not been investigated for the formation of simultaneous conduction pathways for transporting multiple energy charges or excitons. These exciton shelves can be formed by coupling the conduction band, valence band, and hot-carrier states in QDs with different HOMO-LUMO levels of DNA nucleobases, resulting from varying degrees of conjugation in the nucleobases. Here we present studies on the electronic density of states in four naturally occurring nucleobases (guanine, thymine, cytosine, and adenine), which energetically couple to quantized states in semiconductor QDs. Using scanning tunneling spectroscopy of single nanoparticle-DNA constructs, we demonstrate composite DOS of chemically coupled DNA oligonucleotides and cadmium chalcogenide QDs (CdS, CdSe, CdTe). While perfectly aligned CdTe QD-DNA states lead to exciton shelves for multiple energy charge transport, mismatched energy levels in CdSe QD-DNA introduce intrabandgap states that can lead to charge trapping and recombination. Although further investigations are required to study the rates of charge transfer, recombination, and back-electron transfer, these results can have important implications for the development of a new class of nanobioelectronics and biological transducers. PMID:26278768

  14. Hydrogen-bond interactions in organically-modified polysiloxane networks studied by 1D and 2D CRAMPS and double-quantum 1H MAS NMR

    Brus, Jiří; Dybal, Jiří

    2002-01-01

    Roč. 35, č. 27 (2002), s. 10038-10047. ISSN 0024-9297 R&D Projects: GA ČR GA203/98/P290; GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : Hydrogen bonding * polysiloxane * 1H MAS NMR Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.751, year: 2002

  15. Multiple quantum well AlGaAs nanowires.

    Chen, Chen; Braidy, Nadi; Couteau, Christophe; Fradin, Cécile; Weihs, Gregor; LaPierre, Ray

    2008-02-01

    This letter reports on the growth, structure, and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy performed on individual NWs are consistent with a configuration composed of conical segments stacked along the NW axis. Microphotoluminescence measurements and confocal microscopy showed enhanced light emission from the MQW NWs as compared to nonsegmented NWs due to carrier confinement and sidewall passivation. PMID:18184023

  16. HgCdTe/CdTe multiple quantum wells

    This paper reports on HgCdTe/CdTe multiple quantum wells by molecular beam epitaxy which show room temperature photoluminescence and sharp absorption steps at mid-infrared wavelengths. Quantitative chemical mapping, performed by transmission electron microscopy, indicates minimal interdiffusion during growth. Annealing experiments performed at higher temperatures show that the interdiffusion coefficient is a strong function of the depth of the interface below the surface. Absorption spectra have been accurately modeled with a square well/envelope function approach. The films have been used to passively mode lock color center lasers and produce pulses as short as 120 fsec near 2.7 μm

  17. Extraction of multiple pure component 1H and 13C NMR spectra from two mixtures: Novel solution obtained by sparse component analysis-based blind decomposition

    Sparse component analysis (SCA) is demonstrated for blind extraction of three pure component spectra from only two measured mixed spectra in 13C and 1H nuclear magnetic resonance (NMR) spectroscopy. This appears to be the first time to report such results and that is the first novelty of the paper. Presented concept is general and directly applicable to experimental scenarios that possibly would require use of more than two mixtures. However, it is important to emphasize that number of required mixtures is always less than number of components present in these mixtures. The second novelty is formulation of blind NMR spectra decomposition exploiting sparseness of the pure components in the wavelet basis defined by either Morlet or Mexican hat wavelet. This enabled accurate estimation of the concentration matrix and number of pure components by means of data clustering algorithm and pure components spectra by means of linear programming with constraints from both 1H and 13C NMR experimental data. The third novelty is capability of proposed method to estimate number of pure components in demanding underdetermined blind source separation (uBSS) scenario. This is in contrast to majority of the BSS algorithms that assume this information to be known in advance. Presented results are important for the NMR spectroscopy-associated data analysis in pharmaceutical industry, medicine diagnostics and natural products research.

  18. Synthesis, structural, and spectroscopic (FT-IR, NMR, and UV) Characterization of 1-(Cyclohexylmethyl)-2-(pyridin-2-yl)-1 H-benzo[ d]imidazole by experimental techniques and quantum chemical calculations

    Özdemir, Namık; Dayan, Osman; Demirmen, Selin

    2016-05-01

    The title compound ( II), 1-(cyclohexylmethyl)-2-(pyridin-2-yl)-1 H-benzo[ d]imidazole (C19H21N3), was synthesized via N-alkylation of 2-(pyridin-2-yl)-1 H-benzo[ d]imidazole ( I). Both compounds I and II were characterized by IR, NMR and UV-vis spectroscopy. Solid-state structure of compound II was determined by single-crystal X-ray diffraction technique. Furthermore, quantum chemical calculations employing density functional theory (DFT/B3LYP) method with the 6-311++ G( d, p) basis set were performed for the theoretical characterization of the molecular and spectroscopic features of the compounds. Using the TD-DFT method, electronic absorption spectra of the compounds have been predicted at same level. When the obtained results were compared with the experimental findings, it is seen that theoretical results support the experimental data and a good agreement exists between them.

  19. 1-Vinyl-5-amino-1 H-tetrazole: X-ray molecular and crystal structures and quantum-chemical DFT calculations

    Lyakhov, Alexander S.; Matulis, Vadim E.; Gaponik, Pavel N.; Voitekhovich, Sergei V.; Ivashkevich, Oleg A.

    2008-03-01

    The crystal and molecular structures of 1-vinyl-5-amino-1 H-tetrazole (VAT) were determined by single crystal X-ray diffraction. The amino group lies in the plane of the tetrazole ring and valence angles around the N atom are close to 120°, the exocyclic C sbnd N amino bond being substantially shorter in comparison with "normal" C sbnd N bond. Natural bond orbital analysis was performed, using density functional theory B3LYP method, to explain the structural peculiarities of crystalline VAT. By using MO calculations, relative stability of all possible tautomeric forms of protonated VAT molecule was investigated.

  20. Quantum-chemical insight into structure-reactivity relationship in 4,5,6,7-tetrahalogeno-1H-benzimidazoles: a combined X-ray, DSC, DFT/QTAIM, Hirshfeld surface-based, and molecular docking approach.

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Maurin, Jan Krzysztof; Orzeszko, Andrzej; Kazimierczuk, Zygmunt

    2014-03-20

    The weak interaction patterns in 4,5,6,7-tetrahalogeno-1H-benzimidazoles, protein kinase CK2 inhibitors, in solid state are studied by the X-ray method and quantum chemistry calculations. The crystal structures of 4,5,6,7-tetrachloro- and 4,5,6,7-tetrabromo-1H-benzimidazole are determined by X-ray diffraction and refined to a final R-factor of 3.07 and 3.03%, respectively, at room temperature. The compound 4,5,6,7-tetrabromo-1H-benzimidazole, which crystallizes in the I41/a space group, is found to be isostructural with previously studied 4,5,6,7-tetraiodo-1H-benzimidazole in contrast to 4,5,6,7-tetrachloro-1H-benzimidazole, which crystallizes as triclinic P1̅ with 4 molecules in elementary unit. For 4,5,6,7-tetrachloro-1H-benzimidazole, differential scanning calorimetry (DSC) revealed a second order glassy phase transition at Tg = 95°/106° (heating/cooling), an indication of frozen disorder. The lack of 3D isostructurality found in all 4,5,6,7-tetrahalogeno-1H-benzimidazoles is elucidated on the basis of the intra- and intermolecular interactions (hydrogen bonding, van der Waals contacts, and C-H···π interactions). The topological Bader's Quantum Theory of Atoms in Molecules (QTAIM) and Spackman's Hirshfeld surface-based approaches reveal equilibration of electrostatic matching and dispersion van der Waals interactions between molecules consistent with the crystal site-symmetry. The weakening of van der Waals forces accompanied by increasing strength of the hydrogen bond (N-H···N) result in a decrease in the crystal site-symmetry and a change in molecular packing in the crystalline state. Crystal packing motifs were investigated with the aid of Hirshfeld surface fingerprint plots. The ordering 4,5,6,7-tetraiodo > 4,5,6,7-tetrabromo > 4,5,6,7-tetrachloro > 4,5,6,7-tetrafluoro reflects not only a decrease in crystal symmetry but also increase in chemical reactivity (electronic activation), which could explain some changes in biological activity of

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

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

    2009-01-01

    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 and...... the full quantum model of multiple scattering....

  2. Spatial quantum correlations induced by random multiple scattering of quadrature squeezed light

    Lodahl, Peter

    The authors demonstrates that spatial quantum correlations are induced by multiple scattering of quadrature squeezed light through a random medium. As a consequence, light scattered along two different directions by the random medium will not be independent, but be correlated to an extent that can...... only be described by a quantum mechanical theory for multiple scattering. The spatial quantum correlation is revealed in the fluctuations of the total intensity transmission or reflection through the multiple scattering medium....

  3. Primidone - An antiepileptic drug - characterisation by quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR and UV-Visible) investigations

    Arjunan, V.; Santhanam, R.; Subramanian, S.; Mohan, S.

    2013-05-01

    The solid phase FTIR and FT-Raman spectra of primidone were recorded in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The vibrational spectra were analysed and the observed fundamentals were assigned and analysed. The experimental wavenumbers were compared with the theoretical scaled vibrational wavenumbers determined by DFT methods. The Raman intensities were also determined with B3LYP/6-31G(d,p) method. The total electron density and molecular electrostatic potential surface of the molecule were constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The HOMO and LUMO energies were measured. Natural bond orbital analysis of primidone has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR spectra were recorded and the chemical shifts of the molecule were calculated.

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

    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 χ2 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)

  5. Quantum teleportation scheme by selecting one of multiple output ports

    Ishizaka, Satoshi; Hiroshima, Tohya

    2009-04-01

    The scheme of quantum teleportation, where Bob has multiple (N) output ports and obtains the teleported state by simply selecting one of the N ports, is thoroughly studied. We consider both the deterministic version and probabilistic version of the teleportation scheme aiming to teleport an unknown state of a qubit. Moreover, we consider two cases for each version: (i) the state employed for the teleportation is fixed to a maximally entangled state and (ii) the state is also optimized as well as Alice’s measurement. We analytically determine the optimal protocols for all the four cases and show the corresponding optimal fidelity or optimal success probability. All these protocols can achieve the perfect teleportation in the asymptotic limit of N→∞ . The entanglement properties of the teleportation scheme are also discussed.

  6. Multiple quantum wells for passive ultra short laser pulse generation

    Quintero-Torres, R; Rodriguez-Rodriguez, E; Stintz, Andreas; Diels, Jean-Claude

    2007-01-01

    Solid state lasers are demanding independent control in the gain media and cavity loss to achieve ultra short laser pulses using passive mode-locking. Recently, laser mode-locking is achieved with a MBE structure with multiple quantum wells, designed to achieve two functions; Bragg mirror and changes in absorption to control the cavity dynamics. The use of an AlGaAs/AlAs Bragg mirror with a 15 nm GaAs saturable absorber used in a Cr:LiSAF tuneable laser proved to be effective to produce femtosecond pulses. The use of saturable absorbers thus far is a trial and error procedure that is changing due to the correlation with more predictive procedures.

  7. Quantum mechanical investigation of 2,3-dihydro-1-methyl-2-thioxopyrimidin-4(1H-one tautomers and their complexes with iodine.

    T. Hadadi

    2015-03-01

    Full Text Available DFT and AB initio theoretical methods were used to calculate the relative stability of tautomers and complexes with iodine in the 2,3-dihydro-1-methyl-2-thioxopyrimidin-4(1H-one. This compound can be used to treat hyper thyroidism due to their ability to make complexes with iodine.All tautomers and complexes are optimized using the B3LYP Method with two different energies, the relative energies shows that in all tautomers and complexes. Thione forms are more stable than thieolforms.The NBO calculation is carried out for tautomers and complexes to obtain atomic charges and accept donor interactions. These result confirm the ability ofT tautomers to form complexes and show that the planar complexes has more effective interaction than the perpendicular complex.The atom in molecule (AIM analysis show that the charge density and its laplacian at the S-I bond critical point of the planar complex is greater than the perpendicular complex.

  8. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of O-desmethyltramadol hydrochloride an active metabolite in tramadol - An analgesic drug

    Arjunan, V.; Santhanam, R.; Marchewka, M. K.; Mohan, S.

    2014-03-01

    O-desmethyltramadol is one of the main metabolites of tramadol widely used clinically and has analgesic activity. The FTIR and FT-Raman spectra of O-desmethyl tramadol hydrochloride are recorded in the solid phase in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The observed fundamentals are assigned to different normal modes of vibration. Theoretical studies have been performed as its hydrochloride salt. The structure of the compound has been optimised with B3LYP method using 6-31G** and cc-pVDZ basis sets. The optimised bond length and bond angles are correlated with the X-ray data. The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT methods. The IR and Raman intensities are determined with B3LYP method using cc-pVDZ and 6-31G(d,p) basic sets. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/cc-pVDZ method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of O-desmethyltramadol hydrochloride has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR chemical shifts of the molecule have been anlysed.

  9. MR Imaging with Intermolecular Multiple quantum Coherences (iMQCs):Fundamental Questions and Potentials

    2002-01-01

    @@ Pursuit of new contrast in imaging has been the driving force behind many innovative applications of physics in medical MRI. Even though the use of intramolecular multiple quantum coherence in NMR spectroscopy has a long history, intermolecular multiple quantum coherence (iMQC) among spins on different molecules, such as protonproton iMQC in water, was considered impossible for many years.

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

    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

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

    Makhov, Dmitry V.; Glover, William J.; Martinez, Todd J.; Shalashilin, Dmitrii V.

    2014-08-01

    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.

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

    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.

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

    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 DQ and geometric discord DG). 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.

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

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

    2012-01-01

    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...... 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...

  15. Equations of Motion with Multiple Proper Time: A New Interpretation of Basic Quantum Physics

    Chen, Xiaodong

    2005-01-01

    Equations of motion for single particle under two proper time model and three proper time model have been proposed and analyzed. The motions of particle are derived from pure classical method but they exhibit the same properties of quantum physics: the quantum wave equation, de Broglie equations, uncertainty relation, statistical result of quantum wave-function. This shows us a possible new way to interpret quantum physics. We will also prove that physics with multiple proper time does not ca...

  16. Stochastic Integral Representations of Quantum Martingales on Multiple Fock Space

    Un Cig Ji

    2006-11-01

    In this paper a quantum stochastic integral representation theorem is obtained for unbounded regular martingales with respect to multidimensional quantum noise. This simultaneously extends results of Parthasarathy and Sinha to unbounded martingales and those of the author to multidimensions.

  17. Comment on "Quantum Superimposing Multiple Anti-Cloning Machine"

    Chang, Da-Wei

    2015-03-01

    Recently, Li et al. (Int. J. Theor. Phys. 46, 2599, 2007) has constructed the quantum superimposing multiple anti-cloning machine, moreover established the sufficient and necessary condition of this machine exists. In the proofs given by Li et al. (Int. J. Theor. Phys. 46, 2599, 2007), claimed that the following key fact to hold : Fact For an arbitrary unknown state | ψ> belongs to n-dimensional Hilbert space, there exists an antiunitary operator K such that K| ψ>=| ψ ⊥> here the state | ψ ⊥> is an orthogonal complement state of | ψ>, that is, it satisfies the following two conditions ==0 and ==1 In this Comment, we would like to point out that (a). In 1-dimensional Hilbert space, for an arbitrary unknown state | ψ>, the antiunitary operator K and the orthogonal complement state both do not exist in general. (b). In 3-dimensional Hilbert space, for an arbitrary unknown state | ψ>, the antiunitary operator K do not exist in general, there are uncountably many orthogonal complement states that can be constructed through the skew-symmetric operator, but is not unitary one. Which shows that above Fact given by Li et al. [1] is incorrect in general for both 1 and 3-dimensional Hilbert space

  18. Single-photon quantum router with multiple output ports.

    Yan, Wei-Bin; Fan, Heng

    2014-01-01

    The routing capability is a requisite in quantum network. Although the quantum routing of signals has been investigated in various systems both in theory and experiment, the general form of quantum routing with many output terminals still needs to be explored. Here we propose a scheme to achieve the multi-channel quantum routing of the single photons in a waveguide-emitter system. The channels are composed by the waveguides and are connected by intermediate two-level emitters. By adjusting the intermediate emitters, the output channels of the input single photons can be controlled. This is demonstrated in the cases of one output channel, two output channels and the generic N output channels. The results show that the multi-channel quantum routing of single photons can be well achieved in the proposed system. This offers a scheme for the experimental realization of general quantum routing of single photons. PMID:24769619

  19. Implementation of non-local quantum controlled-NOT gate with multiple targets

    Libing Chen(陈立冰); Hong Lu(路洪)

    2004-01-01

    We show how a non-local quantum controlled-NOT (CNOT) gate with multiple targets can be implemented with unit fidelity and unit probability. The explicit quantum circuit for implementing the operation is presented. Two schemes for probabilistic implementing the operation via partially entangled quantum channels with unit fidelity are put forward. The overall physical resources required for accomplishing these schemes are different, and the successful implementation probabilities are also different.

  20. Skyrmion Burst and Multiple Quantum Walk in Thin Ferromagnetic Films

    Ezawa, Motohiko

    2011-01-01

    A giant Skyrmion collapses to a singular point by emitting spin waves in a thin ferromagnetic film, when external magnetic field is increased beyond the critical one. The remnant is a single-spin flipped (SSF) point. The SSF point has a quantum diffusion dynamics governed by the Heisenberg model. We determine its time evolution and show the diffusion process is a continuous-time quantum walk. We also analyze an interference of two SSF points after two Skyrmion bursts. Quantum walks for $S=1/2...

  1. Multiple surface plasmons in an unbounded quantum plasma half-space

    Palade, D. I.

    2016-07-01

    The propagation of surface plasmons on a quantum plasma half-space in the absence of any external confinement is investigated. By means of the Quantum Hydrodynamic Model in the electrostatic limit, it is found that the equilibrium density profile is a smooth continuous function which, in the linear regime, supports multiple non-normal surface modes. Defining a spectrum function and using a cutting condition, the dispersion relations of these modes and their relevance for realistic dynamics are computed. It is found that the multiple surface plasmons present a significant red-shift with respect to the case of fully bounded quantum plasmas.

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

    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)

  3. Multiple surface plasmons on an unbounded quantum plasma half-space

    Palade, D I

    2016-01-01

    The propagation of surface plasmons on a quantum plasma half-space in the absence of any external confinement is investigated. By means of Quantum Hydrodynamic Model in the electrostatic limit it is found that the equilibrium density profile is a smooth continuous function which, in the linear regime, supports multiple non-normal surface modes. Defining a spectrum function and using a cutting condition, the dispersion relations of these modes and their relevance for realistic dynamics are computed. It is found that the multiple surface plasmons present a significant red-shift with respect to the case of fully bounded quantum plasmas.

  4. Time Dependent Study of Multiple Exciton Generation in Nanocrystal Quantum Dots

    Damtie, Fikeraddis A.; Wacker, Andreas

    2016-03-01

    We study the exciton dynamics in an optically excited nanocrystal quantum dot. Multiple exciton formation is more efficient in nanocrystal quantum dots compared to bulk semiconductors due to enhanced Coulomb interactions and the absence of conservation of momentum. The formation of multiple excitons is dependent on different excitation parameters and the dissipation. We study this process within a Lindblad quantum rate equation using the full many-particle states. We optically excite the system by creating a single high energy exciton ESX in resonance to a double exciton EDX. With Coulomb electron-electron interaction, the population can be transferred from the single exciton to the double exciton state by impact ionisation (inverse Auger process). The ratio between the recombination processes and the absorbed photons provide the yield of the structure. We observe a quantum yield of comparable value to experiment assuming typical experimental conditions for a 4 nm PbS quantum dot.

  5. Multiple quantum filtered nuclear magnetic resonance spectroscopy of spin 7/2 nuclei in solution

    Tsoref, L.; Eliav, U.; Navon, G.

    1996-03-01

    Multiple quantum dynamics of spin I=7/2 are presented considering modulation of quadrupolar interaction as the relaxation mechanism. The equation of motion of the spin system is calculated in Liouville space using irreducible spherical tensor operators as the orthonormal basis. Relaxation matrices are given explicitly for coherences one to seven. Experiments for measuring the creation of multiple rank tensors and multiple quantum relaxation for spin 7/2 are described and analyzed. Results of double quantum and triple quantum filtered spectra of Cs+ bound to the crown ether 18-crown-6, dissolved in glycerol, were analyzed in terms of the microscopic parameters of the system, the reorientation correlation time and the quadrupolar coupling constant. Numerical calculations indicated that the expected MQF signal intensities decrease in the order TQF≳DQF≫5QF≳4QF≫7QF≳6QF.

  6. Radiation induced crosslinking in a silica-filled silicone elastomer as investigated by multiple quantum H NMR

    Maxwell, R S; Chinn, S C; Solyom, D; Cohenour, R

    2005-05-24

    DC745 is a commercially available silicone elastomer consisting of dimethyl, methylphenyl, and vinyl-methyl siloxane monomers crosslinked with a peroxide vinyl specific curing agent. It is generally considered to age gracefully and to be resistant to chemical and thermally harsh environments. However, little data exists on the radiation resistance of this commonly used silicone elastomer. We report static {sup 1}H NMR studies of residual dipolar couplings in DC745 solid elastomers subject to exposure to ionizing gamma radiation. {sup 1}H spin-echo NMR data shows that with increasing dose, the segmental dynamics decrease is consistent with radiatively induced crosslinking. {sup 1}H multiple quantum NMR was used to assess changes in the network structure and observed the presence of a bimodal distribution of residual dipolar couplings, <{Omega}{sub d}>, that were dose dependent. The domain with the lower <{Omega}{sub d}> has been assigned to the polymer network while the domain with the higher <{Omega}{sub d}> has been assigned to polymer chains interacting with the inorganic filler surfaces. In samples exposed to radiation, the residual dipolar couplings in both reservoirs were observed to increase and the populations were observed to be dose dependent. The NMR results are compared to Differential Scanning Calorimetry (DSC) and a two-step solvent swelling technique. The solvent swelling data lend support to the interpretation of the NMR results and the DSC data show both a decrease in the melt temperature and the heat of fusion with cumulative dose, consistent with radiative crosslinking. In addition, DSC thermograms obtained following a 3 hr isothermal soak at -40 C showed the presence of a second melt feature at T{sub m} {approx} -70 C consistent with a network domain with significantly reduced segmental motion.

  7. Quantum teleportation of multiple degrees of freedom of a single photon.

    Wang, Xi-Lin; Cai, Xin-Dong; Su, Zu-En; Chen, Ming-Cheng; Wu, Dian; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei

    2015-02-26

    Quantum teleportation provides a 'disembodied' way to transfer quantum states from one object to another at a distant location, assisted by previously shared entangled states and a classical communication channel. As well as being of fundamental interest, teleportation has been recognized as an important element in long-distance quantum communication, distributed quantum networks and measurement-based quantum computation. There have been numerous demonstrations of teleportation in different physical systems such as photons, atoms, ions, electrons and superconducting circuits. All the previous experiments were limited to the teleportation of one degree of freedom only. However, a single quantum particle can naturally possess various degrees of freedom--internal and external--and with coherent coupling among them. A fundamental open challenge is to teleport multiple degrees of freedom simultaneously, which is necessary to describe a quantum particle fully and, therefore, to teleport it intact. Here we demonstrate quantum teleportation of the composite quantum states of a single photon encoded in both spin and orbital angular momentum. We use photon pairs entangled in both degrees of freedom (that is, hyper-entangled) as the quantum channel for teleportation, and develop a method to project and discriminate hyper-entangled Bell states by exploiting probabilistic quantum non-demolition measurement, which can be extended to more degrees of freedom. We verify the teleportation for both spin-orbit product states and hybrid entangled states, and achieve a teleportation fidelity ranging from 0.57 to 0.68, above the classical limit. Our work is a step towards the teleportation of more complex quantum systems, and demonstrates an increase in our technical control of scalable quantum technologies. PMID:25719668

  8. Quantum teleportation of multiple degrees of freedom of a single photon

    Wang, Xi-Lin; Cai, Xin-Dong; Su, Zu-En; Chen, Ming-Cheng; Wu, Dian; Li, Li; Liu, Nai-Le; Lu, Chao-Yang; Pan, Jian-Wei

    2015-02-01

    Quantum teleportation provides a `disembodied' way to transfer quantum states from one object to another at a distant location, assisted by previously shared entangled states and a classical communication channel. As well as being of fundamental interest, teleportation has been recognized as an important element in long-distance quantum communication, distributed quantum networks and measurement-based quantum computation. There have been numerous demonstrations of teleportation in different physical systems such as photons, atoms, ions, electrons and superconducting circuits. All the previous experiments were limited to the teleportation of one degree of freedom only. However, a single quantum particle can naturally possess various degrees of freedom--internal and external--and with coherent coupling among them. A fundamental open challenge is to teleport multiple degrees of freedom simultaneously, which is necessary to describe a quantum particle fully and, therefore, to teleport it intact. Here we demonstrate quantum teleportation of the composite quantum states of a single photon encoded in both spin and orbital angular momentum. We use photon pairs entangled in both degrees of freedom (that is, hyper-entangled) as the quantum channel for teleportation, and develop a method to project and discriminate hyper-entangled Bell states by exploiting probabilistic quantum non-demolition measurement, which can be extended to more degrees of freedom. We verify the teleportation for both spin-orbit product states and hybrid entangled states, and achieve a teleportation fidelity ranging from 0.57 to 0.68, above the classical limit. Our work is a step towards the teleportation of more complex quantum systems, and demonstrates an increase in our technical control of scalable quantum technologies.

  9. Optimized In composition and quantum well thickness for yellow-emitting (Ga,In)N/GaN multiple quantum wells

    Lekhal, Kaddour; Hussain, Sakhawat; De Mierry, Philippe; Vennéguès, Philippe; Nemoz, Maud; Chauveau, Jean-Michel; Damilano, Benjamin

    2016-01-01

    Yellow-emitting InxGa1-xN/GaN multiple quantum wells (MQWs) with different pairs of In composition and QW thickness have been grown by metal-organic chemical vapor deposition on sapphire substrates. We show that a trade-off between the MQW crystalline quality and the quantum confined Stark effect has to be found to maximize the room temperature photoluminescence efficiency. With our growth conditions, an optimum design of the MQW is obtained for x=0.21 and a QW thickness of 3.6 nm.

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

    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.

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

    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

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

    Lai, Kunyu

    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.

  13. Quantum superadditivity in linear optics networks: Sending bits via multiple-access Gaussian channels

    Superadditivity effects of communication capacities are known in the case of discrete variable quantum channels. We describe the continuous variable analog of one of these effects in the framework of Gaussian multiple access channels (MACs). Classically, superadditivity-type effects are strongly restricted: For example, adding resources to one sender is never advantageous to other senders in sending their respective information to the receiver. We show that this rule can be surpassed using quantum resources, giving rise to a type of truly quantum superadditivity. This is illustrated here for two examples of experimentally feasible Gaussian MACs.

  14. Multiplicative properties of a quantum Caldero-Chapoton map associated to valued quivers

    Ding, Ming

    2011-01-01

    We prove a multiplication theorem of a quantum Caldero-Chapoton map associated to valued quivers which extends the results in \\cite{DX}\\cite{D}. As an application, when $Q$ is a valued quiver of finite type or rank 2, we obtain that the algebra $\\mathcal{AH}_{|k|}(Q)$ generated by all cluster characters (see Definition \\ref{def}) is exactly the quantum cluster algebra $\\mathcal{EH}_{|k|}(Q)$ and various bases of the quantum cluster algebras of rank 2 can naturally be deduced.

  15. Controlled quantum perfect teleportation of multiple arbitrary multi-qubit states

    Shi, Runhua; Huang, Liusheng; Yang, Wei; Zhong, Hong

    2011-12-01

    We present an efficient controlled quantum perfect teleportation scheme. In our scheme, multiple senders can teleport multiple arbitrary unknown multi-qubit states to a single receiver via a previously shared entanglement state with the help of one or more controllers. Furthermore, our scheme has a very good performance in the measurement and operation complexity, since it only needs to perform Bell state and single-particle measurements and to apply Controlled-Not gate and other single-particle unitary operations. In addition, compared with traditional schemes, our scheme needs less qubits as the quantum resources and exchanges less classical information, and thus obtains higher communication efficiency.

  16. Entanglement distribution over quantum code-division multiple-access networks

    Zhu, Chang-long; Yang, Nan; Liu, Yu-xi; Nori, Franco; Zhang, Jing

    2015-10-01

    We present a method for quantum entanglement distribution over a so-called code-division multiple-access network, in which two pairs of users share the same quantum channel to transmit information. The main idea of this method is to use different broadband chaotic phase shifts, generated by electro-optic modulators and chaotic Colpitts circuits, to encode the information-bearing quantum signals coming from different users and then recover the masked quantum signals at the receiver side by imposing opposite chaotic phase shifts. The chaotic phase shifts given to different pairs of users are almost uncorrelated due to the randomness of chaos and thus the quantum signals from different pair of users can be distinguished even when they are sent via the same quantum channel. It is shown that two maximally entangled states can be generated between two pairs of users by our method mediated by bright coherent lights, which can be more easily implemented in experiments compared with single-photon lights. Our method is robust under the channel noises if only the decay rates of the information-bearing fields induced by the channel noises are not quite high. Our study opens up new perspectives for addressing and transmitting quantum information in future quantum networks.

  17. Solution behavior and complete 1H and 13C NMR assignments of the coenzyme B12 derivative (5'-deoxyadenosyl)cobinamide using modern 2D NMR experiments, including 600-MHz 1H NMR data

    Two-dimensional (2D) NMR methods have been used to assign completely the 1H and 13C NMR spectra of the (5'-deoxyadenosyl)cobinamide cation (AdoCbi+) in D2O. Most of the 1H spectral assignments were made by using 2D homonuclear shift correlation spectroscopy (COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), absorption-mode (phase sensitive) 2D nuclear Overhauser effect (NOE) spectroscopy, and spin-locked NOE spectroscopy (also called ROESY, for rotating-frame Overhauser enhancement spectroscopy). Most of the protonated carbon resonances were assigned by using 1H-detected heteronuclear multiple-quantum coherence (HMQC) spectroscopy. The nonprotonated carbon resonances, as well as the remaining unassigned 1H and 13C NMR signals, were assigned from long-range 1H-13C connectivities determined from 1H-detected multiple-bond heteronuclear multiple-quantum coherence spectroscopy (HMBC). Comparison of the 13C chemical shifts and 1H NOEs of AdoCbi+ with those of coenzyme B12 ((5'-deoxyadenosyl)cobalamin) and its benzimidazole-protonated, base-off form indicates that the electronic properties and structure of AdoCbi+ are similar to that of coenzyme B12 in the protonated, base-off form. The 13C chemical shifts of most of the carbons of AdoCbi+ do not vary significantly from those of base-off, benzimidazole-protonated coenzyme B12, indicating that the electronic environment of the corrin ring is also similar in both compounds. However, significant differences in the chemical shifts of some of the corresponding carbons of the b, d, e, and f corrin side chains in AdoCbi+ and in base-off, benzimidazole-protonated coenzyme B12 indicate that the positions of these side chains may be different in AdoCbi+ compared to base-off coenzyme B12

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

    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.

  19. Multi-bands photoconductive response in AlGaN/GaN multiple quantum wells

    Chen, G.; Rong, X.; Xu, F. J.; Tang, N. [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Wang, X. Q., E-mail: wangshi@pku.edu.cn; Shen, B., E-mail: bshen@pku.edu.cn [State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Fu, K.; Zhang, B. S. [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Ruoshui Road 398, 215123 Suzhou (China); Hashimoto, H.; Yoshikawa, A. [Center for SMART Green Innovation Research, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ge, W. K. [Department of Physics, Tsinghua University, Beijing 100871 (China)

    2014-04-28

    Based on the optical transitions among the quantum-confined electronic states in the conduction band, we have fabricated multi-bands AlGaN/GaN quantum well infrared photodetectors. Crack-free AlGaN/GaN multiple quantum wells (MQWs) with atomically sharp interfaces have been achieved by inserting an AlN interlayer, which releases most of the tensile strain in the MQWs grown on the GaN underlayer. With significant reduction of dark current by using thick AlGaN barriers, photoconductive responses are demonstrated due to intersubband transition in multiple regions with center wavelengths of 1.3, 2.3, and 4 μm, which shows potential applications on near infrared detection.

  20. Multi-bands photoconductive response in AlGaN/GaN multiple quantum wells

    Based on the optical transitions among the quantum-confined electronic states in the conduction band, we have fabricated multi-bands AlGaN/GaN quantum well infrared photodetectors. Crack-free AlGaN/GaN multiple quantum wells (MQWs) with atomically sharp interfaces have been achieved by inserting an AlN interlayer, which releases most of the tensile strain in the MQWs grown on the GaN underlayer. With significant reduction of dark current by using thick AlGaN barriers, photoconductive responses are demonstrated due to intersubband transition in multiple regions with center wavelengths of 1.3, 2.3, and 4 μm, which shows potential applications on near infrared detection

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

    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

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

    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. B...

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

    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....

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

    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...

  5. Dislocation Behavior in AlGaN/GaN Multiple Quantum-Well Films Grown with Different Interlayers

    Dislocation behaviors are analyzed in AlGaN/GaN multiple-quantum-well films grown with different strain-modified interlayers. In the case of multiple-quantum-well layers grown on a GaN buffer layer without the interlayer, many threading dislocations interact and annihilate within about 100 nm below the multiple quantum well layer. For multiple-quantum-well layers grown with the AlGaN interlayer, misfit dislocations between the GaN buffer layer and the AlGaN interlayer enter multiple-quantum-well layers and result in an increase of threading dislocation density. Besides misfit dislocations, the edge-type dislocation is another dislocation origin attributed to the dissociation of Shockley partials bounding the stacking fault in AlN/GaN superlattices below the interlayer interface

  6. Excitonic transitions in Be-doped GaAs/AlAs multiple quantum well

    Wei-Min, Zheng; Su-Mei, Li; Wei-Yan, Cong; Ai-Fang, Wang; Bin, Li; Hai-Bei, Huang

    2016-04-01

    A series of GaAs/AlAs multiple-quantum wells doped with Be is grown by molecular beam epitaxy. The photoluminescence spectra are measured at 4, 20, 40, 80, 120, and 200 K, respectively. The recombination transition emission of heavy-hole and light-hole free excitons is clearly observed and the transition energies are measured with different quantum well widths. In addition, a theoretical model of excitonic states in the quantum wells is used, in which the symmetry of the component of the exciton wave function representing the relative motion is allowed to vary between the two- and three-dimensional limits. Then, within the effective mass and envelope function approximation, the recombination transition energies of the heavy- and light-hole excitons in GaAs/AlAs multiple-quantum wells are calculated each as a function of quantum well width by the shooting method and variational principle with two variational parameters. The results show that the excitons are neither 2D nor 3D like, but are in between in character and that the theoretical calculation is in good agreement with the experimental results. Project supported by the National Natural Science Foundation of China (Grant No. 61178039) and the Natural Science Foundation of Shandong Province, China (Grant No. ZR2012FM028).

  7. Synthesis of cadmium chalcogenide based quantum dots for enhanced multiple exciton generation

    Page, Robert Christopher

    2014-01-01

    Quantum dots (QDs) have the potential to produce more than one exciton per incident photon, if the photon energy is greater than twice the band gap energy. This process of multiple exciton generation (MEG) has the potential to lead to a step change in the efficiency of solar panels, by utilising energy commonly wasted as heat in conventional solar cells. A wide range of CdSe/CdTe and CdTe/CdSe quantum dots with and without a CdS shell were synthesised with varying core sizes and shell thickne...

  8. High-Efficiency White Organic Light-Emitting Devices Based on Multiple Quantum-Well Structure

    DUAN Yu; HOU Jing-Ying; WU Zhi-Jun; CHENG Gang; ZHAO Yi; LIU Shi-Yong

    2004-01-01

    @@ We report the white organic-light devices (WOLEDs) employing a multiple quantum-well (MQW) structure,which consist of alternate layers of 4,48-bis(2,28-diphenylvinyl)-1,18-biphenyl (DPVBi) and (DPVBi:Rubrene) as the potential barrier and the potential well, respectively. The results demonstrate that the MQW structure can prominently increase the performance of WOLEDs, the double quantum well device exhibits the efficiency up to 5.4 cd/A, and yields a peak luminance of 14206 cd/m2. It is also interesting to find that the MQW structure can enhance the colour stability of WOLEDs at different voltages.

  9. Motional Quantum-State Engineering and Implementation of a Quantum Phase-Gate for Multiple Trapped Ions

    YANG Wen-Xing

    2006-01-01

    We propose a scheme to generate a superposition of motional coherent states with arbitrary coefficients on a line in phase space and implement a quantum controlled phase-gate for multiple trapped ions with a single standing-wave laser pulse whose carrier frequency is tuned to the ions transition. In the scheme each ion does not need to be exactly positioned at the node of the standing wave, which is very important from viewpoint of experiment. Furthermore, our scheme may allow the generation of a superposition of coherent states with large mean phonon number for a large number of trapped ions in a fast way by choosing suitable laser intensity. We show that it can also be used to generate maximally entangled states of multiple trapped ions.

  10. Effective one-body dynamics in multiple-quantum NMR experiments

    Rufeil-Fiori, E.; Sánchez, C. M.; Oliva, F. Y.; Pastawski, H. M.; Levstein, P. R.

    2009-03-01

    A suitable NMR experiment in a one-dimensional dipolar coupled spin system allows one to reduce the natural many-body dynamics into effective one-body dynamics. We verify this in a polycrystalline sample of hydroxyapatite (HAp) by monitoring the excitation of NMR many-body superposition states: the multiple-quantum coherences. The observed effective one-dimensionality of HAp relies on the quasi-one-dimensional structure of the dipolar coupled network that, as we show here, is dynamically enhanced by the quantum Zeno effect. Decoherence is also probed through a Loschmidt echo experiment, where the time reversal is implemented on the double-quantum Hamiltonian, HDQ∝Ii+Ij++Ii-Ij- . We contrast the decoherence of adamantane, a standard three-dimensional system, with that of HAp. While the first shows an abrupt Fermi-type decay, HAp presents a smooth exponential law.

  11. Highly efficient multiple-layer CdS quantum dot sensitized III-V solar cells.

    Lin, Chien-Chung; Han, Hau-Vei; Chen, Hsin-Chu; Chen, Kuo-Ju; Tsai, Yu-Lin; Lin, Wein-Yi; Kuo, Hao-Chung; Yu, Peichen

    2014-02-01

    In this review, the concept of utilization of solar spectrum in order to increase the solar cell efficiency is discussed. Among the three mechanisms, down-shifting effect is investigated in detail. Organic dye, rare-earth minerals and quantum dots are three most popular down-shift materials. While the enhancement of solar cell efficiency was not clearly observed in the past, the advances in quantum dot fabrication have brought strong response out of the hybrid platform of a quantum dot solar cell. A multiple layer structure, including PDMS as the isolation layer, is proposed and demonstrated. With the help of pulse spray system, precise control can be achieved and the optimized concentration can be found. PMID:24749412

  12. Multiple-photon spectrum of CdS semiconductor quantum dot for bioimaging

    We study the dynamic processes of multiple-photon absorption and emission in a semiconductor quantum dot. By the non-perturbative time-dependent Schroedinger equation, it is shown that electrons in the quantum dot can be optically excited from the valence band to the conduction band via multiphoton processes, leaving holes in the valence band. The radiative recombination of the conduction-band electrons with the valence-band holes results in optical emission of a single photon having an energy which is larger than the input photon energy, resulting in the high-photon-energy luminescence from the quantum dot activated by low-energy photons to emit radiation in the visible optical regime for bioimaging application

  13. Defect structures in InGaN/GaN multiple quantum wells on Si(111 substrates

    G.M. Wu

    2006-08-01

    Full Text Available Purpose: Nitrides are compound semiconductor nanomaterials that are suitable for use in light-emitting diodes.It has been desired to grow high quality gallium nitride crystal thin film on silicon substrates because siliconsubstrates have the advantages of low cost, large wafer size, and good electrical and thermal conductivity.However, the higher defect density can limit the industrial applications due to lower quantum efficiency. Thepurpose of this study has been to investigate the crystal defect structure within InGaN/GaN multiple quantumwells on Si(111 substrates. In addition, the variation in quantum well thickness was also explained by theselective area growth model.Design/methodology/approach: InGaN/GaN nano-structures were prepared by metal-organic chemicalvapor phase epitaxy (MOVPE using composite buffer layers. The crystal defect structures in the buriedmultiple quantum wells on both (0001 and {10-11} sidewalls were carefully studied by transmission electronmicroscopy. Previous studies on sapphire substrates have been compared and discussed.Findings: The V defect structures have been found in InGaN/GaN multiple quantum wells on Si(111 substrates.A simplified structural model with increasing barrier thickness has been reported. The barrier thickness increasedon both (0001 and {10-11} facets along thin film growth. A decreased fill factor based on the selective areagrowth model was proposed. In addition, the average thin film growth rate was found to be four times higheralong (0001 than that along {10-11} facet. As the number of multiple quantum wells increased, the barrierthickness increasing was also intensified.Research limitations/implications: The understanding in defect structure could help to modify the processingand design parameters.Originality/value: The V-defect structure and model were reported for the first time using silicon substrates.The different growth rates along defect structures were quantified. High quality gallium

  14. Suppression of decoherence in gallium arsenide multiple quantum wells by means of bang-bang control

    Takasago, K. [Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan)], E-mail: takasago.k.aa@m.titech.ac.jp; Ogawa, Y.; Minami, F. [Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan)

    2008-05-15

    We performed a three-pulse six-wave mixing (SWM) measurement on a gallium arsenide (GaAs) multiple quantum well and observed the time-resolved SWM signal using the heterodyne detection technique. The second pulse acts as a {pi} pulse that reverses the time evolution of the non-Markovian dynamics. By changing the pulse interval conditions, we confirmed the suppression of exciton decoherence by {pi} pulse irradiation (bang-bang control)

  15. One-dimensional multiple-well oscillators: A time-dependent quantum mechanical approach

    Neetu Gupta; Amlan K Roy; B M Deb

    2002-10-01

    Time-dependent Schrödinger equation (TDSE) is solved numerically to calculate the ground- and first three excited-state energies, expectation values $\\langle x^{2j}\\rangle$, $j=1,2,\\ldots,6$ and probability densities of 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 densities and the effect of an asymmetry parameter on pseudodegeneracy are discussed.

  16. Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

    Corfdir, P.; Levrat, J.; Rossbach, G; Butte, R.; Feltin, E.; Carlin, J.-F.; Christmann, G.; Lefebvre, P.; Ganiere, J. -D.; Grandjean, N.; Deveaud-Pledran, B.

    2012-01-01

    We report on the direct observation of biexcitons in a III-nitride based multiple quantum well microcavity operating in the strong light-matter coupling regime by means of nonresonant continuous wave and time-resolved photoluminescence at low temperature. First, the biexciton dynamics is investigated for the bare active medium (multiple quantum wells alone) evidencing localization on potential fluctuations due to alloy disorder and thermalization between both localized and free excitonic and ...

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

    Solaimani, M.; Morteza, Izadifard [Faculty of Physics, Shahrood University of technology, Shahrood (Iran, Islamic Republic of); Arabshahi, H., E-mail: arabshahi@um.ac.ir [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Physics Department, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of); Reza, Sarkardehi Mohammad [Physics Department, Al-Zahra University, Vanak, Tehran (Iran, Islamic Republic of)

    2013-02-15

    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{sub x}Ga{sub (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: Black-Right-Pointing-Pointer OptiOptical Non-Linear. Black-Right-Pointing-Pointer Total Effective Length. Black-Right-Pointing-Pointer Multiple Quantum Wells System - genetic algorithm Black-Right-Pointing-Pointer Schroedinger equation solution. Black-Right-Pointing-Pointer Nanostructure.

  18. Direction Tracking of Multiple Moving Targets Using Quantum Particle Swarm Optimization

    Gao Hongyuan

    2016-01-01

    Full Text Available Based on weighted signal covariance (WSC matrix and maximum likelihood (ML estimation, a directionof-arrival (DOA estimation method of multiple moving targets is designed and named as WSC-ML in the presence of impulse noise. In order to overcome the shortcoming of the multidimensional search cost of maximum likelihood estimation, a novel continuous quantum particle swarm optimization (QPSO is proposed for this continuous optimization problem. And a tracking method of multiple moving targets in impulsive noise environment is proposed and named as QPSO-WSC-ML. Later, we make use of rank-one updating to update the weighted signal covariance matrix of WSC-ML. Simulation results illustrate the proposed QPSO-WSC-ML method is efficient and robust for the direction tracking of multiple moving targets in the presence of impulse noise.

