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Sample records for single inas quantum

  1. Quantum Sensing of Mechanical Motion with a Single InAs Quantum Dot

    Science.gov (United States)

    2017-03-01

    Wenner, J. M. Martinis, and A. N. Cleland, “ Quantum ground state and single- phonon control of a mechanical resonator.,” Nature, vol. 464, no...G. Nogues, S. Seidelin, J. Poizat, O. Arcizet, and M. Richard, “Strain-mediated coupling in a quantum dot- mechanical oscillator hybrid system...Pos 4 Dep 5 School of N upling quantu ctive for funda dded a semico nical resonat vances in thi es large ch ell as the spin for quantum s antum Dots

  2. Superconducting transport in single and parallel double InAs quantum dot Josephson junctions with Nb-based superconducting electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shoji, E-mail: baba@meso.t.u-tokyo.ac.jp; Sailer, Juergen [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Deacon, Russell S. [Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); RIKEN Advanced Science Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oiwa, Akira [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Shibata, Kenji [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai 982-8577 (Japan); Hirakawa, Kazuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); JST CREST, 4-1-8 Hon-cho, Kawaguchi-shi, Saitama 332-0012 (Japan); Tarucha, Seigo [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); INQIE, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); QPEC, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656 (Japan)

    2015-11-30

    We report conductance and supercurrent measurements for InAs single and parallel double quantum dot Josephson junctions contacted with Nb or NbTiN superconducting electrodes. Large superconducting gap energy, high critical field, and large switching current are observed, all reflecting the features of Nb-based electrodes. For the parallel double dots, we observe an enhanced supercurrent when both dots are on resonance, which may reflect split Cooper pair tunneling.

  3. Atomistic calculation of electronic and optical properties of a single InAs quantum dots

    Science.gov (United States)

    Zielinski, M.; Korkusinski, M.; Sheng, W.; Hawrylak, P.

    2008-03-01

    We present an atomistic tight-binding (TB) theory of electronic structure and optical properties of a single self-assembled InAs quantum dot (SAD). In previous work an effective-bond-orbital model (EBOM) was used to calculate electron and hole states of the SAD. The strain distribution was calculated using the continuum elasticity theory and EBOM was coupled to the strain via the Bir-Pikus Hamiltonian. However, the properties of these multimillion-atom systems are influenced by the presence of crystal facets and the symmetry of underlying zinc-blende lattice. In current work we present a fully atomistic TB model, accounting for the atomistic symmetry, and extended to include d-orbitals for proper treatment of interband/intervalley couplings. Strain is included in the Hamiltonian via Slater-Koster rules and a generalized Harrison law, with the equilibrium positions of atoms calculated using the valence force field method. Coulomb matrix elements are found using the TB functions, and electronic properties of N confined excitons (N=1-6) are determined in the CI approach. Emission spectra of multiexcitons are also obtained. Comparison with the previous approach and the experimental results is presented.

  4. Telecommunication Wavelength-Band Single-Photon Emission from Single Large InAs Quantum Dots Nucleated on Low-Density Seed Quantum Dots.

    Science.gov (United States)

    Chen, Ze-Sheng; Ma, Ben; Shang, Xiang-Jun; He, Yu; Zhang, Li-Chun; Ni, Hai-Qiao; Wang, Jin-Liang; Niu, Zhi-Chuan

    2016-12-01

    Single-photon emission in the telecommunication wavelength band is realized with self-assembled strain-coupled bilayer InAs quantum dots (QDs) embedded in a planar microcavity on GaAs substrate. Low-density large QDs in the upper layer active for ~1.3 μm emission are fabricated by precisely controlling the indium deposition amount and applying a gradient indium flux in both QD layers. Time-resolved photoluminescence (PL) intensity suggested that the radiative lifetime of their exciton emission is 1.5~1.6 ns. The second-order correlation function of g (2)(0) < 0.5 which demonstrates a pure single-photon emission.

  5. Electron transport in InAs nanowire quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Fuhrer, Andreas [Nanometer Structure Consortium, Lund Universtity, Box 118, S-221 00 Lund (Sweden); School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Fasth, Carina; Samuelson, Lars [Nanometer Structure Consortium, Lund Universtity, Box 118, S-221 00 Lund (Sweden)

    2008-07-01

    We investigate electron transport in single and double quantum dots defined in catalytically grown InAs nanowires containing down to a single electron. We determine g-factor and strength of the spin-orbit interaction directly from excited state measurements in these few electron quantum dots. Using local gates to deplete homogeneous InAs nanowires offers a high degree of tunability for defining double quantum dots. Here we show that such systems are ideally suited to manipulate single spins and charges for electron pumping, charge read-out and spin manipulation applications.

  6. Electronic fine structure and recombination dynamics in single InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Seguin, R.

    2008-01-28

    In the work at hand single InAs/GaAs quantum dots (QDs) are examined via cathodoluminescence spectroscopy. A thorough analysis of the spectra leads to an unambiguous assignment of the lines to the decay of specific excitonic complexes. A special aspect of the Coulomb interaction, the exchange interaction, gives rise to a fine structure in the initial and final states of an excitonic decay. This leads to a fine structure in the emission spectra that again is unique for every excitonic complex. The exchange interaction is discussed in great detail in this work.QDs of different sizes are investigated and the influence on the electronic properties is monitored. Additionally, the structure is modified ex situ by a thermal annealing process. The changes of the spectra under different annealing temperatures are traced. Finally, recombination dynamics of different excitonic complexes are examined by performing time-resolved cathodoluminescence spectroscopy. (orig.)

  7. Single-photon emission at 1.55 μm from MOVPE-grown InAs quantum dots on InGaAs/GaAs metamorphic buffers

    Science.gov (United States)

    Paul, Matthias; Olbrich, Fabian; Höschele, Jonatan; Schreier, Susanne; Kettler, Jan; Portalupi, Simone Luca; Jetter, Michael; Michler, Peter

    2017-07-01

    By metal-organic vapor-phase epitaxy, we have fabricated InAs quantum dots (QDs) on InGaAs/GaAs metamorphic buffer layers on a GaAs substrate with area densities that allow addressing single quantum dots. The photoluminescence emission from the quantum dots is shifted to the telecom C-band at 1.55 μm with a high yield due to the reduced stress in the quantum dots. The lowered residual strain at the surface of the metamorphic buffer layer results in a reduced lattice mismatch between the quantum dot material and growth surface. The quantum dots exhibit resolution-limited linewidths (mean value: 59 μeV) and low fine-structure splittings. Furthermore, we demonstrate single-photon emission ( g ( 2 ) ( 0 ) = 0.003 ) at 1.55 μm and decay times on the order of 1.4 ns comparable to InAs QDs directly deposited on GaAs substrates. Our results suggest that these quantum dots can not only compete with their counterparts deposited on InP substrates but also constitute an InAs/GaAs-only approach for the development of non-classical light sources in the telecom C-band.

  8. Two-photon interference using background-free quantum frequency conversion of single photons emitted by an InAs quantum dot.

    Science.gov (United States)

    Ates, Serkan; Agha, Imad; Gulinatti, Angelo; Rech, Ivan; Rakher, Matthew T; Badolato, Antonio; Srinivasan, Kartik

    2012-10-05

    We show that quantum frequency conversion (QFC) can overcome the spectral distinguishability common to inhomogeneously broadened solid-state quantum emitters. QFC is implemented by combining single photons from an InAs/GaAs quantum dot (QD) at 980 nm with a 1550 nm pump laser in a periodically poled lithium niobate (PPLN) waveguide to generate photons at 600 nm with a signal-to-background ratio exceeding 100:1. Photon correlation and two-photon interference measurements confirm that both the single photon character and wave packet interference of individual QD states are preserved during frequency conversion. Finally, we convert two spectrally separate QD transitions to the same wavelength in a single PPLN waveguide and show that the resulting field exhibits nonclassical two-photon interference.

  9. Lasing characteristics of InAs quantum dot laers on InP substrate

    Science.gov (United States)

    Yang, Y.; Qiu, D.; Uhl, R.; Chacon, R.

    2003-01-01

    Single-stack InAs self-assembled quantum dots (QD) lasers based on InP substrate have been grown by metalorganic vapor phase epitaxy. The narrow ridge waveguide lasers lased up to 260 K in continuous wave operation, and near room temperature in pulsed mode, with wavelengths between 1.59 to 1.74 mu m.

  10. Long-range ordered self-assembled InAs quantum dots epitaxially grown on (110) GaAs

    Science.gov (United States)

    Bauer, J.; Schuh, D.; Uccelli, E.; Schulz, R.; Kress, A.; Hofbauer, F.; Finley, J. J.; Abstreiter, G.

    2004-11-01

    We report on a promising approach for positioning of self-assembled InAs quantum dots on (110) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on previously grown and in situ cleaved substrates (cleaved-edge overgrowth), arrays of long-range ordered InAs quantum dots have been fabricated. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control size, position, and ordering of the quantum dots. Furthermore, single dot photoluminescence investigations confirm the high optical quality of the quantum dots fabricated.

  11. Electrical and optical measurements on a single InAs quantum dot using ion-implanted micro-LEDs; Elektrische und optische Untersuchungen an einem einzelnen InAs-Quantenpunkt mit Hilfe ionenstrahlimplantierter Mikro-LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, R.F.

    2006-10-19

    The goal of this present thesis was to electrically and optically address a single InAs quantum dot. Therefore micro-structured quantum-dot-LEDs with an emission area smaller than 1 {mu}m{sup 2} were developed. One major part of this work was contributed to optimizing several steps of the micro-LED fabrication process. To be able to compare the electrical conductivity obtained from Hall-measurements to the expected values, the implantation profile was investigated both theoretically and experimentally. As the thermal annealing step had to be performed in the growth chamber of the MBE-system several annealing parameters had to be modified to achieve optimum electrical conductivity and quantum dot growth. For one of the Be-implanted pin-samples the principle of the single-quantum-dot-LEDs could be proved. The smallest device of this sample, with nominal stripe widths of 150 nm (FIB-stripe) and 400 nm (top-stripe), showed typical features of a single quantum dot. In the high-resolution EL-spectra of this device three extremely sharp emission lines were observed which clearly could be assigned to the electron-hole recombination from a single quantum dot. To further identify the origin of these lines their optical intensities were plotted against the injection current. From this plot it could be deduced, that the first evolving line clearly belongs to the simple exciton 1X. The following lines could be assigned to the decay of the biexciton 2X and the triexciton 3X{sub s}, respectively. With increasing bias all three lines show a pronounced red-shift due to the quantum confined Stark effect (QCSE). To identify the charge state of the observed excitonic lines, additional high-resolution IV curves were taken. (orig.)

  12. Electronic properties of excited states in single InAs quantum dots; Elektronische Struktur angeregter Zustaende einzelner InAs-Quantenpunkte

    Energy Technology Data Exchange (ETDEWEB)

    Warming, Till

    2009-02-20

    The application of quantum-mechanical effects in semiconductor nanostructures enables the realization of novel opto-electronic devices. Examples are given by single-photon emitters and emitters of entangled photon pairs, both being essential for quantum cryptography, or for qubit systems as needed for quantum computing. InAs/GaAs quantum dots are one of the most promising candidates for such applications. A detailed knowledge of the electronic properties of quantum dots is a prerequisite for this development. The aim of this work is an experimental access to the detailed electronic structure of the excited states in single InAs/GaAs quantum dots including few-particle effects and in particular exchange interaction. The experimental approach is micro photoluminescence excitation spectroscopy ({mu}PLE). One of the main difficulties using {mu}PLE to probe single QDs is the unambiguous assignment of the observed resonances in the spectrum to specific transitions. By comparing micro photoluminescence ({mu}PL) and {mu}PLE spectra, the identification of the main resonances becomes possible. The key is given by the fine structure of the hot trion. Excitation spectroscopy on single charged QDs enables for the first time the complete observation of a non-trivial fine structure of an excitonic complex in a QD, the hot trion. Modelling based on eight-band k.p theory in combination with a configuration interaction scheme is in excellent agreement. Therewith the simulation also enables realistic predictions on the fine structure of the ground-state exciton which is of large importance for single quantum dot devices. Theory concludes from the observed transitions that the structural symmetry of the QDs is broken. Micro photoluminescence excitation spectroscopy combined with resonantly excited micro photoluminescence enables an optical access to the single particle states of the hole without the influence of few-particle coulomb interactions. Based on this knowledge the exciton

  13. Quantum efficiency and oscillator strength of site-controlled InAs quantum dots

    DEFF Research Database (Denmark)

    Albert, F.; Stobbe, Søren; Schneider, C.

    2010-01-01

    We report on time-resolved photoluminescence spectroscopy to determine the oscillator strength (OS) and the quantum efficiency (QE) of site-controlled InAs quantum dots nucleating on patterned nanoholes. These two quantities are determined by measurements on site-controlled quantum dot (SCQD...

  14. Spin Relaxation in InAs Columnar Quantum Dots

    Science.gov (United States)

    Umi, Takehiko; Nosho, Hidetaka; Lu, Shulong; Li, Lianhe; Fiore, Andrea; Tackeuchi, Atsushi

    2009-04-01

    We have investigated carrier spin dynamics in InAs columnar quantum dots (CQDs) by time-resolved photoluminescence (PL) measurement. The CQDs were formed by depositing a 1.8 monolayer InAs seed dot layer and a short-period GaAs/InAs superlattice (SL). The spin relaxation time was found to be prolonged from 1.6 to 5.3 ns by increasing the number of SL periods from 3 to 35. The PL decay time also increased from 0.93 to 1.9 ns, indicating a decrease in the spatial overlap of electron and hole wave functions. The changes in both the spin relaxation time and the PL decay time suggest that the Bir-Aronov-Pikus process is the main spin relaxation mechanism.

  15. Class-A Operation of InAs Quantum Dash-based Vertical-External-Cavity Surface-Emitting Laser

    OpenAIRE

    Pes, Salvatore; Audo, Kevin; Paranthoen, Cyril; Levallois, Christophe; Chevalier, Nicolas; Loas, Goulc'Hen; Bouhier, Steve; Hamel, Cyril; Gomez, Carmen; Harmand, Jean-Christophe; Bouchoule, Sophie; Folliot, Hervé; Alouini, Mehdi

    2017-01-01

    International audience; InAs Quantum Dash-based Vertical-External-Cavity Surface-Emitting Laser on InP is demonstrated. Up to 163 mW and 7 mW have been obtained in multi-mode and single-mode operation, respectively. Class-A behavior is demonstrated on such device.

  16. Controlled positioning of self-assembled InAs quantum dots on (1 1 0) GaAs

    Science.gov (United States)

    Schuh, D.; Bauer, J.; Uccelli, E.; Schulz, R.; Kress, A.; Hofbauer, F.; Finley, J. J.; Abstreiter, G.

    2005-02-01

    We report on a new approach for positioning of self-assembled InAs quantum dots on (1 1 0) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on in situ cleaved surfaces (cleaved-edge overgrowth) we have successfully fabricated arrays of long-range ordered InAs quantum dots. Both atomic force microscopy and micro-photoluminescence measurements demonstrate the ability to control position and ordering of the quantum dots with epitaxial precision as well as size and size homogeneity. Furthermore, photoluminescence investigations on dot ensembles and on single dots confirm the high homogeneity and the excellent optical quality of the quantum dots fabricated.

  17. A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

    Science.gov (United States)

    Sharma, Nandlal; Reuter, Dirk

    2017-11-01

    Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

  18. Coupling of self-assembled InAs quantum dots to surface plasmon polaritons

    DEFF Research Database (Denmark)

    Andersen, Mads Lykke; Stobbe, Søren; Johansen, Jeppe

    2008-01-01

    InAs quantum dots have been placed at different distances to a silver mirror. We extract the coupling of quantum dots to surface plasmon polaritons as a function of the distance by time-resolved spontaneous emission measurements.......InAs quantum dots have been placed at different distances to a silver mirror. We extract the coupling of quantum dots to surface plasmon polaritons as a function of the distance by time-resolved spontaneous emission measurements....

  19. InAs quantum dot micro-disk lasers grown on (001) Si emitting at communication wavelengths

    Science.gov (United States)

    Lau, Kei May; Shi, Bei; Wan, Yating; Liu, Alan Y.; Li, Qiang; Zhu, Si; Gossard, Arthur C.; Bowers, John E.; Hu, Evelyn L.

    2017-02-01

    Continuous-wave optically-pumped micro-disk lasers epitaxially grown on silicon with single mode lasing at communication wavelengths from liquid helium to room temperature is reported. Growth of the InAs quantum dots (QDs) gain medium was carried out on high crystalline quality GaAs/InP-on-silicon templates. Special defect filtering techniques have been employed to minimize the impact of the highly lattice-mismatched heteroepitaxial growth on (001) silicon substrates. Compared with quantum wells, the multi-stack InAs QDs are less sensitive to residual defects originated from the hetero-interfaces. Using QDs in a micro-disk resonant cavity with minimized non-radiative surface recombination leads to low-threshold lasing in the micro-disks with a few microns in diameter.

  20. InAs quantum dots nucleation on (100) and anisotropic (631)-oriented GaAs substrates

    Science.gov (United States)

    Eugenio-López, E.; Lopez-Lopez, M.; Gorbatchev, A. Yu.; Espinosa-Vega, L. I.; Cortes-Mestizo, I. E.; Mercado-Ornelas, C. A.; Del Rı´o-De Santiago, A.; Méndez-García, Victor H.

    2018-01-01

    Different mechanisms of adatoms nucleation are studied for the self-assembling of InAs quantum dots (QDs) on smooth and nanoscale faceted GaAs surface morphologies. The experiments were performed on GaAs(100) and GaAs(631), and prior to the arrival of InAs the GaAs surface morphology was intentionally altered by changing the growth temperature of the buffer layer, TBL. For the reflection high-energy electron diffraction (RHEED) analysis, an equilibrium interlayer mass transport model is proposed through which, the critical thickness (Hc) and the InAs diffusion length can be estimated. For InAs growth on (100) substrates the Hc did not show significant dependence on TBL, but the adatoms diffusion length slightly reduced as TBL increases, which is in agreement with the changes on QDs density as observed by atomic force microscopy (AFM). For samples grown on GaAs (631)-oriented substrates it was found that both the nucleation mode of InAs and the Hc depends on TBL. The changes are associated to the growth of InAs on GaAs surface faceted corrugation that allows the self-organizing InAs QDs along [-113].

  1. InAs nanowire with epitaxial aluminium as a single-electron transistor with fixed tunnel barriers

    DEFF Research Database (Denmark)

    Taupin, M.; Mannila, E.; Krogstrup, P.

    2016-01-01

    We report on fabrication of single-electron transistors using InAs nanowires with epitaxial aluminium with fixed tunnel barriers made of aluminium oxide. The devices exhibit a hard superconducting gap induced by the proximized aluminium cover shell and they behave as metallic single-electron tran......We report on fabrication of single-electron transistors using InAs nanowires with epitaxial aluminium with fixed tunnel barriers made of aluminium oxide. The devices exhibit a hard superconducting gap induced by the proximized aluminium cover shell and they behave as metallic single......-electron transistors. In contrast to the typical few channel contacts in semiconducting devices, our approach forms opaque multichannel contacts to a semiconducting wire and thus provides a complementary way to study them. In addition, we confirm that unwanted extra quantum dots can appear at the surface...