  19. Electric field dependent Electroreflectance of GaAs/AlGaAs multiple quantum well Bragg structure at second quantum state

    Nakarmi, Mim; Shakya, Naresh; Chaldyshev, Vladimir

    Electroreflectance Spectroscopy was employed to study the effect of electric field on the excitonic transitions in a GaAs/AlGaAs multiple quantum well (MQW) Bragg structure. The sample used in this experiment consists of 60 periods of quantum well structures with GaAs well layer (~13 nm) and AlGaAs barrier layer (~94 nm), grown by molecular beam expitaxy on a semi-insulating GaAs substrate. The sample structure was designed to coincide the Bragg resonance peak with the x(e2-hh2) exciton transitions. We observed a significant enhancement of excitonic feature around the x(e2-hh2) exciton transition due to the double resonance along with the sharp features of x(e1-hh1) and x(e1-lh1) ground state exciton transitions by tuning the angle of incidence of the light. We will present the results on electric field dependent electroreflectance measurements of this structure and discuss the effect of electric field on the first and second energy states.

  20. GaN/AlGaN Multiple-Quantum-Well Ultraviolet Schottky Photodetectors

    We report on characterization and operation principle of a set of GaN/AlGaN multiple-quantum-well (MQW) photovoltaic detectors. The structures were grown by molecular beam epitaxy (MBE) on c-plane sapphire substrates and fabricated in the back illuminated vertical Schottky geometry. Introduction of MQWs into the active region of devices is expected to enhance the quantum efficiency due to the high absorption coefficient. A nearly flat spectral responsivity between 325nm and 350nm with 0.054 A/W peak responsivity was achieved from the single-side polished backside (rough) illuminated GaN/AlGaN multiple quantum well devices. The cutoff wavelength MQWs photodetector can be tuned by adjusting the well width, well compasition, and barrier height. A model has also been developed to gauge the performance and gain insight into the operation principles of MQWs photodiodes. We observed that the peak responsivity was device parameter dependent and increased with decreasing barrier thickness due to enhanced tunneling of photo generated carriers

  1. Polarizabilities of Impurity Doped Quantum Dots Under Pulsed Field: Role of Multiplicative White Noise

    Saha, Surajit; Ghosh, Manas

    2016-02-01

    We perform a rigorous analysis of the profiles of a few diagonal and off-diagonal components of linear ( α xx , α yy , α xy , and α yx ), first nonlinear ( β xxx , β yyy , β xyy , and β yxx ), and second nonlinear ( γ xxxx , γ yyyy , γ xxyy , and γ yyxx ) polarizabilities of quantum dots exposed to an external pulsed field. Simultaneous presence of multiplicative white noise has also been taken into account. The quantum dot contains a dopant represented by a Gaussian potential. The number of pulse and the dopant location have been found to fabricate the said profiles through their interplay. Moreover, a variation in the noise strength also contributes evidently in designing the profiles of above polarizability components. In general, the off-diagonal components have been found to be somewhat more responsive to a variation of noise strength. However, we have found some exception to the above fact for the off-diagonal β yxx component. The study projects some pathways of achieving stable, enhanced, and often maximized output of linear and nonlinear polarizabilities of doped quantum dots driven by multiplicative noise.

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

    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.

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

    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. PMID:27533524

  4. Luminescence and ultrafast phenomena in InGaN multiple quantum wells

    High quality In0.13Ga0.87N/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

  5. Protected quantum computation with multiple resonators in ultrastrong coupling circuit QED

    Nataf, Pierre

    2011-01-01

    We investigate theoretically the dynamical behavior of a qubit obtained with the two ground eigenstates of an ultrastrong coupling circuit-QED system consisting of a finite number of Josephson fluxonium atoms inductively coupled to a transmission line resonator. We show an universal set of quantum gates by using multiple transmission line resonators (each resonator represents a single qubit). We discuss the intrinsic 'anisotropic' nature of noise sources for fluxonium artificial atoms. Through a master equation treatment with colored noise and manylevel dynamics, we prove that, for a general class of anisotropic noise sources, the coherence time of the qubit and the fidelity of the quantum operations can be dramatically improved in an optimal regime of ultrastrong coupling, where the ground state is an entangled photonic 'cat' state.

  6. Growth and structural characterization of GaAsBi/GaAs multiple quantum wells

    GaAsBi/GaAs multiple quantum well (MQW) p–i–n diodes are grown by molecular beam epitaxy. Transmission electron microscope images of the diodes show good agreement between the intended and measured MQW periods, but poor agreement between the intended and measured GaAsBi quantum well thicknesses. This is likely due to the incorporation of Bi from a physisorbed surface layer that takes a finite time to accumulate during growth. The diodes with more than 40 wells show dislocations that indicate strain relaxation. This is supported by x-ray diffraction analysis, which also suggests that the i-region of the 54 well diode is tilted with respect to the substrate. (paper)

  7. The role of the fano resonance in multiple exciton generation in quantum dots

    Oksengendler, B. L.; Marasulov, M. B.; Nikiforov, V. N.

    2016-02-01

    The phenomenon of interference between two pathways of electron transfer from the valence to the conduction band at a quantum dot is considered. The first way is the conventional "valence band-conduction band" transition, while the second is the transition via a virtual two-electron state on the Tamm level in a quantum dot (QD) followed by the Auger effect, which ejects one electron from the Tamm level to the conduction band. In the case of a coherent addition of these ionization pathways, the Fano resonance can take place, this leading to an increase in the coefficient of photon absorption. This results in increasing internal efficiency of light conversion and can provide a basis for increasing the efficiency of solar cells due to the phenomenon of multiple exciton generation.

  8. Tunable Symmetries of Integer and Fractional Quantum Hall Phases in Heterostructures with Multiple Dirac Bands

    Stepanov, Petr; Barlas, Yafis; Espiritu, Tim; Che, Shi; Watanabe, Kenji; Taniguchi, Takashi; Smirnov, Dmitry; Lau, Chun Ning

    2016-08-01

    The copresence of multiple Dirac bands in few-layer graphene leads to a rich phase diagram in the quantum Hall regime. Using transport measurements, we map the phase diagram of BN-encapsulated A B A -stacked trilayer graphene as a function charge density n , magnetic field B , and interlayer displacement field D , and observe transitions among states with different spin, valley, orbital, and parity polarizations. Such a rich pattern arises from crossings between Landau levels from different subbands, which reflect the evolving symmetries that are tunable in situ. At D =0 , we observe fractional quantum Hall (FQH) states at filling factors 2 /3 and -11 /3 . Unlike those in bilayer graphene, these FQH states are destabilized by a small interlayer potential that hybridizes the different Dirac bands.

  9. Scale-estimation of quantum coherent energy transport in multiple-minima systems.

    Farrow, Tristan; Vedral, Vlatko

    2014-01-01

    A generic and intuitive model for coherent energy transport in multiple minima systems coupled to a quantum mechanical bath is shown. Using a simple spin-boson system, we illustrate how a generic donor-acceptor system can be brought into resonance using a narrow band of vibrational modes, such that the transfer efficiency of an electron-hole pair (exciton) is made arbitrarily high. Coherent transport phenomena in nature are of renewed interest since the discovery that a photon captured by the light-harvesting complex (LHC) in photosynthetic organisms can be conveyed to a chemical reaction centre with near-perfect efficiency. Classical explanations of the transfer use stochastic diffusion to model the hopping motion of a photo-excited exciton. This accounts inadequately for the speed and efficiency of the energy transfer measured in a series of recent landmark experiments. Taking a quantum mechanical perspective can help capture the salient features of the efficient part of that transfer. To show the versatility of the model, we extend it to a multiple minima system comprising seven-sites, reminiscent of the widely studied Fenna-Matthews-Olson (FMO) light-harvesting complex. We show that an idealised transport model for multiple minima coupled to a narrow-band phonon can transport energy with arbitrarily high efficiency. PMID:24980547

  10. Design and Realization of InP/AlGaInAs Multiple Quantum Well Ring Laser

    谢生; 郭婧; 管坤; 毛陆虹; 郭维廉; 齐利芳; 李献杰

    2014-01-01

    Using beam propagation method (BPM), key optical design parameters of InP/AlGaInAs multiple quan-tum well (MQW) ring laser were numerically analyzed. The influences of waveguide dimensions, curvature radius and gap size on the coupling efficiency were discussed. An InP/AlGaInAs MQW ring laser with radius of 350μm was designed and realized. The experimental results show that the designed device, lasing at 1 563.2 nm with side mode suppression ratio higher than 20 dB, exhibited unidirectional bistability between the clockwise and counterclockwise modes.

  11. Polariton Resonances for Ultrastrong Coupling Cavity Optomechanics in GaAs/AlAs Multiple Quantum Wells.

    Jusserand, B; Poddubny, A N; Poshakinskiy, A V; Fainstein, A; Lemaitre, A

    2015-12-31

    Polariton-mediated light-sound interaction is investigated through resonant Brillouin scattering experiments in GaAs/AlAs multiple-quantum wells. Photoelastic coupling enhancement at exciton-polariton resonance reaches 10(5) at 30 K as compared to a typical bulk solid room temperature transparency value. When applied to GaAs based cavity optomechanical nanodevices, this result opens the path to huge displacement sensitivities and to ultrastrong coupling regimes in cavity optomechanics with couplings g(0) in the range of 100 GHz. PMID:26765028

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

    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.

  13. Dynamic analysis of multiple-photon optical processes in semiconductor quantum dots

    Semiconductor quantum dots (QDs) have been gaining much attention because of their outstanding properties for multiple-photon microscopy applications. By solving nonperturbatively the time-dependent Schroedinger equation, it has been shown that the large number of energy states densely compacted in both the conduction and valence bands of the QD greatly enhance the inter-band and intra-band optical couplings between two energy states induced by multiple photons from ultra-fast and ultra-intense lasers. The multiphoton absorption processes are further enhanced by many energy relaxation processes in commonly used semiconductors, which are generally represented by the relaxation energy in the order of tens of meV. Numerical calculation of multiphoton processes in QDs agrees with experimental demonstration. After proper designing, QDs can be activated by infrared radiation to emit radiation in the visible optical regime (up-conversion) for bioimaging applications

  14. Dynamic light-matter coupling across multiple spatial dimensions in a quantum dots-in-a-well heterostructure

    Prasankumar, Rohit P [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory; Chow, W W [SNL; Attaluri, R S [UNM; Shenoi, R [UNM

    2009-01-01

    Semiconductor heterostructures incorporating multiple degrees of spatial confinement have recently attracted substantial interest for photonic applications. One example is the quantum dots-in-a-well (DWELL) heterostructure, consisting of zero-dimensional quantum dots embedded in a two-dimensional quantum well and surrounded by three-dimensional bulk material. This structure offers several advantages over conventional photonic devices while providing a model system for the study of light-matter interactions across multiple spatial dimensions. Here, we use ultrafast differential transmission spectroscopy2 to temporally and spectrally resolve density-dependent carrier dynamics in a DWELL heterostructure. We observe excitation-dependent shifts of the quantum dot energy levels at low densities, while at high densities we observe an anomalous induced absorption at the quantum dot excited state that is correlated to quantum well population dynamics. These studies of density-dependent light-matter interactions across multiple coupled spatial dimensions provide clues to the underlying physics governing quantum dot properties, with important implications for DWELL-based photonic devices.

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

    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.

  16. Main: 1H82 [RPSD[Archive

    Full Text Available 1H82 トウモロコシ Corn Zea mays L. Polyamine Oxidase Precursor Name=Pao; Zea Mays Molecul...PEGKGREFFLYASSRRGYYGVWQEFEKQYPDANVLLVTVTDEESRRIEQQSDEQTKAEIMQVLRKMFPGKDVPDATDILVPRWWSDRFYKGTFSNWPVGVNRYEYDQLRAPVGRVYFTGEHTSEHYNGYVHGAYLSGIDSAEILINCAQKKMCKYHVQGKYD corn_1H82.jpg ...

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    Full Text Available 1H84 トウモロコシ Corn Zea mays L. Polyamine Oxidase Precursor Name=Pao; Zea Mays Molecul...GYYGVWQEFEKQYPDANVLLVTVTDEESRRIEQQSDEQTKAEIMQVLRKMFPGKDVPDATDILVPRWWSDRFYKGTFSNWPVGVNRYEYDQLRAPVGRVYFTGEHTSEHYNGYVHGAYLSGIDSAEILINCAQKKMCKYHVQGKYD corn_1H84.jpg ...

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    Full Text Available 1H86 トウモロコシ Corn Zea mays L. Polyamine Oxidase Precursor Name=Pao; Zea Mays Molecul...PEGKGREFFLYASSRRGYYGVWQEFEKQYPDANVLLVTVTDEESRRIEQQSDEQTKAEIMQVLRKMFPGKDVPDATDILVPRWWSDRFYKGTFSNWPVGVNRYEYDQLRAPVGRVYFTGEHTSEHYNGYVHGAYLSGIDSAEILINCAQKKMCKYHVQGKYD corn_1H86.jpg ...

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    Full Text Available 1H83 トウモロコシ Corn Zea mays L. Polyamine Oxidase Precursor Name=Pao; Zea Mays Molecul...GYYGVWQEFEKQYPDANVLLVTVTDEESRRIEQQSDEQTKAEIMQVLRKMFPGKDVPDATDILVPRWWSDRFYKGTFSNWPVGVNRYEYDQLRAPVGRVYFTGEHTSEHYNGYVHGAYLSGIDSAEILINCAQKKMCKYHVQGKYD corn_1H83.jpg ...

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    Full Text Available 1H81 トウモロコシ Corn Zea mays L. Polyamine Oxidase Precursor Name=Pao; Zea Mays Molecul...PEGKGREFFLYASSRRGYYGVWQEFEKQYPDANVLLVTVTDEESRRIEQQSDEQTKAEIMQVLRKMFPGKDVPDATDILVPRWWSDRFYKGTFSNWPVGVNRYEYDQLRAPVGRVYFTGEHTSEHYNGYVHGAYLSGIDSAEILINCAQKKMCKYHVQGKYD corn_1H81.jpg ...

  1. Main: 1H49 [RPSD[Archive

    Full Text Available 1H49 トウモロコシ Corn Zea mays L. Beta-Glucosidase, Chloroplast Precursor Name=Glu1; Zea...NPWIYMYPEGLKDLLMIMKNKYGNPPIYITENGIGDVDTKETPLPMEAALNDYKRLDYIQRHIATLKESIDLGSNVQGYFAWSLLDNFEWFAGFTERYGIVYVDRNNNCTRYMKESAKWLKEFNTAKKPSKKILTPA corn_1H49.jpg ...

  2. Entanglement Entropy Signature of Quantum Phase Transitions in a Multiple Spin Interactions Model

    HUANG Hai-Lin

    2011-01-01

    Through the Jordan-Wigner transformation, the entanglement entropy and ground state phase diagrams of exactly solvable spin model with alternating and multiple spin exchange interactions are investigated by means of Green's function theory.In the absence of four-spin interactions, the ground state presents plentiful quantum phases due to the multiple spin interactions and magnetic fields.It is shown that the two-site entanglement entropy is a good indicator of quantum phase transition (QPT).In addition, the alternating interactions can destroy the magnetization plateau and wash out the spin-gap of low-lying excitations.However, in the presence of four-spin interactions, apart from the second order QPTs, the system manifests the first order QPT at the tricritical point and an additional new phase called "spin waves", which is due to the collapse of the continuous tower-like low-lying excitations modulated by the four-spin interactions for large three-spin couplings.

  3. Theoretical model of optical fiber secure communication system with chaotic multiple-quantum-well lasers

    2007-01-01

    Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchronization system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1 haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communications at wavelength 1.55μm

  4. Theory of multiple quantum dot formation in strained-layer heteroepitaxy

    Du, Lin; Maroudas, Dimitrios

    2016-07-01

    We develop a theory for the experimentally observed formation of multiple quantum dots (QDs) in strained-layer heteroepitaxy based on surface morphological stability analysis of a coherently strained epitaxial thin film on a crystalline substrate. Using a fully nonlinear model of surface morphological evolution that accounts for a wetting potential contribution to the epitaxial film's free energy as well as surface diffusional anisotropy, we demonstrate the formation of multiple QD patterns in self-consistent dynamical simulations of the evolution of the epitaxial film surface perturbed from its planar state. The simulation predictions are supported by weakly nonlinear analysis of the epitaxial film surface morphological stability. We find that, in addition to the Stranski-Krastanow instability, long-wavelength perturbations from the planar film surface morphology can trigger a nonlinear instability, resulting in the splitting of a single QD into multiple QDs of smaller sizes, and predict the critical wavelength of the film surface perturbation for the onset of the nonlinear tip-splitting instability. The theory provides a fundamental interpretation for the observations of "QD pairs" or "double QDs" and other multiple QDs reported in experimental studies of epitaxial growth of semiconductor strained layers and sets the stage for precise engineering of tunable-size nanoscale surface features in strained-layer heteroepitaxy by exploiting film surface nonlinear, pattern forming phenomena.

  5. Comprehensive quantum chemical and spectroscopic (FTIR, FT-Raman, 1H, 13C NMR) investigations of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane

    Arjunan, V.; Anitha, R.; Devi, L.; Mohan, S.; Yang, Haifeng

    2015-01-01

    Aromatic epoxides are causative factors for mutagenic and carcinogenic activity of polycyclic arenes. The 1,2- or 2,3-epoxy compounds are widely used to a considerable extent in the textile, plastics, pharmaceutical, cosmetics, detergent and photochemical industries. The FTIR and FT-Raman spectra of (1,2-epoxyethyl)benzene and (1,2-epoxy-2-phenyl)propane are recorded in the regions 4000-400 cm-1 and 4000-100 cm-1, respectively. The observed fundamentals are assigned to different normal modes of vibration. The structure of the compound has been optimised with B3LYP method using 6-311++G** and cc-pVTZ basis sets. The IR and Raman intensities are determined. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/6-311++G(d,p) method to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of the compounds has been performed to indicate the presence of intramolecular charge transfer. The 1H and 13C NMR chemical shifts of the molecules have been analysed.

  6. Molecular structures and conformations of 1-benzenesulphonyl-2-oxo-5-alkoxypyrrolidines with anti-amnesic activity. X-ray, 1H-NMR and quantum mechanical (PM3) studies

    Amato, Maria E.; Bandoli, Giuliano; Dolmella, Alessandro; Grassi, Antonio; Pappalardo, Giuseppe C.; Toja, Emilio

    1991-04-01

    The crystal and molecular structures of the nootropic agents RU-47001 ((±) 1-(4-nitrobenzenesulphonyl)-2-oxo-5-ethoxypyrrolidine) and RU-47064 ((±) 1-(4-nitrobenzenesulphonyl)-2-oxo-5-isopropyloxypyrrolidine) have been determined by X-ray analysis and their solution conformation has been investigated using 1H NMR spectroscopy. The conformations of these molecules together with those of their analogues RU-35929 ((±) 1-benzenesulphonyl-2-oxo-5-ethoxypyrrolidine), RU-47010 ((±) 1-(3-pyridinylsulphonyl)-2-oxo-5-ethoxypyrrolidine) and RU-35965 ((±) 1-benzenesulphonyl-2-oxo-5-isopropyloxypyrrolidine) have been deduced from semi-quantitative PM3 type theoretical calculations. The main feature of all compounds consists of a common envelope conformation with C (4) at the flap of the pyrrolidinone ring in the solid, that in solution changes into the analogous, but opposite, possible puckered conformational isomer. The 5-alkoxy groups were found rather flexible in solution. Theoretical preferred conformations about NS and SC bonds were in acceptable agreement with those of the solid state. The calculated torsional energetics suggested that 1- 5 do not undergo conformational interconversion.

  7. Measuring out-of-time-order correlations and multiple quantum spectra in a trapped ion quantum magnet

    Gärttner, Martin; Safavi-Naini, Arghavan; Wall, Michael L; Bollinger, John J; Rey, Ana Maria

    2016-01-01

    Highly controllable arrays of ions and ultra-cold atoms are providing exciting opportunities for realizing quantum simulators of complex many-body phenomena that can provide insights into unsolved problems in modern science. A fundamental step towards this goal is the development of protocols that can quantify how a quantum simulator builds up quantum correlations and stores quantum information starting from easily prepared uncorrelated states. Out-of-time-order correlation functions have been recently suggested as ideal probes to accomplish this task, because they can quantify the spreading, or "scrambling", of quantum information and set speed limits for thermalization. They might also enable experimental tests of the holographic duality between quantum and gravitational systems. Here we report experimental measurements of dynamics of out-of-time-order correlations in a quantum simulator of more than 100 ions in a Penning trap by using the many-body echo sequence developed in the context of nuclear magnetic...

  8. Multiple functional UV devices based on III-Nitride quantum wells for biological warfare agent detection

    Wang, Qin; Savage, Susan; Persson, Sirpa; Noharet, Bertrand; Junique, Stéphane; Andersson, Jan Y.; Liuolia, Vytautas; Marcinkevicius, Saulius

    2009-02-01

    We have demonstrated surface normal detecting/filtering/emitting multiple functional ultraviolet (UV) optoelectronic devices based on InGaN/GaN, InGaN/AlGaN and AlxGa1-xN/AlyGa1-yN multiple quantum well (MQW) structures with operation wavelengths ranging from 270 nm to 450 nm. Utilizing MQW structure as device active layer offers a flexibility to tune its long cut-off wavelength in a wide UV range from solar-blind to visible by adjusting the well width, well composition and barrier height. Similarly, its short cut-off wavelength can be adjusted by using a GaN or AlGaN block layer on a sapphire substrate when the device is illuminated from its backside, which further provides an optical filtering effect. When a current injects into the device under forward bias the device acts as an UV light emitter, whereas the device performs as a typical photodetector under reverse biases. With applying an alternating external bias the device might be used as electroabsorption modulator due to quantum confined Stark effect. In present work fabricated devices have been characterized by transmission/absorption spectra, photoresponsivity, electroluminescence, and photoluminescence measurements under various forward and reverse biases. The piezoelectric effect, alloy broadening and Stokes shift between the emission and absorption spectra in different InGaN- and AlGaN-based QW structures have been investigated and compared. Possibilities of monolithic or hybrid integration using such multiple functional devices for biological warfare agents sensing application have also be discussed.

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

    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

  10. Multiple quantum and dipolar correlation effect NMR studies of cross-linking in elastomer systems

    Physical and chemical aging of filled polydimethylsiloxane-polydimphylsiloxane (PDMS-PDPS) copolymer foams is currently being studied to assess engineering performance degradation and to provide fundamental understanding of aging mechanisms for predictive modeling. Nuclear Magnetic Resonance (NMR) spectroscopy has been shown to be a powerful method for the characterization of polymer aging mechanisms. NMR offers the ability to assess speciation changes and changes in motional properties caused by chemical and physical aging mechanisms. In fact, the measurement of 1H transverse relaxation times (T2) of aged silica filled PDMS/PDPS copolymers have been shown to be sensitive to bulk changes in motional processes caused by aging mechanisms such as radiation exposure. However, more subtle aging mechanisms cause only small changes in bulk relaxation times and conclusive interpretation of the NMR data can be difficult. 1H T2 studies of surveillance return samples, for example, have suffered from such an insensitivity to age and no direct correlation between age and relaxation time have been detected, mirroring solvent swelling results. Close examination of the echo decay functions for surveillance return elastomers sample shows that the main difference between samples are (a) the degree of non-exponential decay behavior at early times between samples, and (b) the amount of material that can be characterized by a long T2. Local and long range structure have important implications on the motional properties of the polymer chains. In PDMS based polymers the couplings between protons within methyl groups are attenuated by rapid spinning about the C3 axis and by the more complex translational and rotational motion of the polymer chains. Crosslinks and entanglements reduce the amplitude and frequency of such long-range segmental motions. The result is that dipolar couplings between protons are not completely averaged to zero. The non-exponential decay is a direct consequence of

  11. Multiple exciton generation and ultrafast exciton dynamics in HgTe colloidal quantum dots.

    Al-Otaify, Ali; Kershaw, Stephen V; Gupta, Shuchi; Rogach, Andrey L; Allan, Guy; Delerue, Christophe; Binks, David J

    2013-10-21

    The investigation of sub-nanosecond exciton dynamics in HgTe colloidal quantum dots using ultrafast transient absorption spectroscopy is reported. The transmittance change spectrum acquired immediately after pumping is dominated by a bleach blue-shifted by ~200-300 nm from the photoluminescent emission band. Comparison with a tight-binding model of the electronic structure allows this feature to be attributed to the filling of band edge states. The form of the pump-induced transmittance transients is dependent on the excitation rate and the rate of sample stirring. For moderate pumping of stirred samples, the transmittance transients are well-described by a mono-exponential decay associated with biexciton recombination, with a lifetime of 49 ± 2 ps. For samples that are strongly-pumped or unstirred, the decay becomes bi-exponential in form, indicating that trap-related recombination has become significant. We also present a new analysis that enables fractional transmittance changes to be related to band edge occupation for samples with arbitrary optical density at the pump wavelength. This allows us to identify the occurrence of multiple exciton generation, which results in a quantum yield of 1.36 ± 0.04 for a photon energy equivalent to 3.1 times the band gap, in good agreement with the results of the model. PMID:23999734

  12. Scale-estimation of quantum coherent energy transport in multiple-minima systems

    Farrow, Tristan

    2014-01-01

    A generic and intuitive model for coherent energy transport in multiple minima systems coupled to a quantum mechanical bath is shown. Using a simple spin-boson system, we illustrate how a generic donor-acceptor system can be brought into resonance using a narrow band of vibrational modes, such that the transfer efficiency of an electron-hole pair (exciton) is made arbitrarily high. Coherent transport phenomena in nature are of renewed interest since the discovery that a photon captured by the light-harvesting complex (LHC) in photosynthetic organisms can be conveyed to a chemical reaction centre with near-perfect efficiency. Classical explanations of the transfer use stochastic diffusion to model the hopping motion of a photo-excited exciton. This accounts inadequately for the speed and efficiency of the energy transfer measured in a series of recent landmark experiments. Taking a quantum mechanical perspective can help capture the salient features of the efficient part of that transfer. To show the versatili...

  13. Germanium-tin multiple quantum well on silicon avalanche photodiode for photodetection at two micron wavelength

    Dong, Yuan; Wang, Wei; Lee, Shuh Ying; Lei, Dian; Gong, Xiao; Khai Loke, Wan; Yoon, Soon-Fatt; Liang, Gengchiau; Yeo, Yee-Chia

    2016-09-01

    We report the demonstration of a germanium-tin multiple quantum well (Ge0.9Sn0.1 MQW)-on-Si avalanche photodiode (APD) for light detection near the 2 μm wavelength range. The measured spectral response covers wavelengths from 1510 to 2003 nm. An optical responsivity of 0.33 A W‑1 is achieved at 2003 nm due to the internal avalanche gain. In addition, a thermal coefficient of breakdown voltage is extracted to be 0.053% K‑1 based on the temperature-dependent dark current measurement. As compared to the traditional 2 μm wavelength APDs, the Si-based APD is promising for its small excess noise factor, less stringent demand on temperature stability, and its compatibility with silicon technology.

  14. Stimulated emission in InGaN/GaN multiple quantum wells with different indium content

    We report on high-excitation luminescence spectroscopy of InxGa1-xN/GaN multiple quantum wells with a high indium content (x = 0.22 - 0.30). High excitation conditions enabled to achieve screening of built-in field by free carriers. This allowed for the evaluation of the influence of the band potential fluctuations due to variation in In-content on optical properties. Enhanced spontaneous emission was found for x ≥ 0.22 due to carrier localization within the chaotic band potential. Meanwhile the stimulated emission was found to be the highest for structures with x ∼ 0.25 - 0.27. We attribute the In-content dependence of the stimulated emission intensity to a trade-off between an increased carrier density and a decrease of the density of states. (author)

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

    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.

  16. Dynamics of quantum Fisher information in a two-level system coupled to multiple bosonic reservoirs

    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).

  17. Bound states for multiple Dirac-δ wells in space-fractional quantum mechanics

    Tare, Jeffrey D., E-mail: jeffreytare@gmail.com; Esguerra, Jose Perico H., E-mail: pesguerra@nip.upd.edu.ph [National Institute of Physics, University of the Philippines, Diliman, Quezon City 1101 (Philippines)

    2014-01-15

    Using the momentum-space approach, we obtain bound states for multiple Dirac-δ wells in the framework of space-fractional quantum mechanics. Introducing first an attractive Dirac-comb potential, i.e., Dirac comb with strength −g (g > 0), in the space-fractional Schrödinger equation we show that the problem of obtaining eigenenergies of a system with N Dirac-δ wells can be reduced to a problem of obtaining the eigenvalues of an N × N matrix. As an illustration we use the present matrix formulation to derive expressions satisfied by the bound-state energies of N = 1, 2, 3 delta wells. We also obtain the corresponding wave functions and express them in terms of Fox's H-function.

  18. A multiple quantum NMR (MQNMR) study of hydrogen microstructure in boron doped a-Si:H

    In this paper, an IR and multiple quantum NMR (MQNMR) study of hydrogen microstructure in three boron doped a-Si:H is discussed. The total Si-bonded H content of all films was 6.5 ± 1.0 at. % as determined by the 640 cm-1 IR wagging mode, but their boron content, which was determined by secondary ion mass spectrometry, ranged from 0.02 to 0.3 at %. The number of correlated hydrogen, as measured at a preparation time of 600 μs, was found to be more weakly dependent on the boron content than previously observed in phosphorous-doped glow-discharge films. Upon annealing at 220 degrees C the MQNMR spectrum show a moderate increase in the number of correlated hydrogen in all three samples

  19. Microcavity effect on the pump-probe intersubband response of multiple-quantum-well structures

    We study theoretically the coherent pump-probe intersubband response of a multiple quantum well (MQW) embedded in a semiconductor microcavity. An n-type doped MQW structure with two subbands in the conduction band is considered. Self-consistent numerical calculations are performed for realistic systems employing a semiclassical approach based on the transfer matrix formalism and the so-called sheet model. They show that in the strong coupling limit the pumping of the system leads to evolution of the intersubband cavity polariton doublet into a Mollow-type spectrum. By using appropriate angles, both the pump and the probe light can be tuned into resonance with the cavity mode. In this double-resonance case, simultaneously with a dramatic enhancement of the Rabi flopping frequency, a strong selective enhancement of distinct parts of the Rabi sidebands is possible. (paper)

  20. Infrared Supercontinuum Generation in Multiple Quantum Well Nanostructures under Electromagnetically Induced Transparency

    Borgohain, Nitu; Konar, S

    2015-01-01

    Mid-infrared spectral broadening is of great scientific and technological interest, which till date is mainly achieved using non-silica glass fibers, primarily made of tellurite, fluoride and chalcogenide glasses. We investigate broadband mid-infrared supercontinuum generation at very low power in semiconductor multiple quantum well (MQW) systems facilitated by electromagnetically induced transparency. 100 femto-seconds pulses of peak power close to a Watt have been launched in the electromagnetically induced transparency window of a 30 period 1.374 {\\mu}m long MQW system. Broadband supercontinuum spectra, attributed to self phase modulation and modulation instability, is achievable at the end of the MQW system. The central part of the spectra is dominated by several dips and the far infra-red part of the spectra is more broadened in comparison to the infra-red portion. Key advantage of the proposed scheme is that the supercontinuum source could be easily integrated with other semiconductor devices.

  1. The multiple quantum NMR dynamics in systems of equivalent spins with the dipolar ordered initial state

    Doronin, S I; Zenchuk, A I

    2011-01-01

    The multiple quantum (MQ) NMR dynamics in the system of equivalent spins with the dipolar ordered initial state is considered. The high symmetry of the MQ Hamiltonian is used in order to develop the analytical and numerical methods for an investigation of the MQ NMR dynamics in the systems consisting of hundreds of spins from "the first principles". We obtain the dependence of the intensities of the MQ NMR coherences on their orders (profiles of the MQ NMR coherences) for the systems of $200 - 600$ spins. It is shown that these profiles may be well approximated by the exponential distribution functions. We also compare the MQ NMR dynamics in the systems of equivalent spins having two different initial states, namely the dipolar ordered state and the thermal equilibrium state in the strong external magnetic field.

  2. Optical Properties of GaN Nanorods Containing a Single or Multiple InGaN Quantum Wells

    Zhuang, Yi D.; Lis, Szymon; Bruckbauer, Jochen; O'Kane, Simon E. J.; Shields, Philip A.; Edwards, Paul R.; Sarma, Jayanta; Martin, Robert W.; Allsopp, Duncan W. E.

    2013-08-01

    Measurements of light emission from GaN nanorods of diameter between 80 and 350 nm, containing either a three-well multiple InGaN quantum well or a single quantum well, have been performed by photoluminescence (PL) and cathodoluminescence (CL) hyperspectral imaging. The PL underwent a Stark shift to the blue as the nanorod diameter was reduced, indicating substantial relaxation of the compressive strain in the quantum wells. The intensity of the nanorod emission per unit area can exceed that of the planar starting material. The CL measurements revealed that the wavelength of the quantum well emission varied with radial position in the nanorod. Simulations by a modal expansion method revealed that the light extraction efficiency varies with radial position and the variation is dependent on nanorod diameter. Finite difference time domain simulations showed that Bloch mode formation in the buffer layer below the nanorods impacts on the light extraction.

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

    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...... mechanisms by spectrally resolving the transient four-wave-mixing signal....

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

    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...

  5. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

    2015-02-08

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

  6. The two-mode quantum Fresnel operator and the multiplication rule of 2D Collins diffraction formula

    Xie, Chuan-Mei; Fan, Hong-Yi

    2012-04-01

    By using the two-mode Fresnel operator we derive a multiplication rule of two-dimensional (2D) Collins diffraction formula, the inverse of 2D Collins diffraction integration can also be conveniently derived in this way in the context of quantum optics theory.

  7. The two-mode quantum Fresnel operator and the multiplication rule of 2D Collins diffraction formula

    By using the two-mode Fresnel operator we derive a multiplication rule of two-dimensional (2D) Collins diffraction formula, the inverse of 2D Collins diffraction integration can also be conveniently derived in this way in the context of quantum optics theory. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. {sup 1}H MR spectroscopy in epilepsy

    Hajek, Milan [MR Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague (Czech Republic)], E-mail: miha@medicon.cz; Dezortova, Monika [MR Unit, Department of Diagnostic and Interventional Radiology, Institute for Clinical and Experimental Medicine, Videnska 1958/9, 140 21 Prague (Czech Republic)], E-mail: mode@medicon.cz; Krsek, Pavel [Department of Pediatric Neurology, Charles University, Second Medical School, Motol Hospital, V Uvalu 84, 150 06 Prague 5 (Czech Republic)], E-mail: pavel.krsek@post.cz

    2008-08-15

    The introduction to the application of {sup 1}H MR spectroscopy for clinical and research studies of mesial temporal and extratemporal epilepsies is done. The techniques of single voxel and spectroscopic imaging are discussed and the analysis of {sup 1}H MR spectra together with basic metabolic descriptions is presented.

  9. 1H MR spectroscopy in epilepsy

    The introduction to the application of 1H MR spectroscopy for clinical and research studies of mesial temporal and extratemporal epilepsies is done. The techniques of single voxel and spectroscopic imaging are discussed and the analysis of 1H MR spectra together with basic metabolic descriptions is presented

  10. Influence of Dry Etching Damage on the Internal Quantum Efficiency of Nanorod InGaN/GaN Multiple Quantum Wells

    The influence of dry etching damage on the internal quantum efficiency of InGaN/GaN nanorod multiple quantum wells (MQWs) is studied. The samples were etched by inductively coupled plasma (ICP) etching via a self-assembled nickel nanomask, and examined by room-temperature photoluminescence measurement. The key parameters in the etching process are rf power and ICP power. The internal quantum efficiency of nanorod MQWs shows a 5.6 times decrease substantially with the rf power increasing from 3 W to 100 W. However, it is slightly influenced by the ICP power, which shows 30% variation over a wide ICP power range between 30 W and 600 W. Under the optimized etching condition, the internal quantum efficiency of nanorod MQWs can be 40% that of the as-grown MQW sample, and the external quantum efficiency of nanorod MQWs can be about 4 times that of the as-grown one. (cross-disciplinary physics and related areas of science and technology)

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

    Tang, Jian-Shun; 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 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 multi-photons (multi-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 scal...

  12. Study of multiple InAs/GaAs quantum-well structures by electroreflectance spectroscopy

    Bolshakov, A. S., E-mail: bolsh-as@mail.ioffe.ru; Chaldyshev, V. V., E-mail: chald.gvg@mail.ioffe.ru; Babichev, A. V. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Kudryashov, D. A.; Gudovskikh, A. S.; Morozov, I. A.; Sobolev, M. S.; Nikitina, E. V. [Russian Academy of Sciences, Saint Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation)

    2015-11-15

    A periodic Bragg heterostructure with three ultrathin InAs/GaAs quantum wells in a period is fabricated and studied. The splitting energy of exciton transitions in quantum wells is determined by the electroreflectance- spectroscopy method and numerical quantum-mechanical calculation. The significant influence of interference effects on individual peak areas in the electroreflectance spectrum is detected.

  13. Effect of exciton oscillator strength on upconversion photoluminescence in GaAs/AlAs multiple quantum wells

    Kojima, Osamu, E-mail: kojima@phoenix.kobe-u.ac.jp; Okumura, Shouhei; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Akahane, Kouichi [National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2014-11-03

    We report upconversion photoluminescence (UCPL) in GaAs/AlAs multiple quantum wells. UCPL from the AlAs barrier is caused by the resonant excitation of the excitons in the GaAs well. When the quantum well has sufficient miniband width, UCPL is hardly observed because of the small exciton oscillator strength. The excitation-energy and excitation-density dependences of UCPL intensity show the exciton resonant profile and a linear increase, respectively. These results demonstrate that the observed UCPL caused by the saturated two-step excitation process requires a large number of excitons.

  14. Continuous-variable quantum teleportation with non-Gaussian entangled states generated via multiple-photon subtraction and addition

    Wang, Shuai; Chen, Xian-Feng; Xu, Xue-Fen

    2014-01-01

    We investigate the Einstein-Podolsky-Rosen correlation (EPR), the quadrature squeezing and the continuous variable quantum teleportation when considering non-Gaussian entangled states generated by applying multiple-photon addition and multiple-photon subtraction to a two-mode squeezed vacuum state (TMSVs). Our results indicate that, in the case of symmetric multiple-photon-subtracted TMSVs, the corresponding EPR correlation, the two-mode squeezing, the sum squeezing and the fidelity of teleporting a coherent state and a squeezed vacuum state can be enhanced for any squeezing parameter $r$, and these enhancements increase with the number of the operations in small-squeezing regime. While asymmetric multiple-photon subtractions will generally reduce these quantities. For the multiple-photon added TMSVs, although it holds stronger entanglement, its EPR correlation, two-mode squeezing, sum squeezing and the fidelity of a coherent state are always smaller than that of the TMSVs. Only when considering teleporting a...

  15. Multiple-Resonance Local Wave Functions for Accurate Excited States in Quantum Monte Carlo.

    Zulfikri, Habiburrahman; Amovilli, Claudio; Filippi, Claudia

    2016-03-01

    We introduce a novel class of local multideterminant Jastrow-Slater wave functions for the efficient and accurate treatment of excited states in quantum Monte Carlo. The wave function is expanded as a linear combination of excitations built from multiple sets of localized orbitals that correspond to the bonding patterns of the different Lewis resonance structures of the molecule. We capitalize on the concept of orbital domains of local coupled-cluster methods, which is here applied to the active space to select the orbitals to correlate and construct the important transitions. The excitations are further grouped into classes, which are ordered in importance and can be systematically included in the Jastrow-Slater wave function to ensure a balanced description of all states of interest. We assess the performance of the proposed wave function in the calculation of vertical excitation energies and excited-state geometry optimization of retinal models whose π → π* state has a strong intramolecular charge-transfer character. We find that our multiresonance wave functions recover the reference values of the total energies of the ground and excited states with only a small number of excitations and that the same expansion can be flexibly used at very different geometries. Furthermore, significant computational saving can also be gained in the orbital optimization step by selectively mixing occupied and virtual orbitals based on spatial considerations without loss of accuracy on the excitation energy. Our multiresonance wave functions are therefore compact, accurate, and very promising for the calculation of multiple excited states of different character in large molecules. PMID:26761421

  16. Carrier localization effect in polarized InGaN multiple quantum wells

    Carrier localization effects in polarized InGaN/GaN multiple quantum wells (MQWs) were investigated as a function of well width, d, and In content, x. Using photoreflectance (PR), photoluminescence (PL), PL excitation (PLE), selective excitation of PL, PL excitation power, and time-resolved PL spectroscopy, the dominance of the localization effect against the built-in field effect on carrier recombination dynamics in InxGa1-xN MQWs of different well width (d = 2.0-4.0 nm, x ∼ 0.15) and In content (x ∼ 0.22-0.27, d = 2.5 nm) was revealed. Based on the modeling of the PL spectra by Monte Carlo simulation of exciton hopping and the spectroscopic reference provided by PR, increased In content and well width were found to increase the band potential fluctuations and carrier localization depth. The density of localized states deduced from the simulation was found to be in a fair agreement with the PLE data. The built-in field strength in InGaN QWs containing 15% of In was estimated to be of 0.5 MV/cm. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    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.

  18. Anomalous disorder-related phenomena in InGaN/GaN multiple quantum well heterosystems

    Hu, Y.-J. [Department of Electrical Engineering, Technology and Science Institute of Northern Taiwan, Taipei 112, Taiwan (China); Huang, Y.-W.; Fang, C.-H.; Wang, J.-C.; Chen, Y.-F. [Group of Abel and Lie Operations In Sciences and Quantum Electro-optical Science and Technology Laboratory (GALOIS-Quest-Lab), Department of Electronic Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan (China); Nee, T.-E., E-mail: neete@mail.cgu.edu.t [Group of Abel and Lie Operations In Sciences and Quantum Electro-optical Science and Technology Laboratory (GALOIS-Quest-Lab), Department of Electronic Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan (China)

    2010-06-15

    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.

  19. Vertical coupling in multiple stacks quantum-dot semiconductor optical amplifiers

    The characteristics of vertically coupled multiple stacks quantum-dot (QD) semiconductor optical amplifiers (SOAs) are studied taking into account the effect of carrier coupling between adjacent stacks. We find that QD-SOAs that consist of a few numbers of stacks provide higher optical gain at lower applied current. Our analysis shows that the optical gain of the amplifier can be considerably enhanced due to short tunnelling lifetimes between adjacent stacks. Also, our analysis reveals that short coupling lifetimes can significantly reduce the transparency current and improve the uniformity of the active region since the net coupling rate is a linear function of the injection rate. Long coupling lifetime, on the other hand, produces non-linear and non-uniform coupling rates, which reduce the optical gain and increase the transparency current of the amplifier. We also find that the degradation in the unsaturated optical gain due to long coupling lifetimes is more severe in p-type doped QD-SOA compared with un-doped QD-SOA.

  20. Anisotropy mapping in rat brains using Intermolecular Multiple Quantum Coherence Effects

    Han, Yi

    2014-01-01

    This document reports an unconventional and rapidly developing approach to magnetic resonance imaging (MRI) using intermolecular multiple-quantum coherences (iMQCs). Rat brain images are acquired using iMQCs. We detect iMQCs between spins that are 10 {\\mu}m to 500 {\\mu}m apart. The interaction between spins is dependent on different directions. We can choose the directions on physical Z, Y and X axis by choosing correlation gradients along those directions. As an important application, iMQCs can be used for anisotropy mapping. In the rat brains, we investigate tissue microstructure. We simulated images expected from rat brains without microstructure. We compare those with experimental results to prove that the dipolar field from the overall shape only has small contributions to the experimental iMQC signal. Because of the underlying low signal to noise ratio (SNR) in iMQCs, this anisotropy mapping method still has comparatively large potentials to grow. The ultimate goal of my project is to develop creative a...