  2. Optical characterization of InAs quantum wells and dots grown radially on wurtzite InP nanowires.

    Science.gov (United States)

    Lindgren, David; Kawaguchi, Kenichi; Heurlin, Magnus; Borgström, Magnus T; Pistol, Mats-Erik; Samuelson, Lars; Gustafsson, Anders

    2013-06-07

    Correlated micro-photoluminescence (μPL) and cathodoluminescence (CL) measurements are reported for single core-shell InP-InAs wurtzite nanowires grown using metal-organic vapor phase epitaxy. Samples covering a radial InAs shell thickness of 1-12 ML were investigated. The effective masses for the wurtzite material were determined from the transition energy dependence of the InAs shell thickness, using a model based on linear deformation potential theory. InP cores with segments of mixed zincblende and wurtzite, on which quantum dots nucleated selectively, were also investigated. Narrow peaks were observed by μPL and the spatial origin of the emission was identified with CL imaging.

  3. Growth of InAs Quantum Dots on Germanium Substrate Using Metal Organic Chemical Vapor Deposition Technique

    Directory of Open Access Journals (Sweden)

    Tyagi Renu

    2009-01-01

    Full Text Available Abstract Self-assembled InAs quantum dots (QDs were grown on germanium substrates by metal organic chemical vapor deposition technique. Effects of growth temperature and InAs coverage on the size, density, and height of quantum dots were investigated. Growth temperature was varied from 400 to 450 °C and InAs coverage was varied between 1.40 and 2.35 monolayers (MLs. The surface morphology and structural characteristics of the quantum dots analyzed by atomic force microscope revealed that the density of the InAs quantum dots first increased and then decreased with the amount of InAs coverage; whereas density decreased with increase in growth temperature. It was observed that the size and height of InAs quantum dots increased with increase in both temperature and InAs coverage. The density of QDs was effectively controlled by growth temperature and InAs coverage on GaAs buffer layer.

  4. Self-assembly of InAs quantum dots on GaAs(001) by molecular beam epitaxy

    Science.gov (United States)

    Wu, Ju; Jin, Peng

    2015-02-01

    Currently, the nature of self-assembly of three-dimensional epitaxial islands or quantum dots (QDs) in a lattice-mismatched heteroepitaxial growth system, such as InAs/GaAs(001) and Ge/Si(001) as fabricated by molecular beam epitaxy (MBE), is still puzzling. The purpose of this article is to discuss how the self-assembly of InAs QDs in MBE InAs/GaAs(001) should be properly understood in atomic scale. First, the conventional kinetic theories that have traditionally been used to interpret QD self-assembly in heteroepitaxial growth with a significant lattice mismatch are reviewed briefly by examining the literature of the past two decades. Second, based on their own experimental data, the authors point out that InAs QD self-assembly can proceed in distinctly different kinetic ways depending on the growth conditions and so cannot be framed within a universal kinetic theory, and, furthermore, that the process may be transient, or the time required for a QD to grow to maturity may be significantly short, which is obviously inconsistent with conventional kinetic theories. Third, the authors point out that, in all of these conventional theories, two well-established experimental observations have been overlooked: i) A large number of "floating" indium atoms are present on the growing surface in MBE InAs/GaAs(001); ii) an elastically strained InAs film on the GaAs(001) substrate should be mechanically unstable. These two well-established experimental facts may be highly relevant and should be taken into account in interpreting InAs QD formation. Finally, the authors speculate that the formation of an InAs QD is more likely to be a collective event involving a large number of both indium and arsenic atoms simultaneously or, alternatively, a morphological/structural transformation in which a single atomic InAs sheet is transformed into a three-dimensional InAs island, accompanied by the rehybridization from the sp 2-bonded to sp 3-bonded atomic configuration of both indium

  5. The equilibrium shape of InAs quantum dots grown on a GaAs(001) substrate

    CERN Document Server

    Pehlke, E; Scheffler, M; Pehlke, Eckhard; Moll, Nikolaj; Scheffler, Matthias

    1996-01-01

    The equilibrium shape of strained InAs quantum dots grown epitaxially on a GaAs(001) substrate is derived as a function of volume. InAs surface energies are calculated within density-functional theory, and a continuum approach is applied for the elastic relaxation energies.

  6. The Superconducting Quantum Interference through Trivial Edge States in InAs

    Science.gov (United States)

    de Vrikert K.; Timmerman, Tom; Ostroukh, Viacheslav P.; van Veen, Jasper; Beukman, Arjan J. A.; Qu, Fanming; Wimmer, Michael; Nguyen, Binh-Minh; Kiselev, Andrey A.; Yi, Wei; Sokolich, Marko; Manfra, Michael J.; Marcus, Charles M.; Kouwenhoven, Leo P.

    2018-01-01

    Josephson junctions defined in strong spin orbit semiconductors are highly interesting for the search for topological systems. However, next to topological edge states that emerge in a sufficient magnetic field, trivial edge states can also occur. We study the trivial edge states with superconducting quantum interference measurements on nontopological InAs Josephson junctions. We observe a SQUID pattern, an indication of superconducting edge transport. Also, a remarkable h /e SQUID signal is observed that, as we find, stems from crossed Andreev states.

  7. Ultra-Low Power Optical Transistor Using a Single Quantum Dot Embedded in a Photonic Wire

    DEFF Research Database (Denmark)

    Nguyen, H.A.; Grange, T.; Malik, N.S.

    2017-01-01

    Using a single InAs quantum dot embedded in a GaAs photonic wire, we realize a giant non-linearity between two optical modes to experimentally demonstrate an all-optical transistor triggered by 10 photons.......Using a single InAs quantum dot embedded in a GaAs photonic wire, we realize a giant non-linearity between two optical modes to experimentally demonstrate an all-optical transistor triggered by 10 photons....

  8. Optical control of electron spin qubit in InAs self-assembled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Emary, Clive [TU Berlin, Sekr. PN 7-1, Institut fuer Theoretische Physik, Hardenbergstr. 36, D-10623 Berlin (Germany); Sham, Lu Jeu [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States)

    2008-07-01

    The spin of an electron trapped in a self-assembled quantum dot is viewed as a promising quantum bit. We present here a theory of the control of such qubits using short laser pulses to excite virtual trion states within the dots. We describe mechanisms for qubit initialisation and for performing universal one and two qubit operations. We show that, for InAs dots, initialisation can be achieved on the nanosecond time-scale, and that coherent operations can performed with laser pulses with durations of tens of picoseconds. These results are of direct relevance to current experiments.

  9. Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots

    Directory of Open Access Journals (Sweden)

    Lin Chien-Hung

    2011-01-01

    Full Text Available Abstract In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states on photoluminescence excitation (PLE spectra of InAs quantum dots (QDs was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.

  10. Room-Temperature Dephasing in InAs Quantum Dots

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Mørk, Jesper

    2000-01-01

    The room temperature dephasing in InAs/InGaAs/GaAs self-assembled quantum dots, embedded in a waveguide for laser applications, is measured using two independent methods: spectral hole burning and four-wave mixing. Without the application of bias current for electrical carrier injection......, a dephasing time of ~260 fs, weakly dependent on the optical excitation density, is found and attributed to phonon interaction. The application of bias current, leading to population inversion in the dot ground state and optical gain, strongly decreases the dephasing time to less than 50 fs, likely due...

  11. h/e Superconducting Quantum Interference through Trivial Edge States in InAs.

    Science.gov (United States)

    de Vries, Folkert K; Timmerman, Tom; Ostroukh, Viacheslav P; van Veen, Jasper; Beukman, Arjan J A; Qu, Fanming; Wimmer, Michael; Nguyen, Binh-Minh; Kiselev, Andrey A; Yi, Wei; Sokolich, Marko; Manfra, Michael J; Marcus, Charles M; Kouwenhoven, Leo P

    2018-01-26

    Josephson junctions defined in strong spin orbit semiconductors are highly interesting for the search for topological systems. However, next to topological edge states that emerge in a sufficient magnetic field, trivial edge states can also occur. We study the trivial edge states with superconducting quantum interference measurements on nontopological InAs Josephson junctions. We observe a SQUID pattern, an indication of superconducting edge transport. Also, a remarkable h/e SQUID signal is observed that, as we find, stems from crossed Andreev states.

  12. Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

    Energy Technology Data Exchange (ETDEWEB)

    Fehr, Matthias; Uccelli, Emanuele; Dasgupta, Shivaji; Bichler, Max; Steinke, Lucia; Abstreiter, Gerhard [Walter Schottky Institute, Technische Universitaet Muenchen, Garching (Germany); Grayson, Matthew [Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois (United States); Morral i Fontcuberta, Anna [Walter Schottky Institute, Technische Universitaet Muenchen, Garching (Germany); Laboratoire des Materiaux Semiconducteurs, Institut des Materiaux, Ecole Polytechnique Federale de Lausanne (Switzerland)

    2009-07-15

    A contacting scheme to measure the transport properties into self-assembled InAs Quantum Wires (QWRs) or Quantum Dots (QDs) is presented. The nanostructures are formed on the (110) cleaved edge of a AlAs/AlGaAs heterostructure substrate by means of the Cleaved Edge Overgrowth (CEO) technique and Molecular Beam Epitaxy (MBE). The InAs nanostructure grows directly on top of the AlAs layer, which hosts a two dimensional electron gas (2DEG). In a transistor-like schematic of the device, the 2DEG acts as a contact to the InAs nanostructure. A top gate is used to deplete the 2DEG, thereby defining the InAs nanostructure as a channel between source and drain. Measurements confirm that the device can be operated as a field-effect transistor, but no evidence of a current flow through the InAs QWRs can be found. Numerical calculations of the electron density and the device band structure confirm that a depletion zone is present in the AlAs layer close to the cleaved edge and the InAs QWR seems electrically isolated from the AlAs 2DEG leads. Possible solutions could be an additional Schottky gate contact on the CEO side or selective doping inside the CEO barrier. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

    Science.gov (United States)

    Qiu, Y.; Uhl, D.

    2002-01-01

    InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

  14. QUANTUM CRYPTOGRAPHY: Single Photons.

    Science.gov (United States)

    Benjamin, S

    2000-12-22

    Quantum cryptography offers the potential of totally secure transfer of information, but as Benjamin discusses in this Perspective, its practical implementation hinges on being able to generate single photons (rather than two or more) at a time. Michler et al. show how this condition can be met in a quantum dot microdisk structure. Single molecules were also recently shown to allow controlled single-photon emission.

  15. Self-assembled InAs quantum dots in an InGaAsN matrix on GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Egorov, A.Yu. [Infineon Technologies, Corporate Research Photonics, Muenchen (Germany); Ioffe Physico-Technical Inst., St. Petersburg (Russian Federation); Bedarev, D. [Ioffe Physico-Technical Inst., St. Petersburg (Russian Federation); Bernklau, D.; Riechert, H. [Infineon Technologies, Corporate Research Photonics, Muenchen (Germany); Dumitras, G. [Technical Univ. of Munich, Garching (Germany). Dept. of Physics E16

    2001-04-01

    Self-assembled InAs quantum dots (QDs) are fabricated in In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} and In{sub 0.06}Ga{sub 0.94}As{sub 0.98}N{sub 0.02} matrices on GaAs by solid source molecular beam epitaxy. The influence of InAs average layer thickness and matrix material on photoluminescence properties are studied. We observe a photoluminescence peak wavelength up to 1.49 {mu}m from structures with a nominal InAs thickness of four monolayers (ML). For QD structures emitting at 1.3 {mu}m, no saturation of ground state luminescence and no excited state photoluminescence are detected. This should lead to an improved performance of 1.3 {mu}m quantum dot lasers on GaAs. (orig.)

  16. On the limits to mobility in InAs quantum wells with nearly lattice-matched barriers

    DEFF Research Database (Denmark)

    Shojaei, B.; Drachmann, A. C. C.; Pendharkar, M.

    2016-01-01

    The growth and the density dependence of the low temperature mobility of a series of two-dimensional electron systems confined to un-intentionally doped, low extended defect density InAs quantum wells with Al$_{1-x}$Ga$_{x}$Sb barriers are reported. The electron mobility limiting scattering mecha...

  17. Adding GaAs Monolayers to InAs Quantum-Dot Lasers on (001) InP

    Science.gov (United States)

    Qiu, Yueming; Chacon, Rebecca; Uhl, David; Yang, Rui

    2005-01-01

    In a modification of the basic configuration of InAs quantum-dot semiconductor lasers on (001)lnP substrate, a thin layer (typically 1 to 2 monolayer thick) of GaAs is incorporated into the active region. This modification enhances laser performance: In particular, whereas it has been necessary to cool the unmodified devices to temperatures of about 80 K in order to obtain lasing at long wavelengths, the modified devices can lase at wavelengths of about 1.7 microns or more near room temperature. InAs quantum dots self-assemble, as a consequence of the lattice mismatch, during epitaxial deposition of InAs on ln0.53Ga0.47As/lnP. In the unmodified devices, the quantum dots as thus formed are typically nonuniform in size. Strainenergy relaxation in very large quantum dots can lead to poor laser performance, especially at wavelengths near 2 microns, for which large quantum dots are needed. In the modified devices, the thin layers of GaAs added to the active regions constitute potential-energy barriers that electrons can only penetrate by quantum tunneling and thus reduce the hot carrier effects. Also, the insertion of thin GaAs layer is shown to reduce the degree of nonuniformity of sizes of the quantum dots. In the fabrication of a batch of modified InAs quantum-dot lasers, the thin additional layer of GaAs is deposited as an interfacial layer in an InGaAs quantum well on (001) InP substrate. The device as described thus far is sandwiched between InGaAsPy waveguide layers, then further sandwiched between InP cladding layers, then further sandwiched between heavily Zn-doped (p-type) InGaAs contact layer.

  18. Single photon quantum cryptography.

    Science.gov (United States)

    Beveratos, Alexios; Brouri, Rosa; Gacoin, Thierry; Villing, André; Poizat, Jean-Philippe; Grangier, Philippe

    2002-10-28

    We report the full implementation of a quantum cryptography protocol using a stream of single photon pulses generated by a stable and efficient source operating at room temperature. The single photon pulses are emitted on demand by a single nitrogen-vacancy color center in a diamond nanocrystal. The quantum bit error rate is less that 4.6% and the secure bit rate is 7700 bits/s. The overall performances of our system reaches a domain where single photons have a measurable advantage over an equivalent system based on attenuated light pulses.

  19. Optical bistability in a two-section InAs quantum-dot laser

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Liwen; Ye Xiaoling; Zhou Xiaolong; Jin Peng; Lue Xueqin; Wang Zhanguo, E-mail: tonyjiang1124@semi.ac.cn [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2010-11-15

    Room temperature, continuous-wave bistable operation is achieved in two-section 1.24 {mu}m InAs quantum-dot (QD) lasers with integrated intracavity QD saturable absorbers (SA). It is found that the hysteresis width is narrowed with increasing reverse bias voltage, and broadened with increasing length of saturable absorber. This can be explained by the competition between QD absorption and electroabsorption in the SA section. In addition, a larger hysteresis width is realized than other reports so far, which can be attributed to a greater number of stacked layers of active region in our case. The experimental results can be explained by a modified threshold current model.

  20. Coherent Transport in a Linear Triple Quantum Dot Made from a Pure-Phase InAs Nanowire.

    Science.gov (United States)

    Wang, Ji-Yin; Huang, Shaoyun; Huang, Guang-Yao; Pan, Dong; Zhao, Jianhua; Xu, H Q

    2017-07-12

    A highly tunable linear triple quantum dot (TQD) device is realized in a single-crystalline pure-phase InAs nanowire using a local finger gate technique. The electrical measurements show that the charge stability diagram of the TQD can be represented by three kinds of current lines of different slopes and a simulation performed based on a capacitance matrix model confirms the experiment. We show that each current line observable in the charge stability diagram is associated with a case where a QD is on resonance with the Fermi level of the source and drain reservoirs. At a triple point where two current lines of different slopes move together but show anticrossing, two QDs are on resonance with the Fermi level of the reservoirs. We demonstrate that an energetically degenerated quadruple point at which all three QDs are on resonance with the Fermi level of the reservoirs can be built by moving two separated triple points together via sophistically tuning of energy levels in the three QDs. We also demonstrate the achievement of direct coherent electron transfer between the two remote QDs in the TQD, realizing a long-distance coherent quantum bus operation. Such a long-distance coherent coupling could be used to investigate coherent spin teleportation and superexchange effects and to construct a spin qubit with an improved long coherent time and with spin state detection solely by sensing the charge states.

  1. Improvement of performance of InAs quantum dot solar cell by inserting thin AlAs layers

    Directory of Open Access Journals (Sweden)

    McPheeters Claiborne

    2011-01-01

    Full Text Available Abstract A new measure to enhance the performance of InAs quantum dot solar cell is proposed and measured. One monolayer AlAs is deposited on top of InAs quantum dots (QDs in multistack solar cells. The devices were fabricated by molecular beam epitaxy. In situ annealing was intended to tune the QD density. A set of four samples were compared: InAs QDs without in situ annealing with and without AlAs cap layer and InAs QDs in situ annealed with and without AlAs cap layer. Atomic force microscopy measurements show that when in situ annealing of QDs without AlAs capping layers is investigated, holes and dashes are present on the device surface, while capping with one monolayer AlAs improves the device surface. On unannealed samples, capping the QDs with one monolayer of AlAs improves the spectral response, the open-circuit voltage and the fill factor. On annealed samples, capping has little effect on the spectral response but reduces the short-circuit current, while increasing the open-circuit voltage, the fill factor and power conversion efficiency.

  2. Effect of antimony incorporation on the density, shape, and luminescence of InAs quantum dots

    Science.gov (United States)

    Chen, J. F.; Chiang, C. H.; Wu, Y. H.; Chang, L.; Chi, J. Y.

    2008-07-01

    This work investigates the surfactant effect on exposed and buried InAs quantum dots (QDs) by incorporating Sb into the QD layers with various Sb beam equivalent pressures (BEPs). Secondary ion mass spectroscopy shows the presence of Sb in the exposed and buried QD layers with the Sb intensity in the exposed layer substantially exceeding that in the buried layer. Incorporating Sb can reduce the density of the exposed QDs by more than two orders of magnitude. However, a high Sb BEP yields a surface morphology with a regular periodic structure of ellipsoid terraces. A good room-temperature photoluminescence (PL) at ˜1600 nm from the exposed QDs is observed, suggesting that the Sb incorporation probably improves the emission efficiency by reducing the surface recombination velocity at the surface of the exposed QDs. Increasing Sb BEP causes a blueshift of the emission from the exposed QDs due to a reduction in the dot height as suggested by atomic force microscopy. Increasing Sb BEP can also blueshift the ˜1300 nm emission from the buried QDs by decreasing the dot height. However, a high Sb BEP yields a quantum well-like PL feature formed by the clustering of the buried QDs into an undulated planar layer. These results indicate a marked Sb surfactant effect that can be used to control the density, shape, and luminescence of the exposed and buried QDs.

  3. Characteristics of highly stacked InAs quantum-dot laser grown on vicinal (001)InP substrate

    Science.gov (United States)

    Akahane, Kouichi; Umezawa, Toshimasa; Matsumoto, Atsushi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

    2016-04-01

    We fabricate broad-area laser diodes consisting of 30-layer stacks of InAs quantum dots by using a strain-compensation technique on a vicinal (001)InP substrate. These laser diodes exhibit ground-state lasing at 1576 nm in the pulsed mode with a high characteristic temperature of 111 K at around room temperature (20-80 °C).