  1. Carrier localization effect in polarized InGaN multiple quantum wells

    Zukauskas, A.; Kazlauskas, K.; Tamulaitis, G.; Mickevicius, J.; Jursenas, S.; Kurilcik, G.; Miasojedovas, S. [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio al. 9, Build. III, 10222 Vilnius (Lithuania); Springis, M.; Tale, I. [Institute of Solid State Physics, University of Latvia, Kengaraga iela 8, Riga 1063 (Latvia); Cheng, Yung-Chen; Wang, Hsiang-Chen; Huang, Chi-Feng; Yang, C.C. [Graduate Institute of Electro-Optical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei (Taiwan)

    2005-05-01

    Carrier localization effects in polarized InGaN/GaN multiple quantum wells (MQWs) were investigated as a function of well width, d, and In content, x. Using photoreflectance (PR), photoluminescence (PL), PL excitation (PLE), selective excitation of PL, PL excitation power, and time-resolved PL spectroscopy, the dominance of the localization effect against the built-in field effect on carrier recombination dynamics in In{sub x}Ga{sub 1-x}N MQWs of different well width (d = 2.0-4.0 nm, x {approx} 0.15) and In content (x {approx} 0.22-0.27, d = 2.5 nm) was revealed. Based on the modeling of the PL spectra by Monte Carlo simulation of exciton hopping and the spectroscopic reference provided by PR, increased In content and well width were found to increase the band potential fluctuations and carrier localization depth. The density of localized states deduced from the simulation was found to be in a fair agreement with the PLE data. The built-in field strength in InGaN QWs containing 15% of In was estimated to be of 0.5 MV/cm. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Analytical and numerical study of GaAs/AlGaAs based multiple quantum wells heigh electron mobility transistors (HEMTs)

    Nawaz, M.; Jensen, G.U.

    1995-02-01

    The authors have developed an analytical charge control model for GaAs/AlGaAs multiple quantum wells based Highly Electron Mobility Transistors (HEMTs). The validity of the developed model was tested with a separate numerical calculation based on self consistent solution of Poisson and Schroedinger equations. The analytical expressions for dependence of sheet charge density on the gate bias for different quantum well structures developed in this model, provides excellent agreement with numerical results as well as experimental data. Furthermore, simple expressions are developed for location of sheet charge density from the top and bottom interfaces inside the GaAs quantum well. This model provides a good tool for the design and optimization of microwave circuit design. 12 refs., 7 figs.

  3. The influence of quasi-quantum dots on the physical properties of blue InGaN/GaN multiple quantum wells

    Lai, Y-L [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan (China); Liu, C-P [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan (China); Hsueh, T-H [Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, Taiwan (China); Lin, Y-H [Department of Electronic Engineering, Chang Gung University, KweiShan, TaoYuan, Taiwan (China); Chung, H-C [Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan (China); Lin, R-M [Department of Electronic Engineering, Chang Gung University, KweiShan, TaoYuan, Taiwan (China); Chen, Z-Q [Genesis Photonics Inc, Hsien, Tainan, Taiwan (China)

    2006-09-14

    The effect of barrier growth temperatures on blue InGaN (2 nm)/GaN (12 nm) multiple quantum wells was studied with samples grown by metallorganic chemical vapour deposition. It was found that InGaN active layers composed of InGaN quasi-dots of 2 {+-} 0.2 nm in diameter, changing from their homogeneous nature, could be obtained by elevating the barrier growth temperature from 700 to 800 deg. C based on the results of energy-filtered high resolution transmission electron microscopy. These dots may have formed during the ramping process by in situ annealing. Strong piezoelectric field, 'S-shape-like' carrier transition and high internal quantum efficiency of 71.3% were observed in the sample with a higher barrier growth temperature closely related to the dot formation. Furthermore, the forward voltage and the light output power at 20 mA of light emitting diodes from the sample with dots were 0.3 V lower and 11% higher than that from the homogeneous multiple quantum wells.

  4. The influence of quasi-quantum dots on the physical properties of blue InGaN/GaN multiple quantum wells

    The effect of barrier growth temperatures on blue InGaN (2 nm)/GaN (12 nm) multiple quantum wells was studied with samples grown by metallorganic chemical vapour deposition. It was found that InGaN active layers composed of InGaN quasi-dots of 2 ± 0.2 nm in diameter, changing from their homogeneous nature, could be obtained by elevating the barrier growth temperature from 700 to 800 deg. C based on the results of energy-filtered high resolution transmission electron microscopy. These dots may have formed during the ramping process by in situ annealing. Strong piezoelectric field, 'S-shape-like' carrier transition and high internal quantum efficiency of 71.3% were observed in the sample with a higher barrier growth temperature closely related to the dot formation. Furthermore, the forward voltage and the light output power at 20 mA of light emitting diodes from the sample with dots were 0.3 V lower and 11% higher than that from the homogeneous multiple quantum wells

  5. Dynamic stereochemistry of erigeroside by measurement of 1H- 1H and 13C- 1H coupling constants

    Tafazzoli, Mohsen; Ghiasi, Mina; Moridi, Mahdi

    2008-07-01

    Erigeroside was extracted from Satureja khuzistanica Jamzad (Marzeh Khuzistani in Persian, family of lamiaceae), and 1H, 13C, 13C{ 1H}, 1H- 1H COSY, HMQC and J-HMBC were obtained to identify this compound and determine a complete set of J-coupling constants ( 1JC-H, 2JC-H, 3JC-H and 3JH-H) values within the exocyclic hydroxymethyl group (CH 2OH) and anomeric center. In parallel, density functional theory (DFT) using B3LYP functional and split-valance 6-311++G** basis set has been used to optimized the structures and conformers of erigeroside. In all calculations solvent effects were considered using a polarized continuum (overlapping spheres) model (PCM). The dependencies of 1J, 2J and 3J involving 1H and 13C on the C 5'-C 6' ( ω), C 6'-O 6' ( θ) and C 1'-O 1' ( φ) torsion angles in erigeroside were computed using DFT method. Complete hyper surfaces for 1JC1',H1', 2JC5',H6'R, 2JC5',H6'S, 2JC6',H5', 3JC4',H6'R, 3JC4',H6'S and 2JH6'R-H5'S as well as 3JH5',H6'R were obtained and used to derive Karplus equations to correlate these couplings to ω, θ and φ. These calculated J-couplings are in agreement with experimental values. These results confirm the reliability of DFT calculated coupling constants in aqueous solution.

  6. Correlation between dark current RTS noise and defects for AlGaInP multiple-quantum-well laser diode

    The correlation model between dark current RTS noise and defects for AlGaInP multiple-quantum-well laser diode is derived. Experimental results show that dark current RTS noise caused carrier number fluctuations at the interface of the heterojunction in the active region. According to this correlation model, the defect types are determined, and the defects' energy levels are quantitatively determined. The corner frequency of RTS noise power spectral density is analyzed. The experimental results are in good agreement with the theoretical. This result provided an effective method for estimating the deep-level traps in the active region of AlGaInP multiple quantum well laser diode. (semiconductor devices)

  7. Photoexcited electron and hole dynamics in semiconductor quantum dots: phonon-induced relaxation, dephasing, multiple exciton generation and recombination.

    Kim, Hyeon-Deuk; Prezhdo, Oleg V.

    2012-01-01

    Photoexcited dynamics of electrons and holes in semiconductor quantum dots (QD), including phonon-induced relaxation, multiple exciton generation, fission and recombination (MEG, MEF and MER), were simulated by combining ab initio time-dependent density functional theory and non-adiabatic molecular dynamics. These nonequilibrium phenomena govern the optical properties and photoexcited dynamics of QDs, determining the branching between electronic processes and thermal energy losses. Our approa...

  8. Demonstration of optically controlled data routing with the use of multiple-quantum-well bistable and electro-optical devices

    Koppa, Pàl; Chavel, Pierre; Oudar, Jean-Louis; Kuszelewicz, Robert; Schnell, Jean-Philippe; Pocholle, Jean-Paul

    1997-01-01

    We present experimental results on a 1-to-64-channel free-space photonic switching demonstration system based on GaAs/GaAlAs multiple-quantum-well active device arrays. Two control schemes are demonstrated: data transparent optical self-routing usable in a packet-switching environment and direct optical control with potential signal amplification for circuit switching. The self-routing operation relies on the optical recognition of the binary destination address coded in each packet header. A...

  9. Multiple quantum NMR of spin-carrying molecules in nanopores: high order corrections to the two-spin/two-quantum Hamiltonian

    Doronina, Sergei I; Fel’dmana, Edward B; Zenchuka, Alexander I

    2010-01-01

    This paper is devoted to the multiple-quantum (MQ) NMR spectroscopy in nanopores filled by a gas of spin-carrying molecules (s=1/2) in the strong external magnetic field. It turned out that the high symmetry of the spin system in nanopores yields a possibility to overcome the problem of the exponential growth of the Hilbert space dimension with an increase in a number of spins and to investigate MQ NMR dynamics in systems consisting of several hundreds of spins. We investigate the dependence of the MQ coherence intensities on their order (the profile of the MQ coherence intensities) for the spin system governed by the standard MQ NMR Hamiltonian (the nonsecular two-quantum/two-spin Hamiltonian) together with the second order correction of the average Hamiltonian theory. It is shown that the profile depends on the value of this correction and varies from the exponential to the logarithmic one.

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

    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.

  11. Quantum

    Al-Khalili, Jim

    2003-01-01

    In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.

  12. Role of thermal stress on the magnetophonon peak structure in the parallel transport of the GaAs/AlGaAs multiple quantum wells

    The magnetophonon resonance in parallel transport of two types multiple quantum wells was studied. The transverse magnetresonance was measured in pulsed magnetic fields up to 30 T (within temperature region from 77 to 340 K). A fine structure of magnetophonon resonance peaks which depends on temperature and does not depend on the type of multiple quantum wells, was observed. This effect could be attributed to two phenomena: contribution of barrier phonons and influence of thermostresses. (author)

  13. Correlation between the structural and cathodoluminescence properties in InGaN/GaN multiple quantum wells with large number of quantum wells

    Yang, Jing; Zhao, Degang, E-mail: dgzhao@red.semi.ac.cn; Jiang, Desheng; Chen, Ping; Zhu, Jianjun; Liu, Zongshun; Le, Lingcong; He, Xiaoguang; Li, Xiaojing [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, PO BOX 912, Beijing 100083 (China); Wang, Hui; Yang, Hui [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Jahn, Uwe [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin (Germany)

    2014-09-01

    Cathodoluminescence (CL) characteristics on 30-period InGaN/GaN multiple quantum well (MQW) solar cell structures are investigated, revealing the relationship between optical and structural properties of the MQW structures with a large number of quantum wells. In the bottom MQW layers, a blueshift of CL peak along the growth direction is found and attributed to the decrease of indium content due to the compositional pulling effect. An obvious split of emission peak and a redshift of the main emission energy are found in the top MQW layers when the MQW grows above the critical layer thickness. They are attributed to the segregation of In-rich InGaN clusters rather than the increase of indium content in quantum well layer. The MQW structure is identified to consist of two regions: a strained one in the bottom, where the indium content is gradually decreased, and a partly relaxed one in the top with segregated In-rich InGaN clusters.

  14. Correlation between the structural and cathodoluminescence properties in InGaN/GaN multiple quantum wells with large number of quantum wells

    Cathodoluminescence (CL) characteristics on 30-period InGaN/GaN multiple quantum well (MQW) solar cell structures are investigated, revealing the relationship between optical and structural properties of the MQW structures with a large number of quantum wells. In the bottom MQW layers, a blueshift of CL peak along the growth direction is found and attributed to the decrease of indium content due to the compositional pulling effect. An obvious split of emission peak and a redshift of the main emission energy are found in the top MQW layers when the MQW grows above the critical layer thickness. They are attributed to the segregation of In-rich InGaN clusters rather than the increase of indium content in quantum well layer. The MQW structure is identified to consist of two regions: a strained one in the bottom, where the indium content is gradually decreased, and a partly relaxed one in the top with segregated In-rich InGaN clusters

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

    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

  16. Simultaneous SU(2) rotations on multiple quantum dot exciton qubits using a single shaped pulse

    Mathew, Reuble; Yang, Hong Yi Shi; Hall, Kimberley C.

    2015-10-01

    Recent experimental demonstration of a parallel (π ,2 π ) single qubit rotation on excitons in two distant quantum dots [Nano Lett. 13, 4666 (2013), 10.1021/nl4018176] is extended in numerical simulations to the design of pulses for more general quantum state control, demonstrating the feasibility of full SU(2) rotations of each exciton qubit. Our results show that simultaneous high-fidelity quantum control is achievable within the experimentally accessible parameter space for commercial Fourier-domain pulse shaping systems. The identification of a threshold of distinguishability for the two quantum dots (QDs) for achieving high-fidelity parallel rotations, corresponding to a difference in transition energies of ˜0.25 meV , points to the possibility of controlling more than 10 QDs with a single shaped optical pulse.

  17. Multiple Metamagnetic Quantum Criticality in Sr_{3}Ru_{2}O_{7}.

    Tokiwa, Y; Mchalwat, M; Perry, R S; Gegenwart, P

    2016-06-01

    Bilayer strontium ruthenate Sr_{3}Ru_{2}O_{7} displays pronounced non-Fermi liquid behavior at magnetic fields around 8 T, applied perpendicular to the ruthenate planes, which previously has been associated with an itinerant metamagnetic quantum critical end point (QCEP). We focus on the magnetic Grüneisen parameter Γ_{H}, which is the most direct probe to characterize field-induced quantum criticality. We confirm quantum critical scaling due to a putative two-dimensional QCEP near 7.845(5) T, which is masked by two ordered phases A and B, identified previously by neutron scattering. In addition, we find evidence for a QCEP at 7.53(2) T and determine the quantum critical regimes of both instabilities and the effect of their superposition. PMID:27314732

  18. Multiple Metamagnetic Quantum Criticality in Sr3 Ru2 O7

    Tokiwa, Y.; Mchalwat, M.; Perry, R. S.; Gegenwart, P.

    2016-06-01

    Bilayer strontium ruthenate Sr3 Ru2 O7 displays pronounced non-Fermi liquid behavior at magnetic fields around 8 T, applied perpendicular to the ruthenate planes, which previously has been associated with an itinerant metamagnetic quantum critical end point (QCEP). We focus on the magnetic Grüneisen parameter ΓH, which is the most direct probe to characterize field-induced quantum criticality. We confirm quantum critical scaling due to a putative two-dimensional QCEP near 7.845(5) T, which is masked by two ordered phases A and B , identified previously by neutron scattering. In addition, we find evidence for a QCEP at 7.53(2) T and determine the quantum critical regimes of both instabilities and the effect of their superposition.

  19. Decoherence-Free Subspaces for Multiple-Qubit Errors (II) Universal, Fault-Tolerant Quantum Computation

    Lidar, D A; Kempe, J; Whaley, K B; Lidar, Daniel A.; Bacon, David; Kempe, Julia

    2001-01-01

    Decoherence-free subspaces (DFSs) shield quantum information from errors induced by the interaction with an uncontrollable environment. Here we study a model of correlated errors forming an Abelian subgroup (stabilizer) of the Pauli group (the group of tensor products of Pauli matrices). Unlike previous studies of DFSs, this type of errors does not involve any spatial symmetry assumptions on the system-environment interaction. We solve the problem of universal, fault-tolerant quantum computation on the associated class of DFSs.

  20. Enhanced performance of InGaN/GaN multiple quantum well solar cells with double indium content

    Zhao Bi-Jun; Chen Xin; Ren Zhi-Wei; Tong Jin-Hui; Wang Xing-Fu; Li Dan-Wei; Zhuo Xiang-Jing

    2013-01-01

    The performance of a multiple quantum well (MQW) InGaN solar cell with double indium content is investigated.It is found that the adoption of a double indium structure can effectively broaden the spectral response of the external quantum efficiencies and optimize the overall performance of the solar cell.Under AM1.5G illumination,the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 65% and 13% compared with those of a normal single-indium-content MQW solar cell.These improvements are mainly attributed to the expansion of the absorption spectrum and better extraction efficiency of the photon-generated carriers induced by higher polarization.

  1. Constructing a Multiple-Choice Assessment For Upper-Division Quantum Physics From An Open-Ended Tool

    Sadaghiani, Homeyra; Pollock, Steven; Rehn, Daniel

    2013-01-01

    As part of an ongoing investigation of student learning in upper-division quantum mechanics, we needed a high-quality conceptual assessment instrument for comparing outcomes of different curricular approaches. The 14 item open-ended Quantum Mechanics Assessment Tool (QMAT) was previously developed for this purpose. However, open-ended tests require complex scoring rubrics, are difficult to score consistently, and demand substantial investment of faculty time to grade. Here, we present the process of converting open-ended questions to multiple-choice (MC) format. We highlight the construction of effective distractors and the use of student interviews to revise and validate questions and distractors. We examine other elements of the process, including results of a preliminary implementation of the MC assessment given at Cal Poly Pomona and CU Boulder.

  2. Storage and retrieval of vector beams of light in a multiple-degree-of-freedom quantum memory

    Parigi, V; Arnold, C; Marrucci, L; Sciarrino, F; Laurat, J

    2015-01-01

    The full structuration of light in the transverse plane, including intensity, phase and polarization, holds the promise of unprecedented capabilities for applications in classical optics as well as in quantum optics and information sciences. Harnessing special topologies can lead to enhanced focusing, data multiplexing or advanced sensing and metrology. Here we experimentally demonstrate the storage of such spatio-polarization-patterned beams into an optical memory. A set of vectorial vortex modes is generated via liquid crystal cell with topological charge in the optic axis distribution, and preservation of the phase and polarization singularities is demonstrated after retrieval, at the single-photon level. The realized multiple-degree-of-freedom memory can find applications in classical data processing but also in quantum network scenarios where structured states have been shown to provide promising attributes, such as rotational invariance.

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

    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.

  4. Multiple-quantum magic-angle spinning: high-resolution solid state NMR spectroscopy of half-integer quadrupolar nuclei

    Experimental and theoretical aspects of the multiple-quantum magic-angle spinning experiment (MQMAS) are discussed in this review. The significance of this experiment, introduced by Frydman and Harwood, is in its ability to provide high-resolution NMR spectra of half-integer quadrupolar nuclei (I /geq 3/2). This technique has proved to be useful in various systems ranging from inorganic materials to biological samples. This review addresses the development of various pulse schemes aimed at improving the signal-to-noise ratio and anisotropic lineshapes. Representative spectra are shown to underscore the importance and applications of the MQMAS experiment. Refs. 97 (author)

  5. Quantum Path Interference and Multiple Electron Scattering in Soft X-Ray High-Order Harmonic Generation

    Jozsef Seres

    2015-01-01

    Full Text Available High-order harmonic generation is an important mechanism to generate coherent radiation in the few–100-eV spectral range with ultrashort laser pulses. Moreover, a closer inspection of the measured spectra provides unique information about the underlying physics and allows deriving guidelines for improvements. The long-range modulation of the spectral envelope is linked to phase matching, and we will show how to improve it with a double-pulse excitation scheme. Additionally, the spectrum contains only every fourth harmonic, which can be well explained by the quantum interference of multiple scattered electrons, and two dominant electron trajectories were selected by X-ray parametric interaction.

  6. Spatial search by continuous-time quantum walk with multiple marked vertices

    Wong, Thomas G.

    2016-04-01

    In the typical spatial search problems solved by continuous-time quantum walk, changing the location of the marked vertices does not alter the search problem. In this paper, we consider search when this is no longer true. In particular, we analytically solve search on the "simplex of K_M complete graphs" with all configurations of two marked vertices, two configurations of M+1 marked vertices, and two configurations of 2(M+1) marked vertices, showing that the location of the marked vertices can dramatically influence the required jumping rate of the quantum walk, such that using the wrong configuration's value can cause the search to fail. This sensitivity to the jumping rate is an issue unique to continuous-time quantum walks that does not affect discrete-time ones.

  7. Generating free charges by carrier multiplication in quantum dots for highly efficient photovoltaics.

    Ten Cate, Sybren; Sandeep, C S Suchand; Liu, Yao; Law, Matt; Kinge, Sachin; Houtepen, Arjan J; Schins, Juleon M; Siebbeles, Laurens D A

    2015-02-17

    CONSPECTUS: In a conventional photovoltaic device (solar cell or photodiode) photons are absorbed in a bulk semiconductor layer, leading to excitation of an electron from a valence band to a conduction band. Directly after photoexcitation, the hole in the valence band and the electron in the conduction band have excess energy given by the difference between the photon energy and the semiconductor band gap. In a bulk semiconductor, the initially hot charges rapidly lose their excess energy as heat. This heat loss is the main reason that the theoretical efficiency of a conventional solar cell is limited to the Shockley-Queisser limit of ∼33%. The efficiency of a photovoltaic device can be increased if the excess energy is utilized to excite additional electrons across the band gap. A sufficiently hot charge can produce an electron-hole pair by Coulomb scattering on a valence electron. This process of carrier multiplication (CM) leads to formation of two or more electron-hole pairs for the absorption of one photon. In bulk semiconductors such as silicon, the energetic threshold for CM is too high to be of practical use. However, CM in nanometer sized semiconductor quantum dots (QDs) offers prospects for exploitation in photovoltaics. CM leads to formation of two or more electron-hole pairs that are initially in close proximity. For photovoltaic applications, these charges must escape from recombination. This Account outlines our recent progress in the generation of free mobile charges that result from CM in QDs. Studies of charge carrier photogeneration and mobility were carried out using (ultrafast) time-resolved laser techniques with optical or ac conductivity detection. We found that charges can be extracted from photoexcited PbS QDs by bringing them into contact with organic electron and hole accepting materials. However, charge localization on the QD produces a strong Coulomb attraction to its counter charge in the organic material. This limits the production

  8. 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

    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

  9. Photoluminescence temperature behavior and Monte Carlo simulation of exciton hopping in InGaN multiple quantum wells

    Kazlauskas, K.; Tamulatis, G.; Pobedinskas, P.; Zukauskas, A. [Institute of Materials Science and Applied Research, Vilnius University, Sauletekio 9, Build. III, 10222 Vilnius (Lithuania); Huang, Chi-Feng; Cheng, Yung-Chen; Wang, Hsiang-Chen; Yang, C.C. [Graduate Institute of Electro-Optical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei (Taiwan)

    2005-05-01

    Application of Monte Carlo simulation of exciton (carrier) hopping for the analysis of the photoluminescence (PL) temperature behavior in In{sub 0.2}Ga{sub 0.8}N/GaN multiple quantum wells is reported. The PL linewidth and peak position measured in the 10-300 K range exhibited a W-shaped and S-shaped temperature behavior, respectively. The W-shaped linewidth dependence was fitted with the results of Monte Carlo simulation, which involved phonon-assisted exciton hopping through energy states confined in the band potential fluctuation minima. The simulation yielded the values of the standard deviation for potential fluctuations within In-rich regions (31 meV), dispersion of the average exciton energy in different regions (29 meV), and the temperature dependence of the band gap, which was found to be in a fair agreement with the photoreflectance data. Our results, which infer in-plane motion of localized excitons within the wells, are consistent with the model of large In-rich regions (''segmented quantum wells'' or ''quantum discs'') with band potential fluctuations inside these regions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    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.

  11. Highly efficient flexible organic light-emitting devices utilizing F4-TCNQ/m-MTDATA multiple quantum well structures

    Wu Xiaoming, E-mail: wxm@mail.nankai.edu.cn [School of Materials Science and Engineering, Tianjin University of Technology, Key Laboratory of Display Materials and Photoelectric devices, Ministry of Education, Tianjin Key Laboratory of Photoelectric Materials and Devices, Tianjin 300384 (China); Shen Liying; Hua Yulin; Dong Musen; Su Yueju; Jiao Zhiqiang; Yang Xiaoyan; Yin Shougen [School of Materials Science and Engineering, Tianjin University of Technology, Key Laboratory of Display Materials and Photoelectric devices, Ministry of Education, Tianjin Key Laboratory of Photoelectric Materials and Devices, Tianjin 300384 (China)

    2012-05-15

    Flexible organic light-emitting devices (FOLEDs) based on multiple quantum well (MQW) structures, which consist of alternate layers of 2,3,5,6-Tetrafluoro-7,7,8,8,-tetracyano-quinodimethane (F4-TCNQ) and 4,4 Prime ,4 Double-Prime -tris-(3-methylphenylphe-nylamino)tripheny-lamine (m-MTDATA) have been fabricated. The Alq{sub 3}-based device with double quantum well (DQW) structure exhibits the remarkable electroluminescent (EL) performances for the brightness of 23,500 cd/m{sup 2} at 14 V and the maximum current efficiency of 7.0 cd/A at 300.3 mA/cm{sup 2}, respectively, which are greatly improved by 114% and 56% compared with the brightness of 10,958 cd/m{sup 2} at 14 V and the maximum current efficiency of 4.5 cd/A at 174.0 mA/cm{sup 2} for the conventional device without MQW structures. These results demonstrate that the EL performances of FOLEDs could be greatly improved by utilizing the novel MQW structures, and the reason for this improvement has also been explained by the effect of interfacial dipole and interfacial doping between F4-TCNQ and m-MTDATA in this article. - Highlights: Black-Right-Pointing-Pointer We introduce multiple-quantum-well structures in flexible OLEDs for the first time. Black-Right-Pointing-Pointer The MQW structures consist of alternate layers of F4-TCNQ and m-MTDATA. Black-Right-Pointing-Pointer The EL performances of FOLEDs are greatly improved by utilizing these MQW structures.

  12. Optical polarisation anisotropy in a-plane GaN/AlGaN multiple quantum well structures

    Badcock, Tom J.; Dawson, Philip [School of Physics and Astronomy, Photon Science Institute, Alan Turing Building, University of Manchester, Manchester, M13 9PL (United Kingdom); Kappers, Menno J.; McAleese, Clifford; Hollander, Jonathan L.; Johnston, Carol F.; Sridhara Rao, Duggi V.; Sanchez, Ana M.; Humphreys, Colin J. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom)

    2009-06-15

    In this paper we report on the optical properties of a series of a-plane GaN/AlGaN multiple quantum well structures of varying well width. The low temperature photoluminescence spectrum of each structure is characterised by two distinct emission bands, both of which shift to higher energy with decreasing well thickness. The origin of the lower energy emission band is attributed to the recombination of carriers trapped in regions of the quantum wells intersected by basal plane stacking faults. The higher energy feature is assigned to localised exciton recombination at well width fluctuations. We have used photoluminescence excitation spectroscopy to reveal details of the bandstructure of the quantum wells. Excitation with unpolarised light resulted in the observation of exciton transitions associated with the n = 1 and n = 2 electron sub-bands. For linearly polarised (E perpendicular to c and E parallel c) excitation, both the transitions observed with unpolarised light were shown to consist of overlapping transitions involving heavy and light hole like valence subbands. Their observed polarisation anisotropy was attributed to anisotropic biaxial compressive strain in the GaN film. As well as the exciton transitions we were also able to resolve well defined continuum edges in some of the excitation spectra. This enabled us to estimate the exciton binding energy of the n=1 heavy and light hole states for quantum wells of differing width. Values were found to lie in the range of 38 to 76 {+-}5 meV. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Quantum Darwinism

    Zurek, Wojciech H [Los Alamos National Laboratory

    2008-01-01

    Quantum Darwinism - proliferation, in the environment, of multiple records of selected states of the system (its information-theoretic progeny) - explains how quantum fragility of individual state can lead to classical robustness of their multitude.

  14. Ultrafast Supercontinuum Spectroscopy of Carrier Multiplication and Biexcitonic Effects in Excited States of PbS Quantum Dots

    Sfeir M. Y.; Gesuele, F.; Koh, W.-K.; Murray, C.B.; Heinz, T.F.; Wong, C.W.

    2012-06-01

    We examine the population dynamics of multiple excitons in PbS quantum dots using spectrally resolved ultrafast supercontinuum transient absorption (SC-TA) measurements. We simultaneously probe the first three excitonic transitions. The transient spectra show the presence of bleaching of absorption for the 1S{sub h}-1S{sub e} transition, as well as transients associated with the 1P{sub h}-1P{sub e} transition. We examine signatures of carrier multiplication (multiple excitons arising from a single absorbed photon) from analysis of the bleaching features in the limit of low absorbed photon numbers (multiple-exciton generation is discussed both in terms of the ratio between early- to long-time transient absorption signals and of a broadband global fit to the data. Analysis of the population dynamics shows that bleaching associated with biexciton population is red shifted with respect to the single exciton feature, which is in accordance with a positive binding energy for the biexciton.

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

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

    2016-04-01

    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.

  16. Very high efficiency photovoltaic cells based on fully organic multiple quantum wells. Quarterly technical progress report, 15 February 1995--15 May 1995

    Forrest, S R [Princeton Univ., NJ (United States)

    1997-03-01

    The principal project objective is to demonstrate relatively high solar conversion efficiency using extremely low-cost, thin-film technology based on crystalline organic multiple quantum well (MQW) photovoltaic cells. The authors base their work on recent observations both in the laboratory and elsewhere that have indicated the quantum efficiency of organic photoconductors based on vacuum-deposited thin films can be increased by at least two orders of magnitude (to at least 10%) if the organic films are grown in a highly ordered manner, and if organic multiple quantum wells are used in the absorption region. The authors are investigating the physical origin of this phenomenon, and they are growing thin-film MQW cells that demonstrate relatively high quantum efficiencies to determine the practicality of crystalline organic thin-film cells for solar power applications. The investigations are based on a unique, ultrahigh-vacuum organic molecular beam deposition system in the laboratory.

  17. Quantum gauge confinement of multiple quarks based on the homogeneous 5D projection theory

    Wong, K W; Jungner, H

    2015-01-01

    A quick and simplified review of the 5D quantum field theory is presented. The role of topological mapping, which must preserve gauge invariance, is done in two ways, leading to the realization of the gauge transformation in the 5D space-time becoming two separate gauge constraints, one for the multi-quark state quark constituents, while the other is the quantum confinement imposed on the gluon potentials, formed from products of vector potentials generated by products of the fractional charged quark currents. The procedure presented clearly shows multi-quark states can be designed and that they can be verified by experiments, such as the penta-quark state reported. Based on these gauge constraints we propose the existence of 4, 5 and 6 quark states.

  18. 1H NMR in a-Si

    Carlos, W. E.; Taylor, P. C.

    1982-10-01

    Results of pulsed NMR studies of hydrogen in a-Si: H prepared at several laboratories by glow discharge of silane are presented. The origins of the two 1H NMR lines seen in almost all samples of a-Si: H are discussed. Solid-echo measurements are presented which indicate that these two components are due to spatially isolated groups of protons. We attribute the narrow line to protons slightly clustered in the bulk of the material and the broad line to protons distributed on internal surfaces. The spin-lattice relaxation time shows a minimum at T~30 K which is interpreted as due to relaxation via spin diffusion to a small number of H2 molecules acting as relaxation centers. Annealing results suggest that all the hydrogen molecules are trapped in very similar sites.

  19. Quantum spin chains of Temperley-Lieb type: periodic boundary conditions, spectral multiplicities and finite temperature

    Aufgebauer, Britta; Kluemper, Andreas

    2010-01-01

    We determine the spectra of a class of quantum spin chains of Temperley-Lieb type by utilizing the concept of Temperley-Lieb equivalence with the S=1/2 XXZ chain as a reference system. We consider open boundary conditions and in particular periodic boundary conditions. For both types of boundaries the identification with XXZ spectra is performed within isomorphic representations of the underlying Temperley-Lieb algebra. For open boundaries the spectra of these models differ from the spectrum ...

  20. A numerical study of the quantum oscillations in multiple dangling rings

    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

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

    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.

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

    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

  3. Optical Study of Exciton Localization Phenomena in Semimagnetic Semiconductors and Their Multiple Quantum Wells.

    Zhang, Xi-Cheng

    1986-12-01

    The results of picosecond photomodulation and photoluminescence spectroscopies in novel II-VI semimagnetic semiconductors Cd(,1-x)Mn(,x)Te (x CdTe/Cd(,1 -x)Mn(,x)Te MQW samples at low temperature shows intense excitonic emission where their radiative quantum efficiencies are two or three orders of magnitude larger than that of the high quality CdTe bulk samples. Time-resolved photoluminescence shows that the excitons have relatively short lifetime (500 picosecond). High quantum efficiency and short exciton lifetime suggest that the radiative recombination is a dominating factor in the excitonic-decay processes in the MQW samples. In general, excitonic emission energies in CdMnTe MQW samples are lower than the free exciton energies (typically 20-40 meV lower as noted from the reflectance spectra). The behavior of these emissions under an external magnetic field (up to 36 tesla) shows that excitons prefer to be localized at the heterointerfaces rather than at the center of the wells in MQW samples. The kinetics of the free and the heterointerface localized excitons in the Cd(,1-x)Mn(,x)Te/Cd(,1-y)Mn(,y)Te MQW samples have been studied by using a transient photoluminescence technique. Exciton lifetimes have been measured in several samples with various quantum well widths. The trapping time of the free exciton localized at the interface has been observed in the wide quantum well samples. The average energy loss rate of localized excitons has been calculated. The resonance excitation spectra of steady-state and transient luminescence show that the exciton spectra are spatially inhomogeneously broadened. An external magnetic field accelerates the localized exciton recombination processes. The dynamics of the excitons in CdMnTe MQW samples suggests that quasi-2D bound magnetic polarons (BMP) exist. A discussion of this quasi-2D BMP and the influence of an external magnetic field on exciton lifetime and exciton dynamics in Cd(,1 -x)Mn(,x)Te MQW is included.

  4. Localization effect in green light emitting InGaN/GaN multiple quantum wells with varying well thickness

    Liu, W. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); School of Electronic and Electrical Engineering, Chongqing University of Arts and Sciences, Chongqing 402160 (China); Zhao, D.G., E-mail: dgzhao@red.semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Jiang, D.S.; Chen, P.; Liu, Z.S.; Zhu, J.J.; Shi, M.; Zhao, D.M.; Li, X. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Liu, J.P.; Zhang, S.M.; Wang, H. [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Yang, H. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2015-03-15

    Highlights: • A macroscopic method is used to investigate the microscopic localization effect. • Two origins of localization states in InGaN quantum wells are distinguished. • The composition-related deep localization states dominate luminescence in thin wells. • The shallow localization states dominate luminescence in thick wells. - Abstract: Green light emitting InGaN/GaN multiple-quantum-well (MQW) structures with varying well thickness are grown via metal-organic chemical vapor deposition (MOCVD). The localization effect in these samples is studied by means of temperature-dependent photoluminescence (PL) measurements. The S-shape shift of PL peak energy with increasing temperature is observed, from which the extent of localization effect is determined quantitatively by using a band-tail model. It is found that the composition-related deep localization states dominate the light emission in thin-well MQWs, while in thick-well MQWs the shallow localization states induced by the fluctuations of InGaN well thickness dominate the luminescence efficiency. It is considered that in the thinner wells the improved emitting efficiency may partially originate from the stronger localization effect.

  5. Intra-acceptor hole relaxation in Be 5-doped GaAs/A1As multiple quantum wells

    Li Su-Mei; Zheng Wei-Min; Song Ying-Xin; Liu Jing; Chu Ning-Ning

    2009-01-01

    This paper studies the dynamics of intra-acceptor hole relaxation in Be 5-doped GaAs/AlAs multiple quantum wells (MQW) with doping at the centre by time-resolved pump-probe spectroscopy using a picosecond free electron laser for infrared experiments. Low temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of the Be acceptor from the ground state to the first three odd-parity excited states respectively.The pump-probe experiments are performed at different temperatures and different pump pulse wavelengths. The hole relaxation time from 2p excited state to ls ground state in MQW is found to be much shorter than that in bulk GaAs,and shown to be independent of temperature but strongly dependent on wavelength. The zone-folded acoustic phonon emission and slower decay of the wavefunctions of impurity states are suggested to account for the reduction of the 2p excited state lifetime in MQW. The wavelength dependence of the 2p lifetime is attributed to the diffusion of the Be atom 5-layer in quantum wells.

  6. Localization effect in green light emitting InGaN/GaN multiple quantum wells with varying well thickness

    Highlights: • A macroscopic method is used to investigate the microscopic localization effect. • Two origins of localization states in InGaN quantum wells are distinguished. • The composition-related deep localization states dominate luminescence in thin wells. • The shallow localization states dominate luminescence in thick wells. - Abstract: Green light emitting InGaN/GaN multiple-quantum-well (MQW) structures with varying well thickness are grown via metal-organic chemical vapor deposition (MOCVD). The localization effect in these samples is studied by means of temperature-dependent photoluminescence (PL) measurements. The S-shape shift of PL peak energy with increasing temperature is observed, from which the extent of localization effect is determined quantitatively by using a band-tail model. It is found that the composition-related deep localization states dominate the light emission in thin-well MQWs, while in thick-well MQWs the shallow localization states induced by the fluctuations of InGaN well thickness dominate the luminescence efficiency. It is considered that in the thinner wells the improved emitting efficiency may partially originate from the stronger localization effect

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

    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)

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

    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.

  9. Electronic and Optical Properties of GaN / AlN Multiple Quantum Wells under Static External Magnetic Field

    M. Solaimani

    2013-07-01

    Full Text Available In this work, we have investigated the effect of an external magnetic field and, for the first time, number of wells with constant total effective length to study the degeneracy in electronic energy levels. We have used constant total effective length because it is technologically important. Then we have tried to remove the n-fold degeneracy of the n-well multiple quantum well by means of the external magnetic field but the two-fold degeneracy was remain and not removed. Finally, the effect of the external magnetic field on the number of bound states and the situation of unchanging absorption coefficient in a wide magnetic field interval are also investigated.

  10. CdTe-Cd1 - xMnxTe multiple quantum well structures grown by pulsed laser evaporation and epitaxy

    Dubowski, J. J.; Roth, A. P.; Wasilewski, Z. R.; Rolfe, S. J.

    1991-09-01

    Structural and optical properties of (001) CdTe-Cd1-xMnxTe (x=0.10) multiple quantum well structures grown by pulsed laser evaporation and epitaxy (PLEE) are investigated. The layers are grown on (001) CdZnTe wafers held at a temperature in the range of 210-230 °C. Secondary-ion mass spectroscopy in-depth profiles reveal that highly uniform structures are grown. Numerical analysis of double crystal x-ray diffraction results demonstrates high structural quality of the layers and indicates partial relaxation of the strain in these structures. Low-temperature photoluminescence exhibits excitonic recombinations in the CdTe wells whereas photoluminescence from the Cd1-xMnxTe barriers is not observed. The chemical composition of the barriers deduced from photoluminescence is in excellent agreement with the intended chemical composition set during growth.

  11. Growth of GaNAs/GaAs multiple quantum well by molecular beam epitaxy using modulated N radical beam source

    GaNAs/GaAs multiple quantum well (MQW) structures have been grown on GaAs(001) substrates by molecular beam epitaxy (MBE) using modulated N radical beam source under optimized conditions, wherein the amount of N2 gas flow, RF-power and shutter sequence are systematically controlled. Clear and flat GaNAs/GaAs interfaces were observed in the cross-sectional transmission electron microscopy (TEM) measurements. Fine MQW structures originating from the precise control of the modulated N radical beam have been demonstrated as clear satellite peaks from the X-ray diffraction (XRD) measurements and sharp photoluminescence (PL) peaks. The step-like behaviors in the absorption spectra which reflect the density of state in two-dimensional systems, were clearly observed for all MQW samples. (authors)

  12. Integrated p–n junction InGaN/GaN multiple-quantum-well devices with diverse functionalities

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

    2016-05-01

    We propose, fabricate, and demonstrate integrated p–n junction InGaN/GaN multiple-quantum-well devices with diverse functionalities on a GaN-on-silicon platform. Suspended devices with a common n-contact are realized using a wafer-level process. For the integrated devices, part of the light emitted by a light-emitting diode (LED) is guided in-plane through a suspended waveguide and is sensed by another photodiode. The induced photocurrent is tuned by the LED. The integrated devices can act as two independent LEDs to deliver different signals simultaneously for free-space visible light communication. Furthermore, the suspended devices can be used as two separate photodiodes to detect incident light with a distinct on/off switching performance.

  13. Enhanced performance of InGaN/GaN multiple quantum well solar cells with patterned sapphire substrate

    In this paper, the enhanced performance of InGaN/GaN multiple quantum well solar cells grown on patterned sapphire substrates (PSS) was demonstrated. The short-circuit current (Jsc) density of the solar cell grown on PSS showed an improvement of 60%, compared to that of solar cells grown on conventional sapphire substrate. The improved performance is primarily due to the reduction of edge dislocations and the increased light absorption path by the scattering from the textured surface of the PSS. It shows that the patterned sapphire technology can effectively alleviate the problem of high-density dislocations and low Jsc caused by thinner absorption layers of the InGaN based solar cell, and it is promising to improve the efficiency of the solar cell. (semiconductor devices)

  14. Quantum Jarzynski equality with multiple measurement and feedback for isolated system

    Shubhashis Rana; Sourabh Lahiri; A M Jayannavar

    2012-08-01

    In this paper, we derive the Jarzynski equality (JE) for an isolated quantum system in three different cases: (i) the full evolution is unitary with no intermediate measurements, (ii) with intermediate measurements of arbitrary observables being performed, and (iii) with intermediate measurements whose outcomes are used to modify the external protocol (feedback). We assume that the measurements will involve errors that are purely classical in nature. Our treatment is based on path probability in state space for each realization. This is in contrast with the formal approach based on projection operator and density matrices. We find that the JE remains unaffected in the second case, but gets modified in the third case where the mutual information between the measured values with the actual eigenvalues must be incorporated into the relation.

  15. A learner's multiple views of the connection between mathematics and quantum mechanics

    Dini, Vesal; Hammer, David

    Students' physical intuitions and prior knowledge are critical to making sense of and solving problems in classical mechanics. In quantum mechanics (qm), coordinating concepts connected to such everyday thinking becomes more difficult. How then can students develop coherence in their knowledge of qm? Consider how experts do it: they build meaning in, around, and through the mathematics of the theory. This view on the role of mathematics, which is one of among many possible to take, seems most productive for qm. In our work to characterize student views of knowledge that emerge in the context of qm coursework, we came to analyze one student who mostly adopted such a view until a shift in context moved him to express an alternative. We present his case and discuss important implications for instruction.

  16. Exciton Kinetics in Strained II-Vi Semiconductor Multiple Quantum Wells.

    Hefetz, Yaron

    1987-09-01

    Two groups of wide gap II-VI semiconductor superlattices based on ZnSe/Zn(,1-x)Mn(,x)Se and CdTe/ZnTe were investigated using CW and time-resolved photoluminescence, excitation, reflectance, and photomodulated reflectance spectroscopy at various temperatures and under an external magnetic field. All these lattice mismatch strained layer structures were grown by MBE technique and exhibit strong excitonic photoluminescence at low temperatures. By studying the dynamics of the exciton recombination processes, the role of strain, quantum confinement and localization effects were revealed. In the CdTe/ZnTc system where the lattice mismatch is (DELTA)a/a (TURNEQ) 6% the inhomogeneously broadened ((TURN)40 mev) luminescence line is governed by excitonic localization in well width fluctuations. Exchange interactions of the carriers with the Mn('++) ions in the dilute magnetic semiconductor Zn(,1-x)Mn(,x)Se in thin film and the barrier of the MQW structures influence their optical behavior in an exernal magnetic field. "Giant" Zeeman splittings of up to (TURN)10 mev/Tesla were measured in samples with moderate Mn concentration (x = .23). Antiferromagnetic interaction reduces these splittings in samples with higher Mn concentrations. In observing the time evolution of the carrier in Zn(,1-x)Mn(,x)Se MQW we found that the capture time of these carriers into the well is on the order of 1 psec but the last stages of thermalization, exciton formations and localization is (TURN)70 ps. The fast capture of electrons and holes into the quantum wells bypass the energy transfer into the Mn internal transition that is responsible to the efficient "yellow" luminescence in ZnMnSe mixed crystals.