  4. Growth of isolated InAs quantum dots on core-shell GaAs/InP nanowire sidewalls by MOCVD

    Science.gov (United States)

    Yan, Xin; Tang, Fengling; Wu, Yao; Li, Bang; Zhang, Xia; Ren, Xiaomin

    2017-06-01

    We demonstrate the growth of isolated InAs quantum dots on the sidewalls of core-shell GaAs/InP nanowires based on the vapor-liquid-solid MOCVD method. The quantum dots are grown under the Stranski-Krastanov mode and exhibit defect-free zinc blende structure. Discrete sharp emission peaks are observed in the range of 1.37-1.39 eV, with linewidths ranging from several hundred μeV to 1 meV or more. Excitonic and biexcitonic emissions are observed, exhibiting different power-dependent intensity and linewidth behavior. This work may open a way for the fabrication of single photon devices based on the vapor-liquid-solid MOCVD method.

  5. Fabrication of InAs quantum dot stacked structure on InP(311)B substrate by digital embedding method

    Science.gov (United States)

    Akahane, Kouichi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

    2015-12-01

    Self-assembled InAs quantum dots (QDs) grown on an InP(311)B substrate were embedded using lattice-matched InAlAs/InGaAs superlattice with the digital embedding method. The thickness of quantum wells and barriers of the superlattice varied from 2 to 16 monolayers. The six layer stacking structures were successfully grown without any degradation of the QD and superlattice structure. The cross-sections of QDs embedded within the superlattice were visualized by scanning transmission microscope. The emission wavelength of the QDs was measured by photoluminescence and could be changed by changing the thickness of the superlattice.

  6. Quantum Hall effect in n-InGaAs/InAlAs metamorphic nanoheterostructures with high InAs content

    Science.gov (United States)

    Gudina, Svetlana V.; Arapov, Yurii G.; Savelyev, Alexander P.; Neverov, Vladimir N.; Podgornykh, Sergey M.; Shelushinina, Nina G.; Yakunin, Michail V.; Rogacki, Krzysztof; Vasil'evskii, Ivan S.; Vinichenko, Alexander N.

    2017-10-01

    For an investigation of the quantum Hall effect on n-In0.85Ga0.18As/In0.82Al0.82As metamorphic nanoheterostructures with high InAs content the longitudinal and Hall magnetoresistances were measured in magnetic fields up to 9 T at T = (1.8 ÷ 30) K . The results for a temperature dependence of conductivity on the delocalized states at the center of Landau level were analysed within the scaling concept for a plateau-plateau transition in quantum Hall regime.

  7. The role of strain-driven in migration in the growth of self-assembled InAs quantum dots on InP

    CERN Document Server

    Yoon, S H; Lee, T W; Hwang, H D; Yoon, E J; Kim, Y D

    1999-01-01

    Self-assembled InAs quantum dots (SAQDs) were grown on InP by metalorganic chemical vapor deposition. The amount of excess InAs and the aspect ratio of the SAQD increased with temperature and V/III ratio. It is explained that the As/P exchange reaction at the surface played an important role in the kinetics of SAQD formation. Insertion of a lattice-matched InGaAs buffer layer suppressed the excess InAs formation, and lowered the aspect ratio. Moreover, the dots formed on InGaAs buffer layers were faceted, whereas those on InP were hemispherical, confirming the effect of the As/P exchange reaction. The shape of InAs quantum dots on InGaAs buffer layers was a truncated pyramid with four [136] facets and base edges parallel to directions.

  8. Heterogeneous integration for on-chip quantum photonic circuits with single quantum dot devices.

    Science.gov (United States)

    Davanco, Marcelo; Liu, Jin; Sapienza, Luca; Zhang, Chen-Zhao; De Miranda Cardoso, José Vinícius; Verma, Varun; Mirin, Richard; Nam, Sae Woo; Liu, Liu; Srinivasan, Kartik

    2017-10-12

    Single-quantum emitters are an important resource for photonic quantum technologies, constituting building blocks for single-photon sources, stationary qubits, and deterministic quantum gates. Robust implementation of such functions is achieved through systems that provide both strong light-matter interactions and a low-loss interface between emitters and optical fields. Existing platforms providing such functionality at the single-node level present steep scalability challenges. Here, we develop a heterogeneous photonic integration platform that provides such capabilities in a scalable on-chip implementation, allowing direct integration of GaAs waveguides and cavities containing self-assembled InAs/GaAs quantum dots-a mature class of solid-state quantum emitter-with low-loss Si3N4 waveguides. We demonstrate a highly efficient optical interface between Si3N4 waveguides and single-quantum dots in GaAs geometries, with performance approaching that of devices optimized for each material individually. This includes quantum dot radiative rate enhancement in microcavities, and a path for reaching the non-perturbative strong-coupling regime.Effective use of single emitters in quantum photonics requires coherent emission, strong light-matter coupling, low losses and scalable fabrication. Here, Davanco et al. stride toward this goal by hybrid on-chip integration of Si3N4 waveguides and GaAs nanophotonic geometries with InAs quantum dots.

  9. Quantum Dots obtained by LPE from under-saturated In-As liquid phases on GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz F E; Mishurnyi V; Gorbatchev A; De Anda F [Universidad Autonoma de San Luis Potosi, Instituto de Investigacion en Comunicacion Optica, Av. Karacorum 1470, Col. Lomas 4a Sec., CP 78210San Luis PotosI (Mexico); Prutskij T, E-mail: fcoe_ov@prodigy.net.mx, E-mail: andre@cactus.iico.uaslp.mx [BUAP, Instituto de Ciencias, Apartado Postal 207, 72000, Puebla (Mexico)

    2011-01-01

    In this work we inform about quantum dots (QD) obtained by Liquid Phase Epitaxy (LPE) on GaAs substrates from under-saturated In-As liquid phases. In our processes, we have prepared saturated In-rich liquid phases by dissolving an InAs wafer at one of the temperatures interval from 450 to 414 C for 60 minutes. The contact between In-As liquid phase and the GaAs substrate was always done at a constant temperature of 444 C for 5 seconds. Thus, the growth temperature for most of the samples was higher than the liquidus temperature. We think that the growth driving force is related to a transient process that occurs when the system is trying to reach equilibrium. Under the atom force microscope (AFM) we have observed nano-islands on the surfaces of the samples obtained from under-saturated liquid phases prepared at 438, 432 and 426 C. The 25 K photoluminescence spectrum shows a peak at a 1.33 eV, in addition to the GaAs related line.

  10. Shape control of III-V semiconductor nanocrystals: synthesis and properties of InAs quantum rods.

    Science.gov (United States)

    Kan, ShiHai; Aharoni, Assaf; Mokari, Taleb; Banin, Uri

    2004-01-01

    A novel approach for synthesis of soluble semiconductor quantum rods using metal nanoparticles to direct and catalyze one-dimensional growth is developed. The method is useful in particular for III-V semiconductors with cubic lattice, where the utilization of surfactant-controlled rod-growth is not easily realized. The growth takes place via the solution-liquid-solid (SLS) mechanism where proper precursors are injected into a coordinating solvent. Centrifugation is used for separation of rod-fractions with different lengths. The reaction is demonstrated for InAs, InP and GaAs. Focusing on InAs rods as a model system, we examined the effects of the type of metal catalyst, and the tuning of reaction conditions with respect to temperature, concentration, catalyst content and reaction time. Within the three types of metal catalysts used--Au, Ag and In, Au was found to provide the best control for achieving rod-growth even though the melting point of bulk gold is significantly higher then the reaction temperature. The structural properties of the rods were characterized by transmission electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy. Rods have a cubic lattice and grow mainly along the [111] direction. The relative gold content decreases in shorter rods suggesting Au depletion as a cause for limiting the growth. Room and low temperature absorption and photoluminescence measurements show that the band-gap shifts to the red upon increasing rod length revealing strong quantum confinement along the long axis in InAs rods, providing spectral coverage of the near-IR range relevant for telecommunication applications. Emission intensity also decreases with increased rod-length. These length dependent properties manifest the transition from 0D to 1D quantum confined systems.

  11. Influence of GaAs Substrate Orientation on InAs Quantum Dots: Surface Morphology, Critical Thickness, and Optical Properties

    Directory of Open Access Journals (Sweden)

    Liang BL

    2007-01-01

    Full Text Available AbstractInAs/GaAs heterostructures have been simultaneously grown by molecular beam epitaxy on GaAs (100, GaAs (100 with a 2° misorientation angle towards [01−1], and GaAs (n11B (n = 9, 7, 5 substrates. While the substrate misorientation angle increased from 0° to 15.8°, a clear evolution from quantum dots to quantum well was evident by the surface morphology, the photoluminescence, and the time-resolved photoluminescence, respectively. This evolution revealed an increased critical thickness and a delayed formation of InAs quantum dots as the surface orientation departed from GaAs (100, which was explained by the thermal-equilibrium model due to the less efficient of strain relaxation on misoriented substrate surfaces.

  12. Improved optical properties of InAs quantum dots for intermediate band solar cells by suppression of misfit strain relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Xie, H. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona 85287-6106 (United States); Prioli, R. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Departamento de Física, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Fischer, A. M.; Ponce, F. A., E-mail: ponce@asu.edu [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States); Kawabata, R. M. S.; Pinto, L. D.; Souza, P. L. [LabSem, CETUC, Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro 22452-900 RJ (Brazil); Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Jakomin, R. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Campus de Xerem, UFRJ, Duque de Caxias-RJ (Brazil); Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutores – DISSE – PUC-Rio, RJ (Brazil); Instituto de Física, UFRJ, Rio de Janeiro-RJ (Brazil)

    2016-07-21

    The properties of InAs quantum dots (QDs) have been studied for application in intermediate band solar cells. It is found that suppression of plastic relaxation in the QDs has a significant effect on the optoelectronic properties. Partial capping plus annealing is shown to be effective in controlling the height of the QDs and in suppressing plastic relaxation. A force balancing model is used to explain the relationship between plastic relaxation and QD height. A strong luminescence has been observed from strained QDs, indicating the presence of localized states in the desired energy range. No luminescence has been observed from plastically relaxed QDs.

  13. Comparative study of low temperature growth of InAs and InMnAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Placidi, E [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Zallo, E; Arciprete, F; Fanfoni, M; Patella, F; Balzarotti, A, E-mail: ernesto.placidi@ism.cnr.it [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' , via della Ricerca Scientifica 1, I-00133 Roma (Italy)

    2011-05-13

    The evolution of InAs and In{sub 0.85}Mn{sub 0.15}As quantum dots grown at 270 deg. C is studied as a function of coverage. We show that, in contrast to what occurs at high temperature, the two-dimensional to three-dimensional transition is not abrupt but rather slow. This is due to the finding that part of the deposited material also contributes to the wetting layer growth after quantum dot formation. This aspect is particularly accentuated in In{sub 0.85}Mn{sub 0.15}As deposition. The Voronoi area analysis reveals a significant spatial correlation between islands.

  14. Experimental and theoretical studies of electronic energy levels in InAs quantum dots grown on (001) and (113)B InP substrates

    CERN Document Server

    Miska, P; Even, J; Bertru, N; Corre, A L; Dehaese, O

    2002-01-01

    An experimental and theoretical comparative study of InAs quantum dots grown on (001) and (113)B InP substrates is performed. The difference between the optical transitions in the dots on the two substrates is attributed to strain effects. The influence of the first InP capping layer is also studied.

  15. Defect characterization of proton irradiated GaAs pn-junction diodes with layers of InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shin-ichiro, E-mail: sato.shinichiro@jaea.go.jp [Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, Takasaki 370-1292 (Japan); Optoelectronics and Radiation Effects Branch, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Schmieder, Kenneth J.; Warner, Jeffrey H.; Walters, Robert J. [Optoelectronics and Radiation Effects Branch, U.S. Naval Research Laboratory, Washington, DC 20375 (United States); Hubbard, Seth M.; Forbes, David V. [NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York 14623 (United States); Ohshima, Takeshi [Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, Takasaki 370-1292 (Japan)

    2016-05-14

    In order to expand the technology of III-V semiconductor devices with quantum structures to both terrestrial and space use, radiation induced defects as well as native defects generated in the quantum structures should be clarified. Electrically active defects in GaAs p{sup +}n diodes with embedded ten layers of InAs quantum dots (QDs) are investigated using Deep Level Transient Fourier Spectroscopy. Both majority carrier (electron) and minority carrier (hole) traps are characterized. In the devices of this study, GaP layers are embedded in between the QD layers to offset the compressive stress introduced during growth of InAs QDs. Devices are irradiated with high energy protons for three different fluences at room temperature in order to characterize radiation induced defects. Seven majority electron traps and one minority hole trap are found after proton irradiation. It is shown that four electron traps induced by proton irradiation increase in proportion to the fluence, whereas the EL2 trap, which appears before irradiation, is not affected by irradiation. These defects correspond to electron traps previously identified in GaAs. In addition, a 0.53 eV electron trap and a 0.14 eV hole trap are found in the QD layers before proton irradiation. It is shown that these native traps are also unaffected by irradiation. The nature of the 0.14 eV hole trap is thought to be Ga-vacancies in the GaP strain balancing layers.

  16. Effects of annealing on self-assembled InAs quantum dots and wetting layer in GaAs matrix

    Energy Technology Data Exchange (ETDEWEB)

    Jasinski, J.; Babinski, A.; Bozek, R.; Szepielow, A.; Baranowski, J.M.

    2001-04-18

    Post-growth thermal annealing effects on InAs/GaAs quantum dots (QDs) near Stransky-Krastanow transformation were investigated. Self-assembled QDs of average size of about 10 nm were grown by metal organic vapour phase epitaxy. The photoluminescence (PL) due to emission from QDs as well as two peaks due to emission from the strained InAs wetting layer (WL) were observed in as-grown samples. Bimodal structure of the WL PL was attributed to WL regions of different thickness. There was almost no difference in the PL spectrum after 30 s annealing at 600 C. However, annealing at temperatures in the range between 700 C and 950 C resulted in quenching of the PL from QDs and the thinner WL. The PL peak from the new, thicker WL blue-shifted and narrowed with increasing annealing temperature. This behavior was in agreement with TEM observations. Complete dissolution of the QDs and substantial broadening of the WL was observed. All our results indicate that thermally induced modifications of the WL rather than QDs can be responsible for the blue-shift and narrowing of the PL peaks in structures containing InAs QDs.

  17. Effects of annealing on self-assembled InAs quantum dots and wetting layer in GaAs matrix

    Energy Technology Data Exchange (ETDEWEB)

    Jasinski, J.; Babinski, A.; Bozek, R.; Szepielow, A.; Baranowski, J.M.

    2001-04-18

    Post-growth thermal annealing effects on InAs/GaAs quantum dots (QDs) near Stransky-Krastanow transformation were investigated. Self-assembled QDs of average size of about 10 nm were grown by metal-organic vapor phase epitaxy. The photoluminescence (PL) due to emission from QDs as well as two peaks due to emission from the strained InAs wetting layer (WL) were observed in as-grown samples. Bimodal structure of the WL PL was attributed to WL regions of different thickness. There was almost no difference in the PL spectrum after 30 s annealing at 600 C. However, annealing at temperatures in the range between 700 C and 950 C resulted in quenching of the PL from QDs and the thinner WL. The PL peak from the new, thicker WL blue-shifted and narrowed with increasing annealing temperature. This behavior was in agreement with TEM observations. Complete dissolution of the QDs and substantial broadening of the WL was observed. All our results indicate that thermally induced modifications of the WL rather than QDs can be responsible for the blue-shift and narrowing of the PL peaks in structures containing InAs QDs.

  18. Carrier dynamics of strain-engineered InAs quantum dots with (In)GaAs surrounding material

    Science.gov (United States)

    Nasr, O.; Chauvin, N.; Alouane, M. H. Hadj; Maaref, H.; Bru-Chevallier, C.; Sfaxi, L.; Ilahi, B.

    2017-02-01

    The present study reports on the optical properties of epitaxially grown InAs quantum dots (QDs) inserted within an InGaAs strain-reducing layer (SRL). The critical energy states in such QD structures have been identified by combining photoluminescence (PL) and photoluminescence of excitation (PLE) measurements. Carrier lifetime is investigated by time-resolved photoluminescence (TRPL), allowing us to study the impact of the composition of the surrounding materials on the QD decay time. Results showed that covering the InAs QDs with, or embedding them within, an InGaAs SRL increases the carrier dynamics, while a shorter carrier lifetime has been observed when they are grown on top of an InGaAs SRL. Investigation of the dependence of carrier lifetime on temperature showed good stability of the decay time, deduced from the consequences of improved QD confinement. The findings suggest that embedding or capping the QDs with SRL exerts optimization of their room temperature optical properties.

  19. Temperature Dependence of Spin Relaxation Time in InAs Columnar Quantum Dots at 10 to 150 K

    Science.gov (United States)

    Nakanishi, Sota; Sasayama, Kazutoshi; Oyanagi, Yoshitsugu; Yamaguchi, Ryo; Lu, Shulong; Li, Lianhe; Fiore, Andrea; Tackeuchi, Atsushi

    2012-04-01

    We have investigated carrier spin relaxation in InAs columnar quantum dots (CQDs) using time-resolved photoluminescence measurement. The CQDs were formed by depositing a 1.8 monolayer InAs seed dot layer and a short-period GaAs/InAs superlattice (SL). The spin relaxations of the 3- and 35-period SL CQDs show double exponential decay up to 50 and 130 K, respectively. The spin relaxation times of the fast component, whose amplitudes are 4-11 times larger than that of the slow component, are around 100 ps for the two samples. For the 3-period SL CQDs, the fast spin relaxation time shows no temperature dependence up to around 50 K, indicating the relevance of the Bir-Aronov-Pikus process. The slow spin relaxation time of the 35-period SL CQDs was found to decrease from 3.42 ns at 10 K to 0.849 ns at 130 K. This large change may be explained by the Elliott-Yafet process considering acoustic phonon scattering.

  20. Ultra-small near-infrared multi-wavelength light source using a heterojunction photonic crystal waveguide and self-assembled InAs quantum dots

    Science.gov (United States)

    Uchida, Sho; Ozaki, Nobuhiko; Nakahama, Teruyuki; Oda, Hisaya; Ikeda, Naoki; Sugimoto, Yoshimasa

    2017-05-01

    We herein propose and verify an ultra-small near-infrared (NIR) multi-wavelength light source using a heterojunction photonic crystal waveguide (PC-WG) and quantum dots (QDs). A heterojunction two-dimensional PC-WG, which consists of multiple PC-WGs with sequentially shifted structural parameters, is fabricated on a GaAs-slab including InAs QDs. Spontaneous emission (SE) from embedded InAs QDs was enhanced at multiple wavelengths resonating with slow-light regions of the PC-WG modes. The enhanced SE was propagated and detected through the heterojunction PC-WG. These results indicate the feasibility of the proposed light source.

  1. Volmer–Weber InAs quantum dot formation on InP (113)B substrates under the surfactant effect of Sb

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yu, E-mail: yu.zhao@insa-rennes.fr; Bertru, Nicolas; Folliot, Hervé; Rohel, Tony [Université Européenne de Bretagne, INSA, FOTON, UMR-CNRS 6082, 20 Avenue des Buttes de Coësmes, F-35708 Rennes Cedex 7 (France); Mauger, Samuel J. C.; Koenraad, Paul M. [COBRA Inter-University Research Institute, Eindhoven University of Technology, P.O. Box 513, NL-5600MB Eindhoven (Netherlands)

    2014-07-21

    We report on Sb surfactant growth of InAs nanostructures on GaAs{sub 0.51}Sb{sub 0.49} layers deposited on InP (001) and on (113)B oriented substrates. On the (001) orientation, the presence of Sb significantly favors the two-dimensional growth regime. Even after the deposition of 5 mono-layers of InAs, the epitaxial film remains flat and InAs/GaAs{sub 0.51}Sb{sub 0.49} type-II quantum wells are achieved. On (113)B substrates, same growth runs resulted in formation of high density InAs islands. Microscopic studies show that wetting layer is missing on (113)B substrates, and thus, a Volmer-Weber growth mode is concluded. These different behaviors are attributed to the surface energy changes induced by Sb atoms on surface.

  2. Stacking InAs quantum dots over ErAs semimetal nanoparticles on GaAs (0 0 1) using molecular beam epitaxy

    Science.gov (United States)

    Zhang, Yuanchang; Eyink, Kurt G.; Grazulis, Lawrence; Hill, Madelyn; Peoples, Joseph; Mahalingam, Krishnamurthy

    2017-11-01

    Hybrid nanostructures are known to elicit an enhanced optical response. We study the directed alignment of ErAs metal nanoparticle (NP) and InAs quantum dot (QD) using molecular beam eptaxy (MBE) in a GaAs matrix. Due to high surface free energy caused by the crystal structure difference, overgrowth of an ErAs NP with GaAs forms a depression that condenses subsequent InAs adatoms to form an inverted QD self-aligned to the underlying ErAs NP. The ErAs NP growth, GaAs overgrowth, and InAs QD deposition were carefully controlled and studied with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to investigate their effects on the QD-NP alignment.

  3. GaAsSb/GaAsN short-period superlattices as a capping layer for improved InAs quantum dot-based optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Utrilla, A. D.; Ulloa, J. M., E-mail: jmulloa@isom.upm.es; Guzman, A.; Hierro, A. [Institute for Systems based on Optoelectronics and Microtechnology (ISOM) and Departamento de Ingeniería Electrónica, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain); Reyes, D. F.; González, D.; Ben, T. [Departamento de Ciencia de los Materiales e IM y QI, Universidad de Cádiz, 11510 Puerto Real (Cádiz) (Spain)

    2014-07-28

    The application of a GaAsSb/GaAsN short-period superlattice capping layer (CL) on InAs/GaAs quantum dots (QDs) is shown to be an option for providing improved luminescence properties to this system. Separating both GaAsSb and GaAsN ternaries during the growth in 2 monolayer-thick phases solves the GaAsSbN immiscibility-related problems. Strong fluctuations in the CL composition and strain field as well as in the QD size distribution are significantly reduced, and a more regular CL interface is also obtained. Room-temperature (RT) photoluminescence (PL) is obtained for overall N contents as high as 3%, yielding PL peak wavelengths beyond 1.4 μm in samples with a type-II band alignment. High external quantum efficiency electroluminescence and photocurrent from the QD ground state are also demonstrated at RT in a single QD-layer p-i-n device. Thus, it becomes possible to combine and transfer the complementary benefits of Sb- and N-containing GaAs alloys to InAs QD-based optoelectronics.

  4. Exploring coherence of individual excitons in InAs quantum dots embedded in natural photonic defects: Influence of the excitation intensity

    Science.gov (United States)

    Wigger, D.; Mermillod, Q.; Jakubczyk, T.; Fras, F.; Le-Denmat, S.; Reiter, D. E.; Höfling, S.; Kamp, M.; Nogues, G.; Schneider, C.; Kuhn, T.; Kasprzak, J.

    2017-10-01

    The exact optical response of quantum few-level systems depends crucially on the exact choice of the incoming pulse areas. We use four-wave mixing (FWM) spectroscopy to infer the coherent response and dynamics of single InAs quantum dots (QDs) and study their pulse area dependence. By combining atomic force microscopy with FWM hyperspectral imaging, we show that the retrieved FWM signals originate from individual QDs enclosed in natural photonic defects. The optimized light-matter coupling in these defects allows us to perform our studies in a wide range of driving field amplitudes. When varying the pulse areas of the exciting laser pulses, Rabi rotations of microscopic interband coherences can be resolved by the two-pulse FWM technique. We investigate these Rabi coherence rotations within two- and three-level systems, both theoretically and experimentally, and explain their damping by the coupling to acoustic phonons. To highlight the importance of the pulse area influence, we show that the phonon-induced dephasing of QD excitons depends on the pulse intensity.

  5. Interaction and Cooperative Nucleation of InAsSbP Quantum Dots and Pits on InAs(100 Substrate

    Directory of Open Access Journals (Sweden)

    Gambaryan Karen

    2009-01-01

    Full Text Available Abstract An example of InAsSbP quaternary quantum dots (QDs, pits and dots–pits cooperative structures’ growth on InAs(100 substrates by liquid phase epitaxy (LPE is reported. The interaction and surface morphology of the dots–pits combinations are investigated by the high-resolution scanning electron microscope. Bimodal growth mechanism for the both QDs and pits nucleation is observed. Cooperative structures consist of the QDs banded by pits, as well as the “large” pits banded by the quantum wires are detected. The composition of the islands and the pits edges is found to be quaternary, enriched by antimony and phosphorus, respectively. This repartition is caused by dissociation of the wetting layer, followed by migration (surface diffusion of the Sb and P atoms in opposite directions. The “small” QDs average density ranges from 0.8 to 2 × 109 cm−2, with heights and widths dimensions from 2 to 20 nm and 5 to 45 nm, respectively. The average density of the “small” pits is equal to (6–10 × 109 cm−2 with dimensions of 5–40 nm in width and depth. Lifshits–Slezov-like distribution for the amount and surface density of both “small” QDs and pits versus their average diameter is experimentally detected. A displacement of the absorption edge toward the long wavelength region and enlargement toward the short wavelength region is detected by the Fourier transform infrared spectrometry.

  6. Studying the InAs quantum points on the vicinal surface of a GaAs crystal by the atomic force microscopy

    CERN Document Server

    Evtikhiev, V P; Kotelnikov, E Y; Matveentsev, A V; Titkov, A N; Shkolnik, A S

    2002-01-01

    The methodology for processing the images, obtained through the atomic force microscopy, is proposed. It is shown by the concrete example, how the parameters of the InAs clusters on the vicinal surface of the GaAs crystal are determined. This makes it possible to calculate the energy levels of the electrons and holes in the quantum point with application of the previously developed cluster spherical model

  7. The presence of INA proteins on the surface of single cells of Pseudomonas syringae R10.79 isolated from rain

    Science.gov (United States)

    Šantl-Temkiv, Tina; Ling, Meilee; Holm, Stine; Finster, Kai; Boesen, Thomas

    2016-04-01

    One of the important open questions in atmospheric ice nucleation is the impact of bioaerosols on the ice content of mix phase clouds (DeMott and Prenni 2010). Biogenic ice nuclei have a unique capacity of facilitating ice formation at temperatures between -1 and -10 °C. The model biogenic ice nuclei are produced by a few species of plant-surface bacteria, such as Pseudomonas syringae, that are commonly transported through the atmosphere. These bacterial species have highly specialized proteins, the so-called ice nucleation active (INA) proteins, which are exposed at the outer membrane surface of the cell where they promote ice particle formation. The mechanisms behind the onset of INA protein synthesis in single bacterial cells are not well understood. We performed a laboratory study in order to (i) investigate the presence of INA proteins on single bacterial cells and (ii) understand the conditions that induce INA protein production. We previously isolated an INA-positive strain of Pseudomonas syringae from rain samples collected in Denmark. Bacterial cells initiated ice nucleation activity at temperatures ≤-2°C and the cell fragments at temperatures ≤-8°C (Šantl-Temkiv et al 2015). We determined the amino-acid sequence of the INA protein and used the sequence to produce custom-made antibodies (GenScript, Germany). These antibodies were used to specifically stain and visualize the INA protein on the surfaces of single cells, which can then be quantified by a technique called flow cytometry. The synthesis of INA proteins by individual cells was followed during a batch growth experiment. An unusually high proportion of cells that were adapting to the new conditions prior to growth produced INA proteins (~4.4% of all cells). A smaller fraction of actively growing cells was carrying INA proteins (~1.2 % of all cells). The cells that stopped growing due to unfavorable conditions had the lowest fraction of cells carrying INA proteins (~0.5 % of all cells). To

  8. Pressure-induced interband optical transitions in an InAs0.8P0.2/InP quantum wire

    Science.gov (United States)

    Saravanan, S.; Peter, A. John; Lee, Chang Woo

    2015-12-01

    Hydrostatic pressure-induced exciton binding energy in an InAs0.8P0.2/InP quantum well wire is investigated taking into account the geometrical confinement effect. Numerical calculations are carried out using variational approach within the single-band effective-mass approximation. The compressive strain contribution to the confinement potential is included throughout the calculations. The energy difference of the ground and the first excited state is found with the consideration of spatial confinement effect in the influence of pressure. The second-order susceptibility of harmonic generation is carried out using the compact density method. The optical gain as a function of incident photon energy is computed in the presence of the hydrostatic pressure. The result shows that the range of wavelength for the potential applications of telecommunications (1.3-1.55 μm) can be obtained by the application of the hydrostatic pressure. We believe that the obtained results can be applied for tuning the ranges of fibre optical wavelength in telecommunications.

  9. Towards quantitative three-dimensional characterisation of buried InAs quantum dots

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; Semenova, Elizaveta; Schubert, Martin

    2011-01-01

    and compositional measurements of quantum dots using transmission electron microscopy can be ambiguous because the recorded signal is usually a projection through the thickness of the specimen. Here, we discuss the application of scanning transmission electron microscopy tomography to the morphological and chemical...... characterisation of surface and buried quantum dots. We highlight some of the challenges involved and introduce a new specimen preparation method for creating needle-shaped specimens that each contain multiple dots and are suitable for both scanning transmission electron microscopy tomography and atom probe......InAs quantum dots grown on InP or InGaAsP are used for optical communication applications operating in the 1.3 – 1.55 μm wavelength range. It is generally understood that the optical properties of such dots are highly dependent on their structural and chemical profiles. However, morphological...

  10. Charge transport through single molecules, quantum dots and quantum wires.

    Science.gov (United States)

    Andergassen, S; Meden, V; Schoeller, H; Splettstoesser, J; Wegewijs, M R

    2010-07-09

    We review recent progress in the theoretical description of correlation and quantum fluctuation phenomena in charge transport through single molecules, quantum dots and quantum wires. Various physical phenomena are addressed, relating to cotunneling, pair-tunneling, adiabatic quantum pumping, charge and spin fluctuations, and inhomogeneous Luttinger liquids. We review theoretical many-body methods to treat correlation effects, quantum fluctuations, non-equilibrium physics, and the time evolution into the stationary state of complex nanoelectronic systems.

  11. Coherent versus incoherent dynamics in InAs quantum-dot active wave guides

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, W.; Hvam, Jørn Märcher

    2001-01-01

    Coherent dynamics measured by time-resolved four-wave mixing is compared to incoherent population dynamics measured by differential transmission spectroscopy on the ground-state transition at room temperature of two types of InAs-based quantum dots with different confinement energies...

  12. Photoluminescence of InAs quantum dots embedded in AlGaAs/InGaAs quantum wells with strain reducing layer

    Science.gov (United States)

    Cisneros Tamayo, R.; Torchynska, T. V.; Polupan, G.; Guerrero Moreno, I. J.; Velázquez Lozada, E.; Shcherbyna, L.

    2014-07-01

    Photoluminescence (PL) of InAs quantum dots (QDs) embedded in the Al0.30Ga0.70As/In0.15Ga0.85As/InGaAlAs/GaAs quantum wells (QWs) have been investigated in the temperature range of 10-500 K for as grown samples and after thermal annealing at 640 °C or 710 °C for two hours. QD samples with the different InAlGaAs capping layers (GaAs or Al0.1Ga0.75 In0.15As) have been studied. The higher PL intensity and lower energy of ground state (GS) emission are detected in the structure with Al0.1Ga0.75 In0.15As layer. This QD structure in as grown state has smaller PL thermal decay in comparison with this parameter in the structure with GaAs layer. The variation of PL intensities and peak positions at annealing are more essential in the QD structure with Al0.1Ga0.75 In0.15As capping layer, apparently, due to more efficient Ga(Al)/In intermixing.

  13. Lasing from a single quantum wire

    OpenAIRE

    Hayamizu, Yuhei; Yoshita, Masahiro; Watanabe, Shinichi; Akiyama, Hidefumi; Pfeiffer, Loren N.; West, Ken W.

    2002-01-01

    A laser with an active volume consisting of only a single quantum wire in the 1-dimensional (1-D) ground state is demonstrated. The single wire is formed quantum-mechanically at the T-intersection of a 14 nm Al_{0.07}Ga_{0.93}As quantum well and a 6 nm GaAs quantum well, and is embedded in a 1-D single-mode optical waveguide. We observe single-mode lasing from the quantum wire ground state by optical pumping. The laser operates from 5 to 60 K, and has a low threshold pumping power of 5 mW at ...

  14. Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices.

    Science.gov (United States)

    Sapienza, Luca; Liu, Jin; Song, Jin Dong; Fält, Stefan; Wegscheider, Werner; Badolato, Antonio; Srinivasan, Kartik

    2017-07-24

    We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots. The motivation of this work is to determine an approach that allows to assess single quantum dots as candidates for quantum nanophotonic devices. By combining optical and scanning probe characterization techniques, we find that single quantum dots often appear in the vicinity of comparatively large topographic features. Despite this, the quantum dots generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions, and this behavior is observed across multiple wafers produced in different growth chambers. Such large surface features are nevertheless a detriment to applications in which single quantum dots are embedded within nanofabricated photonic devices: they are likely to cause large spectral shifts in the wavelength of cavity modes designed to resonantly enhance the quantum dot emission, thereby resulting in a nominally perfectly-fabricated single quantum dot device failing to behave in accordance with design. We anticipate that the approach of screening quantum dots not only based on their optical properties, but also their surrounding surface topographies, will be necessary to improve the yield of single quantum dot nanophotonic devices.

  15. Vertical stacking of InAs quantum dots for polarization-insensitive semiconductor optical amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, T; Asada, M; Kita, T; Wada, O [Department of Electrical and Electronic Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Yasuoka, N, E-mail: t_inoue@person.kobe-u.ac.j [Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197 (Japan)

    2010-09-01

    In this paper, we report a control of the polarization property in quantum dot semiconductor optical amplifiers (QD-SOAs) using vertically-stacked, electronically-coupled InAs/GaAs QDs grown by molecular beam epitaxy. By optimizing the number of stacked layers and intermediate GaAs thickness, the 9-stacked QDs demonstrated the polarization-insensitive operation within 1.2 dB in the 1.3-mm optical communication band. Our results demonstrate that the electronically-coupled QDs are useful to realize the polarization-insensitive QD-SOAs.

  16. Emission-wavelength tuning of InAs quantum dots grown on nitrogen-δ-doped GaAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Kaizu, Toshiyuki, E-mail: kaizu@crystal.kobe-u.ac.jp [Center for Supports to Research and Education Activities, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Department of Electrical and Electronic Engineering, Faculty of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan); Taguchi, Kohei; Kita, Takashi [Department of Electrical and Electronic Engineering, Faculty of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2016-05-21

    We studied the structural and photoluminescence (PL) characteristics of InAs quantum dots (QDs) grown on nitrogen (N) δ-doped GaAs(001). The emission wavelength for low-density N-δ doping exhibited a blueshift with respect to that for undoped GaAs and was redshifted with increasing N-sheet density. This behavior corresponded to the variation in the In composition of the QDs. N-δ doping has two opposite and competing effects on the incorporation of Ga atoms from the underlying layer into the QDs during the QD growth. One is the enhancement of Ga incorporation induced by the lattice strain, which is due to the smaller radius of N atoms. The other is an effect blocking for Ga incorporation, which is due to the large bonding energy of Ga-N or In-N. At a low N-sheet density, the lattice-strain effect was dominant, while the blocking effect became larger with increasing N-sheet density. Therefore, the incorporation of Ga from the underlying layer depended on the N-sheet density. Since the In-Ga intermixing between the QDs and the GaAs cap layer during capping also depended on the size of the as-grown QDs, which was affected by the N-sheet density, the superposition of these three factors determined the composition of the QDs. In addition, the piezoelectric effect, which was induced with increased accumulation of lattice strain and the associated high In composition, also affected the PL properties of the QDs. As a result, tuning of the emission wavelength from 1.12 to 1.26 μm was achieved at room temperature.

  17. Nonradiative centers in InAs quantum dots revealed by two-wavelength excited photoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, N. [Department of Functional Materials Science, Saitama University, 255 Shimo-Ohkubo, Sakura-ku, Saitama-shi, Saitama 338-8570 (Japan)]. E-mail: kamata@fms.saitama-u.ac.jp; Saravanan, S. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Zanardi Ocampo, J.M. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Vaccaro, P.O. [Department of Nonlinear Science, ATR Wave Engineering. Laboratories, Kyoto 619-0288 (Japan); Arakawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8505 (Japan)

    2006-04-01

    We studied nonradiative recombination centers in MBE-grown InAs/GaAs quantum dot (QD) structures with photoluminescence (PL) peak energies between 1.12 and 1.29 eV by the scheme of two-wavelength excitation. Temporally chopped below-gap excitation (BGE) light of 0.75 eV was superposed on a CW above-gap excitation light of 1.59 eV on the sample surface, and the resultant PL intensity change due to the BGE (BGE effect) was measured. Observed 25-35% decrease in PL intensity at 80-90 K implies a first discrimination of a pair of nonradiative centers activated at 0.75 eV inside the band gap of the QD region. Due to trap-filling, the BGE effect showed saturation with increasing BGE power. Its temperature dependence below 50 K was different from that of quantum wells, reflecting carrier dynamics peculiar to the QD.

  18. InAs quantum dot morphology after capping with In, N, Sb alloyed thin films

    Energy Technology Data Exchange (ETDEWEB)

    Keizer, J. G.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven (Netherlands); Ulloa, J. M.; Utrilla, A. D. [Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2014-02-03

    Using a thin capping layer to engineer the structural and optical properties of InAs/GaAs quantum dots (QDs) has become common practice in the last decade. Traditionally, the main parameter considered has been the strain in the QD/capping layer system. With the advent of more exotic alloys, it has become clear that other mechanisms significantly alter the QD size and shape as well. Larger bond strengths, surfactants, and phase separation are known to act on QD properties but are far from being fully understood. In this study, we investigate at the atomic scale the influence of these effects on the morphology of capped QDs with cross-sectional scanning tunneling microscopy. A broad range of capping materials (InGaAs, GaAsSb, GaAsN, InGaAsN, and GaAsSbN) are compared. The QD morphology is related to photoluminescence characteristics.

  19. RADIATION PERFORMANCE OF GAN AND INAS/GAAS QUANTUM DOT BASED DEVICES SUBJECTED TO NEUTRON RADIATION

    Directory of Open Access Journals (Sweden)

    Dhiyauddin Ahmad Fauzi

    2017-05-01

    Full Text Available In addition to their useful optoelectronics functions, gallium nitride (GaN and quantum dots (QDs based structures are also known for their radiation hardness properties. With demands on such semiconductor material structures, it is important to investigate the differences in reliability and radiation hardness properties of these two devices. For this purpose, three sets of GaN light-emitting diode (LED and InAs/GaAs dot-in-a well (DWELL samples were irradiated with thermal neutron of fluence ranging from 3×1013 to 6×1014 neutron/cm2 in PUSPATI TRIGA research reactor. The radiation performances for each device were evaluated based on the current-voltage (I-V and capacitance-voltage (C-V electrical characterisation method. Results suggested that the GaN based sample is less susceptible to electrical changes due to the thermal neutron radiation effects compared to the QD based sample.