  17. Influence of Rapid Thermal Annealing on Carrier Dynamics in GaInNAs/GaAs Multiple Quantum Wells

    ZHOU Wei; YANG Jie; XIA Su-Jing; LI Xiang; TANG Wu

    2011-01-01

    The excitation intensity and time-resolved photoluminescence spectroscopy are used to investigate the impact of annealing on the carrier dynamics in the Ga0.66In0.34N0.013As0.987 /GaAs multiple quantum well structure grown by metalorganic chemical vapor deposition.The measurement of excitation intensity photoluminescence (PL),performed for as-grown and annealed samples at different temperatures,indicates that the localized potential has come down slightly after annealing but does not alter the fact that PL emission at low temperature is dominated by localized exciton recombination.In contrast,free carrier recombination is magnified by post-grown annealing at room temperature.Our results show that the decay times are 0.587 and 0.327ns at 10K for the as-grown and annealed samples,and radiative decay times also shorten significantly after annealing at all temperatures.Hence the improvement of luminescence efficiency after annealing is caused by the reduction of localization and enhancement of radiative recombination rate.The reduction of the density of nonradiative centers is demonstrated indirectly after annealing.Recently,GaInNAs alloys have attracted an increasing amount of attention,driven by not only their potential applications in various electronic and optoelectronics devices but also their intriguing physical properties.[1] It has been demonstrated that the optical quality of GaInNAs/GaAs quantum wells can be improved by rapid thermal annealing (RTA).[2,3]%The excitation intensity and time-resolved photoluminescence spectroscopy are used to investigate the impact of annealing on the carrier dynamics in the Ga0.66ln0.34N0.013As0.987/GaAs multiple quantum well structure grown by metalorganic chemical vapor deposition. The measurement of excitation intensity photoluminescence (PL), performed for as-grown and annealed samples at different temperatures, indicates that the localized potential has come down slightly after annealing but does not alter the fact that PL

  18. Crystalline 1H-1,2,3-triazol-5-ylidenes

    Bertrand, Guy; Gulsado-Barrios, Gregorio; Bouffard, Jean; Donnadieu, Bruno

    2016-08-02

    The present invention provides novel and stable crystalline 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes. The present invention also provides methods of making 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes. The present invention also provides methods of using 1H-1,2,3 triazolium carbenes and metal complexes of 1H-1,2,3 triazolium carbenes in catalytic reactions.

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

    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.

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

    Radosavljević, S.; Radovanović, J.; Milanović, V.; Tomić, S.

    2014-07-01

    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.

  1. Exclusive quantum channels in quantum networks

    Chen, Xi; Wang, He-Ming; Mu, Liang-Zhu; Fan, Heng

    2014-01-01

    Quantum state can be teleported to a remote site by only local measurement and classical communication if the prior Einstein-Podolsky-Rosen quantum channel is available between the sender and the receiver. Those quantum channels shared by multiple nodes can constitute a quantum network. Yet, studies on the efficiency of quantum communication between nodes of quantum networks remain limited, which differs from classical case in that the quantum channel will be consumed if teleportation is perf...

  2. Improving the performance of tensor matrix vector multiplication in quantum chemistry codes.

    Gropp, W. D.; Kaushik, D. K.; Minkoff, M.; Smith, B. F.

    2008-05-08

    Cumulative reaction probability (CRP) calculations provide a viable computational approach to estimate reaction rate coefficients. However, in order to give meaningful results these calculations should be done in many dimensions (ten to fifteen). This makes CRP codes memory intensive. For this reason, these codes use iterative methods to solve the linear systems, where a good fraction of the execution time is spent on matrix-vector multiplication. In this paper, we discuss the tensor product form of applying the system operator on a vector. This approach shows much better performance and provides huge savings in memory as compared to the explicit sparse representation of the system matrix.

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

    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.

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

    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

  5. Enhanced photoluminescence of Co2+ ions in ZnCoO/ZnMgO multiple quantum wells and the fluorescence energy transfer mechanism

    Using a pulsed laser deposition system, ZnCoO/ZnMgO multiple quantum well (MQW) samples were grown on c-plane sapphire substrate with a ∼20 nm thick ZnO buffer layer. Compared with monolayer ZnCoO film, the MQW samples exhibited obviously enhanced Co2+ photoluminescence (PL) at ∼1.80 eV and multiple-phonon resonant Raman scattering (RRS). The enhancement in multiple-phonon RRS was due to the introduction of ZnMgO barrier layer. The enhanced Co2+ PL was assigned to the quantum confinement effect (QCE) of MQW samples. However, QCE was found not helpful to prevent the band-gap PL quenching. Co2+ 3d electronic states were proved to be highly localized and a mechanism of fluorescence resonance energy transfer (FRET) between ZnO excitons and the localized Co2+ 3d states was proposed. - Highlights: • Enhanced Co2+ PL and multiple-phonon RRS have been observed in ZnCoO/ZnMgO MQW samples. • Quantum confinement effect and ZnMgO barrier layers are responsible for the enhancement of Co2+ PL and multiple-phonon RRS, respectively. • Band-gap PL quenching is suggested to be due to the fluorescence resonance energy transfer from the excitons to the localized Co2+ 3d states

  6. Dangling-bond logic gates on a Si(100)-(2 × 1)-H surface

    Atomic-scale Boolean logic gates (LGs) with two inputs and one output (i.e. OR, NOR, AND, NAND) were designed on a Si(100)-(2 × 1)-H surface and connected to the macroscopic scale by metallic nano-pads physisorbed on the Si(100)-(2 × 1)-H surface. The logic inputs are provided by saturating and unsaturating two surface Si dangling bonds, which can, for example, be achieved by adding and extracting two hydrogen atoms per input. Quantum circuit design rules together with semi-empirical elastic-scattering quantum chemistry transport calculations were used to determine the output current intensity of the proposed switches and LGs when they are interconnected to the metallic nano-pads by surface atomic-scale wires. Our calculations demonstrate that the proposed devices can reach ON/OFF ratios of up to 2000 for a running current in the 10 µA range. (paper)

  7. Computing and deflating eigenvalues while solving multiple right hand side linear systems in Quantum Chromodynamics

    Stathopoulos, Andreas

    2007-01-01

    We present a new algorithm that computes eigenvalues and eigenvectors of a Hermitian positive definite matrix while solving a linear system of equations with Conjugate Gradient (CG). The algorithm capitalizes on the vectors already available from CG, building a small window of vectors that approximates the eigenvectors. While this window is restarted in a locally optimal way, the CG is not. Our algorithm converges almost identically to unrestarted Lanczos, yet without the need to store all Lanczos vectors. After the solution of the linear system, eigenvectors that have not accurately converged can be improved in an incremental fashion by solving additional linear systems. When solving systems with multiple right hand sides, eigenvectors identified in earlier linear systems can be used to deflate, and thus accelerate, the convergence of subsequent systems. We have used this algorithm with excellent results in lattice QCD applications, where hundreds of right hand sides may be needed. Specifically, our deflatio...

  8. Precise structural and functional analyses of cytochrome c' revealed by quantum beams and other multiple methods

    Cytochrome c' (cyt c') is a hemeprotein found in some proteobacteria. It contains a 5-coordinate (5c) His-ligated heme (heme c). Interestingly, NO is bound to the proximal side of the ferrous heme replacing the endogenous His ligand: the 5th ligand His flips away. In a previously reported crystal structure of the NO-bound cyt c', the electron density for the putative NO was in ''Y'' shape and NO was modeled in two alternative bent conformations. We have suspected this ambiguous structure, and we planned to determine the crystal structures of cyt c' in several states by ourselves and to elucidate the NO binding properties and mechanism by using multiple methods. (author)

  9. Multiple logic functions from extended blockade region in a silicon quantum-dot transistor

    We demonstrate multiple logic-functions at room temperature on a unit device of the Si single electron transistor (SET). Owing to the formation of the multi-dot system, the device exhibits the enhanced Coulomb blockade characteristics (e.g., large peak-to-valley current ratio ∼200) that can improve the reliability of the SET-based logic circuits. The SET displays a unique feature useful for the logic applications; namely, the Coulomb oscillation peaks are systematically shifted by changing either of only the gate or the drain voltage. This enables the SET to act as a multi-functional one-transistor logic gate with AND, OR, NAND, and XOR functions

  10. RESONANT ZENER TUNNELING OF ELECTRONS ACROSS THE BAND-GAP BETWEEN BOUND STATES IN THE VALENCE- AND CONDUCTION-BAND QUANTUM WELLS IN A MULTIPLE QUANTUM-WELL STRUCTURE

    Allam, J.; Beltram, F.; Capasso, F; Cho, A.

    1987-01-01

    We report the observation of resonant tunneling effects at high applied fields in a multiple quantum-well P-I-N diode. The Al0.48In0.52As/Ga0.47In0.53As structure shows features in the dark current due to Zener tunneling of electrons from the lowest sub-band in a valence-band quantum well to the first and second sub-bands of an adjacent conduction-band well.

  11. Sensitive targeted multiple protein quantification based on elemental detection of Quantum Dots

    Highlights: • Novel generic platform for multiparametric quantification of proteins. • QDs labeling and ICP-MS detection allow significant analytical signal amplification. • ICP-MS mass balances information provided an internal validation of the immunoassay. • Multiparametric determination of 5 proteins in human serum samples. • ICP-MS reduced matrix effects as compared to other conventional detection techniques. - Abstract: A generic strategy based on the use of CdSe/ZnS Quantum Dots (QDs) as elemental labels for protein quantification, using immunoassays with elemental mass spectrometry (ICP-MS), detection is presented. In this strategy, streptavidin modified QDs (QDs-SA) are bioconjugated to a biotinylated secondary antibody (b-Ab2). After a multi-technique characterization of the synthesized generic platform (QDs-SA-b-Ab2) it was applied to the sequential quantification of five proteins (transferrin, complement C3, apolipoprotein A1, transthyretin and apolipoprotein A4) at different concentration levels in human serum samples. It is shown how this generic strategy does only require the appropriate unlabeled primary antibody for each protein to be detected. Therefore, it introduces a way out to the need for the cumbersome and specific bioconjugation of the QDs to the corresponding specific recognition antibody for every target analyte (protein). Results obtained were validated with those obtained using UV–vis spectrophotometry and commercial ELISA Kits. As expected, ICP-MS offered one order of magnitude lower DL (0.23 fmol absolute for transferrin) than the classical spectrophotometric detection (3.2 fmol absolute). ICP-MS precision and detection limits, however turned out to be compromised by procedural blanks. The full analytical performance of the ICP-MS-based immunoassay proposed was assessed for detection of transferrin (Tf), present at the low ng mL−1 range in a complex “model” synthetic matrix, where the total protein concentration was

  12. Sensitive targeted multiple protein quantification based on elemental detection of Quantum Dots

    Montoro Bustos, Antonio R.; Garcia-Cortes, Marta [Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería 8, Oviedo 33006 (Spain); González-Iglesias, Hector [Fundación de Investigación Oftalmológica, Instituto Oftalmológico Fernandez-Vega, Avenida Doctores Fernández-Vega, 34, Oviedo 33012 (Spain); Ruiz Encinar, Jorge, E-mail: ruizjorge@uniovi.es [Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería 8, Oviedo 33006 (Spain); Costa-Fernández, José M. [Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería 8, Oviedo 33006 (Spain); Coca-Prados, Miguel [Fundación de Investigación Oftalmológica, Instituto Oftalmológico Fernandez-Vega, Avenida Doctores Fernández-Vega, 34, Oviedo 33012 (Spain); Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06510 (United States); Sanz-Medel, Alfredo, E-mail: asm@uniovi.es [Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería 8, Oviedo 33006 (Spain)

    2015-06-16

    Highlights: • Novel generic platform for multiparametric quantification of proteins. • QDs labeling and ICP-MS detection allow significant analytical signal amplification. • ICP-MS mass balances information provided an internal validation of the immunoassay. • Multiparametric determination of 5 proteins in human serum samples. • ICP-MS reduced matrix effects as compared to other conventional detection techniques. - Abstract: A generic strategy based on the use of CdSe/ZnS Quantum Dots (QDs) as elemental labels for protein quantification, using immunoassays with elemental mass spectrometry (ICP-MS), detection is presented. In this strategy, streptavidin modified QDs (QDs-SA) are bioconjugated to a biotinylated secondary antibody (b-Ab{sub 2}). After a multi-technique characterization of the synthesized generic platform (QDs-SA-b-Ab{sub 2}) it was applied to the sequential quantification of five proteins (transferrin, complement C3, apolipoprotein A1, transthyretin and apolipoprotein A4) at different concentration levels in human serum samples. It is shown how this generic strategy does only require the appropriate unlabeled primary antibody for each protein to be detected. Therefore, it introduces a way out to the need for the cumbersome and specific bioconjugation of the QDs to the corresponding specific recognition antibody for every target analyte (protein). Results obtained were validated with those obtained using UV–vis spectrophotometry and commercial ELISA Kits. As expected, ICP-MS offered one order of magnitude lower DL (0.23 fmol absolute for transferrin) than the classical spectrophotometric detection (3.2 fmol absolute). ICP-MS precision and detection limits, however turned out to be compromised by procedural blanks. The full analytical performance of the ICP-MS-based immunoassay proposed was assessed for detection of transferrin (Tf), present at the low ng mL{sup −1} range in a complex “model” synthetic matrix, where the total protein

  13. Absorption enhancement through Fabry-Pérot resonant modes in a 430 nm thick InGaAs/GaAsP multiple quantum wells solar cell

    We study light management in a 430 nm-thick GaAs p-i-n single junction solar cell with 10 pairs of InGaAs/GaAsP multiple quantum wells (MQWs). The epitaxial layer transfer on a gold mirror improves light absorption and increases the external quantum efficiency below GaAs bandgap by a factor of four through the excitation of Fabry-Perot resonances. We show a good agreement with optical simulation and achieve around 10% conversion efficiency. We demonstrate numerically that this promising result can be further improved by anti-reflection layers. This study paves the way to very thin MQWs solar cells

  14. Effect of low-energy electron irradiation on the optical properties of structures containing multiple InGaN/GaN quantum well

    Data on the temperature dependence of the cathodoluminescence intensity in multiple InGaN/GaN quantum-well structures in the temperature range 80–300 K are reported. Unirradiated structures and structures irradiated with electrons with subthreshold energy are studied. It is shown that, upon irradiation, the temperature dependence becomes weaker. From analysis of the results obtained in this study and previously, it can be suggested that electron irradiation initiates the relaxation of strains produced in quantum wells due to the InGaN-GaN lattice mismatch

  15. Multi-color quantum dot-based fluorescence immunoassay array for simultaneous visual detection of multiple antibiotic residues in milk.

    Song, Erqun; Yu, Mengqun; Wang, Yunyun; Hu, Weihua; Cheng, Dan; Swihart, Mark T; Song, Yang

    2015-10-15

    Antibiotic residues, which are among the most common contaminants in animal-based food products such as milk, have become a significant public health concern. Here, we combine a multicolor quantum dot (QD)-based immunofluorescence assay and an array analysis method to achieve simultaneous, sensitive and visual detection of streptomycin (SM), tetracycline (TC), and penicillin G (PC-G) in milk. Antibodies (Abs) for SM, TC and PC-G were conjugated to QDs with different emission wavelengths (QD 520 nm, QD 565 nm and QD 610 nm) to serve as detection probes (QD-Ab). Then a direct competitive fluorescent immunoassay was performed in antigen-coated microtiter plate wells for simultaneous qualitative and quantitative detection of SM, TC, and PC-G residues, based on fluorescence of the QD-Ab probes. The linear ranges for SM, TC and PC-G were 0.01-25 ng/mL, 0.01-25 ng/mL and 0.01-10 ng/mL, respectively, with detection limit of 5 pg/mL for each of them. Based on fluorescence of the QD-Ab probes, residues of the three antibiotics were determined visually and simultaneously. Compared with a commercial enzyme-linked immunosorbent assay kit, our method could achieve simultaneous analysis of multiple target antibiotics in multiple samples in a single run (high-throughput analysis) and improved accuracy and sensitivity for analysis of residues of the three antibiotics in authentic milk samples. This new analytical tool can play an important role in ameliorating the negative impact of the residual antibiotics on human health and the ecosystem. PMID:26002016

  16. Simultaneous quantitative detection of multiple tumor markers with a rapid and sensitive multicolor quantum dots based immunochromatographic test strip.

    Wang, Chunying; Hou, Fei; Ma, Yicai

    2015-06-15

    A novel multicolor quantum dots (QDs) based immunochromatographic test strip (ICTS) was developed for simultaneous quantitative detection of multiple tumor markers, by utilizing alpha fetoprotein (AFP) and carcinoembryonic antigen (CEA) as models. The immunosensor could realize simultaneous quantitative detection of tumor markers with only one test line and one control line on the nitrocellulose membrane (NC membrane) due to the introduction of multicolor QDs. In this method, a mixture of mouse anti-AFP McAb and mouse anti-CEA McAb was coated on NC membrane as test line and goat anti-mouse IgG antibody was coated as control line. Anti-AFP McAb-QDs546 conjugates and anti-CEA McAb-QDs620 conjugates were mixed and applied to the conjugate pad. Simultaneous quantitative detection of multiple tumor markers was achieved by detecting the fluorescence intensity of captured QDs labels on test line and control line using a test strip reader. Under the optimum conditions, AFP and CEA could be detected as low as 3 ng/mL and 2 ng/mL in 15 min with a sample volume of 80 μL, and no obvious cross-reactivity was observed. The immunosensor was validated with 130 clinical samples and in which it exhibited high sensitivity (93% for AFP and 87% for CEA) and specificity (94% for AFP and 97% for CEA). The immunosensor also demonstrated high recoveries (87.5-113% for AFP and 90-97.3% for CEA) and low relative standard deviations (RSDs) (2.8-6.2% for AFP and 4.9-9.6% for CEA) when testing spiked human serum. This novel multicolor QDs based ICTS provides an easy and rapid, simultaneous quantitative detecting strategy for point-of-care testing of tumor markers. PMID:25562743

  17. Onset of surface stimulated emission at 260 nm from AlGaN multiple quantum wells

    We demonstrated onset of deep-ultraviolet (DUV) surface stimulated emission (SE) from c-plane AlGaN multiple-quantum well (MQW) heterostructures grown on a sapphire substrate by optical pumping at room temperature. The onset of SE became observable at a pumping power density of 630 kW/cm2. Spectral deconvolution revealed superposition of a linearly amplified spontaneous emission peak at λ ∼ 257.0 nm with a full width at half maximum (FWHM) of ∼12 nm and a superlinearly amplified SE peak at λ ∼ 260 nm with a narrow FWHM of less than 2 nm. In particular, the wavelength of ∼260 nm is the shortest wavelength of surface SE from III-nitride MQW heterostructures to date. Atomic force microscopy and scanning transmission electron microscopy measurements were employed to investigate the material and structural quality of the AlGaN heterostructures, showing smooth surface and sharp layer interfaces. This study offers promising results for AlGaN heterostructures grown on sapphire substrates for the development of DUV vertical cavity surface emitting lasers (VCSELs)

  18. Achieving Uniform Carriers Distribution in MBE Grown Compositionally Graded InGaN Multiple-Quantum-Well LEDs

    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.

  19. Computation of Hydration Free Energies Using the Multiple Environment Single System Quantum Mechanical/Molecular Mechanical Method.

    König, Gerhard; Mei, Ye; Pickard, Frank C; Simmonett, Andrew C; Miller, Benjamin T; Herbert, John M; Woodcock, H Lee; Brooks, Bernard R; Shao, Yihan

    2016-01-12

    A recently developed MESS-E-QM/MM method (multiple-environment single-system quantum mechanical molecular/mechanical calculations with a Roothaan-step extrapolation) is applied to the computation of hydration free energies for the blind SAMPL4 test set and for 12 small molecules. First, free energy simulations are performed with a classical molecular mechanics force field using fixed-geometry solute molecules and explicit TIP3P solvent, and then the non-Boltzmann-Bennett method is employed to compute the QM/MM correction (QM/MM-NBB) to the molecular mechanical hydration free energies. For the SAMPL4 set, MESS-E-QM/MM-NBB corrections to the hydration free energy can be obtained 2 or 3 orders of magnitude faster than fully converged QM/MM-NBB corrections, and, on average, the hydration free energies predicted with MESS-E-QM/MM-NBB fall within 0.10-0.20 kcal/mol of full-converged QM/MM-NBB results. Out of five density functionals (BLYP, B3LYP, PBE0, M06-2X, and ωB97X-D), the BLYP functional is found to be most compatible with the TIP3P solvent model and yields the most accurate hydration free energies against experimental values for solute molecules included in this study. PMID:26613419

  20. Design and Performance of a Sensor System for Detection of Multiple Chemicals Using an External Cavity Quantum Cascade Laser

    Phillips, Mark C.; Taubman, Matthew S.; Bernacki, Bruce E.; Cannon, Bret D.; Schiffern, John T.; Myers, Tanya L.

    2010-01-23

    We describe the performance of a sensor system designed for simultaneous detection of multiple chemicals with both broad and narrow absorption features. The sensor system consists of a broadly tunable external cavity quantum cascade laser (ECQCL), multi-pass Herriott cell, and custom low-noise electronics. The ECQCL features a rapid wavelength tuning rate of 2265 cm 1/s (15660 nm/s) over its tuning range of 1150-1270 cm 1 (7.87-8.70 μm), which permits detection of molecules with broad absorption features and dynamic concentrations, while the 0.2 cm-1 spectral resolution of the ECQCL system allows measurement of small molecules with atmospherically broadened absorption lines. High-speed amplitude modulation and low-noise electronics are used to improve the ECQCL performance for direct absorption measurements. We demonstrate simultaneous detection of Freon-134a (1,1,1,2-tetrafluoroethane), ammonia (NH3), and nitrous oxide (N2O) at low-ppb concentrations in field measurements of atmospheric chemical releases from a point source.

  1. Controlling optical polarization of {11-22} semipolar multiple quantum wells using relaxed underlying InGaN buffer layers

    Okada, Narihito; Okamura, Yasuhiro; Uchida, Katsumi; Tadatomo, Kazuyuki

    2016-08-01

    We successfully fabricated {11-22} multiple quantum wells (MQWs) having different emission peak wavelengths on partially or completely relaxed thick InGaN buffer layers with different In contents formed on a semipolar {11-22} GaN layer, which was grown on a patterned r-plane sapphire substrate. The polarization properties changed significantly with changing in In content and thickness for InGaN buffer layer. For the same In content of the InGaN buffer layer, the optical polarization changed with an increase in the thickness of the underlying InGaN buffer layer, indicating a change in the relaxation ratio of the InGaN buffer layer. Similarly, for the same thickness of the InGaN buffer layer, the optical polarization changed by changing In content of the InGaN buffer layer. Thus, the degree of optical polarization could be controlled by varying the In content of the underlying InGaN buffer layer.

  2. Photoreflectance and differential surface photovoltage studies of δ-doped GaAs/AlAs multiple quantum wells

    Cechavičius, Bronislovas; Kavaliauskas, Julius; Krivaite, Gene; Seliuta, Dalius; Valusis, Gintaras; Halsall, Matthew P.; Steer, Matthew J.; Harrison, Paul

    2005-08-01

    We measured the photoreflectance (PR) and wavelength-modulated differential surface photovoltage (DSPV) spectra of δ-doped GaAs/AlAs multiple quantum wells (MQW) with different well widths and doping levels. We demonstrated that PR and DSPV are powerful contactless tools for the characterization of MQW structures. We observed Franz-Keldysh oscillations in the PR spectra, which enabled us to determine the built-in electric fields in the GaAs/AlAs MQW structures. As it turned out, in the GaAs buffedcap layers the field strength is in the range of 18-20 kV/cm. It was found that a buried interface rather than the structure surface very probably governs the SPV effect. Sharp features associated with excitonic optical transitions were revealed in both, PR and DSPV spectra. From the line shape analysis of the modulation spectra, we estimated optical transition energies and broadening parameters. The energy levels and interband transition energies calculated by the transfer matrix method are in good agreement with the experimental values. The influence of the doping on the broadening of exciton resonances was observed and investigated.

  3. Non-protein coding RNA-based genosensor with quantum dots as electrochemical labels for attomolar detection of multiple pathogens.

    Vijian, Dinesh; Chinni, Suresh V; Yin, Lee Su; Lertanantawong, Benchaporn; Surareungchai, Werasak

    2016-03-15

    The ability of a diagnostic test to detect multiple pathogens simultaneously is useful to obtain meaningful information for clinical treatment and preventive measures. We report a highly sensitive and specific electrochemical biosensor assay for simultaneous detection of three gene targets using quantum dots (QDs). The targets are novel non-protein coding RNA (npcRNA) sequences of Vibrio cholerae, Salmonella sp. and Shigella sp., which cause diarrheal diseases. QDs (PbS, CdS, ZnS) were synthesized and functionalized with DNA probes that were specific to each pathogen. Electrochemical detection of QDs was performed using square wave anodic stripping voltammetry (SWASV). The QDs gave distinct peaks at 0.5 V (PbS), 0.75 V (CdS) and 1.1 V (ZnS). There was no interference in signal response when all three QDs were mixed and detected simultaneously. The detection limits of single and multiplex assays with linear targets and PCR products were in the attomolar ranges. The high assay sensitivity, in combination with specific npcRNA sequences as novel diagnostic targets, makes it a viable tool for detecting pathogens from food, environment and clinical samples. PMID:26513287

  4. Onset of surface stimulated emission at 260 nm from AlGaN multiple quantum wells

    Li, Xiaohang, E-mail: xiaohang.li@kaust.edu.sa, E-mail: dupuis@gatech.edu [Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955 (Saudi Arabia); Xie, Hongen; Ponce, Fernando A. [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States); Ryou, Jae-Hyun [Department of Mechanical Engineering, Materials Science and Engineering Program, and Texas Center for Superconductivity at the University of Houston (TcSUH), University of Houston, Houston, Texas 77204 (United States); Detchprohm, Theeradetch; Dupuis, Russell D., E-mail: xiaohang.li@kaust.edu.sa, E-mail: dupuis@gatech.edu [Center for Compound Semiconductors and School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-12-14

    We demonstrated onset of deep-ultraviolet (DUV) surface stimulated emission (SE) from c-plane AlGaN multiple-quantum well (MQW) heterostructures grown on a sapphire substrate by optical pumping at room temperature. The onset of SE became observable at a pumping power density of 630 kW/cm{sup 2}. Spectral deconvolution revealed superposition of a linearly amplified spontaneous emission peak at λ ∼ 257.0 nm with a full width at half maximum (FWHM) of ∼12 nm and a superlinearly amplified SE peak at λ ∼ 260 nm with a narrow FWHM of less than 2 nm. In particular, the wavelength of ∼260 nm is the shortest wavelength of surface SE from III-nitride MQW heterostructures to date. Atomic force microscopy and scanning transmission electron microscopy measurements were employed to investigate the material and structural quality of the AlGaN heterostructures, showing smooth surface and sharp layer interfaces. This study offers promising results for AlGaN heterostructures grown on sapphire substrates for the development of DUV vertical cavity surface emitting lasers (VCSELs)

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

    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.

  6. Analysis list: NR1H3 [Chip-atlas[Archive

    Full Text Available NR1H3 Adipocyte,Blood + hg19 http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/target.../NR1H3.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/NR1H3.5.tsv http://dbarchive.bioscienced...bc.jp/kyushu-u/hg19/target/NR1H3.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/NR1H3.Adipocyte....tsv,http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/NR1H3.Blood.tsv http://dbarchive.bioscience...dbc.jp/kyushu-u/hg19/colo/Adipocyte.gml,http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/Blood.gml ...

  7. Synthesis, characterization and computational study on ethyl 4-(3-Furan-2yl-acryloyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate

    Singh, R. N.; Rawat, Poonam; Sahu, Sangeeta

    2014-11-01

    As part of study on pyrrole derivatives, we have synthesized a pyrrole chalcone derivative: ethyl 4-(3-Furan-2yl-acryloyl)-3,5-dimethyl-1H-pyrrole-2-carboxylate (EFADPC) by aldol condensation of ethyl 3, 5-dimethyl-4-actyl-1H-pyrrole-2-carboxylate with furan-2-carbaldehyde in the presence of strong hydroxyl base as catalyst. The product EFADPC has been confirmed by spectroscopic (FT-IR, 1H NMR, and UV-visible) analyses. Quantum chemical calculation also provides good correlation with experimental data. The molecular electrostatic potential surface (MEP), natural bond orbital interactions (NBO), electronic descriptors, quantum theory of atoms' in molecules (QTAIM) and experimental FT-IR spectrum have been used to predict the sites and nature of interactions which indicate that the dimer formation with multiple interactions through Nsbnd H···O and Csbnd H···O. The vibrational analysis shows red shifts in νNsbnd H and νCdbnd O as result of dimer formation. The binding energy of dimer is calculated as 13.82, 15.24 kcal/mol using DFT, QTAIM analysis, respectively. The result of ellipticity confirms the existence of resonance assisted hydrogen bonds (RAHB) in dimer. The MEP and local reactivity descriptors analyses have been performed and the results indicate that carbonyl carbon and β-carbon of chalcone frame have been prone to nucleophilic attack and lead to large number of heterocyclic compounds such as oxirane, oxazoles, pyrazoles, pyridines, pyrimidines, and pyran.

  8. Accurate molecular dynamics and nuclear quantum effects at low cost by multiple steps in real and imaginary time: Using density functional theory to accelerate wavefunction methods

    Kapil, V.; VandeVondele, J.; Ceriotti, M.

    2016-02-01

    The development and implementation of increasingly accurate methods for electronic structure calculations mean that, for many atomistic simulation problems, treating light nuclei as classical particles is now one of the most serious approximations. Even though recent developments have significantly reduced the overhead for modeling the quantum nature of the nuclei, the cost is still prohibitive when combined with advanced electronic structure methods. Here we present how multiple time step integrators can be combined with ring-polymer contraction techniques (effectively, multiple time stepping in imaginary time) to reduce virtually to zero the overhead of modelling nuclear quantum effects, while describing inter-atomic forces at high levels of electronic structure theory. This is demonstrated for a combination of MP2 and semi-local DFT applied to the Zundel cation. The approach can be seamlessly combined with other methods to reduce the computational cost of path integral calculations, such as high-order factorizations of the Boltzmann operator or generalized Langevin equation thermostats.

  9. Accurate molecular dynamics and nuclear quantum effects at low cost by multiple steps in real and imaginary time: Using density functional theory to accelerate wavefunction methods

    Kapil, V.; Ceriotti, M., E-mail: michele.ceriotti@epfl.ch [Laboratory of Computational Science and Modelling, Institute of Materials, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); VandeVondele, J., E-mail: joost.vandevondele@mat.ethz.ch [Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)

    2016-02-07

    The development and implementation of increasingly accurate methods for electronic structure calculations mean that, for many atomistic simulation problems, treating light nuclei as classical particles is now one of the most serious approximations. Even though recent developments have significantly reduced the overhead for modeling the quantum nature of the nuclei, the cost is still prohibitive when combined with advanced electronic structure methods. Here we present how multiple time step integrators can be combined with ring-polymer contraction techniques (effectively, multiple time stepping in imaginary time) to reduce virtually to zero the overhead of modelling nuclear quantum effects, while describing inter-atomic forces at high levels of electronic structure theory. This is demonstrated for a combination of MP2 and semi-local DFT applied to the Zundel cation. The approach can be seamlessly combined with other methods to reduce the computational cost of path integral calculations, such as high-order factorizations of the Boltzmann operator or generalized Langevin equation thermostats.

  10. Structure of CdTe-Cd1 - xMnxTe multiple quantum wells grown on (001) InSb substrates by molecular beam epitaxy

    Williams, G. M.; Cullis, A. G.; Whitehouse, C. R.; Ashenford, D. E.; Lunn, B.

    1989-09-01

    Molecular beam epitaxy has been used to prepare multiple quantum well structures of CdTe/Cd1-xMnxTe on (001) InSb substrates. The growth of such a system on InSb allows the use of particularly low growth temperatures, hence minimizing interdiffusion effects. This study presents the first transmission electron microscope investigation of this multilayer system grown on InSb. The work clearly demonstrates that multiple quantum wells of high structural quality can be grown reproducibly over a wide range of layer thicknesses. The importance of efficient substrate surface cleaning prior to growth is demonstrated. In order to grow high structural quality multilayers, the choice of buffer layer is also important and a possible explanation for this observation is given.

  11. Accurate molecular dynamics and nuclear quantum effects at low cost by multiple steps in real and imaginary time: Using density functional theory to accelerate wavefunction methods

    The development and implementation of increasingly accurate methods for electronic structure calculations mean that, for many atomistic simulation problems, treating light nuclei as classical particles is now one of the most serious approximations. Even though recent developments have significantly reduced the overhead for modeling the quantum nature of the nuclei, the cost is still prohibitive when combined with advanced electronic structure methods. Here we present how multiple time step integrators can be combined with ring-polymer contraction techniques (effectively, multiple time stepping in imaginary time) to reduce virtually to zero the overhead of modelling nuclear quantum effects, while describing inter-atomic forces at high levels of electronic structure theory. This is demonstrated for a combination of MP2 and semi-local DFT applied to the Zundel cation. The approach can be seamlessly combined with other methods to reduce the computational cost of path integral calculations, such as high-order factorizations of the Boltzmann operator or generalized Langevin equation thermostats

  12. Multiple cations interdiffusion in In0.53Ga0.47As/In0.52Al0.48As quantum well

    Chan, Y.; Shiu, WC; Li, EH; Tsui, WK

    1997-01-01

    Multiple cations interdiffusion in Ino.53Gao.47As/Ino.52Alo.48As quantum well (QW) structure is investigated by using the model of expanded form of Fick's second law. The model is fitted to the measured concentration data in order to determine their diffusion coefficients. Once the concentration distribution is obtained, the types of strain and their variation across the QW can be determined, thus the subbands and transitions can be gathered. Result shows interesting phenomena due to this thr...

  13. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to √{ s} = 7 TeV

    Ghosh, Premomoy

    2011-11-01

    Proton-proton collisions at new high energies (√{ s} = 2.36 and 7 TeV) at LHC resulted into greater mean multiplicities () of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval | η | distributions of charged hadrons from proton-proton collisions at centre-of-mass energies √{ s} = 0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals | η | of increasing width around the centre-of-mass pseudorapidity ηcm = 0. The model, based on Quantum Statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a chaotic component, and a Poisson Distribution (PD), representing a coherent component of particle productions. The behaviour of characteristic parameters of the model is followed by the LHC data, while a scaling law, involving information entropy in quantum statistical viewpoint and derived as a function of chaotic multiplicity obtained from the two-component model, is not obeyed by the data, satisfactorily. An attempt to match the measured multiplicity distributions and suggested convolutions with values of characteristic parameters extracted from the data confirms disagreement between the data and the model.

  14. 4-Bromo-3-methoxy-1-phenyl-1H-pyrazole

    Algirdas Šačkus

    2009-11-01

    Full Text Available The title compound was prepared by treatment of 4-bromo-1-phenyl-1H-pyrazol-3-ol with sodium hydride/methyl iodide in good yield. Detailed spectroscopic data (1H NMR, 13C NMR, 15N NMR, IR, MS are presented.

  15. Balo's concentric sclerosis: a correlative study of MRI, 1H-MR spectroscopy and biopsy

    Objective: To describe the features of Balo's concentric sclerosis on MRI and 1H-MRS. Methods: Three patients of Balo's concentric sclerosis were reported on the basis of brain MRI and stereotactic brain biopsy. Proton MR spectroscopy was carried out on 1 patient. Results: Multiple ring-like lesions of laminated demyelination alternating with spared white matter were demonstrated in all 3 patients, and the lesions were best seen in post-contrast images. 1H-MRS showed a decreased NAA peak, an increased choline peak, and the presence of large lipid peak. Conclusion: Balo's concentric sclerosis has characteristic findings on MRI and 1H-MRS. MRI is very useful in the diagnosis of Balo's concentric sclerosis

  16. Accurate Measurements of Heteronuclear 13C-1H Coupling Constants by Phase-sensitive HMQC and HSQC Spectra%应用相敏HMQC和HSQC谱准确测定异核碳-氢偶合常数

    丁克洋

    2001-01-01

    Phase-sensitive HMQC(Heteronuclear Multiple-Quantum Coherence) and HSQC(Heteronuclear Single-Quantum Coherence) experiments with t1-noise reduction are proposed for the accurate measurement of heteronuclear one-bond 13C-1H coupling constants. The resulting 2D spectra give anti-phase splittings of heteronuclear one-bond couplings along ω2-dimension, so that the precision of coupling constant measurement is less subject to the residual t1-noise. By combining use of data-fitting procedure on a spectrum with enough digital resolution and signal-to-noise ratio, a precision of about 0.03 Hz can be achieved in the measurement of heteronuclear one-bond coupling constants. The proposed method can be very useful for the study of residual dipolar couplings caused by the alignment in high magnetic field and the dynamic frequency shift caused by the cross-correlation between chemical shift and spin dipolar interactions.

  17. Dislocation Reduction and Stress Relaxation of GaN and InGaN Multiple Quantum Wells with Improved Performance via Serpentine Channel Patterned Mask.

    Ji, Qingbin; Li, Lei; Zhang, Wei; Wang, Jia; Liu, Peichi; Xie, Yahong; Yan, Tongxing; Yang, Wei; Chen, Weihua; Hu, Xiaodong

    2016-08-24

    The existence of high threading dislocation density (TDD) in GaN-based epilayers is a long unsolved problem, which hinders further applications of defect-sensitive GaN-based devices. Multiple-modulation of epitaxial lateral overgrowth (ELOG) is used to achieve high-quality GaN template on a novel serpentine channel patterned sapphire substrate (SCPSS). The dislocation blocking brought by the serpentine channel patterned mask, coupled with repeated dislocation bending, can reduce the dislocation density to a yet-to-be-optimized level of ∼2 × 10(5) to 2 × 10(6) cm(-2). About 80% area utilization rate of GaN with low TDD and stress relaxation is obtained. The periodical variations of dislocation density, optical properties and residual stress in GaN-based epilayers on SCPSS are analyzed. The quantum efficiency of InGaN/GaN multiple quantum wells (MQWs) on it can be increased by 52% compared with the conventional sapphire substrate. The reduced nonradiative recombination centers, the enhanced carrier localization, and the suppressed quantum confined Stark effect, are the main determinants of improved luminous performance in MQWs on SCPSS. This developed ELOG on serpentine shaped mask needs no interruption and regrowth, which can be a promising candidate for the heteroepitaxy of semipolar/nonpolar GaN and GaAs with high quality. PMID:27484167

  18. Influence of substrate misorientation on the photoluminescence and structural properties of InGaAs/GaAsP multiple quantum wells

    Dong, Hailiang; Sun, Jing; Ma, Shufang; Liang, Jian; Lu, Taiping; Liu, Xuguang; Xu, Bingshe

    2016-03-01

    InGaAs/GaAsP multiple quantum wells (MQWs) were grown by metal-organic chemical vapor deposition on vicinal GaAs (001) substrates with different miscut angles of 0°, 2° and 15° towards [110]. The crystal structures of InGaAs/GaAsP were characterized by high-resolution X-ray diffraction and Raman spectroscopy. The surface morphologies of InGaAs/GaAsP MQWs were observed by atomic force microscopy. The mechanisms for step flow, step bunching and pyramid growth on 0°, 2° and 15° misoriented substrates were discussed. The results provide a comprehensive phenomenological understanding of the self-ordering mechanism of vicinal GaAs substrates, which could be harnessed for designing the quantum optical properties of low-dimensional systems. From low-temperature photoluminescence, it was observed that the luminescence from the MQWs grown on a vicinal surface exhibits a red-shift with respect to the 0° case. An extra emission was observed from the 2° and 15° off samples, indicating the characteristics of quantum wire and pyramidal self-controlled quantum-dot systems, respectively. Its absence from the PL spectrum on 0° surfaces indicates that indium segregation is modified on the surfaces. The relationship between InGaAs/GaAsP MQWs grown on vicinal substrates and their optical and structural properties was explained, which provides a technological basis for obtaining different self-controlled nanostructures.

  19. Structural origin of V-defects and correlation with localized excitonic centers in InGaN/GaN multiple quantum wells

    Wu, X. H.; Elsass, C. R.; Abare, A.; Mack, M.; Keller, S.; Petroff, P. M.; DenBaars, S. P.; Speck, J. S.; Rosner, S. J.

    1998-02-01

    In the growth of InGaN/GaN multiple quantum well (MQW) structures, a novel defect (called the "V-defect") initiates at threading dislocations in one of the first quantum wells in a MQW stack. This defect is common to almost all InGaN MQW heterostructures. The nature of the V-defect was evaluated using transmission electron microscopy (TEM), scanning TEM (STEM), and low-temperature cathodoluminescence (CL) on a series of In0.20Ga0.80N/GaN MQW samples. The structure of the V-defect includes buried side-wall quantum wells (on the {101¯1} planes) and an open hexagonal inverted pyramid which is defined by the six {101¯1} planes. Thus, in cross section this defect appears as an open "V". The formation of the V-defect is kinetically controlled by reduced Ga incorporation on the pyramid walls ({101¯1} planes). The V-defect is correlated with the localized excitonic recombination centers that give rise to a long-wavelength shoulder in photoluminescence (PL) and CL spectra. This long-wavelength shoulder has the following characteristics: (i) its intensity is correlated with the side-wall quantum wells; (ii) the temperature independence of the full width at half maximum strongly supports a localized exciton recombination process.

  20. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to {radical}(s)=7 TeV

    Ghosh, Premomoy, E-mail: prem@vecc.gov.in [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700 064 (India)

    2011-11-17

    Proton-proton collisions at new high energies ({radical}(s)=2.36 and 7 TeV) at LHC resulted into greater mean multiplicities (Left-Pointing-Angle-Bracket n Right-Pointing-Angle-Bracket) of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval |{eta}|<2.4. The change is most prominent with data at {radical}(s)=7 TeV. These new observations merit further studies. We consider a two-component model of particle production to analyze multiplicity distributions of charged hadrons from proton-proton collisions at centre-of-mass energies {radical}(s)=0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals |{eta}| of increasing width around the centre-of-mass pseudorapidity {eta}{sub cm}=0. The model, based on Quantum Statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a chaotic component, and a Poisson Distribution (PD), representing a coherent component of particle productions. The behaviour of characteristic parameters of the model is followed by the LHC data, while a scaling law, involving information entropy in quantum statistical viewpoint and derived as a function of chaotic multiplicity obtained from the two-component model, is not obeyed by the data, satisfactorily. An attempt to match the measured multiplicity distributions and suggested convolutions with values of characteristic parameters extracted from the data confirms disagreement between the data and the model.

  1. Effect of variations in the doping profiles on the properties of doped multiple quantum well avalanche photodiodes

    Menkara, H. M.; Wagner, B. K.; Summers, C. J.

    1996-01-01

    The purpose of this study is to use both theoretical and experimental evidence to determine the impact of doping imbalance and symmetry on the physical and electrical characteristics of doped multiple quantum well avalanche photodiodes (APD). Theoretical models have been developed to calculate the electric field valence and conduction bands, capacitance-voltage (CV), and carrier concentration versus depletion depth profiles. The models showed a strong correlation between the p- and n-doping balance inside the GaAs wells and the number of depleted stages and breakdown voltage of the APD. A periodic doping imbalance in the wells has been shown to result in a gradual increase (or decrease) in the electric field profile throughout the device which gave rise to partially depleted devices at low bias. The MQW APD structures that we modeled consisted of a 1 micron top p(+)-doped (3 x 10(exp 18) cm(exp -3)) GaAs layer followed by a 1 micron region of alternating layers of GaAs (500 A) and Al(0.42)Ga(0.58)As (500 A), and a 1 micron n(+) back layer (3 x 10(exp 18) cm(exp -3)). The GaAs wells were doped with p-i-n layers placed at the center of each well. The simulation results showed that in an APD with nine doped wells, and where the 50 A p-doped layer is off by 10% (p = 1.65 x 10(exp 18) cm(exp -3), n = 1.5 x 10(exp 18) cm(exp -3)), almost half of the MQW stages were shown to be undepleted at low bias which was a result of a reduction in the electric field near the p(+) cap layer by over 50% from its value in the balanced structure. Experimental CV and IV data on similar MBE grown MQW structures have shown very similar depletion and breakdown characteristics. The models have enabled us to better interpret our experimental data and to determine both the extent of the doping imbalances in the devices as well as the overall p- or n-type doping characteristics of the structures.

  2. An experimental study about the influence of well thickness on the electroluminescence of InGaN/GaN multiple quantum wells

    The influence of well thickness on the electroluminescence (EL) of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition is investigated. It is found that the peak wavelength of EL increases with the increase of well thickness when the latter is located in the range of 3.0-5.1 nm. The redshift is mainly attributed to the quantum confined Stark effect (QCSE). As a contrast, it is found that the EL intensity of InGaN/GaN MQWs increases with the increase of well thickness in spite of QCSE. The result of X-ray diffraction demonstrates that the interface become smoother with the increase of well thickness and suggests that the reduced interface roughness can be an important factor leading to the increase of EL intensity of InGaN/GaN MQWs.