  20. Lasing characteristics of InP-based InAs quantum dots depending on InGaAsP waveguide conditions.

    Science.gov (United States)

    Jo, Byounggu; Lee, Hyunjung; Choi, Ilgyu; Kim, Jiin; Kim, Jin Soo; Han, Won Seok; Song, Jung Ho; Oh, Dae Kon; Noh, Sam Kyu; Leem, Jae-Young

    2014-12-01

    We report the influences of a dot-in-a-well structure with a thin GaAs layer and the thickness of a waveguide (WG) on the lasing characteristics of InAs quantum dots (QDs) based on InP. The QD laser diodes (QDLDs) consist of seven-stacked InAs QDs separated by a 10 nm-thick InGaAsP (1.15 μm, 1.15Q-InGaAsP) layer, which is further sandwiched by a 800 nm-thick 1.15Q-lnGaAsP WG (reference QDLD). For comparison, the InAs QDs were inserted into the InGaAsP (1.35 μm, 1.35Q-InGaAsP) quantum well embedded in the 1.15Q-InGaAsP matrix at the active layer. And a 2 monolayer (ML)-thick GaAs layer was additionally introduced right before the QD layer (GDWELL-LDs). Lasing emission from the reference QDLD with only the 1.15Q-InGaAsP structure was not observed at room temperature (RT). However, the lasing emission from the GDWELL-LDs was clearly observed at the wavelength of 1.46 μm at RT under continuous-wave (CW) mode. The threshold current density of the GDWELL-LD with the 800 nm-thick InGaAsP WG was measured to be 830 A/cm2, which was lower than that of the GDWELL-LD with the 200 nm-thick WG (900 A/cm2). Also, the slope efficiency of the GDWELL-LD was significantly improved with increasing thickness of the InGaAsP WG.

  1. A single-atom quantum memory.

    Science.gov (United States)

    Specht, Holger P; Nölleke, Christian; Reiserer, Andreas; Uphoff, Manuel; Figueroa, Eden; Ritter, Stephan; Rempe, Gerhard

    2011-05-12

    The faithful storage of a quantum bit (qubit) of light is essential for long-distance quantum communication, quantum networking and distributed quantum computing. The required optical quantum memory must be able to receive and recreate the photonic qubit; additionally, it must store an unknown quantum state of light better than any classical device. So far, these two requirements have been met only by ensembles of material particles that store the information in collective excitations. Recent developments, however, have paved the way for an approach in which the information exchange occurs between single quanta of light and matter. This single-particle approach allows the material qubit to be addressed, which has fundamental advantages for realistic implementations. First, it enables a heralding mechanism that signals the successful storage of a photon by means of state detection; this can be used to combat inevitable losses and finite efficiencies. Second, it allows for individual qubit manipulations, opening up avenues for in situ processing of the stored quantum information. Here we demonstrate the most fundamental implementation of such a quantum memory, by mapping arbitrary polarization states of light into and out of a single atom trapped inside an optical cavity. The memory performance is tested with weak coherent pulses and analysed using full quantum process tomography. The average fidelity is measured to be 93%, and low decoherence rates result in qubit coherence times exceeding 180  microseconds. This makes our system a versatile quantum node with excellent prospects for applications in optical quantum gates and quantum repeaters.

  2. GaAs metal-oxide-semiconductor based non-volatile flash memory devices with InAs quantum dots as charge storage nodes

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Sk Masiul, E-mail: masiulelt@gmail.com; Chowdhury, Sisir; Sarkar, Krishnendu; Nagabhushan, B.; Banerji, P. [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Chakraborty, S. [Applied Materials Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Sector-I, Kolkata 700 064 (India); Mukherjee, Rabibrata [Department of Chemical Engineering, Indian Institute of Technology, Kharagpur 721302 (India)

    2015-06-24

    Ultra-thin InP passivated GaAs metal-oxide-semiconductor based non-volatile flash memory devices were fabricated using InAs quantum dots (QDs) as charge storing elements by metal organic chemical vapor deposition technique to study the efficacy of the QDs as charge storage elements. The grown QDs were embedded between two high-k dielectric such as HfO{sub 2} and ZrO{sub 2}, which were used for tunneling and control oxide layers, respectively. The size and density of the QDs were found to be 5 nm and 1.8×10{sup 11} cm{sup −2}, respectively. The device with a structure Metal/ZrO{sub 2}/InAs QDs/HfO{sub 2}/GaAs/Metal shows maximum memory window equivalent to 6.87 V. The device also exhibits low leakage current density of the order of 10{sup −6} A/cm{sup 2} and reasonably good charge retention characteristics. The low value of leakage current in the fabricated memory device is attributed to the Coulomb blockade effect influenced by quantum confinement as well as reduction of interface trap states by ultra-thin InP passivation on GaAs prior to HfO{sub 2} deposition.

  3. Wavelength extension beyond 1.5 µm in symmetric InAs quantum dots grown on InP(111)A using droplet epitaxy

    Science.gov (United States)

    Ha, Neul; Mano, Takaaki; Wu, Yu-Nien; Ou, Ya-Wen; Cheng, Shun-Jen; Sakuma, Yoshiki; Sakoda, Kazuaki; Kuroda, Takashi

    2016-10-01

    By using a C 3v symmetric (111) surface as a growth substrate, we can achieve high structural symmetry in self-assembled quantum dots, which are suitable for use as quantum-entangled-photon emitters. Here, we report on the wavelength controllability of InAs dots on InP(111)A, which we realized by tuning the ternary alloy composition of In(Al,Ga)As barriers that were lattice-matched to InP. We changed the peak emission wavelength systematically from 1.3 to 1.7 µm by barrier band gap tuning. The observed spectral shift agreed with the result of numerical simulations that assumed a measured shape distribution independent of the barrier choice.

  4. Quantitative analysis of the interplay between InAs quantum dots and wetting layer during the GaAs capping process

    Science.gov (United States)

    González, D.; Braza, V.; Utrilla, A. D.; Gonzalo, A.; Reyes, D. F.; Ben, T.; Guzman, A.; Hierro, A.; Ulloa, J. M.

    2017-10-01

    A procedure to quantitatively analyse the relationship between the wetting layer (WL) and the quantum dots (QDs) as a whole in a statistical way is proposed. As we will show in the manuscript, it allows determining, not only the proportion of deposited InAs held in the WL, but also the average In content inside the QDs. First, the amount of InAs deposited is measured for calibration in three different WL structures without QDs by two methodologies: strain mappings in high-resolution transmission electron microscopy images and compositional mappings with ChemiSTEM x-ray energy spectrometry. The area under the average profiles obtained by both methodologies emerges as the best parameter to quantify the amount of InAs in the WL, in agreement with high-resolution x-ray diffraction results. Second, the effect of three different GaAs capping layer (CL) growth rates on the decomposition of the QDs is evaluated. The CL growth rate has a strong influence on the QD volume as well as the WL characteristics. Slower CL growth rates produce an In enrichment of the WL if compared to faster ones, together with a diminution of the QD height. In addition, assuming that the QD density does not change with the different CL growth rates, an estimation of the average In content inside the QDs is given. The high Ga/In intermixing during the decomposition of buried QDs does not only trigger a reduction of the QD height, but above all, a higher impoverishment of the In content inside the QDs, therefore modifying the two most important parameters that determine the optical properties of these structures.

  5. Probing into hybrid organic-molecule and InAs quantum-dots nanosystem with multistacked dots-in-a-well units

    Energy Technology Data Exchange (ETDEWEB)

    Chen Miaoxiang [Department of Micro- and Nano technology, Technical University of Denmark, Orsteds Plads, 2800 Kgs. Lyngby (Denmark); Kobashi, Kazufumi [Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2012-09-15

    Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist of multistacked dots-in-a-well (DWELL) units. The effects of grafted molecules on the performances of the QDs structures with multistacked DWELLs, however, still remain unclear. Here, we show the significant improvements in the optical properties of InAs QDs in a hybrid nanosystem obtained by grafting biocompatible diazonium salt compound (amine donor) atop InAs QDs structure. Since its interface between the QDs structure and molecular monolayer retains an uncontaminated and non-oxidized condition, the nanosystem is an ideal platform to study the intrinsic properties of charge-carrier transport inside the system. Because of the complexity of the energy-levels in the QDs structure due to the existing surface QDs and DWELLs, selective excitation wavelengths (400, 633, and 885 nm, respectively) with different photo-energies are used to exactly analyze the complete charging mechanism in these QDs. A clear view of charge-carrier transfer inside the nanosystem is revealed by employing photoluminescence technique under selective-wavelength excitations. The present work provides new quantitative evidences for exploiting inorganic QDs applications in complex biological systems.

  6. Effects of Sb-soak on InAs quantum dots grown on (001) and (113)B GaAs substrates

    Science.gov (United States)

    Lu, Xiangmeng; Kumagai, Naoto; Minami, Yasuo; Kitada, Takahiro; Isu, Toshiro

    2017-11-01

    We have investigated the effects of Sb-soak on InAs quantum dots (QDs) grown on (001) and (113)B GaAs substrates by molecular beam epitaxy. Surface morphologies of the QDs were characterized by atomic force microscopy. The optical properties of buried QDs were investigated by photoluminescence (PL). We showed that effects of Sb-soak on density and PL of (001) and (113)B QDs were quite different. The increased density and blue-shift of (001) QDs can be explained by the surfactant effect of Sb atoms which increase the areal density of the kinks for nucleation. On the other hand, for (113)B QDs, the incorporation effect should be responsible for the red-shift because the Sb atoms may be diffused into QDs.

  7. Longitudinal wave function control in single quantum dots with an applied magnetic field

    Science.gov (United States)

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-01

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018

  8. Size dependence of the wavefunction of self-assembled InAs quantum dots from time-resolved optical measurements

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Stobbe, Søren; Nikolaev, Ivan S.

    2008-01-01

    and a theoretical model, we determine the striking dependence of the overlap of the electron and hole wavefunctions on the quantum dot size. We conclude that the optical quality is best for large quantum dots, which is important in order to optimally tailor quantum dot emitters for, e.g., quantum electrodynamics...

  9. Quantum identity authentication with single photon

    Science.gov (United States)

    Hong, Chang ho; Heo, Jino; Jang, Jin Gak; Kwon, Daesung

    2017-10-01

    Quantum identity authentication with single photons is proposed in the paper. It can verify a user's identity without exposing to an authentication key information. The protocol guarantees high efficiency in that it can verify two bits of authentication information using just a single photon. The security of our authentication scheme is analyzed and confirmed in the case of a general attack. Moreover, the proposed protocol is practicable with current technology. Our quantum identity authentication protocol does not require quantum memory registration and any entangled photon sources.

  10. Tuning of in-plane optical anisotropy by inserting ultra-thin InAs layer at interfaces in (001)-grown GaAs/AlGaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Yu, J. L., E-mail: jlyu@semi.ac.cn [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences, Fuzhou 350002 (China); Cheng, S. Y.; Lai, Y. F.; Zheng, Q. [Institute of Micro/Nano Devices and Solar Cells, School of Physics and Information Engineering, Fuzhou University, Fuzhou (China); Chen, Y. H., E-mail: yhchen@semi.ac.cn; Tang, C. G. [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China)

    2015-01-07

    The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness of the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.

  11. A highly efficient single-photon source based on a quantum dot in a photonic nanowire

    DEFF Research Database (Denmark)

    Claudon, Julien; Bleuse, Joel; Malik, Nitin Singh

    2010-01-01

    –4 or a semiconductor quantum dot5–7. Achieving a high extraction efficiency has long been recognized as a major issue, and both classical solutions8 and cavity quantum electrodynamics effects have been applied1,9–12. We adopt a different approach, based on an InAs quantum dot embedded in a GaAs photonic nanowire...

  12. Effects of in situ annealing of GaAs(100) substrates on the subsequent growth of InAs quantum dots by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Cortes, H; Mejia-Garcia, C [Escuela Superior de Fisica y Matematicas del IPN, UPALM, Edif. 9, Col. Lindavista, Mexico DF 07738 (Mexico); Mendez-GarcIa, V H; Vazquez-Cortes, D [Coordinacion para la Innovacion y la Aplicacion de la Ciencia y la TecnologIa, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis PotosI, S L P 78000 (Mexico); Rojas-Ramirez, J S; Contreras-Guerrero, R; RamIrez-Lopez, M; Martinez-Velis, I; Lopez-Lopez, M, E-mail: mlopez@fis.cinvestav.mx [Physics Department, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, Mexico DF 07000 (Mexico)

    2010-04-02

    In the present work, we study the growth by molecular beam epitaxy of InAs self-assembling quantum dots (SAQDs) on GaAs(100) substrates subjected to an in situ annealing treatment. The annealing process consists of the exposition of the GaAs buffer layer surface to high temperatures for a few seconds with the shutter of an arsenic Knudsen cell closed. The purpose of the annealing is to obtain a better uniformity of the SAQD sizes. In our study we prepared different samples using the Stranski-Krastanov growth method to obtain InAs/GaAs(100) quantum dot samples with different annealing times and temperatures. Their structural and optical properties were studied by reflection high-energy electron diffraction (RHEED), high-resolution scanning electron microscopy (HRSEM), atomic force microscopy (AFM), and photoreflectance spectroscopy (PR). According to the results of AFM and HRSEM, by the thermal treatment we obtained a better distribution of quantum dot sizes in comparison with a reference sample with no treatment. The PR spectra from 0.9 to 1.35 eV presented two transitions associated with SAQDs. The energy transitions were obtained by fitting the PR spectra using the third derivative model.

  13. Influence of nitrogen on the growth and the properties of InAs quantum dots; Einfluss von Stickstoff auf das Wachstum und die Eigenschaften von InAs-Quantenpunkten

    Energy Technology Data Exchange (ETDEWEB)

    Schumann, O.

    2004-11-01

    This work investigates the influence of nitrogen incorporation on the growth and the optical properties of InAs quantum dots on GaAs(001) substrates. On the basis of systematic growth interruptions it was shown that the large quantum dots nucleate at dislocations, which are already formed during the growth of the wetting layer. After solving the growth problems, the influence of different combinations of matrix layers on the structural and optical properties of the quantum dots was investigated in the second part of this work. The strain and bandgap of these layers were varied systematically. (orig.)

  14. InAs quantum dot growth on Al{sub x}Ga{sub 1−x}As by metalorganic vapor phase epitaxy for intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jakomin, R., E-mail: robertojakomin@xerem.ufrj.br [Campus de Xerém, Universidade Federal do Rio de Janeiro, UFRJ, Duque de Caxias-RJ (Brazil); Campus de Xerém, Universidade Federal do Rio de Janeiro, UFRJ, Duque de Caxias-RJ (Brazil); Kawabata, R. M. S.; Souza, P. L. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Pontificia Universidade Católica do Rio de Janeiro, Marques de São Vicente 225, Rio de Janeiro, 22452-900 RJ (Brazil); Mourão, R. T.; Pires, M. P. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Instituto de Física, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro-RJ (Brazil); Micha, D. N. [Instituto Nacional de Ciência e Tecnologia de Nanodispositivos Semicondutoires–DISSE–PUC-Rio, RJ (Brazil); Instituto de Física, Universidade Federal do Rio de Janeiro, UFRJ, Rio de Janeiro-RJ (Brazil); Coordenação de Licenciatura em Física, CEFET/RJ, Petrópolis-RJ (Brazil); Xie, H.; Fischer, A. M.; Ponce, F. A. [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2014-09-07

    InAs quantum dot multilayers have been grown using Al{sub x}Ga{sub 1−x}As spacers with dimensions and compositions near the theoretical values for optimized efficiencies in intermediate band photovoltaic cells. Using an aluminium composition of x = 0.3 and InAs dot vertical dimensions of 5 nm, transitions to an intermediate band with energy close to the ideal theoretical value have been obtained. Optimum size uniformity and density have been achieved by capping the quantum dots with GaAs following the indium-flush method. This approach has also resulted in minimization of crystalline defects in the epilayer structure.

  15. Coupling single emitters to quantum plasmonic circuits

    Directory of Open Access Journals (Sweden)

    Huck Alexander

    2016-09-01

    Full Text Available In recent years, the controlled coupling of single-photon emitters to propagating surface plasmons has been intensely studied, which is fueled by the prospect of a giant photonic nonlinearity on a nanoscaled platform. In this article, we will review the recent progress on coupling single emitters to nanowires towards the construction of a new platform for strong light-matter interaction. The control over such a platform might open new doors for quantum information processing and quantum sensing at the nanoscale and for the study of fundamental physics in the ultrastrong coupling regime.

  16. Quantum transport through single molecules

    NARCIS (Netherlands)

    Osorio Oliveros, E.A.

    2009-01-01

    This thesis describes three-terminal transport measurements through single molecules. The interest in this field stems from the dream that single molecules will form the building blocks for future nanoscale electronic devices. The advantages are their small size -nanometers-, and their synthetic

  17. Narrow ridge waveguide high power single mode 1.3-μm InAs/InGaAs ten-layer quantum dot lasers

    Directory of Open Access Journals (Sweden)

    Cao Q

    2007-01-01

    Full Text Available AbstractTen-layer InAs/In0.15Ga0.85As quantum dot (QD laser structures have been grown using molecular beam epitaxy (MBE on GaAs (001 substrate. Using the pulsed anodic oxidation technique, narrow (2 μm ridge waveguide (RWG InAs QD lasers have been fabricated. Under continuous wave operation, the InAs QD laser (2 × 2,000 μm2 delivered total output power of up to 272.6 mW at 10 °C at 1.3 μm. Under pulsed operation, where the device heating is greatly minimized, the InAs QD laser (2 × 2,000 μm2 delivered extremely high output power (both facets of up to 1.22 W at 20 °C, at high external differential quantum efficiency of 96%. Far field pattern measurement of the 2-μm RWG InAs QD lasers showed single lateral mode operation.

  18. Single-charge tunneling in ambipolar silicon quantum dots

    NARCIS (Netherlands)

    Müller, Filipp

    2015-01-01

    Spin qubits in coupled quantum dots (QDs) are promising for future quantum information processing (QIP). A quantum bit (qubit) is the quantum mechanical analogon of a classical bit. In general, each quantum mechanical two-level system can represent a qubit. For the spin of a single charge carrier

  19. Quantum state engineering with single atom laser

    Science.gov (United States)

    Stefanov, V. P.

    2017-11-01

    On the basis of quantum stochastic trajectories approach it is shown that a single atom laser with coherent pumping can generate not only coherent states, but squeezed and Fock states, when different schemes of detection are followed by coherent feedback pulses or feedforward actions.

  20. Single Photon Experiments and Quantum Complementarity

    Directory of Open Access Journals (Sweden)

    Georgiev D. D.

    2007-04-01

    Full Text Available Single photon experiments have been used as one of the most striking illustrations of the apparently nonclassical nature of the quantum world. In this review we examine the mathematical basis of the principle of complementarity and explain why the Englert-Greenberger duality relation is not violated in the configurations of Unruh and of Afshar.