  3. Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells

    Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well (MQW) solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency (EQE) of the solar cells increases in a low energy spectral range (λ > 370 nm) when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths (λ > 370 nm)

  4. Understanding droop effect by analysis on carrier density dependence in InGaN/GaN multiple-quantum-well light-emitting diodes

    Liu, Wei; Zhao, Degang; Jiang, Desheng; Chen, Ping; Liu, Zongshun; Zhu, Jianjun; Yang, Jing; He, Xiaoguang; Li, Xiaojing; Li, Xiang; Liang, Feng; Liu, Jianping; Zhang, Liqun; Yang, Hui; Zhang, Yuantao; Du, Guotong

    2016-08-01

    The droop behaviors of two InGaN/GaN multiple-quantum-well blue-green light-emitting diodes grown on c-plane sapphires with different In content are investigated. The higher-In-content sample exhibits a lower efficiency, followed by a more significant droop as current increases in comparison with the lower-In-content diode. However, it is found that for both samples their efficiency reduction trend with increasing carrier density is nearly the same. Combining with the recombination rate equations, an analysis reveals that at the same injection current level, the carrier density in the higher-In-content quantum wells which have stronger polarization effect is larger due to the smaller bimolecular recombination coefficient, resulting in a more significant droop with current. Therefore, a study on the dependence of efficiency on carrier density can provide a clear elucidation to the physical mechanism of the efficiency droop behavior.

  5. Optical properties of one- and two-dimensional excitons in m-plane ZnO/MgZnO multiple quantum wells

    Five pairs of ZnO/Zn0.9Mg0.1O multiple quantum wells (MQWs) with fixed barrier thickness of 55 nm and three well widths of 4, 8 and 16 nm have been grown on m-plane sapphires by pulsed laser deposition. Due to 2D quantum confinement with decreasing well width, the emission of excitons bound to the basal-plane stacking faults, which are one-dimensionally confined in MQWs, encounters larger blue shift than that of the near-band edge excitons. Furthermore, remarkably reducing coupling of free excitons with A 1 longitudinal optical phonons is closely correlated with increasing exciton binding energy but enhanced coupling of E 2-low phonons is a result of increasing interaction with the interface phonons with decreasing well width. (paper)

  6. A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film deposited on Si(111) substrate and its micromachining

    Hu, F R; Kanamori, Y; Ochi, K; Zhao, Y; Wakui, M; Hane, K [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2008-01-23

    A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film was deposited on Si(111) substrate, with InN as the interlayer, by molecular beam epitaxy. The diameter of the column crystal is about 40 nm. Transmission electron microscopy images showed clear five-period well layers. Photoluminescence measurements demonstrated a wide emission wavelength from about 500 to 800 nm with the full width at half maximum of 107 nm at room temperature. An unusual photoluminescence peak position shift was observed from the optical measurement. The selected area electron diffraction image demonstrated the hexagonal wurtzite structure of the column crystal. A self-supported GaN-based active subwavelength grating was proposed, and the active subwavelength grating structure was fabricated from the InGaN/GaN quantum-well thin film by a Si micromachining process.

  7. A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film deposited on Si(111) substrate and its micromachining.

    Hu, F R; Kanamori, Y; Ochi, K; Zhao, Y; Wakui, M; Hane, K

    2008-01-23

    A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film was deposited on Si(111) substrate, with InN as the interlayer, by molecular beam epitaxy. The diameter of the column crystal is about 40 nm. Transmission electron microscopy images showed clear five-period well layers. Photoluminescence measurements demonstrated a wide emission wavelength from about 500 to 800 nm with the full width at half maximum of 107 nm at room temperature. An unusual photoluminescence peak position shift was observed from the optical measurement. The selected area electron diffraction image demonstrated the hexagonal wurtzite structure of the column crystal. A self-supported GaN-based active subwavelength grating was proposed, and the active subwavelength grating structure was fabricated from the InGaN/GaN quantum-well thin film by a Si micromachining process. PMID:21817568

  8. A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film deposited on Si(111) substrate and its micromachining

    A 100 nm thick InGaN/GaN multiple quantum-well column-crystallized thin film was deposited on Si(111) substrate, with InN as the interlayer, by molecular beam epitaxy. The diameter of the column crystal is about 40 nm. Transmission electron microscopy images showed clear five-period well layers. Photoluminescence measurements demonstrated a wide emission wavelength from about 500 to 800 nm with the full width at half maximum of 107 nm at room temperature. An unusual photoluminescence peak position shift was observed from the optical measurement. The selected area electron diffraction image demonstrated the hexagonal wurtzite structure of the column crystal. A self-supported GaN-based active subwavelength grating was proposed, and the active subwavelength grating structure was fabricated from the InGaN/GaN quantum-well thin film by a Si micromachining process

  9. 1H-1H correlations across N-H···N hydrogen bonds in nucleic acids

    In 2HJNN-COSY experiments, which correlate protons with donor/acceptor nitrogens across Nd···HNa bonds, the receptor nitrogen needs to be assigned in order to unambiguously identify the hydrogen bond. For many situations this is a non-trivial task which is further complicated by poor dispersion of (Na,Nd) resonances. To address these problems, we present pulse sequences to obtain direct, internucleotide correlations between protons in uniformly 13C/15N labeled nucleic acids containing Nd···HNa hydrogen bonds. Specifically, the pulse sequence H2(N1N3)H3 correlates H2(A,ω1):H3(U,ω2) protons across Watson-Crick A-U and mismatched G·A base pairs, the sequences H5(N3N1)H1/H6(N3N1)H1 correlate H5(C,ω1)/H6(C,ω1):H1(G,ω2) protons across Watson-Crick G-C base pairs, and the H2(N2N7)H8 sequence correlates NH2(G,A,C;ω1):H8(G,A;ω2) protons across G·G, A·A, sheared G·A and other mismatch pairs. These 1H-1H connectivities circumvent the need for independent assignment of the donor/acceptor nitrogen and related degeneracy issues associated with poorly dispersed nitrogen resonances. The methodology is demonstrated on uniformly 13C/15N labeled samples of (a) an RNA regulatory element involving the HIV-1 TAR RNA fragment, (b) a multi-stranded DNA architecture involving a G·(C-A) triad-containing G-quadruplex and (c) a peptide-RNA complex involving an evolved peptide bound to the HIV-1 Rev response element (RRE) RNA fragment

  10. Complete {sup 1}H and {sup 13}C NMR structural assignments for a group of four goyazensolide-type furanoheliangolides

    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)

  11. Complete 1H and 13C NMR structural assignments for a group of four goyazensolide-type furanoheliangolides

    Four goyazensolide-type sesquiterpene lactones - lychnofolide, centratherin, goyazensolide and goyazensolide acetate - were thoroughly studied by NMR experimental techniques. 1H NMR, 13C NMR {1H}, 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)

  12. 5.5-MeV proton irradiation of a strained quantum-well laser diode and a multiple quantum-well broad-band LED

    The degradation under 5.5-MeV proton irradiation of two classes of quantum-well-based fiber-optic light sources was evaluated for satellite applications. The first was an InGaAs/GaAs strained-layer quantum-well (QW) laser; the second was a broad-band light-emitting diode (LED) based on dual asymmetric quantum wells in the InGaAs/GaAs/AlGaAs system. In contrast to earlier reports comparing bulk active-region heterostructure LEDs with similarly structured laser diodes, these QW LEDs were more tolerant of proton irradiation (-3dB power at ∼3x1013 protons/cm2) than the QW lasers (-3dB power at ∼3x1012 protons/cm2). The LEDs were operated far into gain saturation with a high-loss cavity structure, while the lasers were operated in a region where gain was more sensitive to current density. Therefore atomic displacement-related recombination sites had a greater detrimental effect upon the lasers than the LEDs. The lasers held constant slope efficiency, and current thresholds increased linearly with proton fluence, while both LED power and slope efficiency decreased with proton fluence. Similar damage factors were found to those predicted from a universal damage factor versus non-ionizing energy deposition relation reported by others, and appears to extend that relation to include these QW photonic devices

  13. Radiative recombination mechanism of carriers in InGaN/AlInGaN multiple quantum wells with varying aluminum content

    Highlights: • Structural and optical properties of In GaN/AlxInyGa1−x−yN 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 In0.20Ga0.80N/AlxInyGa1−x−yN 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 In0.20Ga0.80N 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

  14. Observation of anomalous linear photogalvanic effect and its dependence on wavelength in undoped InGaAs/AlGaAs multiple quantum well.

    Zhu, Laipan; Liu, Yu; Gao, Hansong; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai

    2014-01-01

    We observed an anomalous linear photogalvanic effect (ALPGE) in undoped InGaAs/AlGaAs multiple quantum well and studied its wavelength dependence in details. This effect is believed to originate from the optical momentum alignment effect and the inhomogeneity of light intensity. We find that the spot location with the maximum ALPGE current is wavelength independent. And the normalized ALPGE current decreasing at smaller wavelengths is attributed to the sharp decrease of the momentum and energy relaxation time. The electrical measurement of the spectra dependence of ALPGE is highly sensitive proving to be an effective method for detecting the momentum anisotropy of photoinduced carriers and band coupling. PMID:25258612

  15. Improved light-emitting diode performance by conformal overgrowth of multiple quantum wells and fully coalesced p-type GaN on GaN nanowires

    Frajtag, P.; Hosalli, A. M.; Bradshaw, G. K.; Nepal, N.; El-Masry, N. A.; Bedair, S. M.

    2011-04-01

    We demonstrate a light-emitting diode (LED) structure with multiple quantum wells (MQWs) conformally grown on semipolar and nonpolar plane facets of n-GaN nanowires (NWs), followed by deposition of fully coalesced p-GaN on these nanowires. Overgrowth on the nanowires' tips results in inclusion of high density voids, about one micron in height, in the GaN film. The light output intensity of NWs LEDs is more than three times higher than corresponding c-plane LEDs grown simultaneously. We believe this results from a reduced defect density, increased effective area of conformally grown MQWs, absence of polar plane orientation, and improved light extraction.

  16. Localized surface optical phonon mode in the InGaN/GaN multiple-quantum- wells nanopillars: Raman spectrum and imaging

    Ning, JQ; Xu, SJ; Zhu, JH; Zheng, CC; Zhang, SM; Yang, H.

    2011-01-01

    An interesting phonon mode at around 685-705 cm -1 was clearly observed in the Raman spectra of InGaN/GaN multiple-quantum-wells nanopillars with different diameters at room temperature. The Raman peak position of this mode is found to show a distinct dependence on the nanopillar size, which is in well agreement with theoretical calculation of the surface optical (SO) phonon modes of nanopillars. Moreover, this kind of SO phonon was evidenced to be located on the pillar surface by using scann...

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

    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...

  18. Quantum memory Quantum memory

    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

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

    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.

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

    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

  1. Analysis of intracranial cystic disease on 1H MR spectroscopy

    Objective: To analyze the features of intracrayze the features of intracranial cystic diseases on 1H MRS, and to evaluate the applicable value of 1H MRS. Methods: Fifty-two patients were examinated by single voxel 1H MRS, included I-II graded astrocytomas (n=8), glioblastomas (n=9), metastasis (n=13), brain abscesses (n=10), epidermoids (n=4), anachnoid cysts (n=5), brain Cysticerciasis (n=3). Results: (1) There was only Lac in I-II graded astrocytomas. But in glioblastomas, as were as all showed Lac, 4 cases showed low Cho and NAA and 2 cases Lip. (2) In 13 metastasis patients, 7 cases only presented Lac, 6 cases showed Cho, 3 cases showed low NAA and 6 ones Lip. (3) In brain abscesses, all showed Lac, 9 cases displayed AA, 6 cases showed Ace, 5 cases appeared Suc and Ala, 2 eases had Lip. (4) Four eases of epidermoid showed Lac, one showed Lip. In 4 arachnoid cysts, 2 cases had low Lac, one showed Lip. Three cases of cysticercosis showed Lac, Ace, Suc, Ala and no AA, Cho, NAA. Conclusion: Lac is the most common resonance peak on 1H MRS in intracranial cystic diseases and for no diagnostic specificity. AA combined Ace, Suc, and Ala are highly specificity for brain abscess. Ace, Suc and Ala appearance cues the the possible existence of cysticercosis. 1H MRS is helpful for the qualitative diagnosis of intracranial disease. (authors)

  2. A novel usage of hydrogen treatment to improve the indium incorporation and internal quantum efficiency of green InGaN/GaN multiple quantum wells simultaneously

    Ren, Peng; Zhang, Ning; Xue, Bin; Liu, Zhe; Wang, Junxi; Li, Jinmin

    2016-05-01

    The challenge for improving the internal quantum efficiency (IQE) of InGaN-based light emitting diodes (LED) in the green light range is referred to as the ‘green gap’. However the IQE of InGaN-based LEDs often drops when the emission peak wavelength is adjusted through reducing the growth temperature. Although hydrogen (H2) can improve surface morphology, it reduces the indium incorporation significantly. Here, a novel usage of H2 treatment on the GaN barrier before the InGaN quantum well is demonstrated to enhance indium incorporation efficiency and improve the IQE simultaneously for the first time. The mechanism behind it is systematically investigated and explained in detail. The possible reason for this phenomenon is the strain relieving function by the undulant GaN barrier surface after H2 treatment. Test measurements show that applying 0.2 min H2 treatment on the barrier would reduce defects and enhance indium incorporation, which would improve the localization effect and finally lead to a higher IQE. Although further increasing the treatment time to 0.4 min incorporates more indium atoms, the IQE decreases at the expense of more defects and a larger polarization field than the 0.2 min sample.

  3. Wine analysis to check quality and authenticity by fully-automated 1H-NMR

    Spraul Manfred

    2015-01-01

    Full Text Available Fully-automated high resolution 1H-NMR spectroscopy offers unique screening capabilities for food quality and safety by combining non-targeted and targeted screening in one analysis (15–20 min from acquisition to report. The advantage of high resolution 1H-NMR is its absolute reproducibility and transferability from laboratory to laboratory, which is not equaled by any other method currently used in food analysis. NMR reproducibility allows statistical investigations e.g. for detection of variety, geographical origin and adulterations, where smallest changes of many ingredients at the same time must be recorded. Reproducibility and transferability of the solutions shown are user-, instrument- and laboratory-independent. Sample prepara- tion, measurement and processing are based on strict standard operation procedures which are substantial for this fully automated solution. The non-targeted approach to the data allows detecting even unknown deviations, if they are visible in the 1H-NMR spectra of e.g. fruit juice, wine or honey. The same data acquired in high-throughput mode are also subjected to quantification of multiple compounds. This 1H-NMR methodology will shortly be introduced, then results on wine will be presented and the advantages of the solutions shown. The method has been proven on juice, honey and wine, where so far unknown frauds could be detected, while at the same time generating targeted parameters are obtained.

  4. Study of electro-optic effect in asymmetrically ramped AlInGaAs multiple quantum well structures

    Sadiq, Muhammad Usman; Peters, Frank H.; Corbett, Brian [Tyndall National Institute, Lee Maltings, Cork (Ireland); Department of Physics, University College Cork, Cork (Ireland); O' Callaghan, James; Roycroft, Brendan; Thomas, Kevin; Pelucchi, Emanuele [Tyndall National Institute, Lee Maltings, Cork (Ireland)

    2016-04-15

    We investigate the electro-optic properties of two oppositely ramped asymmetric quantum well structures in the AlInGaAs material system. The grading of the bandgap in the quantum wells has been achieved by changing the ratio of Al to Ga in the quaternary alloy during the epitaxial growth. The surface normal photo-response and the Fabry-Perot fringe shift in straight waveguides are compared for both structures as a function of applied voltage at 1550 nm for TE-polarized light. The measurements show a change in the refractive index due to a red shift of the excitonic resonances due to the quantum-confined Stark effect. The 10 quantum well structure with a ramp up of the bandgap in the growth direction leads to the figure of merit of the voltage for a π phase shift, V{sub π} by length, L, V{sub π} x L, of 6 as compared to 7 V . mm in the structure with a ramp in opposite direction. Further investigations show that the reduction in V{sub π} is due to increased absorption at high reverse bias which induces a non-linear phase change. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Study of electro-optic effect in asymmetrically ramped AlInGaAs multiple quantum well structures

    We investigate the electro-optic properties of two oppositely ramped asymmetric quantum well structures in the AlInGaAs material system. The grading of the bandgap in the quantum wells has been achieved by changing the ratio of Al to Ga in the quaternary alloy during the epitaxial growth. The surface normal photo-response and the Fabry-Perot fringe shift in straight waveguides are compared for both structures as a function of applied voltage at 1550 nm for TE-polarized light. The measurements show a change in the refractive index due to a red shift of the excitonic resonances due to the quantum-confined Stark effect. The 10 quantum well structure with a ramp up of the bandgap in the growth direction leads to the figure of merit of the voltage for a π phase shift, Vπ by length, L, Vπ x L, of 6 as compared to 7 V . mm in the structure with a ramp in opposite direction. Further investigations show that the reduction in Vπ is due to increased absorption at high reverse bias which induces a non-linear phase change. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. 脑胶质瘤的1H MRS

    杨桂芬; 田伟

    2005-01-01

    活体质子磁共振波谱(proton magnetic resonance spectroscopy,1H MRS)由于能够无创性检测肿瘤组织及正常表观组织代谢物的变化,目前在胶质瘤的分级、诊断、范围确定及鉴别诊断中有积极的应用价值。本文主要介绍1H MRS在胶质瘤中的研究现状。

  7. Quantum resource studied from the perspective of quantum state superposition

    Wu, Chengjun; Li, Junhui; Luo, Bin; Guo, Hong

    2014-01-01

    Quantum resources,such as discord and entanglement, are crucial in quantum information processing. In this paper, quantum resources are studied from the aspect of quantum state superposition. We define the local superposition (LS) as the superposition between basis of single part, and nonlocal superposition (NLS) as the superposition between product basis of multiple parts. For quantum resource with nonzero LS, quantum operation must be introduced to prepare it, and for quantum resource with ...

  8. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to $\\sqrt {s}$ = 7 TeV

    Ghosh, Premomoy

    2012-01-01

    Proton-proton collisions at new high energies ($\\sqrt {s} =$ 2.36 and 7 TeV) at LHC resulted into greater mean multiplicities ($$) of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval $|\\eta|<$2.4. The change is most prominent with data at $\\sqrt{s} = 7$ TeV. These new observations merit further studies. We consider a two-component model of particle production to analyze multiplicity distributions of charged hadrons from proton-proton collisions at centre-of-mass energies $\\sqrt{s} = $ 0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals $|\\eta|$ of increasing width around the centre-of-mass pseudorapidity $\\eta_{cm} = 0$. The model, based on quantum statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a cha...

  9. Nanometer-scale monitoring of quantum-confined Stark effect and emission efficiency droop in multiple GaN/AlN quantum disks in nanowires

    Zagonel, L. F.; Tizei, L. H. G.; Vitiello, G. Z.; Jacopin, G.; Rigutti, L.; Tchernycheva, M.; Julien, F. H.; Songmuang, R.; Ostasevicius, T.; de la Peña, F.; Ducati, C.; Midgley, P. A.; Kociak, M.

    2016-05-01

    We report on a detailed study of the intensity dependent optical properties of individual GaN/AlN quantum disks (QDisks) embedded into GaN nanowires (NW). The structural and optical properties of the QDisks were probed by high spatial resolution cathodoluminescence (CL) in a scanning transmission electron microscope (STEM). By exciting the QDisks with a nanometric electron beam at currents spanning over three orders of magnitude, strong nonlinearities (energy shifts) in the light emission are observed. In particular, we find that the amount of energy shift depends on the emission rate and on the QDisk morphology (size, position along the NW and shell thickness). For thick QDisks (>4 nm), the QDisk emission energy is observed to blueshift with the increase of the emission intensity. This is interpreted as a consequence of the increase of carriers density excited by the incident electron beam inside the QDisks, which screens the internal electric field and thus reduces the quantum confined Stark effect (QCSE) present in these QDisks. For thinner QDisks (current threshold above which the energy shifts, marking the transition from unscreened to partially screened QCSE. From the threshold value we estimate the lifetime in the unscreened regime. These observations suggest that, counterintuitively, electrons of high energy can behave ultimately as single electron-hole pair generators. In addition, when we increase the current from 1 to 10 pA the light emission efficiency drops by more than one order of magnitude. This reduction of the emission efficiency is a manifestation of the "efficiency droop" as observed in nitride-based 2D light emitting diodes, a phenomenon tentatively attributed to the Auger effect.

  10. Metabolite Characterization in Peritoneal Dialysis Effluent Using High-resolution 1H and 1H-13C NMR Spectroscopy

    Guleria, Anupam; Rawat, Atul; Khetrapal, C L; Prasad, Narayan; Kumar, Dinesh

    2014-01-01

    Metabolite analysis of peritoneal dialysis (PD) effluent may provide information regarding onset and progression of complications associated with prolonged PD therapy. In this context, the NMR detectable small metabolites of PD effluent samples were characterized using high resolution 1H and 1H-13C NMR spectroscopy. The various spectra were recorded (at 800 MHz proton frequency) on PD effluent samples obtained after 4 hour (intraperitoneal) dwell time from patients with end stage renal failure (ESRF) and continuing normally on PD therapy. Inspite of devastating spectral feature of PD effluent due to the presence of intense resonances from glucose and lactate, we were able to identify about 53 small endogenous metabolites (including many complex coupled spin systems) and more than 90 % of the total CH cross peaks of 1H-13C HSQC spectrum were identified specific to various metabolites of PD effluent. We foresee that the characteristic fingerprints of various metabolites of control PD effluent samples will be us...

  11. Development and application of multiple-quantum coherence techniques for in vivo sodium MRI at high and ultra-high field strengths

    Sodium magnetic resonance imaging (MRI) can quantify directly and non-invasively tissue sodium concentration levels in vivo. Tissue sodium concentration levels are tightly regulated and have been shown to be directly linked to cell viability. The intracellular sodium concentration is an even more specific parameter. The triple-quantum filtering (TQF) technique for sodium MRI has been suggested to detect the intracellular sodium only. Despite their huge potential, only few studies with sodium MRI have been carried out because of the long acquisition times of sodium MRI techniques, their susceptibility to static field inhomogeneities and their limited signal-to-noise ratio compared to proton MRI. Three novel techniques that address these limitations are presented in this thesis: (a) a sodium MRI sequence that acquires simultaneously both tissue sodium concentration maps and TQF images, (b) a phase-rotation scheme that allows for the acquisition of static field inhomogeneity insensitive TQF images, and (c) the combination of the two aforementioned techniques with optimised parameters at the ultra-high fi eld strength of 9.4 T in vivo. The SISTINA sequence - simultaneous single-quantum and triple-quantum filtered imaging of 23Na - is presented. The sequence is based on a TQF acquisition with a Cartesian readout and a three-pulse preparation. The delay between the first two pulses is used for an additional ultra-short echo time 3D radial readout. The method was implemented on a 4T scanner. It is validated in phantoms and in healthy volunteers that this additional readout does not interfere with the TQ preparation. The method is applied to three cases of brain tumours. The tissue sodium concentration maps and TQF images are presented and compared to 1H MR and positron emission tomography images. The three-pulse TQF preparation is sensitive to static field inhomogeneities. This problem is caused by destructive interference of different coherence pathways. To address this

  12. 1H NMR spectroscopy-based interventional metabolic phenotyping

    Lauridsen, Michael B; Bliddal, Henning; Christensen, Robin;

    2010-01-01

    1H NMR spectroscopy-based metabolic phenotyping was used to identify biomarkers in the plasma of patients with rheumatoid arthritis (RA). Forty-seven patients with RA (23 with active disease at baseline and 24 in remission) and 51 healthy subjects were evaluated during a one-year follow-up with...

  13. Main: 1H1Y [RPSD[Archive

    Full Text Available 1H1Y イネ Rice Oryza sativa L. D-Ribulose-5-Phosphate ... 3-Epimerase Oryza Sativa Molecule: D-Ribul ... ose-5-Phosphate ... 3-Epimerase; Chain: A, B; Engineered: Yes Isomeras ... e 5.1.3.1 (D-Ribulose-5-Phosphate ... 3-Epimerase) S.Jelakovic, G.E.Schulz S.Jelakovic, ...

  14. Main: 1H1Z [RPSD[Archive

    Full Text Available 1H1Z イネ Rice Oryza sativa L. D-Ribulose-5-Phosphate ... 3-Epimerase Oryza Sativa Molecule: D-Ribul ... ose-5-Phosphate ... 3-Epimerase; Chain: A, B; Engineered: Yes Isomeras ... e 5.1.3.1 (D-Ribulose-5-Phosphate ... 3-Epimerase) S.Jelakovic, G.E.Schulz S.Jelakovic, ...

  15. Liver Metabolite Concentrations Measured with 1H MR Spectroscopy

    Ouwerkerk, Ronald; PETTIGREW, RODERIC I.; Gharib, Ahmed M.

    2012-01-01

    In vivo measurement of liver choline concentrations in healthy humans is feasible, and even measurement of glycogen can be achieved in some patients at 3.0 T with point-resolved 1H MR spectroscopy by using navigator-guided synchronization to respiratory motion and state-of-the-art B0 field shimming techniques.

  16. Applications of 1H-NMR to Biodiesel Research

    Biodiesel is an alternative diesel fuel derived from vegetable oils, animal fats, or used cooking oils. It is produced by reacting these materials with an alcohol in the presence of a catalyst to give the corresponding mono-alkyl esters. 1H-NMR is a routine analytical method that has been used for...

  17. Braided C*-quantum groups

    Roy, Sutanu

    2016-01-01

    We propose a general theory of braided quantum groups in the C*-algebraic framework. More precisely, we construct braided quantum groups using manageable braided multiplicative unitaries over a regular C*-quantum group. We show that braided C*-quantum groups are equivalent to C*-quantum groups with projection.

  18. Quantum Random Number Generators

    Herrero-Collantes, Miguel; Garcia-Escartin, Juan Carlos

    2016-01-01

    Random numbers are a fundamental resource in science and engineering with important applications in simulation and cryptography. The inherent randomness at the core of quantum mechanics makes quantum systems a perfect source of entropy. Quantum random number generation is one of the most mature quantum technologies with many alternative generation methods. We discuss the different technologies in quantum random number generation from the early devices based on radioactive decay to the multipl...

  19. Radiative recombination mechanism of carriers in InGaN/AlInGaN multiple quantum wells with varying aluminum content

    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.

  20. Mixed Quantum-Classical Dynamics Methods for Strong-Field Processes: Multiple-trajectory Ehrenfest dynamics + decoherence terms

    Suzuki, Yasumitsu; Watanabe, Kazuyuki; Abedi, Ali; Agostini, Federica; Min, Seung Kyu; Maitra, Neepa; Gross, E. K. U.

    The exact factorization of the electron-nuclear wave function allows to define the time-dependent potential energy surfaces (TDPESs) responsible for the nuclear dynamics and electron dynamics. Recently a novel coupled-trajectory mixed quantum-classical (CT-MQC) approach based on this TDPES has been developed, which accurately reproduces both nuclear and electron dynamics. Here we study the TDPES for laser-induced electron localization with a view to developing a MQC method for strong-field processes. We show our recent progress in applying the CT-MQC approach to the systems with many degrees of freedom.

  1. 5-Pentyl-4-phenylsulfonyl-1H-pyrazol-3-ol

    Tara Shahani

    2010-06-01

    Full Text Available In the title compound, C14H18N2O3S, the 1H-pyrazole ring is approximately planar, with a maximum deviation of 0.005 (1 Å. The dihedral angle formed between the 1H-pyrazole and phenyl rings is 79.09 (5°. Pairs of intermolecular N—H...O and O...H...N hydrogen bonds form dimers between neighboring molecules, generating R22(10 ring motifs. These dimers are further linked byintermolecular N—H...O and O—H...N hydrogen bonds into a two-dimensional array parallel to the ac plane. The crystal structure is also stabilized by C—H...π interactions.

  2. 2-Methyl-1H-benzimidazol-3-ium hydrogen phthalate

    YuanQi Yu; Haidong He; Kai Tong; Shouwen Jin; Feng Lin

    2011-01-01

    The asymmetric unit of the title compound, C8H9N2+·C8H5O4−, contains two independent ion pairs. In each 2-methyl-1H-benzimidazolium ion, an intramolecular O—H...O bond forms an S(7) graph-set motif. In the crystal, the components are linked by N—H...O hydrogen bonds, forming chains along [210]. Further stabilization is provided by weak C—H...O hydrogen bonds.

  3. Laundering and Deinking Applications of 1H NMR Imaging

    Tutunjian, P. N.; Borchardt, J. K.; Prieto, N. E.; Raney, K. H.; Ferris, J. A.

    One-dimensional 1H NMR imaging techniques are used to visualize oil removal from fabrics and paper fibers immersed in aqueous solutions of nonionic detergents. The method provides a unique approach to the study of oil-removal kinetics in nonionic detergent systems where traditional optical techniques fail due to solution turbidity. The only requirement of the NMR experiment is the use of deuterated water in order to selectively image the hydrocarbon phase. Preliminary applications to laundering and paper deinking are discussed.

  4. Hochfeld 1H-NMR-Mikroskopie zur biophysikalischen Grundlagenforschung

    Haddad, Daniel

    2005-01-01

    Dank der mit modernen NMR-Spektrometern (Kernspintomographen) routinemäßig realisierbaren isotropen räumlichen Auflösungen von wenigen Mikrometern, ergeben sich für die 1H NMR-Mikroskopie zahlreiche neue Anwendungsgebiete. Allerdings sind die Möglichkeiten und Grenzen der NMR-Mikroskopie bezüglich ihrer praktischen Anwendbarkeit bisher nur wenig untersucht worden. Die vorliegende Arbeit ist im Bereich der biophysikalischen Grundlagenforschung angesiedelt und soll die praktische Anwendbarkeit ...

  5. Site-resolved multiple-quantum filtered correlations and distance measurements by magic-angle spinning NMR: Theory and applications to spins with weak to vanishing quadrupolar couplings

    We discuss and analyze four magic-angle spinning solid-state NMR methods that can be used to measure internuclear distances and to obtain correlation spectra between a spin I = 1/2 and a half-integer spin S > 1/2 having a small quadrupolar coupling constant. Three of the methods are based on the heteronuclear multiple-quantum and single-quantum correlation experiments, that is, high rank tensors that involve the half spin and the quadrupolar spin are generated. Here, both zero and single-quantum coherence of the half spins are allowed and various coherence orders of the quadrupolar spin are generated, and filtered, via active recoupling of the dipolar interaction. As a result of generating coherence orders larger than one, the spectral resolution for the quadrupolar nucleus increases linearly with the coherence order. Since the formation of high rank tensors is independent of the existence of a finite quadrupolar interaction, these experiments are also suitable to materials in which there is high symmetry around the quadrupolar spin. A fourth experiment is based on the initial quadrupolar-driven excitation of symmetric high order coherences (up to p = 2S, where S is the spin number) and subsequently generating by the heteronuclear dipolar interaction higher rank (l + 1 or higher) tensors that involve also the half spins. Due to the nature of this technique, it also provides information on the relative orientations of the quadrupolar and dipolar interaction tensors. For the ideal case in which the pulses are sufficiently strong with respect to other interactions, we derive analytical expressions for all experiments as well as for the transferred echo double resonance experiment involving a quadrupolar spin. We show by comparison of the fitting of simulations and the analytical expressions to experimental data that the analytical expressions are sufficiently accurate to provide experimental 7Li–13C distances in a complex of lithium, glycine, and water. Discussion

  6. Multimode Raman light-atom interface in warm atomic ensemble as multiple three-mode quantum operations

    Parniak, Michał; Wasilewski, Wojciech

    2015-01-01

    We analyze the properties of a Raman quantum light-atom interface in long atomic ensemble and its applications as a quantum memory or two-mode squeezed state generator. We include both Stokes and anti-Stokes scattering and the effects of Doppler broadening in buffer gas assuming frequent velocity-averaging collisions. We find the Green functions describing multimode transformation from input to output fields of photons and atomic excitations. Proper mode basis is found via singular value decomposition. It reveals that triples of modes are coupled by a transformation equivalent to a combination of two beamsplitters and a two-mode squeezing operation. We analyze the possible transformations on an example of warm rubidium-87 vapor. We find that the fidelity of the mapping of a single excitation between the memory and light is strictly limited by the fractional contribution of the Stokes scattering in predominantly anti-Stokes process. The model we present bridges the gap between the Stokes only and anti-Stokes o...

  7. Photocarrier dynamics near V-shaped pits in InxGa1−xN/GaN multiple quantum wells

    Highlights: • Correlations between carrier dynamics and structural defects of InGaN MQWs exist. • PL intensity is much weaker in the V-shaped pits than in the regular c-plane. • Blue-shifted photoluminescence spectrum is not observed at the V-pits. • A kinetic model including carriers recombination and diffusion is presented. • The model estimates the nonradiative recombination time as 10 ps at the V-pits. - Abstract: Space- and time-resolved photoluminescence (PL) has been employed to investigate correlations between the carrier dynamics and structural defects known as V-shaped pits in InGaN/GaN multiple quantum wells (MQWs). The pits exhibit much lower PL intensity compared to MQWs of the normal c-plane indicating a high density of nonradiative recombination centers in the pits. However, the PL peak wavelength, which is expected to experience a blueshift at the pits due to the stronger confinement effect and reduced quantum-confined Stark effect, do not show any spatial dependence that is correlated with the defects. This is ascribed to dominant ultrafast (<10 ps) nonradiative recombination at the pits and additional diffusion into the c-plane leading to radiative recombination. By contrast, weak but clear correlations between the pits and PL decay time were observed on nanosecond timescales. This can be explained by a kinetic model that includes the nonradiative recombination and diffusion of carriers at the pits

  8. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-02-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1.

  9. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  10. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids.

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs' surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  11. Enhanced excitation efficiency of Eu ions in Eu-doped GaN/AlGaN multiple quantum well structures grown by organometallic vapor phase epitaxy

    Arai, Takanori; Timmerman, Dolf; Wakamatsu, Ryuta; Lee, Dong-gun; Koizumi, Atsushi; Fujiwara, Yasufumi, E-mail: fujiwara@mat.eng.osaka-u.ac.jp

    2015-02-15

    We have grown Eu-doped GaN (GaN:Eu)/AlGaN multiple quantum well (MQW:Eu) structures by organometallic vapor phase epitaxy and investigated their Eu luminescence properties. The MQW:Eu structures exhibited enhancement of Eu photoluminescence (PL) intensity with an integrated intensity which was three times higher than that of conventional GaN:Eu structures. PL and time-resolved PL measurements suggest that this enhancement is due to the improvement of the excitation efficiency of Eu ions in the MQW:Eu structure. Following these results, we have successfully fabricated a light-emitting diode based on the MQW:Eu structures, which demonstrated an improved output power efficiency of red light. - Highlights: • Eu doped GaN quantum well structures were grown by OMVPE. • The luminescence properties of these structures were studied. • Both electrical and optical excitations of Eu ions are possible. • Both excitation methods show an increased efficiency. • The mechanism behind the increased efficiency is discussed.

  12. Enhanced excitation efficiency of Eu ions in Eu-doped GaN/AlGaN multiple quantum well structures grown by organometallic vapor phase epitaxy

    We have grown Eu-doped GaN (GaN:Eu)/AlGaN multiple quantum well (MQW:Eu) structures by organometallic vapor phase epitaxy and investigated their Eu luminescence properties. The MQW:Eu structures exhibited enhancement of Eu photoluminescence (PL) intensity with an integrated intensity which was three times higher than that of conventional GaN:Eu structures. PL and time-resolved PL measurements suggest that this enhancement is due to the improvement of the excitation efficiency of Eu ions in the MQW:Eu structure. Following these results, we have successfully fabricated a light-emitting diode based on the MQW:Eu structures, which demonstrated an improved output power efficiency of red light. - Highlights: • Eu doped GaN quantum well structures were grown by OMVPE. • The luminescence properties of these structures were studied. • Both electrical and optical excitations of Eu ions are possible. • Both excitation methods show an increased efficiency. • The mechanism behind the increased efficiency is discussed

  13. Low driving voltage in an organic light-emitting diode using MoO3/NPB multiple quantum well structure in a hole transport layer

    Mu, Xue; Wu, Xiao-Ming; Hua, Yu-Lin; Jiao, Zhi-Qiang; Shen, Li-Ying; Su, Yue-Ju; Bai, Juan-Juan; Bi, Wen-Tao; Yin, Shou-Gen; Zheng, Jia-Jin

    2013-02-01

    The driving voltage of an organic light-emitting diode (OLED) is lowered by employing molybdenum trioxide (MoO3)/N, N'-bis(naphthalene-1-yl)-N,N'-bis(phe-nyl)-benzidine (NPB) multiple quantum well (MQW) structure in the hole transport layer. For the device with double quantum well (DQW) structure of ITO/ [MoO3 (2.5 nm)/NPB (20 nm)]2/Alq3(50 nm)/LiF (0.8 nm)/Al (120 nm)], the turn-on voltage is reduced to 2.8 V, which is lowered by 0.4 V compared with that of the control device (without MQW structures), and the driving voltage is 5.6 V, which is reduced by 1 V compared with that of the control device at the 1000 cd/m2. In this work, the enhancement of the injection and transport ability for holes could reduce the driving voltage for the device with MQW structure, which is attributed not only to the reduced energy barrier between ITO and NPB, but also to the forming charge transfer complex between MoO3 and NPB induced by the interfacial doping effect of MoO3.

  14. Low driving voltage in an organic light-emitting diode using MoO3/NPB multiple quantum well structure in a hole transport layer

    Mu Xue; Wu Xiao-Ming; Hua Yu-Lin; Jiao Zhi-Qiang; Shen Li-Ying; Su Yue-Ju; Bai Juan-Juan

    2013-01-01

    The driving voltage of an organic light-emitting diode (OLED) is lowered by employing molybdenum trioxide (MoO3)/N,N'-bis(naphthalene-l-yl)-N,N'-bis(phe-nyl)-benzidine (NPB) multiple quantum well (MQW) structure in the hole transport layer.For the device with double quantum well (DQW) structure of ITO/ [MoO3 (2.5 nm)/NPB (20 nm)]2/Alq3(50 nm)/LiF (0.8 nm)/Al (120 nm)],the turn-on voltage is reduced to 2.8 V,which is lowered by 0.4 V compared with that of the control device (without MQW structures),and the driving voltage is 5.6 V,which is reduced by l V compared with that of the control device at the 1000 cd/m2.In this work,the enhancement of the injection and transport ability for holes could reduce the driving voltage for the device with MQW structure,which is attributed not only to the reduced energy barrier between ITO and NPB,but also to the forming charge transfer complex between MoO3 and NPB induced by the interfacial doping effect of MoO3.

  15. Low driving voltage in an organic light-emitting diode using MoO3/NPB multiple quantum well structure in a hole transport layer

    The driving voltage of an organic light-emitting diode (OLED) is lowered by employing molybdenum trioxide (MoO3)/N, N'-bis(naphthalene-1-yl)-N,N'-bis(phe-nyl)-benzidine (NPB) multiple quantum well (MQW) structure in the hole transport layer. For the device with double quantum well (DQW) structure of ITO/ [MoO3 (2.5 nm)/NPB (20 nm)]2/Alq3(50 nm)/LiF (0.8 nm)/Al (120 nm)], the turn-on voltage is reduced to 2.8 V, which is lowered by 0.4 V compared with that of the control device (without MQW structures), and the driving voltage is 5.6 V, which is reduced by 1 V compared with that of the control device at the 1000 cd/m2. In this work, the enhancement of the injection and transport ability for holes could reduce the driving voltage for the device with MQW structure, which is attributed not only to the reduced energy barrier between ITO and NPB, but also to the forming charge transfer complex between MoO3 and NPB induced by the interfacial doping effect of MoO3. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Spin transport in undoped InGaAs/AlGaAs multiple quantum well studied via spin photocurrent excited by circularly polarized light.

    Zhu, Laipan; Liu, Yu; Huang, Wei; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai

    2016-12-01

    The spin diffusion and drift at different excitation wavelengths and different temperatures have been studied in undoped InGaAs/AlGaAs multiple quantum well (MQW). The spin polarization was created by optical spin orientation using circularly polarized light, and the reciprocal spin Hall effect was employed to measure the spin polarization current. We measured the ratio of the spin diffusion coefficient to the mobility of spin-polarized carriers. From the wavelength dependence of the ratio, we found that the spin diffusion and drift of holes became as important as electrons in this undoped MQW, and the ratio for light holes was much smaller than that for heavy holes at room temperature. From the temperature dependence of the ratio, the correction factors for the common Einstein relationship for spin-polarized electrons and heavy holes were firstly obtained to be 93 and 286, respectively. PMID:26744148

  17. Enhanced Luminescence Efficiency of InGaN/GaN Multiple Quantum Wells by a Strain Relief Layer and Proper Si Doping

    Tsai, Ping-Chieh; Su, Yan-Kuin; Chen, Wen-Ray; Huang, Chun-Yuan

    2010-04-01

    The effects of a strain relief layer (SRL) employed in the InGaN/GaN light-emitting diodes (LEDs) was demonstrated. The wavelength shift was reduced to as small as 2.5 nm by inserting a SRL between n-GaN and InGaN/GaN multiple quantum wells (MQWs). For the improvement of optical properties, a proper Si-doped layer was simultaneously added in the last several barriers of In0.08Ga0.92N/GaN SRL. It can be found that the output power was increased more than 25% as the Si doping level was increased up to 5 times in the last three barriers of SRL at an injection current of 20 mA. Furthermore, the forward voltages at 20 mA were almost the same for all LEDs with different doping levels and positions.

  18. Evaluation of multiple-quantum-well structure on InGaN template using (11 anti 22) facet growth and mass transport

    Fujita, Daisuke; Miyatake, Takaaki; Shinagawa, Taku; Abe, Yuki; Murakami, Kazuma; Li, Bocheng; Matsumoto, Hiroyuki; Murayama, Satoru; Okada, Narihito; Tadatomo, Kazuyuki [Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai Ube, Yamaguchi, 755-8611 (Japan)

    2010-07-15

    We succeeded in the fabrication of a thick InGaN template by (11 anti 22) facet growth and mass transport. Thick InGaN was grown on a GaN (11 anti 22) facet with a stable facet structure. After 20 min annealing under a flow of NH3 and N2, the InGaN with the (11 anti 22) facet was perfectly embedded owing to mass transport. Subsequently, a multiple-quantum-well structure was fabricated on the InGaN template and characterized using monochromatic cathodoluminescence measurement. As a result, we found that there were two regions with peak emission wavelengths of 420 and 500 nm because of the compositional pulling effect. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Evaluation of multiple-quantum-well structure on InGaN template using (11 anti 22) facet growth and mass transport

    We succeeded in the fabrication of a thick InGaN template by (11 anti 22) facet growth and mass transport. Thick InGaN was grown on a GaN (11 anti 22) facet with a stable facet structure. After 20 min annealing under a flow of NH3 and N2, the InGaN with the (11 anti 22) facet was perfectly embedded owing to mass transport. Subsequently, a multiple-quantum-well structure was fabricated on the InGaN template and characterized using monochromatic cathodoluminescence measurement. As a result, we found that there were two regions with peak emission wavelengths of 420 and 500 nm because of the compositional pulling effect. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Simultaneous light emission and detection of InGaN/GaN multiple quantum well diodes for in-plane visible light communication on a chip

    Wang, Yongjin; Yang, Yongchao; Gao, Xumin; Zhu, Bingcheng; Cai, Wei; Yuan, Jialei; Zhang, Rong; Zhu, Hongbo

    2016-01-01

    This paper presents the design, fabrication, and experimental characterization of monolithically integrated p-n junction InGaN/GaN multiple quantum well diodes (MQWDs) and suspended waveguides. Suspended MQWDs can be used as transmitters and receivers simultaneously, and suspended waveguides are used for light coupling to create an in-plane visible light communication system. Compared to the waveguide with separation trench, the calculated total light efficiency is increased from 18% to 22% for the continuous waveguide. The MQWDs are characterized by their typical current-voltage performance, and the pulse excitation measurements confirm that the InGaN/GaN MQWDs can achieve the light emission and photodetection at the same time. The photocurrent measurements indicate that the photocurrent is modulated by a bias voltage and that the photons are being supplied from another transmitter. An experimental demonstration is presented showing that the proposed device works well for in-plane full-duplex communication u...

  1. Effect of Al Doping in the InGaN/GaN Multiple Quantum Well Light Emitting Diodes Grown by Metalorganic Chemical Vapour Deposition

    LU Yu; YANG Zhi-Jian; PAN Yao-Bo; XU Ke; HU Xiao-Dong; ZHANG Bei; ZHANG Guo-Yi

    2006-01-01

    The effect of Al doping in the GaN layer of InGaN/GaN multiple quantum-well light emitting diodes (LEDs) grown by metalorganic chemical vapour deposition is investigated by using photoluminescence (PL) and high-resolution x-ray diffraction. The full width at half maximum of PL of Al doped LEDs is measured to be about 12nm. The band edge photoluminescence emission intensity is enhanced significantly. In addition, the in-plane compressive strain in the Al-doped LEDs is improved significantly and measured by reciprocal space map. The output power of Al-doped LEDs is 130mW in the case of the induced current of 200mA.