  1. Spin storage in quantum dot ensembles and single quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Heiss, Dominik

    2009-10-15

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T{sub 1}=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T{sub 1}{proportional_to}B{sup -5} has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T{sub 1}{proportional_to}T{sup -1}. The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T{sub 1}{sup h

  2. A double quantum well single charge electrometer

    Science.gov (United States)

    Robinson, Hans D.; Bandaru, Prabhakar; Kosaka, Hideo; Yablonovitch, Eli; Caflisch, Russel E.; Anderson, Chris; Gyure, Mark F.; Croke, Edward T.

    2002-03-01

    In recent years, quantum point contacts and single electron transistors have been shown to be useful as extremely sensitive ( 10-5 e/Hz^1/2) charge sensors. In this talk, we present experimental and numerical results on a new device, based on an InP/InGaAs double quantum well structure, where the charge sensitive channel is realized in the lower quantum well, while a single electron is confined in a quantum dot in the upper well. If the spacer between the wells is made thin enough, then the channel plays the dual role of both supplying the trapped charges and detecting them. We show that it is possible to spin polarize the sensing channel, and that this property will make it possible to read out the spin of the trapped electron. (See the talk by Mark Gyure for further details on this topic.) The spacer can also be made sufficiently wide that tunneling between the wells does not take place, and the device can then be used as a coherent single photon detector.

  3. Spectral and carrier transfer characteristics of 1.55 -μ m InAs /InP coupled-quantum-dot lasers

    Science.gov (United States)

    Lin, Zhiyuan; Wang, Zhuoran; Yuan, Guohui

    2015-07-01

    To explore the spectral and carrier transfer characteristics of 1.55 -μ m InAs /InP coupled-quantum-dot lasers (CQDLs), we develop a probabilistically coupled multipopulation rate equation model (PCMPREM) involving intradot and interdot relaxation, inhomogeneous broadening, and homogeneous broadening. After solving the PCMPREM with the fourth-order Runge-Kutta method, a simultaneous quadruple lasing spectrum is observed and explained by both the carrier competition theory and coupled theory. An analysis of the results shows that the coupling strength between different subbands changes with different current injections, giving a systematic understanding of the operation of CQDLs systems. With a lower threshold, the CQDL has a much broader output range of more than 105.3 nm around 1.55 μ m , which is 7.8 times greater than the uncoupled QDL, indicating that CQDLs can be excellent light sources for not only long-haul ultrahigh capacity optical communications, but also on-chip photonics integrated circuits with low power consumption.

  4. On strain state and pseudo-moire TEM contrast of InSb quantum dots coherently grown on InAs surface

    Energy Technology Data Exchange (ETDEWEB)

    Bert, N.A. [Ioffe Physico-Technical Institute, Polytechnicheskaya 26, 194021 St. Petersburg (Russian Federation); Freidin, A.B.; Kolesnikova, A.L.; Korolev, I.K. [Institute of Problems in Mechanical Engineering, Bolshoj 61, Vas. Ostrov, 199178 St. Petersburg (Russian Federation); Romanov, A.E. [Ioffe Physico-Technical Institute, Polytechnicheskaya 26, 194021 St. Petersburg (Russian Federation); Polytechnique School, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

    2010-10-15

    In this article, we report on the theoretical analysis of transmission electron microscopy (TEM) images of surface InSb quantum dots (QDs) coherently grown on InAs substrate. A finite element method (FEM) is used to calculate elastic fields and total displacements in a QD and an adjusted region of the substrate. The effects of QD form factor and QD aspect ratio {delta} on displacements and TEM images are analyzed. A quasilinear dependence of radial displacements on radial coordinate for spherical, elliptical, and truncated spherical QDs is demonstrated. It has been found that the displacement field does not depend on the shape and aspect ratio for QDs with {delta}>{delta}{sub c1}, and the upper part of a QD remains practically undistorted for QDs with {delta}{>=}{delta}{sub c2}. For InSb/InAs heterosystem these critical values are {delta}{sub c1}{approx} 0.13 and {delta}{sub c2}{approx} 0.33. The total displacements are used for computation of TEM diffraction contrast associated with QDs. To achieve this the Howie-Whelan dynamic approach is utilized. Calculated TEM images of heavily strained QDs demonstrate the picture of pseudo-moire with a strong dependence of moire-like fringe distance {delta} on aspect ratio {delta}. This dependence gives the possibility to determine the aspect ratio and height of QDs from the results of TEM experiments. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  5. Persistent Optical Nuclear Spin Narrowing in a Singly Charged InAs Quantum Dot

    Science.gov (United States)

    2012-02-01

    hole envelope wave function, Ah is the hyper- fine coupling constant, and c0 is the lattice parameter. Since the external magnetic field is in the x̂...February 2012 / J. Opt. Soc. Am. B A121 where γs (γt) is the spin (trion) dephasing rate, χ is half the pump Rabi frequency ΩR (ΩR # μEℏ , where μ is...probe ab- sorption at the dark state dip (αdip) and the Rabi sideband (αpeak): αdip # α0 χ2γs & γt$γ2s% χ4 & 2χ2γtγs & γ2t γ2s ; (11) αpeak # α0 χ2γs

  6. Dry etching of deep air holes in GaAs/AlGaAs-based epi-wafer having InAs quantum dots for fabrication of photonic crystal laser

    Science.gov (United States)

    Zhang, Xiuyu; Takeuchi, Kento; Cong, Xiaolong; Xiong, Yifan; Morifuji, Masato; Maruta, Akihiro; Kajii, Hirotake; Kondow, Masahiko

    2017-12-01

    Photonic crystal (PhC) structures are often fabricated on epi-wafers with a heterostructure to realize various micro- or nanophotonic devices by dry etching processes. We discuss the dry etching process for a GaAs/AlGaAs-based epi-wafer using a resist mask to fabricate a proposed PhC laser. The epi-wafer has multiple stacked layers of InAs quantum dots (QDs) with a high density of 6 × 1010 cm‑2, which cause the reduction of the diameter of the etched air holes. A higher density and more stacked layers of QDs intensify the reduction effect. By enhancing the physical etching effect, the verticality of the profile of the air holes etched in the epi-wafer with a five stacked InAs QD layers is greatly improved. The results show that the improved etching conditions make it feasible to fabricate the proposed PhC laser structure.

  7. CdTe/Zn(Mg)(Se)Te quantum dots for single photon emitters grown by MBE

    Science.gov (United States)

    Sorokin, S. V.; Sedova, I. V.; Gronin, S. V.; Klimko, G. V.; Belyaev, K. G.; Rakhlin, M. V.; Mukhin, I. S.; Toropov, A. A.; Ivanov, S. V.

    2017-11-01

    We report on pseudomorphic MBE growth of CdTe/Zn(Mg)(Se)Te quantum dot (QD) structures on InAs(100) substrates and studies of their structural and optical properties. The QDs were fabricated by using a thermal activation technique comprising deposition of a strained CdTe 2D layer, covering it with amorphous Te, followed by fast thermal desorption of the Te layer, which results in a 2D-3D RHEED pattern transition. The QDs exhibit the surface density as low as 1010 cm-2. The influence of MBE growth parameters and the structure design on photoluminescence properties of the QDs are discussed. Single QD photoluminescence was observed at T=8 K from the 200-nm-wide mesa-structures made of the CdTe QD structures, and the antibunching effect with g(2)(0)=0.16±0.04 was demonstrated. The peculiarities of MBE growth of ZnTe/MgTe/MgSe short-period superlattices nearly lattice-matched to InAs, which could serve as wide gap barriers for efficient electron and hole confinement in the CdTe/Zn(Mg)(Se)Te QDs, are also described.

  8. An elementary quantum network of single atoms in optical cavities.

    Science.gov (United States)

    Ritter, Stephan; Nölleke, Christian; Hahn, Carolin; Reiserer, Andreas; Neuzner, Andreas; Uphoff, Manuel; Mücke, Martin; Figueroa, Eden; Bochmann, Joerg; Rempe, Gerhard

    2012-04-11

    Quantum networks are distributed quantum many-body systems with tailored topology and controlled information exchange. They are the backbone of distributed quantum computing architectures and quantum communication. Here we present a prototype of such a quantum network based on single atoms embedded in optical cavities. We show that atom-cavity systems form universal nodes capable of sending, receiving, storing and releasing photonic quantum information. Quantum connectivity between nodes is achieved in the conceptually most fundamental way-by the coherent exchange of a single photon. We demonstrate the faithful transfer of an atomic quantum state and the creation of entanglement between two identical nodes in separate laboratories. The non-local state that is created is manipulated by local quantum bit (qubit) rotation. This efficient cavity-based approach to quantum networking is particularly promising because it offers a clear perspective for scalability, thus paving the way towards large-scale quantum networks and their applications.

  9. Ultrafast downconversion quantum interface for a single quantum dot spin and 1550-nm single-photon channel

    Science.gov (United States)

    Yu, L.; Pelc, J. S.; de Greve, K.; McMahon, P. L.; Fejer, M. M.; Yamamoto, Y.; Maier, S.; Schneider, C.; Kamp, M.; Hofling, S.; Forchel, A.; Natarajan, C. M.; Hadfield, R. H.

    2013-03-01

    Long-distance quantum communication networks require appropriate interfaces between matter qubit-based nodes and low-loss photonic quantum channels. Quantum frequency conversion (QFC), whereby a photonic qubit's carrier frequency is translated while maintaining its quantum state, is well-suited to the task. Quantum dots have been studied extensively as potential quantum network nodes, but they do not emit indistinguishable single photons at telecomm wavelengths. We report an ultrafast, low-noise downconversion quantum interface, in which 910-nm single photons from a quantum dot are downconverted to the 1.5- μm lowest-loss telecom band, showing near-perfect preservation of antibunched photon statistics. Moreover, the resulting time resolution could also improve photon indistinguishability. Together with the III-V semiconductor quantum dot spin system, this ultrafast downconversion quantum interface provides new possibility to realize long-distance quantum communication networks.

  10. Opto-electronics on Single Nanowire Quantum Dots

    NARCIS (Netherlands)

    Van Kouwen, M.P.

    2010-01-01

    An important goal for nanoscale opto-electronics is the transfer of single electron spin states into single photon polarization states (and vice versa), thereby interfacing quantum transport and quantum optics. Such an interface enables new experiments in the field of quantum information processing.

  11. Experimental quantum tossing of a single coin

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, A T [Service OPERA photonique, CP 194/5, Universite Libre de Bruxelles (ULB), Avenue F D Roosevelt 50, B-1050 Bruxelles (Belgium); Frison, J; Massar, S [Laboratoire dInformation Quantique, CP 225, Universite Libre de Bruxelles (ULB), Boulevard du Triomphe, B-1050 Bruxelles (Belgium); Huy, K Phan [Departement dOptique P M Duffieux, Institut FEMTO-ST, Centre National de la Recherche Scientifique UMR 6174, Universite de Franche-Comte, 25030 Besancon (France)], E-mail: annguyen@ulb.ac.be, E-mail: smassar@ulb.ac.be

    2008-08-15

    The cryptographic protocol of coin tossing consists of two parties, Alice and Bob, who do not trust each other, but want to generate a random bit. If the parties use a classical communication channel and have unlimited computational resources, one of them can always cheat perfectly. If the parties use a quantum communication channel, there exist protocols such that neither party can cheat perfectly, although they may be able to significantly bias the coin. Here, we analyze in detail how the performance of a quantum coin tossing experiment should be compared to classical protocols, taking into account the inevitable experimental imperfections. We then report an all-optical fiber experiment in which a single coin is tossed whose randomness is higher than achievable by any classical protocol and present some easily realizable cheating strategies by Alice and Bob.

  12. Experimental quantum tossing of a single coin

    Science.gov (United States)

    Nguyen, A. T.; Frison, J.; Phan Huy, K.; Massar, S.

    2008-08-01

    The cryptographic protocol of coin tossing consists of two parties, Alice and Bob, who do not trust each other, but want to generate a random bit. If the parties use a classical communication channel and have unlimited computational resources, one of them can always cheat perfectly. If the parties use a quantum communication channel, there exist protocols such that neither party can cheat perfectly, although they may be able to significantly bias the coin. Here, we analyze in detail how the performance of a quantum coin tossing experiment should be compared to classical protocols, taking into account the inevitable experimental imperfections. We then report an all-optical fiber experiment in which a single coin is tossed whose randomness is higher than achievable by any classical protocol and present some easily realizable cheating strategies by Alice and Bob.

  13. Single quantum dots fundamentals, applications, and new concepts

    CERN Document Server

    2003-01-01

    This book reviews recent advances in the exciting and rapid growing field of semiconductor quantum dots by contributions from some of the most prominent researchers in the field. Special focus is given to the optical and electronic properties of single quantum dots due to their potential applications in devices operating with single electrons and/or single photons. This includes quantum dots in electric and magnetic fields, cavity-quantum electrodynamics, nonclassical light generation, and coherent optical control of excitons. Single Quantum Dots also addresses various growth techniques as well as potential device applications such as quantum dot lasers, and new concepts like a single-photon source, and a single quantum dot laser.

  14. Process tomography via sequential measurements on a single quantum system

    CSIR Research Space (South Africa)

    Bassa, H

    2015-09-01

    Full Text Available The authors utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical parameters...

  15. Self-assembled InAs quantum dots. Properties, modification and emission processes; Selbstorganisierte InAs-Quantenpunkte. Eigenschaften, Modifizierung und Emissionsprozesse

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, A.

    2007-09-06

    In this thesis, structural, optical as well as electronic properties of self-assembled InAs quantum dots (QD) were studied by means of atomic force microscopy (AFM), photoluminescence (PL), capacitance spectroscopy (CV) and capacitance transient spectroscopy (DLTS). The quantum dots were grown with molecular beam epitaxy (MBE) and embedded in Schottky diodes for electrical characterization. In this work growth aspects as well as the electronic structures of QD were discussed. By varying the QD growth parameters it is possible to control the structural, and thus the optical and electronic properties of QD. Two methods are presented. Adjusting the QD growth temperature leads either to small QD with a high areal density or to high QDs with a low density. The structural changes of the QD are reflected in the changes of the optical and electronic properties. The second method is to introduce a growth interruption after capping the QD with thin cap layers. It was shown that capping with AlAs leads to a well-developed alternative to control the QD height and thus the ground-state energies of the QD. A post-growth method modifying the QD properties ist rapid thermal annealing (RTA). Raising the RTA temperature causes a lifting of the QD energy states with respect to the GaAs band edge energy due to In/Ga intermixing processes. A further main part of this work covers the emission processes of charge carriers in QD. Thermal emission, thermally assisted tunneling, and pure tunneling emission are studied by capacitance transient spectroscopy techniques. In DLTS experiments a strong impact of the electric field on the activation energies of electrons was found interfering the correct determination of the QD level energies. This behaviour can be explained by a thermally assisted tunneling model. A modified model taking the Coulomb interaction of occupied QD into account describes the emission rates of the electrons. In order to avoid several emission pathes in the experiments

  16. Mixed biexcitons in single quantum wells

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Langbein, Wolfgang Werner; Hvam, Jørn Märcher

    1999-01-01

    Biexcitonic complexes in a ZnSe single quantum well are investigated by spectrally resolved four-wave mixing (FWM). The formation of heavy-heavy-hole XXh and of mixed heavy-light-hole XXm biexcitons showing binding energies of Delta(h) = 4.8 meV and Delta(m)= 2.8 meV is identified by polarization...... selection rules. The coherent dynamics of the FWM response and the observed FWM intensity ratio between the XXh and XXm biexciton-induced nonlinear signals are in agreement with the solution of an extended optical Bloch equation....

  17. Electron transport in InAs nanowires and heterostructure nanowire devices

    Science.gov (United States)

    Thelander, C.; Björk, M. T.; Larsson, M. W.; Hansen, A. E.; Wallenberg, L. R.; Samuelson, L.

    2004-09-01

    Nanowires in the InAs/InP material system are grown with catalyst-assisted chemical beam epitaxy. Ohmic contacts are then fabricated to selected wires, allowing electron transport measurements to be carried out at room-temperature as well as at low T. InAs nanowires show strong quantum confinement effects, where thin wires (Heterostructure barriers of InP are also incorporated into InAs wires to produce resonant tunneling diodes and single-electron transistors (SETs) with different dot lengths. Wires containing dots with a length of 100 nm function as ideal SETs, whereas the transport in wires with 15 nm long dots is strongly governed by quantum confinement and resonant tunneling. For the smaller dots it is possible to observe electron transport through excited states.

  18. Coherent photocurrent spectroscopy of single InP-based quantum dots in the telecom band at 1.5 µm

    Science.gov (United States)

    Gordon, S.; Yacob, M.; Reithmaier, J. P.; Benyoucef, M.; Zrenner, A.

    2016-02-01

    In this work we study the resonant and coherent properties of single InP-based InAs quantum dots, which show an optical emission in the telecom C-band and L-band. High-resolution resonant photocurrent spectroscopy on p-i-n devices reveals narrow linewidths and fully resolved fine structure splittings. We observe Lorentzian line shapes, which allow for the extraction of dephasing times as a function of the applied bias voltage. Coherent ps laser excitation results in pronounced Rabi rotations with increasing pulse area. For π-pulse excitation, we obtain more than 93 % of the theoretically expected photocurrent amplitude. Our results also demonstrate that such state-of-the-art InP-based quantum dots for the telecom band exhibit promising key parameters comparable to well-established InAs/GaAs counterparts.

  19. Quantum key distribution in single-photon communication system

    Science.gov (United States)

    Tretyakov, D. B.; Kolyako, A. V.; Pleshkov, A. S.; Entin, V. M.; Ryabtsev, I. I.; Neizvestny, I. G.

    2016-09-01

    This paper presents a brief review of experimental studies in quantum cryptography and quantum key distribution by single photons in atmospheric and fiber-optic quantum communication channels. Two experimental setups for quantum key distribution developed at the Rzhanov Institute of Semiconductor Physics SB RAS are described. The dependence of the quantum key distribution rate on the average number of photons μ in the laser pulse was studied. For μ > 0.3, there is a discrepancy between theory and experiment. The reasons for this are, first, the nonzero probability of multiphoton pulses occurring in quantum transmission and counted as single photons by single-photon detectors and, second, the rejection of the cases where several single-photon detectors click simultaneously in quantum key sifting because the measurement result is not determined in these cases.

  20. Quantum private comparison employing single-photon interference

    Science.gov (United States)

    Liu, Bin; Xiao, Di; Huang, Wei; Jia, Heng-Yue; Song, Ting-Ting

    2017-07-01

    As a typical quantum cryptographic task between distrustful participants, quantum private comparison (QPC) has attracted a lot of attention in recent years. Here we propose two QPC protocols employing single-photon interference, a typical and interesting technology for quantum communications. Compared with the previous QPC protocols employing normal single states or entangled states, the proposed protocols achieve lower communication complexity utilizing the characteristics of single-photon interference. And we also proved the security of the proposed protocols in theory.

  1. Universal quantum gates for Single Cooper Pair Box based quantum computing

    Science.gov (United States)

    Echternach, P.; Williams, C. P.; Dultz, S. C.; Braunstein, S.; Dowling, J. P.

    2000-01-01

    We describe a method for achieving arbitrary 1-qubit gates and controlled-NOT gates within the context of the Single Cooper Pair Box (SCB) approach to quantum computing. Such gates are sufficient to support universal quantum computation.

  2. Spectroscopy of size dependent many-particle effects in single self-assembled semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Dal Savio, C.