  2. Spin depolarization under low electric fields at low temperatures in undoped InGaAs/AlGaAs multiple quantum well

    The spin polarization under low electric fields (≤300 V/cm) at low temperatures has been studied in undoped InGaAs/AlGaAs multiple quantum well. The spin polarization was created by optical spin orientation using circularly polarized light and the inverse spin-Hall effect was employed to measure the spin polarization current. We observed an obvious spin depolarization especially at lower temperatures (80–120 K). We ascribed the spin depolarization of the photoinduced electrons to the heating effect from the low electric fields (the low field regime 50–300 V/cm). This spin depolarization due to the heating effect is sensitive to temperature and electric field, suggesting a wide range of potential applications and devices.

  3. Growth of InGaAs/GaAsP multiple quantum well solar cells on mis-orientated GaAs substrates

    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.

  4. Strain-compensated (Ga,In)N/(Al,Ga)N/GaN multiple quantum wells for improved yellow/amber light emission

    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. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  6. MgZnO/MgO strained multiple-quantum-well nanocolumnar films: Stress-induced structural transition and deep ultraviolet emission

    Highlights: ► MgZnO/MgO strained multiple-quantum-wells nanocolumnar films are achieved. ► A epitaxial relationship with high-quality interface is established between MgZnO and MgO layers with large lattice mismatch. ► Stress-induced structural transition of MgZnO layers is observed. ► The wavelength-tunable deep-ultraviolet emission is obtained, and the 261 nm is known to be the shortest emission wavelength ever reported for MgZnO material. - Abstract: MgZnO/MgO strained multiple-quantum-wells (S-MQWs) with different structures are grown by pulsed laser deposition. The S-MQW films are composed of closely arranged, vertically oriented nanocolumns. Z-contrast scanning transmission electron microscopy observations and line-scan compositional analysis reveal that the nanocolumns are compositionally modulated along their length and have a MQW structure. A coherent epitaxial relationship with a sharp interface is established between MgZnO and MgO layers with large lattice mismatch. It is worth noting that the MgZnO layer undergoes a structural transition from hexagonal to cubic phase with its thickness decreasing. The calculations reveal that a large in-plane compressive stress dominates such an interesting phase transition process, stabilizes the low Mg-content MgZnO alloy in the anomalous cubic phase, and also leads to a broadening of the band gap. As a result, the wavelength-tunable deep-ultraviolet emission in the range of 261–314 nm is obtained from these S-MQW nanocolumnar films. The 261 nm is known to be the shortest emission wavelength ever reported for MgZnO material.

  7. Rapid solid-state NMR of deuterated proteins by interleaved cross-polarization from 1H and 2H nuclei

    Bjerring, Morten; Paaske, Berit; Oschkinat, Hartmut; Akbey, Ümit; Nielsen, Niels Chr.

    2012-01-01

    We present a novel sampling strategy, interleaving acquisition of multiple NMR spectra by exploiting initial polarization subsequently from 1H and 2H spins, taking advantage of their different T1 relaxation times. Different 1H- and 2H-polarization based spectra are in this way simultaneously recorded improving either information content or sensitivity by adding spectra. The so-called Relaxation-optimized Acquisition of Proton Interleaved with Deuterium (RAPID) 1H → 13C/ 2H → 13C CP/MAS multiple-acquisition method is demonstrated by 1D and 2D experiments using a uniformly 2H, 15N, 13C-labeled α-spectrin SH3 domain sample with all or 30% back-exchanged labile 2H to 1H. It is demonstrated how 1D 13C CP/MAS or 2D 13C- 13C correlation spectra initialized with polarization from either 1H or 2H may be recorded simultaneously with flexibility to be added or used individually for spectral editing. It is also shown how 2D 13C- 13C correlation spectra may be recorded interleaved with 2H- 13C correlation spectra to obtain 13C- 13C correlations along with information about dynamics from 2H sideband patterns.

  8. Proton-detected 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H-1H RFDR mixing on a natural abundant sample under ultrafast MAS

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-09-01

    In this contribution, we have demonstrated a proton detection-based approach on a natural abundant powdered L-Histidine HCl-H2O sample at ultrafast magic angle spinning (MAS) to accomplish 14N/14N correlation from a 3D 14N/14N/1H isotropic shift correlation experiment mediated through 1H finite-pulse radio frequency-driven recoupling (fp-RFDR). Herein the heteronuclear magnetization transfer between 14N and 1H has been achieved by HMQC experiment, whereas 14N/14N correlation is attained through enhanced 1H-1H spin diffusion process due to 1H-1H dipolar recoupling during the RFDR mixing. While the use of ultrafast MAS (90 kHz) provides sensitivity enhancement through increased 1H transverse relaxation time (T2), the use of micro-coil probe which can withstand strong 14N radio frequency (RF) fields further improves the sensitivity per unit sample volume.

  9. Influence of active nano particle size and material composition on multiple quantum emitter enhancements: Their Enhancement and Jamming Effects

    Arslanagic, Samel; Ziolkowski, Richard W.

    2014-01-01

    active coated nano-particles are examined here theoretically with regard to their ability to effectively enhance or jam the responses of quantum emitters, e.g., fluorescing molecules, and nano- antennas to an observer located in their far-field regions. The investigated spherical particles consist of a...... gain-impregnated silica nano-core covered with a nano-shell of a specific plasmonic material. Attention is devoted to the influence of the over-all size of these particles and their material composition on the obtained levels of active enhancement or jamming. Silver, gold and copper are employed as...... their nano- shells. The over-all diameters of the investigated coated nano-particles are taken to be 20 nm, 40 nm, and 60 nm, while maintaining the same ratio of the core radius and shell thickness. It is shown that the jamming levels, particularly when several emitters are present, are significantly...

  10. Quantitative evaluation of the lactate signal loss and its spatial dependence in press localized (1)H NMR spectroscopy.

    Jung, W I; Bunse, M; Lutz, O

    2001-10-01

    Localized (1)H NMR spectroscopy using the 90 degrees -t(1)-180 degrees -t(1)+t(2)-180 degrees -t(2)-Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t(1) and t(2). The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t(1)=t(2)) at an echo time of 2/J (approximately 290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creation of single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX(3) spin system: zero- and multiple-quantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. By calculating the density operator for various of the echo times TE=n/J, n=1, 2, 3,..., we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE=2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT. Taking also the VOD effect into account (2 mT/m slice selection gradients, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sinc pulses of 82% (52% NDOS, 30% PT) at TE=290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using a symmetrical PRESS sequence at TE=2/J. PMID:11567573

  11. Quantitative Evaluation of the Lactate Signal Loss and Its Spatial Dependence in PRESS Localized 1H NMR Spectroscopy

    Jung, Wulf-Ingo; Bunse, Michael; Lutz, Otto

    2001-10-01

    Localized 1H NMR spectroscopy using the 90°-t1-180°-t1+t2-180°-t2-Acq. PRESS sequence can lead to a signal loss for the lactate doublet compared with signals from uncoupled nuclei which is dependent on the choice of t1 and t2. The most striking signal loss of up to 78% of the total signal occurs with the symmetrical PRESS sequence (t1=t2) at an echo time of 2/J (≃290 ms). Calculations have shown that this signal loss is related to the pulse angle distributions produced by the two refocusing pulses which leads to the creation of single quantum polarization transfer (PT) as well as to not directly observable states (NDOS) of the lactate AX3 spin system: zero- and multiple-quantum coherences, and longitudinal spin orders. In addition, the chemical shift dependent voxel displacement (VOD) leads to further signal loss. By calculating the density operator for various of the echo times TE=n/J, n=1, 2, 3, …, we calculated quantitatively the contributions of these effects to the signal loss as well as their spatial distribution. A maximum signal loss of 75% can be expected from theory for the symmetrical PRESS sequence and TE=2/J for Hamming filtered sinc pulses, whereby 47% are due to the creation of NDOS and up to 28% arise from PT. Taking also the VOD effect into account (2 mT/m slice selection gradients, 20-mm slices) leads to 54% signal loss from NDOS and up to 24% from PT, leading to a maximum signal loss of 78%. Using RE-BURP pulses with their more rectangular pulse angle distributions reduces the maximum signal loss to 44%. Experiments at 1.5 T using a lactate solution demonstrated a maximum lactate signal loss for sinc pulses of 82% (52% NDOS, 30% PT) at TE=290 ms using the symmetrical PRESS sequence. The great signal loss and its spatial distribution is of importance for investigations using a symmetrical PRESS sequence at TE=2/J.

  12. Dynamic 1H NMR Studies of Schiff Base Derivatives

    Köylü, M. Z.; Ekinci, A.; Böyükata, M.; Temel, H.

    2016-01-01

    The spin-lattice relaxation time T 1 and the spin-spin relaxation time T 2 of two Schiff base derivatives, N,N'-ethylenebis(salicylidene)-1,2-diaminoethane (H2L1) and N,N'-ethylenebis (salicylidene)-1,3-diaminopropane (H2L2), in DMSO-d6 solvent were studied as a function of temperature in the range of 20-50°C using a Bruker Avance 400.132 MHz 1H NMR spectrometer. Based on the activation energy ( E a) and correlation time (τc), we believe that the Schiff base derivatives perform a molecular tumbling motion.

  13. Localization of epileptogenic focus by 1H MR spectroscopy

    In fourteen patients suffering from pharmacoresistant epilepsy with partial complex seizures, 1H MR spectra from the left and right hippocampus were assessed. From the ratios NAA/Cr, NAA/Cho and NAA/(Cr+Cho) the asymmetry coefficient was calculated which characterizes the reduced NAA (N-acetyl aspartate) concentration in the assumed epileptogenic focus. An agreement between MRS and the EEG findings was found in 10 out of 14 cases, i.e. in 71%. MR spectroscopy is therefore another non-invasive diagnostic method suitable for the assessment of lateralization of an epileptic focus before epileptosurgery. (author) 2 tabs., 3 figs., 30 refs

  14. 2-Methyl-1H-benzimidazol-3-ium hydrogen phthalate

    YuanQi Yu

    2011-10-01

    Full Text Available The asymmetric unit of the title compound, C8H9N2+·C8H5O4−, contains two independent ion pairs. In each 2-methyl-1H-benzimidazolium ion, an intramolecular O—H...O bond forms an S(7 graph-set motif. In the crystal, the components are linked by N—H...O hydrogen bonds, forming chains along [210]. Further stabilization is provided by weak C—H...O hydrogen bonds.

  15. 1H MR spectroscopy characteristics of cerebral alveolar echinococcosis

    Objective: To investigate the characteristics of proton magnetic resonance spectroscopy (1H MRS) in patients with cerebral alveolar echinococcosis (CAE). Methods: Thirteen patients with 33 lesions proven to be CAE histologically and clinically were examined by conventional MRI and 2D multi-voxel spectroscopy with a 3.0 T double gradient superconductivity magnetic resonance scanner. Concentrations of the metabolites containing N-acetyl-aspartic-acid (NAA), Choline (Cho), Creatine (Cr), lipids and lactic acid (Lip + Lac), myo-Inositol (mI) were detected and the value of Cho/Cr, NAA/Cr, (Lip + Lac)/Cr, mI/Cr were calculated. The values of Cho/Cr, NAA/Cr, (Lip + Lac)/Cr, mI/Cr were compared between the lesions and the contralateral normal brain parenchyma. Statistical analysis was performed using the Wilcoxon signed-rank test. Results: CAE 1H MRS in the lesions was characterized by the decrease of Cho, NAA to varying degrees, and a visible lipid with or without lactate peak. Compared with the control group, the ratio of NAA/Cr was decreased markedly, whereas Cho/Cr, mI/Cr increased mildly and (Lip + Lac)/Cr increased markedly in the lesions. The medians and interquartile ranges of Cho/Cr, NAA/Cr, (Lip + Lac)/Cr and mI/Cr in the lesions were: 1.88 (1.24-2.23), 1.32 (1.07-1.58), 32.96 (24.59-47.30) and 0.91 (0.67-1.08), respectively. The medians and interquartile ranges of Cho/Cr, NAA/Cr, (Lip + Lac)/Cr and mI/Cr of control group were 0.84 (0.704-0.98), 2.00 (1.80-2.18), 0.90 (0.74-0.99) and 0.26 (0.18-0.31), respectively. There were statistically significant differences of the measures between the lesions and the control regions (Z=-5.932, -6.086, -6.946, -6.984, P<0.01). Conclusions: Multi-voxel 1H MRS can reflect pathological characteristics of CAE. 1H MRS provides metabolic information for diagnosis of CAE and may be a supplement to conventional magnetic resonance examination. (authors)

  16. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires.

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-01-01

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased. PMID:27556534

  17. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-01-01

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased. PMID:27556534

  18. Temperature dependence of mid-infrared intersubband absorption in AlGaN/GaN multiple quantum wells

    Kotani, Teruhisa, E-mail: tkotani@iis.u-tokyo.ac.jp [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Advanced Technology Research Laboratories, Sharp Corporation, 2613-1 Ichinomoto-cho, Tenri, Nara 632-8567 (Japan); Arita, Munetaka [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Hoshino, Katsuyuki [Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Arakawa, Yasuhiko [Institute for Nano Quantum Information Electronics, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2016-02-01

    The temperature dependence of the mid-infrared intersubband (ISB) absorption in non-polar (m-plane) and polar (c-plane) AlGaN/GaN quantum wells (QWs) is studied. The ISB absorption shifts to higher energy as the temperature is reduced from 300 K to below 10 K. Both m-plane and c-plane QWs show a small energy shift (1.6–2.6 meV) compared to AlGaAs/GaAs (3.5–5.2 meV) and AlSb/InAs (6.2 and 12 meV) QWs. Theoretical calculations considering the temperature induced material constant changes show good agreement with the experimental results. These results suggest that ISB transition energies in AlGaN/GaN QWs are more stable against temperature change mainly because of the heavy effective masses and small nonparabolicities.

  19. Temperature dependence of mid-infrared intersubband absorption in AlGaN/GaN multiple quantum wells

    The temperature dependence of the mid-infrared intersubband (ISB) absorption in non-polar (m-plane) and polar (c-plane) AlGaN/GaN quantum wells (QWs) is studied. The ISB absorption shifts to higher energy as the temperature is reduced from 300 K to below 10 K. Both m-plane and c-plane QWs show a small energy shift (1.6–2.6 meV) compared to AlGaAs/GaAs (3.5–5.2 meV) and AlSb/InAs (6.2 and 12 meV) QWs. Theoretical calculations considering the temperature induced material constant changes show good agreement with the experimental results. These results suggest that ISB transition energies in AlGaN/GaN QWs are more stable against temperature change mainly because of the heavy effective masses and small nonparabolicities

  20. Fabrication of GeSn-multiple quantum wells by overgrowth of Sn on Ge by using molecular beam epitaxy

    We report on the fabrication and structural characterization of epitaxially grown ultra-thin layers of Sn on Ge virtual substrates (Si buffer layer overgrown by a 50 nm thick Ge epilayer followed by an annealing step). Samples with 1 to 5 monolayers of Sn on Ge virtual substrates were grown using solid source molecular beam epitaxy and characterized by atomic force microscopy. We determined the critical thickness at which the transition from two-dimensional to three-dimensional growth occurs. This transition is due to the large lattice mismatch between Ge and Sn (≈14.7%). By depositing Ge on top of Sn layers, which have thicknesses at or just below the critical thickness, we were able to fabricate ultra-narrow GeSn multi-quantum-well structures that are fully embedded in Ge. We report results on samples with one and ten GeSn wells separated by 5 and 10 nm thick Ge spacer layers that were characterized by high resolution transmission electron microscopy and X-ray diffraction. We discuss the structure and material intermixing observed in the samples

  1. Enhancement of photoluminescence efficiency from semi-polar InGaN/GaN multiple quantum wells with silver metal

    We have studied the effect of surface plasmon polariton (SPP) and localized surface plasmon (LSP) on the emission of semi-polar InGaN/GaN light emitting diode (LED) with multi-quantum wells structure. From the photoluminescence (PL) measurement at room temperature, spectrally-integrated enhancements of semi-polar SPP LEDs with 15 and 40-nm-thick Ag films were 1.7 and 2.9, respectively. The absorbance peak of Ag nanoparticles was red-shifted as diameter of Ag nanoparticles increases. However, the absorbance peak of Au nanoparticles was not related with their diameters. Spectrally-integrated enhancement of semi-polar LSP LED with 250-nm-diameter Ag nanoparticles was shown to 1.3. These results showed that the blue emission of semi-polar InGaN/GaN LED can be improved by SPP and LSP. - Highlights: • The enhancement of blue emission from semi-polar LED has been investigated. • The integrated PL intensity of semi-polar LED with 40-nm-thick Ag film was about 2.9. • The integrated PL intensity of semi-polar LED with Ag nanoparticles was about 1.3

  2. Onset of surface stimulated emission at 260 nm from AlGaN multiple quantum wells

    Li, Xiaohang

    2015-12-14

    We demonstrated onset of deep-ultraviolet (DUV) surface stimulated emission (SE) from c-plane AlGaNmultiple-quantum well(MQW)heterostructuresgrown on a sapphire substrate by optical pumping at room temperature. The onset of SE became observable at a pumping power density of 630 kW/cm2. Spectral deconvolution revealed superposition of a linearly amplified spontaneous emission peak at λ ∼ 257.0 nm with a full width at half maximum (FWHM) of ∼12 nm and a superlinearly amplified SE peak at λ ∼ 260 nm with a narrow FWHM of less than 2 nm. In particular, the wavelength of ∼260 nm is the shortest wavelength of surface SE from III-nitride MQWheterostructures to date. Atomic force microscopy and scanning transmission electron microscopy measurements were employed to investigate the material and structural quality of the AlGaNheterostructures, showing smooth surface and sharp layer interfaces. This study offers promising results for AlGaNheterostructuresgrown on sapphire substrates for the development of DUV vertical cavity surface emitting lasers(VCSELs).

  3. Fabrication of GeSn-multiple quantum wells by overgrowth of Sn on Ge by using molecular beam epitaxy

    Oliveira, F. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Fischer, I. A.; Schulze, J. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Benedetti, A. [CACTI, Univ. de Vigo, Campus Universitario Lagoas Marcosende 15, Vigo (Spain); Zaumseil, P. [IHP GmbH, Innovations for High Performance Microelectronics, Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Cerqueira, M. F.; Vasilevskiy, M. I. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Stefanov, S.; Chiussi, S. [Dpto. Fisica Aplicada, Univ. de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2015-12-28

    We report on the fabrication and structural characterization of epitaxially grown ultra-thin layers of Sn on Ge virtual substrates (Si buffer layer overgrown by a 50 nm thick Ge epilayer followed by an annealing step). Samples with 1 to 5 monolayers of Sn on Ge virtual substrates were grown using solid source molecular beam epitaxy and characterized by atomic force microscopy. We determined the critical thickness at which the transition from two-dimensional to three-dimensional growth occurs. This transition is due to the large lattice mismatch between Ge and Sn (≈14.7%). By depositing Ge on top of Sn layers, which have thicknesses at or just below the critical thickness, we were able to fabricate ultra-narrow GeSn multi-quantum-well structures that are fully embedded in Ge. We report results on samples with one and ten GeSn wells separated by 5 and 10 nm thick Ge spacer layers that were characterized by high resolution transmission electron microscopy and X-ray diffraction. We discuss the structure and material intermixing observed in the samples.

  4. A practical guide for the setup of a 1H-31P-13C double cross-polarization (DCP) experiment.

    Ciesielski, Wlodzimierz; Kassassir, Hassan; Potrzebowski, Marek J

    2011-01-01

    O-phospho-L-threonine is a convenient sample to setup a (1)H-(31)P-(13)C double cross-polarization (DCP) Hartmann-Hahn match. The (1)H-(31)P-(13)C technique is extremely sensitive to the rate of the sample spinning. Both zero-quantum (ZQ) and double-quantum (DQ) cross-polarization operate at an average spinning rate (6-7 kHz). At higher spinning rates (10 kHz), the DQCP mechanism dominates and leads to a reduction of signal intensity, in particular for lower (31)P RF field strength. The application of two shape pulses during the second cross-polarization greatly improves the signal to noise ratio allowing the recording of better quality spectra. (31)P-(13)C spectrally induced filtering in combination with cross-polarization (SPECIFIC-CP) experiments can be carried out under ZQCP and DQCP conditions if careful attention is paid to the choice of RF field amplitudes and carriers Ω. Application of 1D and 2D (1)H-(31)P-(13)C experiments is demonstrated on model samples; disodium ATP hydrate and O-phospho-L-tyrosine. PMID:21440422

  5. Angle-resolved photon-coincidence measurements in a multiple-scattering medium

    Smolka, Stephan; Muskens, Otto L.; Lagendijk, Ad; Lodahl, Peter

    2011-01-01

    agreement with the continuous mode quantum theory of multiple scattering of light. The presented experimental technique is essential in order to study quantum phenomena in multiple-scattering random media, such as quantum interference and quantum entanglement of photons....

  6. The Quantum Double in Integrable Quantum Field Theory

    Bernard, D.; Leclair, A.

    1992-01-01

    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. Multiplicative presentations of the Yangian double are analyzed.

  7. Performance evaluation of high-detectivity p-i-n infrared photodetector based on compressively-strained Ge0.964Sn0.036/Ge multiple quantum wells by quantum modelling

    GeSn/Ge p-i-n photodetectors with practical Ge0.964Sn0.036 active layers are theoretically investigated. First, we calculated the electronic band parameters for the heterointerfaces between strained Ge1−xSnx and relaxed (001)-oriented Ge. The carrier transport in a p-i-n photodiode built on a ten-period Ge0.964Sn0.036/Ge multiple quantum well absorber was then analyzed and numerically simulated within the Tsu−Esaki formalism by self-consistently solving the Schrödinger and Poisson equations, coupled to the kinetic rate equations. Photodetection up to a 2.1 μm cut-off wavelength is achieved. High responsivities of 0.62 A W−1 and 0.71 A W−1 were obtained under a reverse bias voltage of −3 V at peak wavelengths of 1550 nm and 1781 nm, respectively. Even for this low Sn-fraction, it is found that the photodetector quantum efficiency (49%@1.55 μm) is higher than those of comparable pure-Ge devices at room temperature. Detectivity of 3.8 × 1010 cm Hz1/2 W−1 and 7.9 × 1010 cm Hz1/2 W−1 at −1 V and −0.5 V, respectively, is achievable at room temperature for a 1550 nm wavelength peak of responsivity. This work represents a step forward in developing GeSn/Ge based infrared photodetectors. (paper)

  8. Photoreflectance and Phototransmittance of Narrow Well Strained Layer InxGa1-xAs/GaAs Coupled Multiple Quantum Well Structures

    Pan, S. H.; Shen, H.; Hang, Z.; Pollak, F. H.; Zhuang, Weihua; Xu, Qian; Roth, A. P.; Masut, R. A.; Lacelle, C.; Morris, D.

    1988-08-01

    We have measured the photoreflectance (PR) spectra at 300K and 77K of two strained layer InxGall-xAs/GaAs (x≍0.12) multiple quantum wells (MQW) with nominal well (Lz) and barrier (LB) widths of 50A/100A and 30A/100A, respectively, as deduced from the growth conditions. Phototransmittance at 77K of the latter sample has been studied. In both samples we have observed a number of features in the PR spectra corresponding to miniband dispersion (coupling between wells) of both confined and unconfined (above the GaAs barrier) transitions. The coupling between wells leads to different transition energies at the mini-Brillouin zone center (Γ) and edge (π) along the growth direction. This is the first observation of unconfined features and miniband dispersion in this system. Even though our samples have fairly wide barriers (LB ≍100A) the coupling between wells is an important effect because of the relatively small confinement energies for x≍0.12. Using the envelope function approach we have calculated the various transition energies taking into account both strain and quantum well effects, including miniband disper-sion. Good agreement with experiment is found for a heavy-hole valence band discontinuity of 0.3±0.05 and LZ/LB = 52±3A/105±5A(x=0.11±0.01) and 32±3A/95±5A(x=0.12±0.01) for the two samples, respectively. The In composition and well/barrier widths are thus in good agreement with the growth conditions. Although the symmetric component of the fundamental light-hole to conduction band transition is a strong feature, the small observed amplitude of the antisymmetric component for both samples is evidence for the type II nature of the light-hole to conduction band transitions.

  9. Hydrophobization of epoxy nanocomposite surface with 1H,1H,2H,2H-perfluorooctyltrichlorosilane for superhydrophobic properties

    Psarski, Maciej; Marczak, Jacek; Celichowski, Grzegorz; Sobieraj, Grzegorz; Gumowski, Konrad; Zhou, Feng; Liu, Weimin

    2012-10-01

    Nature inspires the design of synthetic materials with superhydrophobic properties, which can be used for applications ranging from self-cleaning surfaces to microfluidic devices. Their water repellent properties are due to hierarchical (micrometer- and nanometre-scale) surface morphological structures, either made of hydrophobic substances or hydrophobized by appropriate surface treatment. In this work, the efficiency of two surface treatment procedures, with a hydrophobic fluoropolymer, synthesized and deposited from 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) is investigated. The procedures involved reactions from the gas and liquid phases of the PFOTS/hexane solutions. The hierarchical structure is created in an epoxy nanocomposite surface, by filling the resin with alumina nanoparticles and micron-sized glass beads and subsequent sandblasting with corundum microparticles. The chemical structure of the deposited fluoropolymer was examined using XPS spectroscopy. The topography of the modified surfaces was characterized using scanning electron microscopy (SEM), and atomic force microscopy (AFM). The hydrophobic properties of the modified surfaces were investigated by water contact and sliding angles measurements. The surfaces exhibited water contact angles of above 150° for both modification procedures, however only the gas phase modification provided the non-sticking behaviour of water droplets (sliding angle of 3°). The discrepancy is attributed to extra surface roughness provided by the latter procedure.

  10. Site-resolved multiple-quantum filtered correlations and distance measurements by magic-angle spinning NMR: Theory and applications to spins with weak to vanishing quadrupolar couplings

    Eliav, U., E-mail: amirgo@tau.ac.il, E-mail: eliav@tau.ac.il; Haimovich, A.; Goldbourt, A., E-mail: amirgo@tau.ac.il, E-mail: eliav@tau.ac.il [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2016-01-14

    We discuss and analyze four magic-angle spinning solid-state NMR methods that can be used to measure internuclear distances and to obtain correlation spectra between a spin I = 1/2 and a half-integer spin S > 1/2 having a small quadrupolar coupling constant. Three of the methods are based on the heteronuclear multiple-quantum and single-quantum correlation experiments, that is, high rank tensors that involve the half spin and the quadrupolar spin are generated. Here, both zero and single-quantum coherence of the half spins are allowed and various coherence orders of the quadrupolar spin are generated, and filtered, via active recoupling of the dipolar interaction. As a result of generating coherence orders larger than one, the spectral resolution for the quadrupolar nucleus increases linearly with the coherence order. Since the formation of high rank tensors is independent of the existence of a finite quadrupolar interaction, these experiments are also suitable to materials in which there is high symmetry around the quadrupolar spin. A fourth experiment is based on the initial quadrupolar-driven excitation of symmetric high order coherences (up to p = 2S, where S is the spin number) and subsequently generating by the heteronuclear dipolar interaction higher rank (l + 1 or higher) tensors that involve also the half spins. Due to the nature of this technique, it also provides information on the relative orientations of the quadrupolar and dipolar interaction tensors. For the ideal case in which the pulses are sufficiently strong with respect to other interactions, we derive analytical expressions for all experiments as well as for the transferred echo double resonance experiment involving a quadrupolar spin. We show by comparison of the fitting of simulations and the analytical expressions to experimental data that the analytical expressions are sufficiently accurate to provide experimental {sup 7}Li–{sup 13}C distances in a complex of lithium, glycine, and water

  11. The effect of junction temperature on the optoelectrical properties of InGaN/GaN multiple quantum well light-emitting diodes

    Thermal effects on the optoelectrical characteristics of green InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) have been investigated in detail for a broad temperature range, from 30 °C to 100 °C. The current-dependent electroluminescence (EL) spectra, current–voltage (I–V) curves and luminescence intensity–current (L–I) characteristics of green InGaN/GaN MQW LEDs have been measured to characterize the thermal-related effects on the optoelectrical properties of the InGaN/GaN MQW LEDs. The experimental results show that both the forward voltages decreased with a slope of −3.7 mV/K and the emission peak wavelength increased with a slope of +0.02 nm/K with increasing temperature, indicating a change in the contact resistance between the metal and GaN layers and the existence of a band gap shrinkage effect. The junction temperature estimated from the forward voltage and the emission peak shift varied from 25.6 to 14.5 °C and from 22.4 to 35.6 °C, respectively. At the same time, the carrier temperature decreased from 371.2 to 348.1 °C as estimated from the slope of high-energy side of the emission spectra. With increasing injection current, there was found to be a strong current-dependent blueshift of −0.15 nm/mA in the emission peak wavelength of the EL spectra. This could be attributed to not only the stronger band-filling effect but also the enhanced quantum confinement effect that resulted from the piezoelectric polarization and spontaneous polarization in InGaN/GaN heterostructures. We also demonstrate a helpful and easy way to measure and calculate the junction temperature of InGaN/GaN MQW LEDs. - Highlights: ► We examine the effect of junction temperature on the optoelectrical properties. ► Not only the band-filling effect but also the quantum confinement effect. ► Piezoelectric polarization and the spontaneous polarization in InGaN/GaN structures. ► Carrier transport was responsible for the influences on the

  12. Radio observations of the CMa OB1 H II regions

    A sensitive 100 x 150 13-cm map made of the CMa OB1 H II regions' radio emission shows a strong similarity to Hα emission photographs. Sharpless 296 is shown to consist of a prominent central and western arc completed by a weaker southern loop, and with a faint northern bar. The emission is thermal, superimposed over a predominantly non-thermal background. The H142α recombination line has been detected at eight positions in S296, and in S292 and S297. The average electron temperature in S296 is 6900 +- 1300 K. The UV fluxes from the CMa OB1 stars account for the observed emission measures of the H II regions. The H142α 1sr velocities indicate that the ionized material is in contact with the molecular clouds. (author)

  13. 4-Methyl-5-phenyl-1H-pyrazol-3-ol

    Tara Shahani

    2010-07-01

    Full Text Available The title compound, C10H10N2O, crystallizes with two independent molecules in the asymmetric unit, having closely comparable geometries. The dihedral angles between the 1H-pyrazole and benzene rings in the two molecules are 39.57 (14 and 41.95 (13°. The two molecules are each connected to neighbouring molecules by pairs of intermolecular O—H...N hydrogen bonds, forming dimers with R22(8 ring motifs. These dimers are further linked into R44(10 ring motifs by intermolecular N—H...O hydrogen bonds, forming chains along [101]. The crystal structure is further stabilized by a C—H...π interaction.

  14. 1-Benzyl-1H-benzotriazole 3-oxide–1-hydroxy-1H-benzotriazole (1/1

    P. Selvarathy Grace

    2012-08-01

    Full Text Available In the title compound, C6H5N3O·C13H11N3O, the benzotriazole ring system in the 1-benzyl-1H-benzotriazole 3-oxide (A molecule is close to being planar (r.m.s. deviation = 0.011 Å; its mean plane forms a dihedral angle of 67.56 (7° with that of the attached phenyl ring. The benzotriazole ring system in the 1-hydroxybenzotriazole (B molecule is also close to being planar (r.m.s. deviation = 0.010 Å. In the crystal, weak C—H...O and C—H...π interactions are present. The A and B molecules are linked by an O—H...N hydrogen bond.

  15. Research on the high indium content InGaAs multiple quantum wells wafers for λ > 1.55 μm laser diodes

    Highlights: • The longest wavelength of 1.889 μm among the InGaAs/InGaAsP strained MQWs samples was obtained with high crystal quality. • AsH3 flow rate was found to promote much TMGa pyrolysis than TMIn in The high indium content InGaAs growth. • The peak wavelength shift of the InGaAs/InGaAsP strained MQWs was found to increase at higher AsH3 flow rate. - Abstract: The effects of TMIn flow rate and AsH3 flow rate on the photoluminescence spectra of the high indium content InGaAs multiple quantum wells for λ > 1.55 μm laser diodes have been investigated both experimentally and theoretically. The wavelength peak red-shifted about 4.8 nm for increasing 1 sccm H2 flow rate through TMIn under a AsH3 flow rate of 150 sccm, while the wavelength shift increases to 6.5 nm at a higher AsH3 flow rate of 300 sccm. Results show that more AsH3 flow rate will promote much TMGa pyrolysis than TMIn in the high indium content InGaAs growth. Considering the influence of growth parameters, the longest wavelength of 1.889 μm among the InGaAs/InGaAsP strained MQWs samples was obtained with high crystal quality

  16. Fabrication of nanorod InGaN/GaN multiple quantum wells with self-assembled Ni nano-island masks

    Yang, Guofeng, E-mail: gfyang@jiangnan.edu.cn [School of Science, Jiangnan University, Wuxi 214122 (China); Guo, Ying; Zhu, Huaxin [School of Science, Jiangnan University, Wuxi 214122 (China); Yan, Dawei [Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China); Li, Guohua; Gao, Shumei [School of Science, Jiangnan University, Wuxi 214122 (China); Dong, Kexiu [School of Mechanical and Electronic Engineering, Chuzhou University, Chuzhou 239000 (China)

    2013-11-15

    The evolution of nano-sized Ni metal islands deposited by electron-beam evaporation on InGaN/GaN multiple quantum wells (MQWs) surface as a function of rapid thermal annealing (RTA) temperature and initial deposited Ni film thickness is reported. It is shown that the dimension and density of self-assembled Ni nano-islands depend critically on the annealing temperature and deposited Ni film thickness. The formation of the islands is described in terms of Ostwald ripening and coarsening mechanisms. Subsequently, the nano-masks are successfully applied to fabricate nanorod InGaN/GaN MQWs by using inductively coupled-plasma (ICP) etching. Uniform etching rate has been obtained by comparing the nanorod height etched for different times. Photoluminescence (PL) investigation shows the nanorod MQWs with optimized light output efficiency could be acquired under particular ICP and RF etching power. Strain relaxation and dislocation reduction effect would contribute to enhanced light output of nanorod InGaN/GaN MQWs compared with the as-grown plane MQWs.

  17. Quantum dot imaging in the second near-infrared optical window: studies on reflectance fluorescence imaging depths by effective fluence rate and multiple image acquisition

    Jung, Yebin; Jeong, Sanghwa; Nayoun, Won; Ahn, Boeun; Kwag, Jungheon; Geol Kim, Sang; Kim, Sungjee

    2015-04-01

    Quantum dot (QD) imaging capability was investigated by the imaging depth at a near-infrared second optical window (SOW; 1000 to 1400 nm) using time-modulated pulsed laser excitations to control the effective fluence rate. Various media, such as liquid phantoms, tissues, and in vivo small animals, were used and the imaging depths were compared with our predicted values. The QD imaging depth under excitation of continuous 20 mW/cm2 laser was determined to be 10.3 mm for 2 wt% hemoglobin phantom medium and 5.85 mm for 1 wt% intralipid phantom, which were extended by more than two times on increasing the effective fluence rate to 2000 mW/cm2. Bovine liver and porcine skin tissues also showed similar enhancement in the contrast-to-noise ratio (CNR) values. A QD sample was inserted into the abdomen of a mouse. With a higher effective fluence rate, the CNR increased more than twofold and the QD sample became clearly visualized, which was completely undetectable under continuous excitation. Multiple acquisitions of QD images and averaging process pixel by pixel were performed to overcome the thermal noise issue of the detector in SOW, which yielded significant enhancement in the imaging capability, showing up to a 1.5 times increase in the CNR.

  18. Effect of In incorporation parameters on the electroluminescence of blue-violet InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

    Zhao, D.G., E-mail: dgzhao@red.semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Jiang, D.S.; Le, L.C.; Wu, L.L.; Li, L. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Zhu, J.J.; Wang, H. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Liu, Z.S. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Zhang, S.M. [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Jia, Q.J. [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Yang Hui [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2012-11-05

    Highlights: Black-Right-Pointing-Pointer The interface roughness of InGaN/GaN MQWs are characterized by XRD. Black-Right-Pointing-Pointer Smooth interface is very important for the blue-violet InGaN/GaN MQWs. Black-Right-Pointing-Pointer EL of InGaN MQWs could be improved by controlling In incorporation parameters. - Abstract: The growth parameters which can modify In incorporation and affect electroluminescence (EL) properties of blue-violet InGaN/GaN multiple quantum wells (MQWs) during metalorganic chemical vapor deposition (MOCVD) are investigated. It is found that a suitable increase of trimethylindium (TMIn) flux during the growth of InGaN well can increase both EL intensity and EL peak wavelength. However, when the growth temperature of well decreases from 810 to 800 Degree-Sign C, the EL intensity decreases although the EL peak wavelength increases. X-ray diffraction results demonstrate that the interface roughness plays an important role in determining the EL intensity of InGaN/GaN MQWs. It is suggested to grow blue-violet MQWs with high structural quality by suitably increasing the TMIn flux and at a relatively high growth temperature.

  19. Three-dimensional indium distribution in electron-beam irradiated multiple quantum wells of blue-emitting InGaN/GaN devices

    Jung, Woo-Young; Seol, Jae-Bok; Kwak, Chan-Min; Park, Chan-Gyung

    2016-03-01

    The compositional distribution of In atoms in InGaN/GaN multiple quantum wells is considered as one of the candidates for carrier localization center, which enhances the efficiency of the light-emitting diodes. However, two challenging issues exist in this research area. First, an inhomogeneous In distribution is initially formed by spinodal decomposition during device fabrication as revealed by transmission electron microscopy. Second, electron-beam irradiation during microscopy causes the compositional inhomogeneity of In to appear as a damage contrast. Here, a systematic approach was proposed in this study: Electron-beam with current density ranging from 0 to 20.9 A/cm2 was initially exposed to the surface regions during microscopy. Then, the electron-beam irradiated regions at the tip surface were further removed, and finally, atom probe tomography was performed to run the samples without beam-induced damage and to evaluate the existence of local inhomegenity of In atoms. We proved that after eliminating the electron-beam induced damage regions, no evidence of In clustering was observed in the blue-emitting InGaN/GaN devices. In addition, it is concluded that the electron-beam induced localization of In atoms is a surface-related phenomenon, and hence spinodal decomposition, which is typically responsible for such In clustering, is negligible for biaxially strained blue-emitting InGaN/GaN devices.

  20. Size effect on negative capacitance at forward bias in InGaN/GaN multiple quantum well-based blue LED

    Bourim, El-Mostafa; Han, Jeong In

    2016-01-01

    Size effect of InGaN/GaN multiple quantum well (MQW) blue light emitting diodes (LEDs), on electrical characteristics in forward bias voltage at high injection current in light emission regime, is observed to induce a substantial dispersion in the current density and normalized negative capacitance (NC) (i.e., capacitance per chip area). The correction of normalized NC by considering the LED p- n junction series resistance has been found to be independent of chip area size with lateral dimensions ranging from 100 µm × 100 µm to 400 µm × 400 µm. This fact, confirms that the inductive effect which is usually behind the NC apparition is homogeneously and uniformly distributed across the entire device area and hence the dispersive characteristics are not related to local paths. From the characteristics of NC dependence on temperature, frequency and direct current bias, a mechanism based on the electrons/holes charge carriers conductivity difference is proposed to be responsible for the transient electron-hole pair recombination process inducing NC phenomenon. Direct measurement of light emission brightness under modulated frequency demonstrated that modulated light output evolution follows the same behavioral tendency as measured in NC under alternating current signal modulation. Thus it is concluded that the NC is valuable information which would be of practical interest in improving the characteristics and parameters relevant to LED p- n junction internal structure. [Figure not available: see fulltext.

  1. Effect of localization states on the electroluminescence spectral width of blue–green light emitting InGaN/GaN multiple quantum wells

    The electroluminescence (EL) spectra of blue–green light emitting InGaN/GaN multiple quantum well (MQW) structures grown via metal-organic chemical vapor deposition are investigated. With increasing In content in InGaN well layers, the peak energy redshifts, the emission intensity reduces and the inhomogeneous broadening of the luminescence band increases. In addition, it is found that the EL spectra shrink with increasing injection current at low excitation condition, which may be ascribed to both Coulomb screening of polarization field and carrier transferring from shallower localization states to the deeper ones, while at high currents the state-filling effect in all localization states may become significant and lead to a broadening of EL spectra. However, surprisingly, for the MQW sample with much higher In content, the EL spectral bandwidth can be almost unchanged with increasing current at the high current range, since a large number of carriers may be captured by the nonradiative recombination centers distributed outside the localized potential traps and the state-filling effect in the localization states is suppressed

  2. Effect of In incorporation parameters on the electroluminescence of blue–violet InGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

    Highlights: ► The interface roughness of InGaN/GaN MQWs are characterized by XRD. ► Smooth interface is very important for the blue–violet InGaN/GaN MQWs. ► EL of InGaN MQWs could be improved by controlling In incorporation parameters. - Abstract: The growth parameters which can modify In incorporation and affect electroluminescence (EL) properties of blue–violet InGaN/GaN multiple quantum wells (MQWs) during metalorganic chemical vapor deposition (MOCVD) are investigated. It is found that a suitable increase of trimethylindium (TMIn) flux during the growth of InGaN well can increase both EL intensity and EL peak wavelength. However, when the growth temperature of well decreases from 810 to 800 °C, the EL intensity decreases although the EL peak wavelength increases. X-ray diffraction results demonstrate that the interface roughness plays an important role in determining the EL intensity of InGaN/GaN MQWs. It is suggested to grow blue–violet MQWs with high structural quality by suitably increasing the TMIn flux and at a relatively high growth temperature.

  3. GaInNAs/GaAs Multiple-Quantum Well Resonant-Cavity-Enhanced Photodetectors at 1.3μm

    潘钟; 李联合; 徐应强; 张伟; 林耀望; 张瑞康; 钟源; 任晓敏

    2001-01-01

    A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced photodetector (RCE-PD) operated at a wavelength of 1.3μm with the full width at half maximum of 4nm has been demonstrated. The GaInNAs RCE-PD was grown by molecular beam epitaxy using a homemade ion-removed dc plasma cell as a nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature, which is very beneficial for applications in long-wavelength absorption devices. For a 100μm diameter RCE-PD, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is -18 V. The measured 3 dB bandwidth is 308 MHz, which is limited by the resistance of p-type distributed Bragg reflector mirror. The tunable wavelength in a range of 18nm with the angle of incident light was observed.

  4. Measurements and simulations of the optical gain and anti-reflection coating modal reflectivity in quantum cascade lasers with multiple active region stacks

    We report spectrally resolved gain measurements and simulations for quantum cascade lasers (QCLs) composed of multiple heterogeneous stacks designed for broadband emission in the mid-infrared. The measurement method is first demonstrated on a reference single active region QCL based on a double-phonon resonance design emitting at 7.8 μm. It is then extended to a three-stack active region based on bound-to-continuum designs with a broadband emission range from 7.5 to 10.5 μm. A tight agreement is found with simulations based on a density matrix model. The latter implements exhaustive microscopic scattering and dephasing sources with virtually no fitting parameters. The quantitative agreement is furthermore assessed by measuring gain coefficients obtained by studying the threshold current dependence with the cavity length. These results are particularly relevant to understand fundamental gain mechanisms in complex semiconductor heterostructure QCLs and to move towards efficient gain engineering. Finally, the method is extended to the measurement of the modal reflectivity of an anti-reflection coating deposited on the front facet of the broadband QCL

  5. Measurements and simulations of the optical gain and anti-reflection coating modal reflectivity in quantum cascade lasers with multiple active region stacks

    Bidaux, Y.; Terazzi, R.; Bismuto, A.; Gresch, T.; Blaser, S.; Muller, A.; Faist, J.

    2015-09-01

    We report spectrally resolved gain measurements and simulations for quantum cascade lasers (QCLs) composed of multiple heterogeneous stacks designed for broadband emission in the mid-infrared. The measurement method is first demonstrated on a reference single active region QCL based on a double-phonon resonance design emitting at 7.8 μm. It is then extended to a three-stack active region based on bound-to-continuum designs with a broadband emission range from 7.5 to 10.5 μm. A tight agreement is found with simulations based on a density matrix model. The latter implements exhaustive microscopic scattering and dephasing sources with virtually no fitting parameters. The quantitative agreement is furthermore assessed by measuring gain coefficients obtained by studying the threshold current dependence with the cavity length. These results are particularly relevant to understand fundamental gain mechanisms in complex semiconductor heterostructure QCLs and to move towards efficient gain engineering. Finally, the method is extended to the measurement of the modal reflectivity of an anti-reflection coating deposited on the front facet of the broadband QCL.