    2006-02-20

    Single InAs quantum dots (QDs) grown with the Stranski-Krastanov method in a In{sub 0.12}Ga{sub 0.88}As quantum well embedded in GaAs and emitting in the near infrared have been optically investigated. To perform QD spectroscopy at low temperatures a very stable micro-photoluminescence ({mu}-PL) microscope set-up fully integrated in a liquid helium (LHe) cryostate has been successfully developed. The system is based on the cold finger technique and a Fourier Transform (FT) spectrometer combined with a nitrogen cooled Ge detector. Photoluminescence of the QDs was excited non resonantly with a He-Ne laser and single dot spectroscopy was carried out at temperatures below 60 K. The experimental set-up allows mapping of the optical emission by recording spectra for every point of a scan grid. This mapping mode is used to acquire optical images and to locate a particular dot for investigation. Series of measurement on a single QD were normally performed over a long time (from a few days to a week), with the need of daily adjustment in the sub-micrometer range. At low excitation power a single sharp line (E{sub x}) arising from recombination of a single exciton in the dot is observed. Varying the excitation density the spectra become more complex, with appearance of the biexciton emission line (E{sub xx}) on the lower energies side of the E{sub x} line, followed by emission from excitons occupying higher shells in the dot. Measured biexciton binding energies and power dependence are in good agreement with values reported in the literature. The temperature dependence of the optical emission was investigated. The energy shows the characteristic decrease related to the shrinking of the semiconductor band gap, while the linewidth evolution is compatible with broadening due to coupling with acoustic and optical phonons. A statistics of biexciton binding energies over a dozen of dots was acquired and the results compared with single QD spectroscopy data available in the

  3. Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

    Science.gov (United States)

    Wang, Tong; Puchtler, Tim J.; Patra, Saroj K.; Zhu, Tongtong; Ali, Muhammad; Badcock, Tom J.; Ding, Tao; Oliver, Rachel A.; Schulz, Stefan; Taylor, Robert A.

    2017-07-01

    We report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs), achieved by the use of non-polar InGaN without complex device geometry engineering. Here, we present a comprehensive investigation of the polarization properties of these QDs and their origin with statistically significant experimental data and rigorous k·p modeling. The experimental study of 180 individual QDs allows us to compute an average polarization degree of 0.90, with a standard deviation of only 0.08. When coupled with theoretical insights, we show that these QDs are highly insensitive to size differences, shape anisotropies, and material content variations. Furthermore, 91% of the studied QDs exhibit a polarization axis along the crystal [1-100] axis, with the other 9% polarized orthogonal to this direction. These features give non-polar InGaN QDs unique advantages in polarization control over other materials, such as conventional polar nitride, InAs, or CdSe QDs. Hence, the ability to generate single photons with polarization control makes non-polar InGaN QDs highly attractive for quantum cryptography protocols.

  4. Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

    Directory of Open Access Journals (Sweden)

    Wang Tong

    2017-07-01

    Full Text Available We report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs, achieved by the use of non-polar InGaN without complex device geometry engineering. Here, we present a comprehensive investigation of the polarization properties of these QDs and their origin with statistically significant experimental data and rigorous k·p modeling. The experimental study of 180 individual QDs allows us to compute an average polarization degree of 0.90, with a standard deviation of only 0.08. When coupled with theoretical insights, we show that these QDs are highly insensitive to size differences, shape anisotropies, and material content variations. Furthermore, 91% of the studied QDs exhibit a polarization axis along the crystal [1–100] axis, with the other 9% polarized orthogonal to this direction. These features give non-polar InGaN QDs unique advantages in polarization control over other materials, such as conventional polar nitride, InAs, or CdSe QDs. Hence, the ability to generate single photons with polarization control makes non-polar InGaN QDs highly attractive for quantum cryptography protocols.

  5. Identification of single-input-single-output quantum linear systems

    Science.gov (United States)

    Levitt, Matthew; GuÅ£ǎ, Mǎdǎlin

    2017-03-01

    The purpose of this paper is to investigate system identification for single-input-single-output general (active or passive) quantum linear systems. For a given input we address the following questions: (1) Which parameters can be identified by measuring the output? (2) How can we construct a system realization from sufficient input-output data? We show that for time-dependent inputs, the systems which cannot be distinguished are related by symplectic transformations acting on the space of system modes. This complements a previous result of Guţă and Yamamoto [IEEE Trans. Autom. Control 61, 921 (2016), 10.1109/TAC.2015.2448491] for passive linear systems. In the regime of stationary quantum noise input, the output is completely determined by the power spectrum. We define the notion of global minimality for a given power spectrum, and characterize globally minimal systems as those with a fully mixed stationary state. We show that in the case of systems with a cascade realization, the power spectrum completely fixes the transfer function, so the system can be identified up to a symplectic transformation. We give a method for constructing a globally minimal subsystem direct from the power spectrum. Restricting to passive systems the analysis simplifies so that identifiability may be completely understood from the eigenvalues of a particular system matrix.

  6. Determining the quantum expectation value by measuring a single photon

    Science.gov (United States)

    Piacentini, Fabrizio; Avella, Alessio; Rebufello, Enrico; Lussana, Rudi; Villa, Federica; Tosi, Alberto; Gramegna, Marco; Brida, Giorgio; Cohen, Eliahu; Vaidman, Lev; Degiovanni, Ivo P.; Genovese, Marco

    2017-12-01

    One description provides only probabilities for obtaining various eigenvalues of a quantum variable. The eigenvalues and the corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property of an ensemble of quantum systems. In contrast to this paradigm, here we demonstrate a method for measuring the expectation value of a physical variable on a single particle, namely, the polarization of a single protected photon. This realization of quantum protective measurements could find applications in the foundations of quantum mechanics and quantum-enhanced measurements.

  7. Operating Quantum States in Single Magnetic Molecules: Implementation of Grover's Quantum Algorithm.

    Science.gov (United States)

    Godfrin, C; Ferhat, A; Ballou, R; Klyatskaya, S; Ruben, M; Wernsdorfer, W; Balestro, F

    2017-11-03

    Quantum algorithms use the principles of quantum mechanics, such as, for example, quantum superposition, in order to solve particular problems outperforming standard computation. They are developed for cryptography, searching, optimization, simulation, and solving large systems of linear equations. Here, we implement Grover's quantum algorithm, proposed to find an element in an unsorted list, using a single nuclear 3/2 spin carried by a Tb ion sitting in a single molecular magnet transistor. The coherent manipulation of this multilevel quantum system (qudit) is achieved by means of electric fields only. Grover's search algorithm is implemented by constructing a quantum database via a multilevel Hadamard gate. The Grover sequence then allows us to select each state. The presented method is of universal character and can be implemented in any multilevel quantum system with nonequal spaced energy levels, opening the way to novel quantum search algorithms.

  8. Operating Quantum States in Single Magnetic Molecules: Implementation of Grover's Quantum Algorithm

    Science.gov (United States)

    Godfrin, C.; Ferhat, A.; Ballou, R.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W.; Balestro, F.

    2017-11-01

    Quantum algorithms use the principles of quantum mechanics, such as, for example, quantum superposition, in order to solve particular problems outperforming standard computation. They are developed for cryptography, searching, optimization, simulation, and solving large systems of linear equations. Here, we implement Grover's quantum algorithm, proposed to find an element in an unsorted list, using a single nuclear 3 /2 spin carried by a Tb ion sitting in a single molecular magnet transistor. The coherent manipulation of this multilevel quantum system (qudit) is achieved by means of electric fields only. Grover's search algorithm is implemented by constructing a quantum database via a multilevel Hadamard gate. The Grover sequence then allows us to select each state. The presented method is of universal character and can be implemented in any multilevel quantum system with nonequal spaced energy levels, opening the way to novel quantum search algorithms.

  9. Conversion from Single Photon to Single Electron Spin Using Electrically Controllable Quantum Dots

    Science.gov (United States)

    Oiwa, Akira; Fujita, Takafumi; Kiyama, Haruki; Allison, Giles; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo

    2017-01-01

    Polarization is a fundamental property of light and could provide various solutions to the development of secure optical communications with high capacity and high speed. In particular, the coherent quantum state conversion between single photons and single electron spins is a prerequisite for long-distance quantum communications and distributed quantum computation. Electrically defined quantum dots have already been proven to be suitable for scalable solid state qubits by demonstrations of single-spin coherent manipulations and two-qubit gate operations. Thus, their capacity for quantum information technologies would be considerably extended by the achievement of entanglement between an electron spin in the quantum dots and a photon. In this review paper, we show the basic technologies for trapping single electrons generated by single photons in quantum dots and for detecting their spins using the Pauli effect with sensitive charge sensors.

  10. Resource-optimal single-qubit quantum circuits.

    Science.gov (United States)

    Bocharov, Alex; Svore, Krysta M

    2012-11-09

    Determining the optimal implementation of a quantum gate is critical for designing a quantum computer. We consider the crucial task of efficiently decomposing a general single-qubit quantum gate into a sequence of fault-tolerant quantum operations. For a given single-qubit circuit, we construct an optimal gate sequence consisting of fault-tolerant Hadamard (H) and π/8 rotations (T). Our scheme is based on a novel canonical form for single-qubit quantum circuits and the corresponding rules for exactly reducing a general single-qubit circuit to our canonical form. The result is optimal in the number of T gates. We demonstrate that a precomputed epsilon net of canonical circuits in combination with our scheme lowers the depth of approximation circuits by up to 3 orders of magnitude compared to previously reported results.

  11. Coupling of single quantum dots to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian

    is coupled efficiently to a single enhanced mode. One popular approach has been to couple single quantum dots to a nanocavity but a limiting factor in this configuration is that in order to apply the photon it should subsequently be coupled out of the cavity, reducing the overall efficiency significantly....... An alternative approach is to couple the quantum dot directly to the propagating mode of a photonic waveguide. We demonstrate the coupling of single quantum dots to a photonic crystal waveguide using time-resolved spontaneous emission measurements. A pronounced effect is seen in the decay rates of dots coupled......Efficient and high quality single-photon sources is a key element in quantum information processing using photons. As a consequence, much current research is focused on realizing all-solid-state nanophotonic single-photon sources. Single photons can be harvested with high efficiency if the emitter...

  12. Recording force events of single quantum-dot endocytosis.

    Science.gov (United States)

    Shan, Yuping; Hao, Xian; Shang, Xin; Cai, Mingjun; Jiang, Junguang; Tang, Zhiyong; Wang, Hongda

    2011-03-28

    We applied force spectroscopy based on atomic force microscope (AFM) to demonstrate the possibility of measuring the interaction force between single quantum-dots (QDs) and living cells at single particle level under native conditions. In the force-distance cycle, we recorded the events of cellular uptake of single QDs and single QD detachment from the cell.

  13. Single-photon superradiance from a quantum dot

    DEFF Research Database (Denmark)

    Tighineanu, Petru; Daveau, Raphaël Sura; Lehmann, Tau Bernstorff

    2016-01-01

    and the hole comprising the exciton gives rise to an anharmonic spectrum, which we exploit to prepare the superradiant quantum state deterministically with a laser pulse. We observe a fivefold enhancement of the oscillator strength compared to conventional quantum dots. The enhancement is limited by the base...... temperature of our cryostat and may lead to oscillator strengths above 1000 from a single quantum emitter at optical frequencies....

  14. From single SQUID to superconducting quantum arrays

    Science.gov (United States)

    Kornev, V. K.; Kolotinskiy, N. V.; Sharafiev, A. V.; Soloviev, I. I.; Mukhanov, O. A.

    2017-07-01

    Superconducting quantum arrays (SQAs) capable of providing highly linear voltage response to magnetic signal and high dynamic range have been suggested and developed. Base elements of the arrays, quantum cells, were devised and studied in detail. Using niobium process, SQAs with different number of the cells and prototypes of the SQA-based broadband active electrically small antennas were fabricated and tested.

  15. Suppression of thermal carrier escape and efficient photo-carrier generation by two-step photon absorption in InAs quantum dot intermediate-band solar cells using a dot-in-well structure

    Energy Technology Data Exchange (ETDEWEB)

    Asahi, S.; Teranishi, H.; Kasamatsu, N.; Kada, T.; Kaizu, T.; Kita, T. [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

    2014-08-14

    We investigated the effects of an increase in the barrier height on the enhancement of the efficiency of two-step photo-excitation in InAs quantum dot (QD) solar cells with a dot-in-well structure. Thermal carrier escape of electrons pumped in QD states was drastically reduced by sandwiching InAs/GaAs QDs with a high potential barrier of Al{sub 0.3}Ga{sub 0.7}As. The thermal activation energy increased with the introduction of the barrier. The high potential barrier caused suppression of thermal carrier escape and helped realize a high electron density in the QD states. We observed efficient two-step photon absorption as a result of the high occupancy of the QD states at room temperature.

  16. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot

    DEFF Research Database (Denmark)

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal

    2016-01-01

    We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offe...

  17. Quantum dots with single-atom precision.

    Science.gov (United States)

    Fölsch, Stefan; Martínez-Blanco, Jesús; Yang, Jianshu; Kanisawa, Kiyoshi; Erwin, Steven C

    2014-07-01

    Quantum dots are often called artificial atoms because, like real atoms, they confine electrons to quantized states with discrete energies. However, although real atoms are identical, most quantum dots comprise hundreds or thousands of atoms, with inevitable variations in size and shape and, consequently, unavoidable variability in their wavefunctions and energies. Electrostatic gates can be used to mitigate these variations by adjusting the electron energy levels, but the more ambitious goal of creating quantum dots with intrinsically digital fidelity by eliminating statistical variations in their size, shape and arrangement remains elusive. We used a scanning tunnelling microscope to create quantum dots with identical, deterministic sizes. By using the lattice of a reconstructed semiconductor surface to fix the position of each atom, we controlled the shape and location of the dots with effectively zero error. This allowed us to construct quantum dot molecules whose coupling has no intrinsic variation but could nonetheless be tuned with arbitrary precision over a wide range. Digital fidelity opens the door to quantum dot architectures free of intrinsic broadening-an important goal for technologies from nanophotonics to quantum information processing as well as for fundamental studies of confined electrons.

  18. Visible-to-telecom quantum frequency conversion of light from a single quantum emitter.

    Science.gov (United States)

    Zaske, Sebastian; Lenhard, Andreas; Keßler, Christian A; Kettler, Jan; Hepp, Christian; Arend, Carsten; Albrecht, Roland; Schulz, Wolfgang-Michael; Jetter, Michael; Michler, Peter; Becher, Christoph

    2012-10-05

    We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.

  19. High-efficiency commercial grade 1cm2 AlGaInP/GaAs/Ge solar cells with embedded InAs quantum dots for concentrator demonstration system

    Science.gov (United States)

    Wheeldon, J. F.; Valdivia, C. E.; Masson, D.; Proulx, F.; Riel, B.; Puetz, N.; Desfonds, E.; Fafard, S.; Rioux, B.; SpringThorpe, A. J.; Arès, R.; Aimez, V.; Armstrong, M.; Swinton, M.; Cook, J.; Shepherd, F.; Hall, T. J.; Hinzer, K.

    2010-06-01

    Triple-junction AlGaInP/InGaAs/Ge solar cells with embedded InAs quantum dots are presented, where typical samples obtain efficiencies of > 40% under AM1.5D illumination, over a range of concentrations of 2- to 800-suns (2 kW/m2 to 800 kW/m2). Quantum efficiency measurements show that the embedded quantum dots improve the absorption of the middle subcell in the wavelength range of 900-940 nm, which in turn increases the overall operating current of the solar cell. These results are obtained with 1 cm2 solar cells, and they demonstrate the solar cells' low series resistance, which and makes them ideal for the current generation in commercial concentrator systems. The thermal management and reliability of the solar cell and carrier is demonstrated by testing the experimental samples under flash (up to 1000-suns) solar simulator and continuous (up to 800-suns) solar simulator. Under continuous solar illumination, the solar cell temperature varies between ~Δ3°C at 260-suns linearly to ~Δ33°C at 784-suns when the solar cell is mounted with thermal paste, and ~Δ27°C at 264-suns linearly to ~Δ91°C at 785-suns when no thermal paste is used. The solar cells experience the expected shift in open circuit voltage and efficiency due to temperature, but otherwise operate normally for extended periods of time.

  20. Photoluminescence studies of single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1999-01-01

    Semiconductor quantum dots are considered a promising material system for future optical devices and quantum computers. We have studied the low-temperature photoluminescence properties of single InGaAs quantum dots embedded in GaAs. The high spatial resolution required for resolving single dots...... is obtained by exciting and detecting the photoluminescence through a microscope objective which is located inside the cryostat. Furthermore, e-beam lithography and mesa etching have been used to reduce the size of the detection area to a few hundred nanometers in diameter. These techniques allow us...

  1. Single and Multi-channel Quantum Dragons from Rectangular Nanotubes

    Science.gov (United States)

    Li, Zhou; Novotny, Mark

    2015-03-01

    Recently quantum dragons have been discovered theoretically. Quantum dragons are nanostructures with correlated disorder that permit energy-independent total quantum transmission of electrons. Hence the electrical conductance G in a two-terminal measurement should be the conductance quantum G0 = 2e2 / h . The single-band tight banding model is used. An example of a single-channel quantum dragon is a rectangular nanotube with disorder along the direction z of the electron propagation. Quantum dragons are obtained by solving the time-independent Schrödinger equation to obtain the electrical transmission calT as a function of the incoming electron energy E. A quantum dragon has calT (E) =1 for all energies. This work generalizes the solution of the time-independent Schrödinger equation to the case of more than one open channel, and applies the method to nanotubes formed from rectangular lattices. One can envision such single-walled rectangular nanotubes for iron starting from free-standing single-atom-thick Fe membranes which have recently been obtained experimentally. Supported in part by NSF Grant DMR-1206233.

  2. Linear optical quantum computing in a single spatial mode.

    Science.gov (United States)

    Humphreys, Peter C; Metcalf, Benjamin J; Spring, Justin B; Moore, Merritt; Jin, Xian-Min; Barbieri, Marco; Kolthammer, W Steven; Walmsley, Ian A

    2013-10-11

    We present a scheme for linear optical quantum computing using time-bin-encoded qubits in a single spatial mode. We show methods for single-qubit operations and heralded controlled-phase (cphase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn [Nature (London) 409, 46 (2001)] scheme. Our protocol is suited to currently available photonic devices and ideally allows arbitrary numbers of qubits to be encoded in the same spatial mode, demonstrating the potential for time-frequency modes to dramatically increase the quantum information capacity of fixed spatial resources. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84±0.07.

  3. Two-Way Communication with a Single Quantum Particle

    Science.gov (United States)

    Del Santo, Flavio; Dakić, Borivoje

    2018-02-01

    In this Letter we show that communication when restricted to a single information carrier (i.e., single particle) and finite speed of propagation is fundamentally limited for classical systems. On the other hand, quantum systems can surpass this limitation. We show that communication bounded to the exchange of a single quantum particle (in superposition of different spatial locations) can result in "two-way signaling," which is impossible in classical physics. We quantify the discrepancy between classical and quantum scenarios by the probability of winning a game played by distant players. We generalize our result to an arbitrary number of parties and we show that the probability of success is asymptotically decreasing to zero as the number of parties grows, for all classical strategies. In contrast, quantum strategy allows players to win the game with certainty.