  6. Exciton–phonon interaction in Al0.4Ga0.6N/Al0.53Ga0.47N multiple quantum wells

    Liu, Ya-Li; Jin, Peng; Liu, Gui-Peng; Wang, Wei-Ying; Qi, Zhi-Qiang; Chen, Chang-Qing; Wang, Zhan-Guo

    2016-08-01

    The exciton–phonon interaction in Al0.4Ga0.6N/Al0.53Ga0.47N multiple quantum wells (MQWs) is studied by deep-ultraviolet time-integrated and time-resolved photoluminescence (PL). Up to four longitudinal-optical (LO) phonon replicas of exciton recombination are observed, indicating the strong coupling of excitons with LO phonons in the MQWs. Moreover, the exciton–phonon coupling strength in the MQWs is quantified by the Huang–Rhys factor, and it keeps almost constant in a temperature range from 10 K to 120 K. This result can be explained in terms of effects of fluctuations in the well thickness in the MQWs and the temperature on the exciton–phonon interaction. Project supported by the National Basic Research Program of China (Grant No. 2012CB619306), the Beijing Science and Technology Project, China (Grant No. Z151100003315024), and the National Natural Science Foundation of China (Grant No. 61404132).

  7. Observation of multiple flux quantum periodicities in V-Φ curves of single bulk bridge of Y-Ba-Cu-O superconductor

    This paper discusses a single bulk bridge carved out of a superconducting pellet of YBa2Cu3O7-x made by usual solid state reaction. The I-V curves show large maximum pair current followed by a quasi-particle tunneling regime. In spite of having single bridge geometry, application of external magnetic field leads to periodicites in V-φ curves at 77 K and at lower temperatures. The periodic behavior is akin to dc AQUID characteristics. The shape of individual lobes show large asymmetries indicating presence of parallel superconducting micro networks with several array of junctions with differing critical currents. The individual arm of this network further consists of small superconducting loops. The individual loop itself has been formed of a series of identical granular Josephson weaklings. This network imparts dc SQUID character to the bulk bridge. The proposed model is explained with the help of diagrams. Large periods correspond to large networks with large inductance, while small superposed oscillations pertain to smaller loops with extremely low inductance. This explains occurrence of V-φ curves with assorted flux periods equivalent to some integral multiple of flux quantum (φ0)

  8. Suppression of metastable-phase inclusion in N-polar (0001¯) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    The metastable zincblende (ZB) phase in N-polar (0001¯) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated

  9. Growth and characterization of a-plane InGaN/GaN multiple quantum well LEDs grown on r-plane sapphire

    Non-polar a-plane InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) with different thicknesses and periods of InGaN wells are prepared and characterized. Non-polar a-plane LEDs are grown directly on r-plane sapphire by metalorganic chemical vapor deposition, and LEDs are fabricated. In the electroluminescence (EL) measurements, the relative output power increases slightly with increasing well thickness and the forward operating voltage at 20 mA increases slightly, even though the 4.2 nm thick well exhibits the best photoluminescence (PL) and x-ray diffraction (XRD) results. Although the interface quality degrades with thicker InGaN wells, the relative output power in EL measurement increases due to an increase of carrier capture rate with well thickness. With increasing periods of MQWs up to seven, the relative output power of LEDs is improved due to the increased crystal and interface quality in MQWs. Meanwhile, the forward operating voltage at 20 mA increases from 3.58 to 4.12 V because the series resistance of undoped areas increases with increasing periods of MQWs

  10. Effect of localization states on the electroluminescence spectral width of blue–green light emitting InGaN/GaN multiple quantum wells

    Liu, Wei [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China and School of Electronic and Electrical Engineering, Chongqing University of Arts and Sciences, Chongqing 402160 (China); Zhao, De Gang, E-mail: dgzhao@red.semi.ac.cn; Jiang, De Sheng; Chen, Ping; Liu, Zong Shun; Zhu, Jian Jun; Li, Xiang; Shi, Ming; Zhao, Dan Mei [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Liu, Jian Ping; Zhang, Shu Ming; Wang, Hui; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2015-11-15

    The electroluminescence (EL) spectra of blue–green light emitting InGaN/GaN multiple quantum well (MQW) structures grown via metal-organic chemical vapor deposition are investigated. With increasing In content in InGaN well layers, the peak energy redshifts, the emission intensity reduces and the inhomogeneous broadening of the luminescence band increases. In addition, it is found that the EL spectra shrink with increasing injection current at low excitation condition, which may be ascribed to both Coulomb screening of polarization field and carrier transferring from shallower localization states to the deeper ones, while at high currents the state-filling effect in all localization states may become significant and lead to a broadening of EL spectra. However, surprisingly, for the MQW sample with much higher In content, the EL spectral bandwidth can be almost unchanged with increasing current at the high current range, since a large number of carriers may be captured by the nonradiative recombination centers distributed outside the localized potential traps and the state-filling effect in the localization states is suppressed.

  11. Suppression of metastable-phase inclusion in N-polar (0001{sup ¯}) InGaN/GaN multiple quantum wells grown by metalorganic vapor phase epitaxy

    Shojiki, Kanako, E-mail: k.shojiki@imr.tohoku.ac.jp; Iwabuchi, Takuya; Kuboya, Shigeyuki [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi (Japan); Choi, Jung-Hun; Tanikawa, Tomoyuki; Hanada, Takashi; Katayama, Ryuji; Matsuoka, Takashi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi (Japan); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama (Japan); Usami, Noritaka [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi (Japan)

    2015-06-01

    The metastable zincblende (ZB) phase in N-polar (0001{sup ¯}) (−c-plane) InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic vapor phase epitaxy is elucidated by the electron backscatter diffraction measurements. From the comparison between the −c-plane and Ga-polar (0001) (+c-plane), the −c-plane MQWs were found to be suffered from the severe ZB-phase inclusion, while ZB-inclusion is negligible in the +c-plane MQWs grown under the same growth conditions. The ZB-phase inclusion is a hurdle for fabricating the −c-plane light-emitting diodes because the islands with a triangular shape appeared on a surface in the ZB-phase domains. To improve the purity of stable wurtzite (WZ)-phase, the optimum conditions were investigated. The ZB-phase is dramatically eliminated with decreasing the V/III ratio and increasing the growth temperature. To obtain much-higher-quality MQWs, the thinner InGaN wells and the hydrogen introduction during GaN barriers growth were tried. Consequently, MQWs with almost pure WZ phase and with atomically smooth surface have been demonstrated.

  12. 1H NMR spectroscopic identification of a glue sniffing biomarker.

    Kwon, Bobae; Kim, Siwon; Kim, Sosun; Lee, Dong-Kye; Park, Yu-Jin; Kim, Myung-Duck; Lee, Jae-Shin; Kim, Suhkmann

    2011-06-15

    Organic solvent abuse typically involves sniffing organic solvents to experience the mind-altering conditions they induce. In Republic of Korea, organic solvent abuse is a serious social problem, especially among teenagers. Several studies have addressed the effects of organic solvent abuse on mind and body, but there are no simple methods by which such abuse can be positively identified. In this report, we describe a method for analyzing toluene metabolites (toluene is the main ingredient of glue) in glue-sniffers' urine using (1)H NMR spectroscopy. Toluene is a commonly used solvent in the rubber, paint, plastics, leather, printing, and chemical industries. Inhaled toluene is metabolized to hippuric acid in the liver and excreted in the urine. Hippuric acid is known as a good biomarker for biological monitoring of toluene exposure. We have scanned hippuric acid and other toluene metabolites by NMR spectroscopy and performed statistical multivariate analysis of the data. Based on this analysis, we sought to determine parameters by which glue-sniffing (toluene inhalation) behavior may be verified. We also demonstrate the use of a pattern recognition method for accurate and efficient analysis of NMR data. In comparison to conventional methods, such as mass spectroscopy coupled with liquid chromatography or gas chromatography, nuclear magnetic resonance spectroscopy has several advantages, including simple sample preparation, non-destructive sampling, accuracy, short acquisition time, and reproducibility in the determination of urinary hippuric acid. PMID:21316881

  13. 1H homonuclear editing of rat brain using semiselective pulses

    The authors have used a semiselective Hahn spin-echo sequence of the form (1331)-tau-(2662)-tau-AQ, delivered by a surface coil to obtain high-resolution 1H NMR spectra from the brains of intact dead rats. This sequence gave suppression of the tissue water resonance by a factor of 80,000 when tau = 68 ms. Delivery of a frequency-selective Dante pulse train to the alpha-CH resonance of lactate at 4.11 ppm, simultaneously with the 2662 refocusing pulse, altered the j-modulation in the spin-coupled beta-CH3 protons. Subtraction of this spectrum from one in which the Dante was ineffective gave an edited spectrum containing only the beta-CH3 resonance of lactate at 1.31 ppm. When the position of the Dante was shifted to 3.78 ppm to selectively invert the alpha-CH protons of alanine, an edited spectrum of alanine was obtained

  14. 1H NMR metabolomics of earthworm responses to polychlorinated biphenyl (PCB) exposure in soil.

    Whitfield Åslund, Melissa L; Simpson, André J; Simpson, Myrna J

    2011-06-01

    (1)H NMR-based metabolomics was used to examine the metabolic profile of D(2)O-buffer extracted tissues of Eisenia fetida earthworms exposed for 2 days to an artificial soil spiked with sub-lethal concentrations of polychlorinated biphenyls (PCBs) (0, 0.5, 1, 5, 10, or 25 mg/kg Aroclor 1254). Univariate statistical analysis of the identified metabolites revealed a significant increase in ATP concentration in earthworms exposed to the highest soil PCB concentration, but detected no significant changes in other metabolites. However, a multivariate approach which considers alterations in multiple metabolites simultaneously, identified a significant linear relationship between earthworm metabolic profiles and PCB concentration (cross-validated PLS-regression with 7 components, R(2)X = 0.99, R(2)Y = 0.77, Q(2)Y = 0.45, P earthworms (r = 0.22, P = 0.54), but were positively correlated in earthworms from the 25 mg/kg treatment (r = 0.87, P = 0.001). Overall, the observed metabolic responses suggest that PCBs disrupted both carbohydrate (energy) metabolism and membrane (osmolytic) function in E. fetida. The ability of (1)H NMR-based metabolomics to detect these responses suggests that this method offers significant potential for direct assessment of sub-lethal PCB toxicity in soil. PMID:21424327

  15. The nuclear reaction n + 3He -> 1H + 3H as proximity reaction

    The present thesis tries to give by means of the nuclear reaction n + 3He -> 1H + 3H as proximity reaction on the three-particle system 3He + 9Be -> 1H + 3H + 8Be an experimental verification to the second term of a multiple scattering series. The study of these rescattering effects is of great interest for the present theory of the final-state interaction. At three incident energies (7.08 MeV, 8.98 MeV, and 6.37 MeV) to detector telescopes identify the exit channel of the three-particle system in list-mode coincidence experiments according to protons and tritons. Peaks on the kinematical curves occur. The detailed study of their kinematic behaviour allows to exclude the inconcurrence to the proximity reaction lying cascade decays via intermediate states in 4He, 9B, and 11B. Regarding the Coulomb interaction the experimental results can be also explained in the sense of the classical kinematics by the proximity model. (orig.)

  16. Quantum dots-based quantitative and in situ multiple imaging on ki67 and cytokeratin to improve ki67 assessment in breast cancer.

    Jing Ping Yuan

    Full Text Available As a marker for tumor cell proliferation, Ki67 has important impacts on breast cancer (BC prognosis. Although immunohistochemical staining is the current standard method, variations in analytical practice make it difficult for pathologists to manually measure Ki67 index. This study was to develop a fluorescent spectrum-based quantitative analysis of Ki67 expression by quantum-dots (QDs multiple imaging technique.A QDs-based in situ multiple fluorescent imaging method was developed, which stained nuclear Ki67 as red signal and cytoplasmic cytokeratin (CK as green signal. Both Ki67 and CK signals were automatically separated and quantified by professional spectrum analysis software. This technique was applied to tissue microarrays from 240 BC patients. Both Ki67 and CK values, and Ki67/CK ratio were obtained for each patient, and their prognostic value on 5-year disease free survival was assessed.This method simultaneously stains nuclear Ki67 and cytoplasmic CK with clear signal contrast, making it easy for signal separation and quantification. The total fluorescent signal intensities of both Ki67 sum and CK sum were obtained, and Ki67/CK ratio calculated. Ki67 sum and Ki67/CK ratio were each attributed into two grades by X-tile software based on the best P value principle. Multivariate analysis showed Ki67 grade (P = 0.047 and Ki67/CK grade (P = 0.004 were independent prognostic factors. Furthermore, area under curve (AUC of ROC analysis for Ki67/CK grade (AUC: 0.683, 95%CI: 0.613-0.752 was higher than Ki67 grade (AUC: 0.665, 95%CI: 0.596-0.734 and HER-2 gene (AUC: 0.586, 95%CI: 0.510-0.661, but lower than N stage (AUC: 0.760, 95%CI: 0.696-0.823 and histological grade (AUC: 0.756, 95%CI: 0.692-0.820 on predicting the risk for recurrence.A QDs-based quantitative and in situ multiple imaging on Ki67 and CK was developed to improve Ki67 assessment in BC, and Ki67/CK grade had better performance than Ki67 grade in predicting prognosis.

  17. Quantum Simulation of Phylogenetic Trees

    Ellinas, Demosthenes; Jarvis, Peter

    2011-01-01

    Quantum simulations constructing probability tensors of biological multi-taxa in phylogenetic trees are proposed, in terms of positive trace preserving maps, describing evolving systems of quantum walks with multiple walkers. Basic phylogenetic models applying on trees of various topologies are simulated following appropriate decoherent quantum circuits. Quantum simulations of statistical inference for aligned sequences of biological characters are provided in terms of a quantum pruning map o...

  18. A 1H NMR study of human calcitonin in solution

    Human calcitonin (hCT) has been investigated by NMR at 400 MHz in DMSOd6 and in an 85% DMSOd6-15% 1H2O (v/v) cryoprotective mixture. All backbone and side-chain resonances have been assigned and the secondary structure has been determined in both solvents. In DMSOd6, the simultaneous presence of dαN, dNN, and some specific weak medium-range nuclear Overhauser effects, together with the amide temperature coefficients and the analysis of the NH-αCH spin-spin coupling constants, indicates that hCT is highly flexible but with three domains (comprising segments Asn3-Gly10, Gln14-Thr21, and Thr25-Ala31) in extended conformations which dynamically transform into isolated β turns in the N- and C-terminal regions and into adjacent tight turns, resembling a 310 helix structure, in the central part. The DMSO-water mixture rigidifies the polypeptide chain, favoring and ordered, extended conformation. NOESY data indicate the presence of a short double-stranded antiparallel β sheet in the central region made by residues 16-21 and connected by a two-residue hairpin loop formed by residues 18 and 19. Two tight turns, formed by residues 3-6 and 28-31, were also identified. The central β sheet does not favor an amphipathic distribution of the residues as found for salmon calcitonin. This is in agreement with the smaller tendency of hCT to form the amphipathic α helix, postulated to be responsible for the interaction of hCT with lipids. The possible role of the cis-trans isomerism of Pro is discussed

  19. New 1H-pyrrole-2,5-dione derivatives as efficient organic inhibitors of carbon steel corrosion in hydrochloric acid medium: Electrochemical, XPS and DFT studies

    Highlights: • 1H-pyrrole derivatives act as good corrosion inhibitors for carbon steel in 1 M HCl. • Adsorption of the inhibitors on carbon steel surface obeys Langmuir’s isotherm. • XPS showed that the inhibitors are chemisorbed on the metal surface. • Quantum chemical parameters were correlated with experimental results. - Abstract: New 1H-pyrrole-2,5-dione derivatives, namely 1-phenyl-1H-pyrrole-2,5-dione (PPD) and 1-(4-methylphenyl)-1H-pyrrole-2,5-dione (MPPD) were synthesised and their inhibitive action against the corrosion of carbon steel in 1 M HCl solution were investigated at 308 K by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results showed that the investigated 1H-pyrrole-2,5-dione derivatives are good corrosion inhibitors for carbon steel in 1 M HCl medium, their inhibition efficiency increased with inhibitor concentration, and MPPD is slightly more effective than PPD. Potentiostatic polarization study showed that PPD and MPPD are mixed-type inhibitors in 1 M HCl. Impedance experimental data revealed a frequency distribution of the capacitance, simulated as constant phase element. The results obtained from electrochemical and weight loss studies were in reasonable agreement. The adsorption of MPPD and PPD on steel surface obeyed Langmuir’s adsorption isotherm. Thermodynamic data and XPS analysis clearly indicated that the adsorption mechanism of 1H-pyrrole-2,5-dione derivatives on carbon steel surface in 1 M HCl solution is mainly controlled by a chemisorption process. Quantum chemical calculations using the Density Functional Theory (DFT) were performed on 1H-pyrrole-2,5-dione derivatives to determine the relationship between molecular structures and their inhibition efficiencies

  20. Quantum Permanents and Quantum Hafnians

    Jing, Naihuan; Jian ZHANG

    2015-01-01

    Analogous to the quantum general linear group, a quantum group is investigated on which the quantum determinant is shown to be equal to the quantum permanent. The quantum Hafnian is then computed by a closely related quantum permanent. Similarly the quantum Pfaffian is proved to be identical to the quantum Hafnian on the quantum algebra.

  1. Quantum matrix algebra for the SU(n) WZNW model

    Furlan, Paolo; Isaev, A P; Ogievetsky, O V; Pyatov, P N; Todorov, I T

    2003-01-01

    The zero modes of the chiral SU(n) WZNW model give rise to an intertwining quantum matrix algebra A generated by an n x n matrix a=(a^i_\\alpha) (with noncommuting entries) and by rational functions of n commuting elements q^{p_i}. We study a generalization of the Fock space (F) representation of A for generic q (q not a root of unity) and demonstrate that it gives rise to a model of the quantum universal enveloping algebra U_q(sl_n), each irreducible representation entering F with multiplicity 1. For an integer level k the complex parameter q is an even root of unity, q^h=-1 (h=k+n) and the algebra A has an ideal I_h such that the factor algebra A_h = A/I_h is finite dimensional.

  2. Quasi-Fermi level splitting evaluation based on electroluminescence analysis in multiple quantum-well solar cells for investigating cell performance under concentrated light

    Inoue, Tomoyuki; Toprasertpong, Kasidit; Delamarre, Amaury; Watanabe, Kentaroh; Paire, Myriam; Lombez, Laurent; Guillemoles, Jean-François; Sugiyama, Masakazu; Nakano, Yoshiaki

    2016-03-01

    Insertion of InGaAs/GaAsP strain-balanced multiple quantum wells (MQWs) into i-regions of GaAs p-i-n solar cells show several advantages against GaAs bulk p-i-n solar cells. Particularly under high-concentration sunlight condition, enhancement of the open-circuit voltage with increasing concentration ratio in thin-barrier MQW cells has been reported to be more apparent than that in GaAs bulk cells. However, investigation of the MQW cell mechanisms in terms of I-V characteristics under high-concentration sunlight suffers from the increase in cell temperature and series resistance. In order to investigate the mechanism of the steep enhancement of open-circuit voltage in MQW cells under high-concentration sunlight without affected by temperature, the quasi-Fermi level splitting was evaluated by analyzing electroluminescence (EL) from a cell. Since a cell under current injection with a density Jinjhas similar excess carrier density to a cell under concentrated sunlight with an equivalent short-circuit current Jsc = Jinj, EL measurement with varied Jinj can approximately evaluate a cell performance under a variety of concentration ratio. In addition to the evaluation of quasi-Fermi level splitting, the external luminescence efficiency was also investigated with the EL measurement. The MQW cells showed higher external luminescence efficiency than the GaAs reference cells especially under high-concentration condition. The results suggest that since the MQW region can trap and confine carriers, the localized excess carriers inside the cells make radiative recombination more dominant.

  3. Modulating dual-wavelength multiple quantum wells in white light emitting diodes to suppress efficiency droop and improve color rendering index

    Zhao, Yukun; Wang, Shuai; Zheng, Min; Ding, Wen [Key Laboratory of Physical Electronics and Devices of Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics & Information Technology, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Solid-State Lighting Engineering Research Center, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Yun, Feng, E-mail: fyun2010@mail.xjtu.edu.cn [Key Laboratory of Physical Electronics and Devices of Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics & Information Technology, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Solid-State Lighting Engineering Research Center, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Shaanxi Supernova Lighting Technology Co. Ltd, Xi' an, Shaanxi 710075 (China); Su, Xilin; Yang, Xiangrong; Liu, Shuo [Shaanxi Supernova Lighting Technology Co. Ltd, Xi' an, Shaanxi 710075 (China); Guo, Maofeng [Solid-State Lighting Engineering Research Center, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Shaanxi Supernova Lighting Technology Co. Ltd, Xi' an, Shaanxi 710075 (China); Zhang, Ye [Solid-State Lighting Engineering Research Center, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China)

    2015-10-14

    In this paper, gallium nitride (GaN) based white light-emitting diodes (WLEDs) with modulated quantities of blue (In{sub 0.15}Ga{sub 0.85}N) quantum wells (QWs) and cyan QWs (In{sub 0.18}Ga{sub 0.82}N) in multiple QW (MQW) structures have been investigated numerically and experimentally. It is demonstrated that the optical performance of LEDs is sensitive to the quantities of cyan QWs in dual-wavelength MQW structures. Compared to the LEDs with respective 0, 4, and 8 cyan QWs (12 QWs in total), the optical performance of the sample with 6 cyan QWs is the best. The deterioration of the optical performance in the sample with less (4 pairs) cyan QWs or more (8 pairs) cyan QWs than 6 cyan QWs may be ascribed to weakened reservoir effect or more defects induced. Compared to conventional blue LEDs (12 blue QWs), the sample with 6 cyan QWs could effectively suppress the efficiency droop (the experimental droop ratio decreases from 50.3% to 39.5% at 80 A/cm{sup 2}) and significantly improve the color rendering index (CRI, increases from 66.4 to 77.0) simultaneously. We attribute the droop suppression to the strengthened reservoir effect and carrier confinement of deeper QWs (higher indium composition) incorporated in the dual-wavelength MQW structures, which lead to the better hole spreading and enhanced radiative recombination. Meanwhile, the remarkable experimental CRI improvement may result from the wider full-width at half-maximum of electroluminescence spectra and higher cyan intensity in WLED chips with dual-wavelength MQW structures.

  4. Aptamer-based microfluidic beads array sensor for simultaneous detection of multiple analytes employing multienzyme-linked nanoparticle amplification and quantum dots labels.

    Zhang, He; Hu, Xinjiang; Fu, Xin

    2014-07-15

    This study reports the development of an aptamer-mediated microfluidic beads-based sensor for multiple analytes detection and quantification using multienzyme-linked nanoparticle amplification and quantum dots labels. Adenosine and cocaine were selected as the model analytes to validate the assay design based on strand displacement induced by target-aptamer complex. Microbeads functionalized with the aptamers and modified electron rich proteins were arrayed within a microfluidic channel and were connected with the horseradish peroxidases (HRP) and capture DNA probe derivative gold nanoparticles (AuNPs) via hybridization. The conformational transition of aptamer induced by target-aptamer complex contributes to the displacement of functionalized AuNPs and decreases the fluorescence signal of microbeads. In this approach, increased binding events of HRP on each nanosphere and enhanced mass transport capability inherent from microfluidics are integrated for enhancing the detection sensitivity of analytes. Based on the dual signal amplification strategy, the developed aptamer-based microfluidic bead array sensor could discriminate as low as 0.1 pM of adenosine and 0.5 pM cocaine, and showed a 500-fold increase in detection limit of adenosine compared to the off-chip test. The results proved the microfluidic-based method was a rapid and efficient system for aptamer-based targets assays (adenosine (0.1 pM) and cocaine (0.5 pM)), requiring only minimal (microliter) reagent use. This work demonstrated the successful application of aptamer-based microfluidic beads array sensor for detection of important molecules in biomedical fields. PMID:24534576

  5. Modulating dual-wavelength multiple quantum wells in white light emitting diodes to suppress efficiency droop and improve color rendering index

    In this paper, gallium nitride (GaN) based white light-emitting diodes (WLEDs) with modulated quantities of blue (In0.15Ga0.85N) quantum wells (QWs) and cyan QWs (In0.18Ga0.82N) in multiple QW (MQW) structures have been investigated numerically and experimentally. It is demonstrated that the optical performance of LEDs is sensitive to the quantities of cyan QWs in dual-wavelength MQW structures. Compared to the LEDs with respective 0, 4, and 8 cyan QWs (12 QWs in total), the optical performance of the sample with 6 cyan QWs is the best. The deterioration of the optical performance in the sample with less (4 pairs) cyan QWs or more (8 pairs) cyan QWs than 6 cyan QWs may be ascribed to weakened reservoir effect or more defects induced. Compared to conventional blue LEDs (12 blue QWs), the sample with 6 cyan QWs could effectively suppress the efficiency droop (the experimental droop ratio decreases from 50.3% to 39.5% at 80 A/cm2) and significantly improve the color rendering index (CRI, increases from 66.4 to 77.0) simultaneously. We attribute the droop suppression to the strengthened reservoir effect and carrier confinement of deeper QWs (higher indium composition) incorporated in the dual-wavelength MQW structures, which lead to the better hole spreading and enhanced radiative recombination. Meanwhile, the remarkable experimental CRI improvement may result from the wider full-width at half-maximum of electroluminescence spectra and higher cyan intensity in WLED chips with dual-wavelength MQW structures

  6. Identification, synthesis and characterization of an unknown process related impurity in eslicarbazepine acetate active pharmaceutical ingredient by LC/ESI-IT/MS, 1H, 13C and 1H-1H COSY NMR

    Saji Thomas; Saroj Kumar Paul; Subhash Chandra Joshi; Vineet Kumar; Ashutosh Agarwal; Dharam Vir

    2014-01-01

    A new impurity was detected during high performance liquid chromatographic (HPLC) analysis of eslicarbazepine acetate active pharmaceutical ingredient. The structure of unknown impurity was postulated based on liquid chromatography mass spectrometry using electrospray ionization and ion trap analyzer (LC/ESI-IT/MS) analysis. Proposed structure of impurity was unambiguously confirmed by synthesis followed by characterization using 1H, 13C nuclear magnetic resonance spectrometry (NMR), 1H-1H correlation spectro-scopy (COSY) and infrared spectroscopy (IR). Based on the spectroscopic and spectrometric data, unknown impurity was characterized as 5-carbamoyl-10,11-dihydro-5H-dibenzo[b,f]azepin-10-yl propionate.

  7. Generalized quantum entropies

    A deduction of generalized quantum entropies within the Tsallis and Kaniadakis frameworks is derived using a generalization of the ordinary multinomial coefficient. This generalization is based on the respective deformed multiplication and division. We show that the two above entropies are consistent with ones arbitrarily assumed at other contexts. -- Highlights: → Derivation of generalized quantum entropies. → Generalized combinatorial method. → Non-Gaussian quantum statistics.

  8. Quantum resource studied from the perspective of quantum state superposition

    Quantum resources, such as discord and entanglement, are crucial in quantum information processing. In this paper, quantum resources are studied from the aspect of quantum state superposition. We define the local superposition (LS) as the superposition between basis of single part, and nonlocal superposition (NLS) as the superposition between product basis of multiple parts. For quantum resource with nonzero LS, quantum operation must be introduced to prepare it, and for quantum resource with nonzero NLS, nonlocal quantum operation must be introduced to prepare it. We prove that LS vanishes if and only if the state is classical and NLS vanishes if and only if the state is separable. From this superposition aspect, quantum resources are categorized as superpositions existing in different parts. These results are helpful to study quantum resources from a unified frame. (paper)

  9. Internal dynamics of (C 3N 2H 5) 5Bi 2Cl 11 studied by IINS, 1H NMR and QC methods

    Hołderna-Natkaniec, K.; Natkaniec, I.; Jakubas, R.; Nowak, D.; Medycki, W.

    2008-11-01

    The low temperature inelastic incoherent neutron scattering spectra of pentakis (imidazolium) undecachlorodibismuthate (III) [(C 3N 2H 5) 5Bi 2Cl 11] were discussed versus different models of reference structures obtained by quantum chemical calculations in the energy transfer range up to 1200 cm -1. The second moment of 1H NMR line and spin-lattice relaxation times were employed to study the internal dynamics of imidazolium cation at the ferroelectric-paraelectric phase transition.

  10. Relativistically invariant quantum information

    Bartlett, Stephen D.; Terno, Daniel R.

    2004-01-01

    We show that quantum information can be encoded into entangled states of multiple indistinguishable particles in such a way that any inertial observer can prepare, manipulate, or measure the encoded state independent of their Lorentz reference frame. Such relativistically invariant quantum information is free of the difficulties associated with encoding into spin or other degrees of freedom in a relativistic context.

  11. Interleaved localized 1H/31P nuclear magnetic resonance spectroscopy of skeletal muscle

    creatine, and lactate in human gastrocnemius muscle can be quantified directly, without using physiological model assumptions, while intracellular pH can be derived from the chemical shifts of Pi and PCr in 31P MR spectra. Quantifying intramuscular lactate by NMR spectroscopy is a challenging task, because the lactate signal is overlapped by strong lipid resonances and exhibits modulations which depend on factors hard to control or measure, like muscle fibre orientation relative to the magnetic field, intra- and extracellular compartmentation and relaxation times. The thesis is organized into an introduction to muscle physiology and methods for studying metabolism, followed by a theoretical chapter on localized NMR spectroscopy using STEAM and the localized double quantum filter (DQF) pulse sequence which was implemented for in vivo lactate detection. The theoretical sections are supplemented by an outline of the product operator formalism to describe the NMR spectroscopy experiments mathematically, in the appendix. The second part describes the experiments which have been conducted at the 3 Tesla whole body NMR scanner installed at the 'High Field MR Centre of Excellence', Vienna Medical University: the non-magnetic exercise rig constructed for activation of human calf muscle during NMR measurements is presented. Examples of basic muscle MR spectroscopy are given and the interleaved 1H and 31P STEAM sequence implemented on the NMR scanner is explained in detail along with its application during calf muscle exercise, employing the exercise rig. Then the localized double quantum filter (DQF) pulse sequence is introduced which was developed for detection of the lactate CH3 resonance and suppression of overlaying lipid signals. Lactate quantification is only possible with this method due to the incorporation of knowledge about ordering effects published by other groups in the previous year. The final chapter of the experimental part comprises the time resolved interleaved

  12. Efficient synthesis and in vitro antifungal activity of 1H-benzimidazol-1-yl acetates/propionates containing 1H-1,2,4-triazole moiety

    Pei Zhi Zhang; Shao Fang Zhou; Tian Ren Li; Lin Jiang

    2012-01-01

    A series of novel 1H-benzimidazol-1-yl acetates and 1H-benzimidazol-1-yl propionates containing 1H-1,2,4-triazole moiety were synthesized under microwave irradiation by multi-step reactions,in yields of 87-94%.Their in vitro antifungal activities against Botrytis cinerea and Sclerotinia sclerotiorum were evaluated by mycelial growth rate method.All the target compounds exhibit high activities against B.cinerea with the EC50 values of 7.96-21.74 μg/mL,higher than that of carbendazim.

  13. Quantum Erasure: Quantum Interference Revisited

    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.

  14. Intermixing of InGaAs/GaAs Quantum Well Using Multiple Cycles Annealing Cu-doped SiO2

    Hongpinyo, V; Ding, Y H; Dimas, C E; Wang, Y; Ooi, B S; Qiu, W; Goddard, L L; Behymer, E M; Cole, G D; Bond, T C

    2008-06-11

    The authors investigate the effect of intermixing in InGaAs/GaAs quantum well structure using Cu-doped SiO{sub 2}. The incorporation of Cu into the silica film yields larger bandgap shift than typical impurity-free vacancy diffusion (IFVD) method at a lower activation temperature. We also observe enhancement of the photoluminescence (PL) signal from the intermixed InGaAs/GaAs quantum well structure after being cycle-annealed at 850 C.

  15. Quantum Error Correcting Subsystem Codes From Two Classical Linear Codes

    Bacon, Dave; Casaccino, Andrea

    2006-01-01

    The essential insight of quantum error correction was that quantum information can be protected by suitably encoding this quantum information across multiple independently erred quantum systems. Recently it was realized that, since the most general method for encoding quantum information is to encode it into a subsystem, there exists a novel form of quantum error correction beyond the traditional quantum error correcting subspace codes. These new quantum error correcting subsystem codes diffe...

  16. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: A Novel Investigation on Using Strain in Barriers of 1.3 μm AlGaInAs-InP Uncooled Multiple Quantum Well Lasers

    Bahrami Yekta, Vahid; Kaatuzian, Hassan

    2010-09-01

    In this study we investigate strain effect in barriers of 1.3 μm AlGaInAs-InP uncooled multiple quantum well lasers. Single effective mass and Kohn-Luttinger Hamiltonian equations have been solved to obtain quantum states and envelope wave functions in the structure. In the case of unstrained barriers, our simulations results have good agreement with a real device fabricated and presented in one of the references. Our main work is proposal of 0.2% compressive strain in the structure Barriers that causes significant reduction in Leakage current density and Auger current density characteristics in 85 °C. 20% improvement in mode gain-current density characteristic is also obtained in 85°C.

  17. Evaluating the well-to-well distribution of radiative recombination rates in semi-polar (11\\bar{2}2) InGaN multiple-quantum-well light-emitting diodes

    Funato, Mitsuru; Matsufuji, Kohei; Kawakami, Yoichi

    2016-07-01

    The distribution of well-to-well radiative recombination rates (RRRs) in an electrically driven semi-polar (11\\bar{2}2) InGaN multiple-quantum-well light-emitting diode (LED) is investigated within an electron–hole recombination picture. Compared to the reference (0001) LED, the (11\\bar{2}2) LED exhibits uniform well-to-well RRR distributions, which are less dependent on the injection current, because of the weaker polarization field. The smaller dependence of the RRR distribution on the injection current suggests that (11\\bar{2}2) LEDs can be applied to polychromatic LEDs consisting of quantum wells with different emission colors in electrical series because a current-insensitive apparent emission color is expected. A proof-of-concept polychromatic LED is demonstrated on the semi-polar (11\\bar{2}2) plane.

  18. Decreased insulin clearance in individuals with elevated 1-h post-load plasma glucose levels.

    Maria Adelaide Marini

    Full Text Available Reduced insulin clearance has been shown to predict the development of type 2 diabetes. Recently, it has been suggested that plasma glucose concentrations ≥ 8.6 mmol/l (155 mg/dl at 1 h during an oral glucose tolerance test (OGTT can identify individuals at high risk for type 2 diabetes among those who have normal glucose tolerance (NGT 1 h-high. The aim of this study was to examine whether NGT 1 h-high have a decrease in insulin clearance, as compared with NGT individuals with 1-h post-load glucose <8.6 mmol/l (l (155 mg/dl, NGT 1 h-low. To this end, 438 non-diabetic White individuals were subjected to OGTT and euglycemic-hyperinsulinemic clamp to evaluate insulin clearance and insulin sensitivity. As compared with NGT 1 h-low individuals, NGT 1 h-high had significantly higher 1-h and 2-h post-load plasma glucose and 2-h insulin levels as well as higher fasting glucose and insulin levels. NGT 1 h-high exhibited also a significant decrease in both insulin sensitivity (P<0.0001 and insulin clearance (P = 0.006 after adjusting for age, gender, adiposity measures, and insulin sensitivity. The differences in insulin clearance remained significant after adjustment for fasting glucose (P = 0.02 in addition to gender, age, and BMI. In univariate analyses adjusted for gender and age, insulin clearance was inversely correlated with body weight, body mass index, waist, fat mass, 1-h and 2-h post-load glucose levels, fasting, 1-h and 2-h post-load insulin levels, and insulin-stimulated glucose disposal. In conclusion, our data show that NGT 1 h-high have a reduction in insulin clearance as compared with NGT 1 h-low individuals; this suggests that impaired insulin clearance may contribute to sustained fasting and post-meal hyperinsulinemia.

  19. Role of Metallothionein1H in Cisplatin Resistance of Non-Small Cell Lung Cancer Cells

    Xin-fang Hou; Qing-xia Fan; Liu-xing Wang; Shi-xin Lu

    2009-01-01

    Objective: Despite platinum-based adjuvant chemotherapy has improved greatly patients' outcomes, drug resistance poses a major impediment to the successful use of such an effective agent. Metallothioneins(MTs) are known to play putative roles in cancer cell proliferation, apoptosis, differentiation, drug resistance and prognosis. The present studiy was to investigte the role of metallethioein1H(MT1H) in cisplatin resistance of human non-small cell lung cancer(NSCLC) cell lines in vitro or its possible molecular mechanisms. Methods: MT1H mRNA expression in A549 and A549/DDP cells was detected by RT-PCR. A recombinant eukaryotic expression plasmid pcDNA3.1(-)-MT1H was constructed and transfected into A549 cells which express no MT1H. MT1H siRNA was transfected into A549/DDP cells which express MT1H highly. MT1H expression was detected by RT-PCR and Immunoblot. The chemosensitivity to cisplatin was assessed by MTT assay. Apoptosis rate was determined by Tunel and FCM. Bcl-2 and Bax were determined by immunohistochemistry. Results: MT1H mRNA was expressed in A549/DDP but not in A549. After transfection of MT1H, MT1H expression was enhanced and the chemosensitivity to cisplatin was decreased in A549 cells. Inversely, after transfection of MT1H siRNA, MT1H expression was decreased and the chemosensitivity to cisplatin was increased in A549/DDP. The apoptosis rate induced by cisplatin was increased and Bcl-2 was down-regulated but Bax showed little change in A549/DDP cells interferred with MT1H siRNA. Conclusion: MT1H overexpression can promote drug resistance in A549 cells . Down-regulation of MT1H interfered with siRNA can effectively reverses the drug resistance in A549/DDP cells by down-regulating the expression of Bcl-2 and increasing cisplatin induced apoptosis. SiRNA targeting MT1H combined with chemotherapy may be a very promising strategy for treatment of lung cancer.

  20. Quantum state fusion in photons

    Vitelli, Chiara; Spagnolo, Nicolò; Aparo, Lorenzo; SCIARRINO, Fabio; Santamato, Enrico; Marrucci, Lorenzo

    2012-01-01

    Photons are the ideal carriers of quantum information for communication. Each photon can have a single qubit or even multiple qubits encoded in its internal quantum state, as defined by optical degrees of freedom such as polarization, wavelength, transverse modes, etc. Here, we propose and experimentally demonstrate a physical process, named "quantum state fusion", in which the two-dimensional quantum states (qubits) of two input photons are combined into a single output photon, within a four...

  1. Quantum Key Distribution over Probabilistic Quantum Repeaters

    Amirloo, Jeyran; Razavi, Mohsen; Majedi, A. Hamed

    2010-01-01

    A feasible route towards implementing long-distance quantum key distribution (QKD) systems relies on probabilistic schemes for entanglement distribution and swapping as proposed in the work of Duan, Lukin, Cirac, and Zoller (DLCZ) [Nature 414, 413 (2001)]. Here, we calculate the conditional throughput and fidelity of entanglement for DLCZ quantum repeaters, by accounting for the DLCZ self-purification property, in the presence of multiple excitations in the ensemble memories as well as loss a...

  2. Establishing 1H nuclear magnetic resonance based metabonomics fingerprinting profile for spinal cord injury: a pilot study

    JIANG Hua; PENG Jin; ZHOU Zhi-yuan; DUAN Yu; CHEN Wei; CAI Bin; YANG Hao; ZHANG Wei

    2010-01-01

    Background Spinal cord injury (SCI) is a complex trauma that consists of multiple pathological mechanisms involving cytotoxic, oxidation stress and immune-endocrine. This study aimed to establish plasma metabonomics fingerprinting atlas for SCI using 1H nuclear magnetic resonance (NMR) based metabonomics methodology and principal component analysis techniques.Methods Nine Sprague-Dawley (SD) male rats were randomly divided into SCI, normal and sham-operation control groups. Plasma samples were collected for 1H NMR spectroscopy 3 days after operation. The NMR data were analyzed using principal component analysis technique with Matlab software.Results Metabonomics analysis was able to distinguish the three groups (SCI, normal control, sham-operation). The fingerprinting atlas indicated that, compared with those without SCI, the SCI group demonstrated the following characteristics with regard to second principal component: it is made up of fatty acids, myc-inositol, arginine, very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), triglyceride (TG), glucose, and 3-methyl-histamine.Conclusions The data indicated that SCI results in several significant changes in plasma metabolism early on and that a metabonomics approach based on 1H NMR spectroscopy can provide a metabolic profile comprising several metabolite classes and allow for relative quantification of such changes. The results also provided support for further development and application of metabonomics technologies for studying SCI and for the utilization of multivariate models for classifying the extent of trauma within an individual.

  3. Multiplexed CV quantum teleportation for high rates in quantum communication

    Christ, Andreas; Silberhorn, Christine

    2012-01-01

    A major challenge of today's quantum communication systems lies in the transmission of quantum information with high rates over long distances in the presence of unavoidable losses. Thereby the achievable quantum communication rate is fundamentally limited by the amount of energy that can be transmitted per use of the channel. It is hence vital to develop quantum communication protocols which encode quantum information as energy efficiently as possible. To this aim we investigate continuous-variable quantum teleportation as a method of distributing quantum information. We explore the possibility to encode information on multiple optical modes and derive upper and lower bounds on the achievable quantum channel capacities. This analysis enables us to benchmark single-mode vs. multi-mode entanglement resources. Our research reveals that multiplexing does not only feature an enhanced energy efficiency, significantly increasing the achievable quantum communication rates in comparison to single-mode coding, but als...

  4. Ultrafast carrier relaxation in GaN, In_(0.05)Ga_(0.95)N and an In_(0.05)Ga_(0.95)/In_(0.15)Ga_(0.85)N Multiple Quantum Well

    Ozgur, Umit; Everitt, Henry O.

    2002-01-01

    Room temperature, wavelength non-degenerate ultrafast pump/probe measurements were performed on GaN and InGaN epilayers and an InGaN multiple quantum well structure. Carrier relaxation dynamics were investigated as a function of excitation wavelength and intensity. Spectrally-resolved sub-picosecond relaxation due to carrier redistribution and QW capture was found to depend sensitively on the wavelength of pump excitation. Moreover, for pump intensities above a threshold of 100 microJ/cm2, al...

  5. Transforming quantum operations: quantum supermaps

    Chiribella, G.; D'Ariano, G. M.; Perinotti, P.

    2008-01-01

    We introduce the concept of quantum supermap, describing the most general transformation that maps an input quantum operation into an output quantum operation. Since quantum operations include as special cases quantum states, effects, and measurements, quantum supermaps describe all possible transformations between elementary quantum objects (quantum systems as well as quantum devices). After giving the axiomatic definition of supermap, we prove a realization theorem, which shows that any sup...

  6. Quantum correlation via quantum coherence

    Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing

    2014-01-01

    Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition--------quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes ...

  7. 1H NMR Metabolic Profiling of Biofluids from Rats with Gastric Mucosal Lesion and Electroacupuncture Treatment

    Jingjing Xu

    2015-01-01

    Full Text Available Gastric mucosal lesion (GML is a common gastrointestinal disorder with multiple pathogenic mechanisms in clinical practice. In traditional Chinese medicine (TCM, electroacupuncture (EA treatment has been proven as an effective therapy for GML, although the underlying healing mechanism is not yet clear. Here, we used proton nuclear magnetic resonance- (1H NMR- based metabolomic method to investigate the metabolic perturbation induced by GML and the therapeutic effect of EA treatment on stomach meridian (SM acupoints. Clear metabolic differences were observed between GML and control groups, and related metabolic pathways were discussed by means of online metabolic network analysis toolbox. By comparing the endogenous metabolites from GML and GML-SM groups, the disturbed pathways were partly recovered towards healthy state via EA treated on SM acupoints. Further comparison of the metabolic variations induced by EA stimulated on SM and the control gallbladder meridian (GM acupoints showed a quite similar metabolite composition except for increased phenylacetylglycine, 3,4-dihydroxymandelate, and meta-hydroxyphenylacetate and decreased N-methylnicotinamide in urine from rats with EA treated on SM acupoints. The current study showed the potential application of metabolomics in providing further insight into the molecular mechanism of acupuncture.

  8. Spectral properties of 1H-pyrazolo[3,4-b]quinoline substituted with N,N-diethylamine moiety

    Kolbus, Anna; Grabka, Danuta; Danel, Andrzej; Szary, Karol

    2016-07-01

    Photophysical properties of 6-N,N-diethyl-3-methyl-1-phenyl-1H-pyrazol[3,4-b]quinoline (DEPQ), a potential material for electroluminescent applications, were investigated. The absorption and fluorescence spectra and fluorescence lifetimes were recorded in a great number of solvents with different polarity. The red shifts in absorption and fluorescence maxima with the solvent's polarity were observed. Different trends in values of quantum yield for non-polar and polar solvents suggest two different deactivation ways of the excited state, depending on solvent polarity. DEPQ in non-polar solvents emits from locally excited states while deactivation DEPQ in polar solvents indicates charge transfer (CT) fluorescence. Several electro-optical parameters were also calculated.

  9. Nuclear reaction analysis of 1H and 2H in hafnium silicate films on Si

    The 1H(15N,αγ)12C and 2H(3He,p)4He nuclear reactions were employed to detect, respectively, 1H and 2H in hafnium silicates films on Si. The methods employed to achieve quantitative analyses are described. Moreover, by performing annealing sequences in vacuum or O2 followed by 1H2 or 2H2, it was observed that the O2-preanneled films incorporate less H, either 1H or 2H. This was explained by O-deficient, H-trapping sites that are eliminated by the O2 preannealing

  10. Predictability of 1-h postload plasma glucose concentration: A 10-year retrospective cohort study

    Kuang, Lifen; Huang, Zhimin; Hong, Zhenzhen; Chen, Ailing; Li, Yanbing

    2015-01-01

    Aims/Introduction Elevated 1-h postload plasma glucose concentration (1hPG) during oral glucose tolerance test has been linked to an increased risk of type 2 diabetes and a poorer cardiometabolic risk profile. The present study analyzed the predictability and cut-off point of 1hPG in predicting type 2 diabetes in normal glucose regulation (NGR) subjects, and evaluated the long-term prognosis of NGR subjects with elevated 1hPG in glucose metabolism, kidney function, metabolic states and athero...

  11. Fission reactions of 469-MeV 56Fe+238U: Detection of 4He/1H emission from pre- and post-fission sources

    The emission of 4He and 1H has been measured in coincidence with fission for reactions of 469-MeV 56Fe+238U. By using a gas-ionization telescope in kinematic coincidence with a position-sensitive avalanche detector, the folding angle between two fission fragments was determined in order to distinguish fusion reactions from fission following smaller-momentum-transfer collisions. In both fusion fission and sequential fission reactions, the 4He/1H energy spectra are relatively narrow with relatively flat angular distributions at backward angles and become broader in energy with enhanced cross-sections at forward angles. The extent of forward peaking is significantly greater for peripheral collisions than for central collisions. The light-charged-particle multiplicities are quite similar for 4He and 1H, being much larger for fusion fission than for sequential fission. Detailed comparisons of the spectral shapes with Monte Carlo simulations of reaction kinematics impose strong constraints on the participation of different emission sources. We find important contributions to the observed 4He/1H emission both from accelerated fragments (FE) and from the composite system prior to fission (CE). For 4He emission, the multiplicity of CE is much larger for fusion fission than for sequential fission, possibly as a consequence of the higher spins and shorter reaction times associated with deeply inelastic and quasi-elastic processes. For 1H emission, a corresponding but somewhat smaller difference is observed for the CE multiplicities. An excess of 4He/1H particles, found at forward angles in both fusion and sequential fission processes, cannot be attributed to evaporative emission from any fragments and therefore must originate in pre-thermalization emission. (orig.)

  12. Effect of 1,10-phenanthroline aromaticity in carboxylic acids:1H NMR spectroscopy, GIAO calculations and thermodynamic properties

    Machado, Camila M. B.; Santos, Vanessa F. C.; Belarmino, Marcia K. D. L.; França, José A. A.; Moura, Gustavo L. C.; Lima, Nathalia B. D.

    2016-08-01

    Hydrogen bonding represents a class of chemical interactions, which are directly responsible for several physical properties, such as: energetic stabilities, boiling points, vibrational modes, bond lengths, etc. In this article, we examine from the point of view of 1H NMR spectroscopy and GIAO calculations, the effects associated with the process of formation of the hydrogen bonds as they appear in the chemical shifts of the acidic hydrogens in the complexes between nitrogenated compounds, PHEN, BIPY and DIBIPY, and carboxylic acids, HOOCH, HOOCCH3 and HOOCC6H5. All computational simulations were performed using the quantum chemical methods B3LYP/6-31++G(d,p) and ωB97X-D/def2-TZVP. The 1H NMR spectroscopy results showed that, in both cases, the hydrogen nucleus of the OH group is the most affected in the process of hydrogen bond formation. For the complexes involving PHEN we observed that the hydrogen nucleus is more strongly shielded when compared with this signal in the corresponding complexes involving BIPY and DIBIPY.

  13. Sharp green electroluminescence from 1H-pyrazolo[3,4-b]quinoline-based light-emitting diodes

    Tao, Y. T.; Balasubramaniam, E.; Danel, A.; Jarosz, B.; Tomasik, P.

    2000-09-01

    A multilayer organic light-emitting diode was fabricated using a fluorescent compound {6-N,N-diethylamino-1-methyl-3-phenyl-1H-pyrazolo[3,4-b]quinoline} (PAQ-NEt2) doped into the hole-transporting layer of NPB {4,4'-bis[N-(1-naphthyl-1-)-N-phenyl-amino]-biphenyl}, with the TPBI {2,2',2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole]} as an electrontransporting material. At 16% PAQ-NEt2 doping concentration, the device gave a sharp, bright, and efficient green electroluminescence (EL) peaked at around 530 nm. The full width at half maximum of the EL is 60 nm, which is 60% of the green emission from typical NPB/AlQ [where AlQ=tris(8-hydroxyquinoline) aluminum] device. For the same concentration, a maximum luminance of 37 000 cd/m2 was obtained at 10.0 V and the maximum power, luminescence, and external quantum efficiencies were obtained 4.2 lm/W, 6.0 cd/A, and 1.6%, respectively, at 5.0 V.

  14. 1H magnetic resonance spectroscopy (1H MRS) in the initially differentiating recurrent brain gliomas after radiation therapy from delayed cerebral necrosis

    Objective: To evaluate 1H magnetic resonance spectroscopy (1H MRS) in the differentiating recurrent brain gliomas after radiation therapy from delayed cerebral necrosis. Methods: Fifteen patients who had clinical and CT, MRI changes that suggested a diagnosis of delayed cerebral necrosis or recurrent brain tumor after radiation therapy and 5 patients who had a definite clinical diagnosis of delayed cerebral necrosis underwent single MR spectroscopy simultaneously both in the lesion's region and the contralateral side. Results: Of the former 15 cases who proved by surgical pathology, 14 cases were gliomas, 1 case was delayed cerebral necrosis, and their etiologic diagnoses of 1H MRS were correct. (1) 1H MRS in 14 cases with gliomas exhibited specific spectral peaks including prominent choline-containing compounds (Cho), decreased or absent acetylaspartate (NAA) and total creatine (Cr), and the metabolic ratios showed significantly increased Cho/Cr, decreased NAA/Cr. Twelve cases showed abnormal lactate (Lac). (2) Among 6 cases with delayed cerebral necrosis, 5 cases exhibited decreased or absent Cho, NAA, Cr, and abnormal Lipid, 1 case showed absent Cho, NAA, and Cr with a flat curve without Lac. Conclusion: 1H MRS was positively claimed for differentiating recurrent brain gliomas after radiation therapy from delayed cerebral necrosis

  15. Design analysis of phosphor-free monolithic white light-emitting-diodes with InGaN/ InGaN multiple quantum wells on ternary InGaN substrates

    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

  16. Quantum correlations and light localization in disordered nanophotonic structures

    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...

  17. Electron transport in unipolar InGaN/GaN multiple quantum well structures grown by NH3 molecular beam epitaxy

    Browne, David A.

    2015-05-14

    © 2015 AIP Publishing LLC. Unipolar-light emitting diode like structures were grown by NH3 molecular beam epitaxy on c plane (0001) GaN on sapphire templates. Studies were performed to experimentally examine the effect of random alloy fluctuations on electron transport through quantum well active regions. These unipolar structures served as a test vehicle to test our 2D model of the effect of compositional fluctuations on polarization-induced barriers. Variables that were systematically studied included varying quantum well number from 0 to 5, well thickness of 1.5 nm, 3 nm, and 4.5 nm, and well compositions of In0.14Ga0.86N and In0.19Ga0.81N. Diode-like current voltage behavior was clearly observed due to the polarization-induced conduction band barrier in the quantum well region. Increasing quantum well width and number were shown to have a significant impact on increasing the turn-on voltage of each device. Temperature dependent IV measurements clearly revealed the dominant effect of thermionic behavior for temperatures from room temperature and above. Atom probe tomography was used to directly analyze parameters of the alloy fluctuations in the quantum wells including amplitude and length scale of compositional variation. A drift diffusion Schrödinger Poisson method accounting for two dimensional indium fluctuations (both in the growth direction and within the wells) was used to correctly model the turn-on voltages of the devices as compared to traditional 1D simulation models.

  18. The complete genome sequence of the Arcobacter butzleri cattle isolate 7h1h

    Arcobacter butzleri strain 7h1h was isolated in the UK from a clinically healthy dairy cow. The genome of this isolate was sequenced to completion. Here we present the annotation and analysis of the completed 7h1h genome, as well as comparison of this genome to the existing A. butzleri RM4018 and ED...

  19. {sup 1}H MR spectroscopy in histopathological subgroups of mesial temporal lobe epilepsy

    Hajek, Milan; Dezortova, Monika [Institute for Clinical and Experimental Medicine, MR Unit, Department of Diagnostic and Interventional Radiology, Prague (Czech Republic); Krsek, Pavel; Komarek, Vladimir [Charles University, Department of Pediatric Neurology, Prague 5 (Czech Republic); Marusic, Petr; Tomasek, Martin; Krijtova, Hana [Charles University, Department of Neurology, Prague (Czech Republic); Zamecnik, Josef [Charles University, Department of Pathology and Molecular Medicine, Prague (Czech Republic); Kyncl, Martin [Charles University, Department of Radiology, Prague (Czech Republic)

    2009-02-15

    The aim of the study was to analyze the lateralizing value of proton magnetic resonance spectroscopy ({sup 1}H MRS) in histopathologically different subgroups of mesial temporal lobe epilepsies (MTLE) and to correlate results with clinical, MRI and seizure outcome data. A group of 35 patients who underwent resective epilepsy surgery was retrospectively studied. Hippocampal {sup 1}H MR spectra were evaluated. Metabolite concentrations were obtained using LCModel and NAA/Cr, NAA/Cho, NAA/(Cr+Cho), Cho/Cr ratios and coefficients of asymmetry were calculated. MRI correctly lateralized 89% of subjects and {sup 1}H MRS 83%. MRI together with {sup 1}H MRS correctly lateralized 100% of patients. Nineteen subjects had 'classical' hippocampal sclerosis (HS), whereas the remaining 16 patients had 'mild' HS. Nineteen patients had histopathologically proven malformation of cortical development (MCD) in the temporal pole; 16 subjects had only HS. No difference in {sup 1}H MRS findings was found between patients in different histopathological subgroups of MTLE. Our results support the hypothesis that {sup 1}H MRS abnormalities do not directly reflect histopathological changes in MTLE patients. Subjects with non-lateralized {sup 1}H MRS abnormalities did not have a worse postoperative seizure outcome. We found no significant impact of contralateral {sup 1}H MRS abnormality on post-surgical seizure outcome. (orig.)

  20. 1H MR spectroscopy in histopathological subgroups of mesial temporal lobe epilepsy

    The aim of the study was to analyze the lateralizing value of proton magnetic resonance spectroscopy (1H MRS) in histopathologically different subgroups of mesial temporal lobe epilepsies (MTLE) and to correlate results with clinical, MRI and seizure outcome data. A group of 35 patients who underwent resective epilepsy surgery was retrospectively studied. Hippocampal 1H MR spectra were evaluated. Metabolite concentrations were obtained using LCModel and NAA/Cr, NAA/Cho, NAA/(Cr+Cho), Cho/Cr ratios and coefficients of asymmetry were calculated. MRI correctly lateralized 89% of subjects and 1H MRS 83%. MRI together with 1H MRS correctly lateralized 100% of patients. Nineteen subjects had ''classical'' hippocampal sclerosis (HS), whereas the remaining 16 patients had ''mild'' HS. Nineteen patients had histopathologically proven malformation of cortical development (MCD) in the temporal pole; 16 subjects had only HS. No difference in 1H MRS findings was found between patients in different histopathological subgroups of MTLE. Our results support the hypothesis that 1H MRS abnormalities do not directly reflect histopathological changes in MTLE patients. Subjects with non-lateralized 1H MRS abnormalities did not have a worse postoperative seizure outcome. We found no significant impact of contralateral 1H MRS abnormality on post-surgical seizure outcome. (orig.)

  1. Quantum Instantons and Quantum Chaos

    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.

  2. Quantum metrology

    The statistical error is ineluctable in any measurement. Quantum techniques, especially with the development of quantum information, can help us squeeze the statistical error and enhance the precision of measurement. In a quantum system, there are some quantum parameters, such as the quantum state, quantum operator, and quantum dimension, which have no classical counterparts. So quantum metrology deals with not only the traditional parameters, but also the quantum parameters. Quantum metrology includes two important parts: measuring the physical parameters with a precision beating the classical physics limit and measuring the quantum parameters precisely. In this review, we will introduce how quantum characters (e.g., squeezed state and quantum entanglement) yield a higher precision, what the research areas are scientists most interesting in, and what the development status of quantum metrology and its perspectives are. (topical review - quantum information)

  3. Quantum Computation and Quantum Information

    Wang, Yazhen

    2012-01-01

    Quantum computation and quantum information are of great current interest in computer science, mathematics, physical sciences and engineering. They will likely lead to a new wave of technological innovations in communication, computation and cryptography. As the theory of quantum physics is fundamentally stochastic, randomness and uncertainty are deeply rooted in quantum computation, quantum simulation and quantum information. Consequently quantum algorithms are random in nature, and quantum ...

  4. Helping Students Learn Quantum Mechanics for Quantum Computing

    Singh, Chandralekha

    2016-01-01

    Quantum information science and technology is a rapidly growing interdisciplinary field drawing researchers from science and engineering fields. Traditional instruction in quantum mechanics is insufficient to prepare students for research in quantum computing because there is a lack of emphasis in the current curriculum on quantum formalism and dynamics. We are investigating the difficulties students have with quantum mechanics and are developing and evaluating quantum interactive learning tutorials (QuILTs) to reduce the difficulties. Our investigation includes interviews with individual students and the development and administration of free-response and multiple-choice tests. We discuss the implications of our research and development project on helping students learn quantum mechanics relevant for quantum computing.

  5. Doping dependent blue shift and linewidth broadening of intersubband absorption in non-polar m-plane AlGaN/GaN multiple quantum wells

    Blue shift and broadening of the absorption spectra of mid-infrared intersubband transition in non-polar m-plane AlGaN/GaN 10 quantum wells were observed with increasing doping density. As the doping density was increased from 6.6 × 1011 to 6.0 × 1012 cm−2 per a quantum well, the intersubband absorption peak energy shifted from 274.0 meV to 302.9 meV, and the full width at half maximum increased from 56.4 meV to 112.4 meV. Theoretical calculations reveal that the blue shift is due to many body effects, and the intersubband linewidth in doped AlGaN/GaN QW is mainly determined by scattering due to interface roughness, LO phonons, and ionized impurities

  6. Dimethyl sulfone in human cerebrospinal fluid and blood plasma confirmed by one-dimensional (1)H and two-dimensional (1)H-(13)C NMR.

    Engelke, U.F.H.; Tangerman, A.; Willemsen, M.A.A.P.; Moskau, D.; Loss, S.; Mudd, S.H.; Wevers, R.A.

    2005-01-01

    (1)H-NMR spectroscopy at 500 MHz was used to confirm that a previously unidentified singlet resonance at 3.14 ppm in the spectra of cerebrospinal fluid and plasma samples corresponds to dimethyl sulfone (DMSO(2)). A triple resonance inverse cryogenic NMR probe, with pre-amplifier and the RF-coils co

  7. A new AgI complex based on 1-[(1H-benzimidazol-1-ylmethyl]-1H-1,2,4-triazole

    Yan-zhi Wang

    2011-12-01

    Full Text Available In the title complex, bis{μ-1-[(1H-benzimidazol-1-ylmethyl]-1H-1,2,4-triazole}disilver(I dinitrate, [Ag2(C10H9N52](NO32, the AgI ion is nearly linearly coordinated [N—Ag—N angle is 155.72 (14°] by two 1-[(1H-benzimidazole-1-ylmethyl]-1H-1,2,4-triazole (bmt ligands. In addition, two bmt ligands link two AgI ions, forming a dinuclear unit with an Ag...Ag distance of 5.0179 (15 Å. The whole complex is generated by an inversion centre. The dinuclear units and the NO3− counter-ions are connected by N—H...O hydrogen bonds and weak Ag...O interactions [2.831 (5, 2.887 (5 and 2.908 (5 Å], leading to a three-dimensional structure.

  8. Synthesis and Molecular Structure of 1,5,1',5'-Tetraphenyl-1H,1H'-3,3'-dialkylthio-bi-1,2,4-triazole

    JIANG Wen-Qing; LIU Tian-Bao; ZOU Jian-Ping; ZHANG Yong

    2007-01-01

    The title compound 1,5,1',5'-tetraphenyl-1H,1H'-3,3'-dialkylthio-bi-1,2,4-triazole (2, C28H20N6S2, Mr=504.62) was prepared by the reaction of 1-benzoyl-3-phenylaminothiourea 1 and Mn(OAc)3·2H2O in acetic acid under microwave irradiation. The crystal is of monoclinic, space group P21/c with a=11.3931(10), b=16.5787(14), c=26.470(2) (A), β=98.274(2)°, Z=8, V=4947.8(8) (A)3, Dc=1.355 g/cm3, μ(MoKα) (A) 0.245 mm-1, F(000)=2096, the final R=0.0583 and Wr=0.1502 for 8705 observed reflections (Ⅰ > 2σ(Ⅰ)). X-ray analysis reveals that the title compound is 1,5,1',5'-tetraphenyl-1H,1H'-3,3'-dialkylthio-bi-1,2,4-triazole, and its formation mechanism was proposed.

  9. Structure and properties of bis(1-phenyl-1h-tetrazole-5-thiolate)diiron tetranitrosyl

    Sanina, N. A.; Kozub, G. I.; Kondrat'eva, T. A.; Shilov, G. V.; Korchagin, D. V.; Emel'yanova, N. S.; Poleshchuk, O. Kh.; Chernyak, A. V.; Kulikov, A. V.; Mushenok, F. B.; Ovanesyan, N. S.; Aldoshin, S. M.

    2013-06-01

    New tetranitrosyl binuclear iron complex [Fe2(SС7H5N4)2(NO)4] (I) has been synthesized by interaction of aqueous solutions of anionic salts [Fе(S2O3)2(NO)2]3- and [SС7H5N4]-. The latter one was synthesized by reduction of bis-(1-phenyl-1H-tetrazole-5-yl) disulfide with hydrazine hydrate in ethanol at T = 25 °C. Molecular and crystalline structure of I was determined by X-ray analysis; the complex has binuclear structure of "μ-SCN" type with ˜4.02 Å between the iron atoms. Shortened О⋯О contacts (2.81 Å) between the NO groups of similar type are observed. Parameters of Mössbauer spectrum for I are: isomer shift δFe = 0.311(1) mm/s, quadrupole splitting ΔEQ = 1.044(1) mm/s, line width Γ = 0.267(1) mm/s at 85 K. From SQUID magnetometry data, the temperature and field dependences of the magnetic moment of I are well described in the frame of a simple model of binuclear iron complex with magnetic centers S1 = S2 = ½. In solution, binuclear structure of the complex remains, though the NO groups are non-equivalent. For solutions of I five-line hyperfine structure of spectrum (HFS) is observed, g-factor = 2.03. For polycrystals of I, no HFS was observed due to averaged exchange interaction between the electron spins of adjacent complexes. In polycrystals of I, the number of spins per one binuclear complex is dimethylsulfoxide (DMSO) aqueous solution is ˜13.8 nM, it halves in 8 min after decomposition starts, and reaches ˜3.8 nM in anaerobic conditions at Т = 25 °С, pH 7.0. This is due, according to quantum-chemical calculations, to the presence of a more stable Fesbnd NO bond in I than in its isostructural analog - nitrosyl iron complex with 1-methyltetrazole-5-yl (II).

  10. Quantum Simulation

    Georgescu, I. M.; Ashhab, S.; Nori, Franco

    2013-01-01

    Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry and cosmology. Quantum simulat...

  11. Quantum Coins

    Mosca, Michele

    2009-01-01

    One of the earliest cryptographic applications of quantum information was to create quantum digital cash that could not be counterfeited. In this paper, we describe a new type of quantum money: quantum coins, where all coins of the same denomination are represented by identical quantum states. We state desirable security properties such as anonymity and unforgeability and propose two candidate quantum coin schemes: one using black box operations, and another using blind quantum computation.

  12. Structure and equilibria of Ca 2+-complexes of glucose and sorbitol from multinuclear ( 1H, 13C and 43Ca) NMR measurements supplemented with molecular modelling calculations

    Pallagi, A.; Dudás, Cs.; Csendes, Z.; Forgó, P.; Pálinkó, I.; Sipos, P.

    2011-05-01

    Ca 2+-complexation of D-glucose and D-sorbitol have been investigated with the aid of multinuclear ( 1H, 13C and 43Ca) NMR spectroscopy and ab initio quantum chemical calculations. Formation constants of the forming 1:1 complexes have been estimated from one-dimensional 13C NMR spectra obtained at constant ionic strength (1 M NaCl). Binding sites were identified from 2D 1H- 43Ca NMR spectra. 2D NMR measurements and ab initio calculations indicated that Ca 2+ ions were bound in a tridentate manner via the glycosidic OH, the ethereal oxygen in the ring and the OH on the terminal carbon for the α- and β-anomers of glucose and for sorbitol simultaneous binding of four hydroxide moieties (C1, C2, C4 and C6) was suggested.

  13. Structure-based predictions of 13C-NMR chemical shifts for a series of 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indoles derivatives using GA-based MLR method

    Ghavami, Raouf; Sadeghi, Faridoon; Rasouli, Zolikha; Djannati, Farhad

    2012-12-01

    Experimental values for the 13C NMR chemical shifts (ppm, TMS = 0) at 300 K ranging from 96.28 ppm (C4' of indole derivative 17) to 159.93 ppm (C4' of indole derivative 23) relative to deuteride chloroform (CDCl3, 77.0 ppm) or dimethylsulfoxide (DMSO, 39.50 ppm) as internal reference in CDCl3 or DMSO-d6 solutions have been collected from literature for thirty 2-functionalized 5-(methylsulfonyl)-1-phenyl-1H-indole derivatives containing different substituted groups. An effective quantitative structure-property relationship (QSPR) models were built using hybrid method combining genetic algorithm (GA) based on stepwise selection multiple linear regression (SWS-MLR) as feature-selection tools and correlation models between each carbon atom of indole derivative and calculated descriptors. Each compound was depicted by molecular structural descriptors that encode constitutional, topological, geometrical, electrostatic, and quantum chemical features. The accuracy of all developed models were confirmed using different types of internal and external procedures and various statistical tests. Furthermore, the domain of applicability for each model which indicates the area of reliable predictions was defined.

  14. Membrane quantum mechanics

    Tadashi Okazaki

    2015-01-01

    Full Text Available We consider the multiple M2-branes wrapped on a compact Riemann surface and study the arising quantum mechanics by taking the limit where the size of the Riemann surface goes to zero. The IR quantum mechanical models resulting from the BLG-model and the ABJM-model compactified on a torus are N=16 and N=12 superconformal gauged quantum mechanics. After integrating out the auxiliary gauge fields we find OSp(16|2 and SU(1,1|6 quantum mechanics from the reduced systems. The curved Riemann surface is taken as a holomorphic curve in a Calabi–Yau space to preserve supersymmetry and we present a prescription of the topological twisting. We find the N=8 superconformal gauged quantum mechanics that may describe the motion of two wrapped M2-branes in a K3 surface.

  15. Probabilistic authenticated quantum dialogue

    Hwang, Tzonelih; Luo, Yi-Ping

    2015-12-01

    This work proposes a probabilistic authenticated quantum dialogue (PAQD) based on Bell states with the following notable features. (1) In our proposed scheme, the dialogue is encoded in a probabilistic way, i.e., the same messages can be encoded into different quantum states, whereas in the state-of-the-art authenticated quantum dialogue (AQD), the dialogue is encoded in a deterministic way; (2) the pre-shared secret key between two communicants can be reused without any security loophole; (3) each dialogue in the proposed PAQD can be exchanged within only one-step quantum communication and one-step classical communication. However, in the state-of-the-art AQD protocols, both communicants have to run a QKD protocol for each dialogue and each dialogue requires multiple quantum as well as classical communicational steps; (4) nevertheless, the proposed scheme can resist the man-in-the-middle attack, the modification attack, and even other well-known attacks.

  16. {sup 1}H-MR spectroscopy in anorexia nervosa. Reversible cerebral metabolic changes; {sup 1}H-MR-Spektroskopie bei Anorexia nervosa: Reversible zerebrale Metabolitenaenderungen

    Moeckel, R.; Schlemmer, H.P.; Becker, G.; Koepke, J.; Georgi, M. [Heidelberg Univ. (Germany). Inst. fuer Klinische Radiologie; Gueckel, C.; Goepel, C.; Schmidt, M. [Zentralinstitut fuer Seelische Gesundheit, Mannheim (Germany). Klinik fuer Kinder- und Jugendpsychiatrie; Hentschel, F. [Zentralinstitut fuer Seelische Gesundheit, Mannheim (Germany). Neuroradiologie

    1999-04-01

    Purpose: By using localized {sup 1}H-MR spectroscopy in the brain of patients with anorexia nervosa we wanted to verify our preliminary results and to look for a reversibility of the metabolic changes under therapy. Methods: In 22 patients and 17 healthy volunteers (11 follow-up examinations) single voxel {sup 1}H-MR spectroscopy (TE=50 ms, TM=30 ms, TR=1500 ms, voxel (2 cm){sup 3}, acq.: 256) was used in two different localizations (thalamus and parieto-occipital region). The first examination of the patients was performed before therapy, the follow-up examination at the end of therapy. Results: In both regions of the brain we found a statistically significant elevation of the Cho/Cr-ratio in comparison to normal controls. The follow-up examinations revealed reversibility of the metabolic changes under successful therapy. Conclusion: {sup 1}H-MR spectroscopy reveals metabolic changes in the brain of patients with anorexia nervosa, which are reversible under successful therapy. These metabolic changes can be conclusively explained using a biochemical model. (orig.) [Deutsch] Ziel: Im Rahmen dieser weiterfuehrenden Studie sollten die bisherigen Ergebnisse der lokalisierten {sup 1}H-MR-Spektroskopie des Gehirns an Patienten mit Anorexia nervosa verifiziert werden. Weiter sollte ueberprueft werden, ob die von uns nachgewiesenen metabolischen Veraenderungen unter Therapie reversibel sind. Methode: Die {sup 1}H-MR-Spektren wurden bei 22 Patientinnen und 17 Probanden (11 Verlaufskontrollen) in Einzelvolumentechnik (TE=50 ms, TM=30 ms, TR=1500 ms, Voxel: (2 cm){sup 3}, Acq.: 256) in zwei unterschiedlichen Hirnregionen (Thalamus, parieto-okzipitale Region) durchgefuehrt. Die erste Untersuchung der Patienten erfolgte bei Aufnahme und die Verlaufskontrolle zum Abschluss der stationaeren Behandlung. Ergebnisse: Bei den Patienten wurde in beiden Hirnregionen ein statistisch signifikant erhoehter Wert fuer das Cho/Cr-Verhaeltnis im Vergleich zu dem Normalkollektiv nachgewiesen

  17. Partially entangled states bridge in quantum teleportation

    Cai, Xiao-Fei; Yu, Xu-Tao; Shi, Li-Hui; Zhang, Zai-Chen

    2014-10-01

    The traditional method for information transfer in a quantum communication system using partially entangled state resource is quantum distillation or direct teleportation. In order to reduce the waiting time cost in hop-by-hop transmission and execute independently in each node, we propose a quantum bridging method with partially entangled states to teleport quantum states from source node to destination node. We also prove that the designed specific quantum bridging circuit is feasible for partially entangled states teleportation across multiple intermediate nodes. Compared to two traditional ways, our partially entanglement quantum bridging method uses simpler logic gates, has better security, and can be used in less quantum resource situation.

  18. Ion trapping for quantum information processing

    WAN Jin-yin; WANG Yu-zhu; LIU Liang

    2007-01-01

    In this paper we have reviewed the recent pro-gresses on the ion trapping for quantum information process-ing and quantum computation. We have first discussed the basic principle of quantum information theory and then fo-cused on ion trapping for quantum information processing.Many variations, especially the techniques of ion chips, have been investigated since the original ion trap quantum compu-tation scheme was proposed. Full two-dimensional control of multiple ions on an ion chip is promising for the realization of scalable ion trap quantum computation and the implemen-tation of quantum networks.

  19. Some analogies between quantum cloning and quantum deleting

    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

  20. 1H-MRS study of brain metabolic disorder in patients with cyanosed congenital heart disease

    Objective: To study the metabolic alteration in the brain of patients with cyanosed congenital heart disease (CCHD) by using 1H-magnetic resonance spectroscopy (1H-MRS) and discover the pathophysiology of chronic hypoxic brain, which will help to diagnose and treat this disease completely. Methods: Twenty-five patients with CCHD and 25 controls were performed PRESS 1H-MRS and MRI. The areas under the resonance of metabolites were measured, the ratios of the other metabolites to Cr were calculated and compared. Results: In patients with CCHD, the mean value of NAA/Cr was significantly lower than that in controls (P 0.05). Conclusion: 1H-MRS can detect brain metabolic changes in patients with cyanosed congenital heart disease in vivo noninvasively and can detect the metabolism disorder of the energy and amino acid, so the pathophysiology of this disease can be understood

  1. Synthesis of 2-Substituted Hexahydro-1H-1,4-diazepine Analogues

    2001-01-01

    2-substituted hexahydro-1H-1,4-diazepine analogues were synthesized starting from N,N?-dibenzyl-1,3-propylene diamine and methyl-2,3-dibromo propionate through nucleophilic substitution, reduction, chlorination and debenzylation.

  2. On the {sup 1}H NMR spectra of 2-substituted benzoquinones

    Tedeschi, E.; Rezende, D.B. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Quimica; Arruda Campos, I.P. de, E-mail: ipdacamp@uol.com.br [Universidade Paulista, Sao Paulo, SP (Brazil). Inst. de Ciencias Exatas e Tecnologia. Programa de Pos-Graduacao em Engenharia de Producao

    2009-07-01

    The novel complete analysis of the {sup 1}H NMR spectra of six monosubstituted benzoquinones is reported herein, together with a brief but complete review of the scanty previously published data on benzoquinone and its monosubstituded derivatives. (author)

  3. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu [Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055 (United States); Nishiyama, Yusuke [JEOL RESONANCE Inc., Musashino, Akishima, Tokyo 196-8558 (Japan); RIKEN CLST-JEOL Collaboration Center, RIKEN, Yokohama, Kanagawa 230-0045 (Japan)

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  4. Multiplayer quantum games

    Benjamin, Simon C.; Hayden, Patrick M.

    2001-09-01

    Recently the concept of quantum information has been introduced into game theory. Here we present the first study of quantum games with more than two players. We discover that such games can possess an alternative form of equilibrium strategy, one which has no analog either in traditional games or even in two-player quantum games. In these ``coherent'' equilibria, entanglement shared among multiple players enables different kinds of cooperative behavior: indeed it can act as a contract, in the sense that it prevents players from successfully betraying one another.

  5. Young Quantum Meetings

    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

  6. Quantum Genetics, Quantum Automata and Quantum Computation

    Baianu, Professor I. C.

    2004-01-01

    The concepts of quantum automata and quantum computation are studied in the context of quantum genetics and genetic networks with nonlinear dynamics. In a previous publication (Baianu,1971a) the formal concept of quantum automaton was introduced and its possible implications for genetic and metabolic activities in living cells and organisms were considered. This was followed by a report on quantum and abstract, symbolic computation based on the theory of categories, functors and natural trans...

  7. 1H NMR profiling as an approach to differentiate conventionally and organically grown tomatoes.

    Hohmann, Monika; Christoph, Norbert; Wachter, Helmut; Holzgrabe, Ulrike

    2014-08-20

    This study describes the approach of (1)H NMR profiling for the authentication of organically produced tomatoes (Solanum lycopersicum). Overall, 361 tomato samples of two different cultivars and four different producers were regularly analyzed during a 7 month period. The results of principal component analysis showed a significant trend for the separation between organically and conventionally produced tomatoes (p cultivation method, yet the results indicate significant differences between (1)H NMR spectra of organically and conventionally grown tomatoes. PMID:25066078

  8. Regioselective Synthesis and Base Catalyzed Transacylation of Substituted 1H-Pyrazole-4-carboxamides

    REN,Jun(任军); ZHANG,Xiao-Hong(张晓弘); LIU,Ying(刘莹); CHEN,Wei-Qiang(陈卫强); JIN,Gui-Yu(金桂玉)

    2002-01-01

    New type of substituted 1H-pyrazole-4-carboxamides were obtained by regioselective synthesis under the catalysis of different bases. The structures of the title compounds were confirmed by elemental analysis, 1H NMR, IR, MS and X-ray crystallogaphy. Compounds 1 were transacylated into their corresponding amides 3 in the presence of sodium hydride.Preliminary bioassays indicated that some compounds showed fungicidal activities against Rhizoctonia solani and Sclerotinia sclerotiorum.

  9. Complete (1)H, (15)N and (13)C assignment of trappin-2 and (1)H assignment of its two domains, elafin and cementoin.

    Loth, Karine; Alami, Soha Abou Ibrahim; Habès, Chahrazed; Garrido, Solène; Aucagne, Vincent; Delmas, Agnès F; Moreau, Thierry; Zani, Marie-Louise; Landon, Céline

    2016-04-01

    Trappin-2 is a serine protease inhibitor with a very narrow inhibitory spectrum and has significant anti-microbial activities. It is a 10 kDa cationic protein composed of two distinct domains. The N-terminal domain (38 residues) named cementoin is known to be intrinsically disordered when it is not linked to the elafin. The C-terminal domain (57 residues), corresponding to elafin, is a cysteine-rich domain stabilized by four disulfide bridges and is characterized by a flat core and a flexible N-terminal part. To our knowledge, there is no structural data available on trappin-2. We report here the complete (1)H, (15)N and (13)C resonance assignment of the recombinant trappin-2 and the (1)H assignments of cementoin and elafin, under the same experimental conditions. This is the first step towards the 3D structure determination of the trappin-2. PMID:26878852

  10. catena-Poly[[(diiodidocadmium-μ-{1-[(1H-benzimidazol-2-ylmethyl]-1H-imidazole-κ2N:N′}] N,N-dimethylformamide monosolvate

    Bingtao Liu

    2011-12-01

    Full Text Available In the title complex, {[CdI2(C11H10N4]·C3H7NO}n, the CdII ion is four-coordinated by two N atoms from two 1-[(1H-benzimidazol-1-ylmethyl]-1H-imidazole (bmi ligands and by two terminal I− anions in a distorted tetrahedral geometry. One of the two I− anions is disordered over two sets of sites, with refined occupancies of 0.66 (5 and 0.34 (5. The CdII ions are bridged by bmi ligands, leading to the formation of a chain along [001]. Dimethylformamide solvent molecules are located between these chains. Classical N—H...O hydrogen bonding between the bmi ligands and the solvent molecules leads to a consolidation of the structure.

  11. Tetraaqua{1-[(1H-1,2,3-benzotriazol-1-ylmethyl]-1H-1,2,4-triazole}sulfatocobalt(II dihydrate

    Yu-xian Li

    2011-08-01

    Full Text Available In the title complex, [Co(SO4(C9H8N6(H2O4]·2H2O, the CoII ion is six-coordinated by one N atom from a 1H-1,2,3-benzotriazol-1-ylmethyl]-1H-1,2,4-triazole ligand, one O atom from a monodentate sulfate ligand and four water molecules in a slightly distorted octahedral geometry. The sulfate ligand is rotationally disordered over two sets of sites with refined occupancies of 0.662 (15 and 0.338 (15. In the crystal, complex molecules and solvent water molecules are linked through intermolecular O—H...O and O—H...N hydrogen bonds into a three-dimensional network.

  12. Crystal structures and luminescence properties of two Cd(II) complexes based on 2-(1H-imidazol-1methyl)-6-methyl-1H-benzimidazole

    Zhang, Yuhong; Meng, Xiangru; Wen, Yu; Li, Peng; Ma, Lin [Zhengzhou Univ. (China). College of Chemistry and Molecular Engineering; Zhang, Qiuju [Zhengzhou Univ. (China). Clinical Testing Section

    2015-11-01

    Two new complexes, {[Cd(immb)I_2].DMF}{sub n} (1) and {[Cd_3(immb)(btc)_2]. H_2O}{sub n} (2) (immb = 2-(1H-imidazol- 1-methyl)-6-methyl-1H-benzimidazole, btc = 1,2,3-benzenetricarboxylate, DMF = dimethyl formamide), have been synthesized and characterized. Single crystal X-ray diffraction shows that 1 exhibits a chain structure constructed by immb ligands bridging Cd(II) ions. In 2, Cd(II) ions are linked by immb ligands with bridging mode and btc3- anions with the μ{sub 2}-η{sup 2}:η{sup 1} bonding pattern leading to a 2D structure. Luminescent properties have been investigated in the solid state at room temperature.

  13. On quantum information

    Paszkiewicz, Adam

    2012-01-01

    We investigate the following generalisation of the entropy of quantum measurement. Let H be an infinite-dimensional separable Hilbert space with a 'density' operator {\\rho}, tr {\\rho}=1. Let I(P)\\in R be defined for any partition P = (P_1,...,P_m), P_1+ ... +P_m=1_H, P_i \\in proj H$ and let I(P_i Qj, i \\leq m, j \\leq n) = I(P) + I(Q) for Q =(Q_1,..., Q_n), \\sum Q_j = 1_H and P_iQ_j = Q_j P_i, tr {\\rho} P_iQ_j = tr {\\rho} P_i tr {\\rho} Q_j (P, Q are physically independent). Assuming some continuity properties we give a general form of generalised information I.

  14. Quantum Distinction: Quantum Distinctiones!

    Dainis ZEPS

    2009-07-01

    Full Text Available How many distinctions, in Latin, quantum distinctions have? We suggest approach of anthropic principle based on anthropic reference system which should be applied equally both in theoretical physics and in mathematics. We come to principle that within reference system of life subject of mathematics (that of thinking should be equated with subject of physics (that of nature. For this reason we enter notions of series of distinctions, quantum distinction, and argue that quantum distinction may be considered as freedom of motion.

  15. High quality above 3-μm mid-infrared InGaAsSb/AlGaInAsSb multiple-quantum well grown by molecular beam epitaxy

    The GaSb-based laser shows its superiority in the 3–4 μm wavelength range. However, for a quantum well (QW) laser structure of InGaAsSb/AlGaInAsSb multiple-quantum well (MQW) grown on GaSb, uniform content and high compressive strain in InGaAsSb/AlGaInAsSb are not easy to control. In this paper, the influences of the growth temperature and compressive strain on the photoluminescence (PL) property of a 3.0-μm InGaAsSb/AlGaInAsSb MQW sample are analyzed to optimize the growth parameters. Comparisons among the PL spectra of the samples indicate that the In0.485GaAs0.184Sb/Al0.3Ga0.45In0.25As0.22Sb0.78 MQW with 1.72% compressive strain grown at 460 °C posseses the optimum optical property. Moreover, the wavelength range of the MQW structure is extended to 3.83 μm by optimizing the parameters. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  16. Simulation of p-i-n heterojunctions built on strain-compensated Si/Si0.40Ge0.60/Si multiple quantum wells for photodetection near 1.55 μm

    Self-consistent computations of the potential profile in complex semiconductor heterostructures can be successfully applied for comprehensive simulation of many device characteristics. Such computations have been used for the study of SiGe/Si multiple quantum wells (MQWs) based infrared photodetectors operating in the two low absorption windows of silica fibers, e.g. around λ = 1.3 and λ = 1.55 μm. In this paper, a versatile model is proposed for the design optimization of SiGe/Si MQWs based photodetectors. It is based on the coupled Schroedinger-Poisson equations that allow the determination of the energy quantization levels and the wave functions of charge carriers. The optimum parameters such as the layers thickness, compositions and doping of the relative MQWs based p-i-n photodetectors under an external applied electric field are determined for the aimed range of wavelength

  17. Realization of band gap shrinkage to the spectral characteristics of high-luminous-efficiency 658 nm AlGaInP/GaInP multiple quantum well lasers at room temperatures

    Chackrabarti, Santosh; Zargar, Rayees A.; Bansal, Jyoti; Zaker, Tho-alfiqar A.; Hafiz, A. K.

    2016-08-01

    The temperature dependent spectral shifts in 658 nm AlGaInP multiple quantum well (MQW) red laser diodes due to band gap narrowing at room temperatures (5 °Csbnd 45 °C) is reported. The density of states effective mass approximation and the conduction band effective mass approximation are employed to formulate the carrier concentrations. The spectral shift mechanism is explored with a threshold current density of 42.28 kA/cm2 and a good characteristic temperature of 149 K. The photoluminescence (PL) peak intensity shifts towards the higher wavelength(red shift) and the full width at half maximum (FWHM) increases with the increase in temperature. The band gap narrowing value determined by a simple formula amounts to 67.4 meV and displays N1/3 dependence at higher densities. The carrier density dependence conveys that the red shift of the spectral emission is due to band gap narrowing.

  18. Epitaxial evolution on buried cracks in a strain-controlled AlN/GaN superlattice interlayer between AlGaN/GaN multiple quantum wells and a GaN template

    Epitaxial evolution of buried cracks in a strain-controlled AlN/GaN superlattice interlayer (IL) grown on GaN template, resulting in crack-free AlGaN/GaN multiple quantum wells (MQW), was investigated. The processes of filling the buried cracks include crack formation in the IL, coalescence from both side walls of the crack, build-up of an MQW-layer hump above the cracks, lateral expansion and merging with the surrounding MQW, and two-dimensional step flow growth. It was confirmed that the filling content in the buried cracks is pure GaN, originating from the deposition of the GaN thin layer directly after the IL. Migration of Ga adatoms into the cracks plays a key role in the filling the buried cracks. (condensed matter: structural, mechanical, and thermal properties)

  19. Nanostructure surface patterning of GaN thin films and application to AlGaN/AlN multiple quantum wells: A way towards light extraction efficiency enhancement of III-nitride based light emitting diodes

    Enhanced light extraction efficiency was demonstrated on nanostructure patterned GaN and AlGaN/AlN Multiple-Quantum-Well (MQW) structures using mass production techniques including natural lithography and interference lithography with feature size as small as 100 nm. Periodic nanostructures showed higher light extraction efficiency and modified emission profile compared to non-periodic structures based on integral reflection and angular-resolved transmission measurement. Light extraction mechanism of macroscopic and microscopic nanopatterning is discussed, and the advantage of using periodic nanostructure patterning is provided. An enhanced photoluminescence emission intensity was observed on nanostructure patterned AlGaN/AlN MQW compared to as-grown structure, demonstrating a large-scale and mass-producible pathway to higher light extraction efficiency in deep-ultra-violet light-emitting diodes

  20. Quantum stochastics

    Chang, Mou-Hsiung

    2015-01-01

    The classical probability theory initiated by Kolmogorov and its quantum counterpart, pioneered by von Neumann, were created at about the same time in the 1930s, but development of the quantum theory has trailed far behind. Although highly appealing, the quantum theory has a steep learning curve, requiring tools from both probability and analysis and a facility for combining the two viewpoints. This book is a systematic, self-contained account of the core of quantum probability and quantum stochastic processes for graduate students and researchers. The only assumed background is knowledge of the basic theory of Hilbert spaces, bounded linear operators, and classical Markov processes. From there, the book introduces additional tools from analysis, and then builds the quantum probability framework needed to support applications to quantum control and quantum information and communication. These include quantum noise, quantum stochastic calculus, stochastic quantum differential equations, quantum Markov semigrou...