  4. Tuning Single Quantum Dot Emission with a Micromirror.

    Science.gov (United States)

    Yuan, Gangcheng; Gómez, Daniel; Kirkwood, Nicholas; Mulvaney, Paul

    2018-01-11

    The photoluminescence of single quantum dots fluctuates between bright (on) and dark (off) states, also termed fluorescence intermittency or blinking. This blinking limits the performance of quantum dot-based devices such as light-emitting diodes and solar cells. However, the origins of the blinking remain unresolved. Here, we use a movable gold micromirror to determine both the quantum yield of the bright state and the orientation of the excited state dipole of single quantum dots. We observe that the quantum yield of the bright state is close to unity for these single QDs. Furthermore, we also study the effect of a micromirror on blinking, and then evaluate excitation efficiency, biexciton quantum yield, and detection efficiency. The mirror does not modify the off-time statistics, but it does change the density of optical states available to the quantum dot and hence the on times. The duration of the on times can be lengthened due to an increase in the radiative recombination rate.

  5. Fast Purcell-enhanced single photon source in 1,550-nm telecom band from a resonant quantum dot-cavity coupling.

    Science.gov (United States)

    Birowosuto, Muhammad Danang; Sumikura, Hisashi; Matsuo, Shinji; Taniyama, Hideaki; van Veldhoven, Peter J; Nötzel, Richard; Notomi, Masaya

    2012-01-01

    High-bit-rate nanocavity-based single photon sources in the 1,550-nm telecom band are challenges facing the development of fibre-based long-haul quantum communication networks. Here we report a very fast single photon source in the 1,550-nm telecom band, which is achieved by a large Purcell enhancement that results from the coupling of a single InAs quantum dot and an InP photonic crystal nanocavity. At a resonance, the spontaneous emission rate was enhanced by a factor of 5 resulting a record fast emission lifetime of 0.2 ns at 1,550 nm. We also demonstrate that this emission exhibits an enhanced anti-bunching dip. This is the first realization of nanocavity-enhanced single photon emitters in the 1,550-nm telecom band. This coupled quantum dot cavity system in the telecom band thus provides a bright high-bit-rate non-classical single photon source that offers appealing novel opportunities for the development of a long-haul quantum telecommunication system via optical fibres.

  6. Effect of Sb and As spray on emission characteristics of InAs quantum dots with AlAs capping layer

    Science.gov (United States)

    Zhang, Z.; Tan, S.; Kim, Y.; Liu, Z.; Reece, P. J.; Bremner, S. P.

    2017-10-01

    We report on the influence of an Sb/As combined spray on the physical and optical characteristics of AlAs-capped InAs/GaAs quantum dots grown by Molecular Beam Epitaxy. Photoluminescence emission from the quantum dots shows a significant peak position shift under different Sb/As spray sequences. A blue-shifted quantum dot emission peak with an initial Sb rest indicates a large-to-small quantum dots transition process, with a bi-modal quantum dot size distribution inferred. High-resolution Transmission Electron Microscopy results reveal a large density of small quantum dots when the Sb spray is treated first. Furthermore, defect passivation in the vicinity of the quantum dots by use of Sb spray was detected.

  7. Efficient quantum private comparison employing single photons and collective detection

    Science.gov (United States)

    Liu, Bin; Gao, Fei; Jia, Heng-yue; Huang, Wei; Zhang, Wei-wei; Wen, Qiao-yan

    2013-02-01

    Two efficient quantum private comparison (QPC) protocols are proposed, employing single photons and collective detection. In the proposed protocols, two distrustful parties (Alice and Bob) compare the equivalence of information with the help of a semi-honest third party (TP). Utilizing collective detection, the cost of practical realization is reduced greatly. In the first protocol, TP gains the result of the comparison. While in the second protocol, TP cannot get the comparison result. In both of our protocols, Alice and Bob only need be equipped with unitary operation machines, such as phase plates. So Alice and Bob need not to have the expensive quantum devices, such as qubit generating machine, quantum memory machine and quantum measuring machine. Security of the protocols is ensured by theorems on quantum operation discrimination.

  8. Quantum non-Gaussian Depth of Single-Photon States.

    Science.gov (United States)

    Straka, Ivo; Predojević, Ana; Huber, Tobias; Lachman, Lukáš; Butschek, Lorenz; Miková, Martina; Mičuda, Michal; Solomon, Glenn S; Weihs, Gregor; Ježek, Miroslav; Filip, Radim

    2014-11-28

    We introduce and experimentally explore the concept of the non-Gaussian depth of single-photon states with a positive Wigner function. The depth measures the robustness of a single-photon state against optical losses. The directly witnessed quantum non-Gaussianity withstands significant attenuation, exhibiting a depth of 18 dB, while the nonclassicality remains unchanged. Quantum non-Gaussian depth is an experimentally approachable quantity that is much more robust than the negativity of the Wigner function. Furthermore, we use it to reveal significant differences between otherwise strongly nonclassical single-photon sources.

  9. Single Channel Quantum Color Image Encryption Algorithm Based on HSI Model and Quantum Fourier Transform

    Science.gov (United States)

    Gong, Li-Hua; He, Xiang-Tao; Tan, Ru-Chao; Zhou, Zhi-Hong

    2017-09-01

    In order to obtain high-quality color images, it is important to keep the hue component unchanged while emphasize the intensity or saturation component. As a public color model, Hue-Saturation Intensity (HSI) model is commonly used in image processing. A new single channel quantum color image encryption algorithm based on HSI model and quantum Fourier transform (QFT) is investigated, where the color components of the original color image are converted to HSI and the logistic map is employed to diffuse the relationship of pixels in color components. Subsequently, quantum Fourier transform is exploited to fulfill the encryption. The cipher-text is a combination of a gray image and a phase matrix. Simulations and theoretical analyses demonstrate that the proposed single channel quantum color image encryption scheme based on the HSI model and quantum Fourier transform is secure and effective.

  10. Room temperature excitation spectroscopy of single quantum dots

    Directory of Open Access Journals (Sweden)

    Christian Blum

    2011-08-01

    Full Text Available We report a single molecule detection scheme to investigate excitation spectra of single emitters at room temperature. We demonstrate the potential of single emitter photoluminescence excitation spectroscopy by recording excitation spectra of single CdSe nanocrystals over a wide spectral range of 100 nm. The spectra exhibit emission intermittency, characteristic of single emitters. We observe large variations in the spectra close to the band edge, which represent the individual heterogeneity of the observed quantum dots. We also find specific excitation wavelengths for which the single quantum dots analyzed show an increased propensity for a transition to a long-lived dark state. We expect that the additional capability of recording excitation spectra at room temperature from single emitters will enable insights into the photophysics of emitters that so far have remained inaccessible.

  11. A nanoscale quantum interface for single atoms

    Science.gov (United States)

    Tiecke, Tobias; Thompson, Jeff; Feist, Johannes; Yu, Chun; Akimov, Alexey; Chang, Darrick; Zibrov, Alexander; Vuletic, Vladan; Park, Hongkun; Lukin, Mikhail

    2012-02-01

    Neutral atoms are ideal quantum systems: they have long ground-state coherence times and strong optical cycling transitions that enable state detection and preparation. Building quantum networks of atoms interacting through photons is challenging, however, as many schemes for atom-photon interaction are inefficient or hard to scale. We propose a scheme to trap neutral atoms near silver nanowires, which are tightly confining waveguides for surface plasmons. The nanowire tip is used to generate a near-field optical trapping potential, and to enhance and efficiently collect spontaneous emission from the atom. We present experimental results on using the atom to sense the optical field at submicron distances from the wire and our current efforts towards loading the nanotrap.

  12. Strong single-photon coupling in superconducting quantum magnetomechanics.

    Science.gov (United States)

    Via, Guillem; Kirchmair, Gerhard; Romero-Isart, Oriol

    2015-04-10

    We show that the inductive coupling between the quantum mechanical motion of a superconducting microcantilever and a flux-dependent microwave quantum circuit can attain the strong single-photon nanomechanical coupling regime with feasible experimental parameters. We propose to use a superconducting strip, which is in the Meissner state, at the tip of a cantilever. A pickup coil collects the flux generated by the sheet currents induced by an external quadrupole magnetic field centered at the strip location. The position-dependent magnetic response of the superconducting strip, enhanced by both diamagnetism and demagnetizing effects, leads to a strong magnetomechanical coupling to quantum circuits.

  13. Single-temperature quantum engine without feedback control

    Science.gov (United States)

    Yi, Juyeon; Talkner, Peter; Kim, Yong Woon

    2017-08-01

    A cyclically working quantum-mechanical engine that operates at a single temperature is proposed. Its energy input is delivered by a quantum measurement. The functioning of the engine does not require any feedback control. We analyze work, heat, and the efficiency of the engine for the case of a working substance that is governed by the laws of quantum mechanics and that can be adiabatically compressed and expanded. The obtained general expressions are exemplified for a spin in an adiabatically changing magnetic field and a particle moving in a potential with slowly changing shape.

  14. Direct spectroscopic observation of quantum jumps of a single molecule

    Science.gov (United States)

    Basché, Th.; Kummer, S.; Bräuchle, C.

    1995-01-01

    BOHR'S notion of quantum jumps between electronic states of an excited atom has now been demonstrated experimentally for single ions confined in radio-frequency traps and interacting with a driving laser field1-3. In these experiments the fluorescence of a strongly allowed transition was shown to cease abruptly when the ion jumped into a metastable state which was coupled to the common electronic ground state by a weak radiative transition. But attempts to monitor quantum jumps of single molecules have been hampered by the fact that the lifetime of the metastable triplet state was too short in relation to the photon detection rate. By using a system with favourable photophysical parameters-terrylene doped into p-terphenyl crystals4-we have now been able to observe directly quantum jumps between electronic states of single terrylene molecules. In contrast to single atoms, here the quantum jumps occur as non-radiative transitions between states of different multiplicity, and are manifested as interruptions of the fluorescence signal. These results demonstrate how single-molecule spectros-copy can reveal truly quantum-mechanical effects in large polyatomic molecules.

  15. Singly and Doubly Occupied Higher Quantum States in Nanocrystals.

    Science.gov (United States)

    Jeong, Juyeon; Yoon, Bitna; Kwon, Young-Wan; Choi, Dongsun; Jeong, Kwang Seob

    2017-02-08

    Filling the lowest quantum state of the conduction band of colloidal nanocrystals with a single electron, which is analogous to the filling the lowest unoccupied molecular orbital in a molecule with a single electron, has attracted much attention due to the possibility of harnessing the electron spin for potential spin-based applications. The quantized energy levels of the artificial atom, in principle, make it possible for a nanocrystal to be filled with an electron if the Fermi-energy level is optimally tuned during the nanocrystal growth. Here, we report the singly occupied quantum state (SOQS) and doubly occupied quantum state (DOQS) of a colloidal nanocrystal in steady state under ambient conditions. The number of electrons occupying the lowest quantum state can be controlled to be zero, one (unpaired), and two (paired) depending on the nanocrystal growth time via changing the stoichiometry of the nanocrystal. Electron paramagnetic resonance spectroscopy proved the nanocrystals with single electron to show superparamagnetic behavior, which is a direct evidence of the SOQS, whereas the DOQS of the two- or zero-electron occupied nanocrystals in the 1Se exhibit diamagnetic behavior. In combination with the superconducting quantum interference device measurement, it turns out that the SOQS of the HgSe colloidal quantum dots has superparamagnetic property. The appearance and change of the steady-state mid-IR intraband absorption spectrum reflect the sequential occupation of the 1Se state with electrons. The magnetic property of the colloidal quantum dot, initially determined by the chemical synthesis, can be tuned from diamagnetic to superparamagnetic and vice versa by varying the number of electrons through postchemical treatment. The switchable magnetic property will be very useful for further applications such as colloidal nanocrystal based spintronics, nonvolatile memory, infrared optoelectronics, catalyst, imaging, and quantum computing.

  16. Single-cell atomic quantum memory for light

    OpenAIRE

    Opatrny, Tomas

    2005-01-01

    Recent experiments demonstrating atomic quantum memory for light [B. Julsgaard et al., Nature 432, 482 (2004)] involve two macroscopic samples of atoms, each with opposite spin polarization. It is shown here that a single atomic cell is enough for the memory function if the atoms are optically pumped with suitable linearly polarized light, and quadratic Zeeman shift and/or ac Stark shift are used to manipulate rotations of the quadratures. This should enhance the performance of our quantum me...

  17. Identification of Ina proteins from Fusarium acuminatum

    Science.gov (United States)

    Scheel, Jan Frederik; Kunert, Anna Theresa; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

    2015-04-01

    Freezing of water above -36° C is based on ice nucleation activity (INA) mediated by ice nucleators (IN) which can be of various origins. Beside mineral IN, biological particles are a potentially important source of atmospheric IN. The best-known biological IN are common plant-associated bacteria. The IN activity of these bacteria is induced by a surface protein on the outer cell membrane, which is fully characterized. In contrast, much less is known about the nature of fungal IN. The fungal genus Fusarium is widely spread throughout the earth. It belongs to the Ascomycota and is one of the most severe fungal pathogens. It can affect a variety of organisms from plants to animals including humans. INA of Fusarium was already described about 30 years ago and INA of Fusarium as well as other fungal genera is assumed to be mediated by proteins or at least to contain a proteinaceous compound. Although many efforts were made the precise INA machinery of Fusarium and other fungal species including the proteins and their corresponding genes remain unidentified. In this study preparations from living fungal samples of F. acuminatum were fractionated by liquid chromatography and IN active fractions were identified by freezing assays. SDS-page and de novo sequencing by mass spectrometry were used to identify the primary structure of the protein. Preliminary results show that the INA protein of F. acuminatum is contained in the early size exclusion chromatography fractions indicating a high molecular size. Moreover we could identify a single protein band from IN active fractions at 130-145 kDa corresponding to sizes of IN proteins from bacterial species. To our knowledge this is for the first time an isolation of a single protein from in vivo samples, which can be assigned as IN active from Fusarium.

  18. Single Molecule Applications of Quantum Dots

    DEFF Research Database (Denmark)

    Rasmussen, Thomas Elmelund; Jauffred, Liselotte; Brewer, Jonathan R.

    2013-01-01

    for tracking single lipids in lipid bilayers, 4) two-photon fluorescence correlation spectroscopy of QDs and 5) optical trapping and excitation of single QDs. In all of these applications, the focus is on the single particle sensitivity level of QDs. The high applicability of QDs in live cell imaging...

  19. Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin.

    Science.gov (United States)

    He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2017-08-11

    Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796±0.020. Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

  20. Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

    Science.gov (United States)

    He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2017-08-01

    Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

  1. Electrical characterization of InAs thin films

    Energy Technology Data Exchange (ETDEWEB)

    Botha, L.; Shamba, P.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2008-07-01

    It is known that parallel conduction as a result of surface and /or interface charge accumulation significantly shields the bulk electrical properties of InAs thin films when characterized using Hall measurements. This parallel conduction in InAs can be modeled by using the two-layer model of Nedoluha and Koch [Zeitschrift fuer Physik 132, 608 (1952)]; where an InAs epilayer is treated as consisting of two conductors connected in parallel viz. a bulk and a surface layer. Here, this two-layer model is used to simulate Hall coefficient and conductivity data of InAs thin films ranging from strongly n-doped (n=10{sup 18} cm{sup -3}) to strongly p-doped (p{proportional_to}10{sup 19} cm{sup -3}) material. Conventional Hall approximations, i.e. those that assume uniform conduction from a single band, are then used to predict the apparent carrier concentration and mobility that will be determined from conventional Hall measurements, with the aim of illustrating the error of such a simplified analysis of InAs Hall data. Results show that, in addition to ignoring parallel conduction, the approximations of conventional Hall data analysis have a further inadequacy for p-type InAs, in that the high electron to hole mobility ratio in InAs is not taken into account. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Quantum interference induced photon blockade in a coupled single quantum dot-cavity system.

    Science.gov (United States)

    Tang, Jing; Geng, Weidong; Xu, Xiulai

    2015-03-18

    We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay g((2))(0) in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing.

  3. On-demand single-photon sources via quantum blockade and applications in decoy-state quantum key distribution.

    Science.gov (United States)

    Li, Ao; Chen, Tian; Zhou, Yiheng; Wang, Xiangbin

    2016-05-01

    Quantum blockades as a nonlinear quantum optical process have been well studied in recent years. Using the quantum trajectory method, we calculate and discuss the output photon number distributions of a single-photon blockade process in a Kerr nonlinear dissipative resonator, revealing that the probability of the single-photon state can be optimized. Then we show through numerical simulations that such a quasi-single-photon source can drastically raise the key rate in the decoy-state quantum key distribution.

  4. Designing single-qutrit quantum gates via tripod adiabatic passage

    Directory of Open Access Journals (Sweden)

    M. Amniat-Talab

    2014-04-01

    Full Text Available In this paper, we use stimulated Raman adiabatic passage technique to implement single-qutrit quantum gates in tripod systems. It is shown by using the Morris-Shore (MS transformation, the six-state problem with 5 pulsed fields can be reduced to a basis that decouples two states from the others. This imposes three pulses not connected to the initial condition with have the same shape. Using this method, the six-state penta-pod system is reduced to a tripod system. We can design single-qutrit quantum gates by ignoring the fragile dynamical phase, and by suitable design of Rabi frequencies of the effective Hamiltonian

  5. Coupling single emitters to quantum plasmonic circuits

    DEFF Research Database (Denmark)

    Huck, Alexander; Andersen, Ulrik Lund

    2016-01-01

    In recent years, the controlled coupling of single-photon emitters to propagating surface plasmons has been intensely studied, which is fueled by the prospect of a giant photonic nonlinearity on a nanoscaled platform. In this article, we will review the recent progress on coupling single emitters...

  6. A molecular quantum spin network controlled by a single qubit.

    Science.gov (United States)

    Schlipf, Lukas; Oeckinghaus, Thomas; Xu, Kebiao; Dasari, Durga Bhaktavatsala Rao; Zappe, Andrea; de Oliveira, Felipe Fávaro; Kern, Bastian; Azarkh, Mykhailo; Drescher, Malte; Ternes, Markus; Kern, Klaus; Wrachtrup, Jörg; Finkler, Amit

    2017-08-01

    Scalable quantum technologies require an unprecedented combination of precision and complexity for designing stable structures of well-controllable quantum systems on the nanoscale. It is a challenging task to find a suitable elementary building block, of which a quantum network can be comprised in a scalable way. We present the working principle of such a basic unit, engineered using molecular chemistry, whose collective control and readout are executed using a nitrogen vacancy (NV) center in diamond. The basic unit we investigate is a synthetic polyproline with electron spins localized on attached molecular side groups separated by a few nanometers. We demonstrate the collective readout and coherent manipulation of very few (≤ 6) of these S = 1/2 electronic spin systems and access their direct dipolar coupling tensor. Our results show that it is feasible to use spin-labeled peptides as a resource for a molecular qubit-based network, while at the same time providing simple optical readout of single quantum states through NV magnetometry. This work lays the foundation for building arbitrary quantum networks using well-established chemistry methods, which has many applications ranging from mapping distances in single molecules to quantum information processing.

  7. Scalable Quantum Photonics with Single Color Centers in Silicon Carbide.

    Science.gov (United States)

    Radulaski, Marina; Widmann, Matthias; Niethammer, Matthias; Zhang, Jingyuan Linda; Lee, Sang-Yun; Rendler, Torsten; Lagoudakis, Konstantinos G; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Wrachtrup, Jörg; Vučković, Jelena

    2017-03-08

    Silicon carbide is a promising platform for single photon sources, quantum bits (qubits), and nanoscale sensors based on individual color centers. Toward this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1400 nm diameters. We obtain high collection efficiency of up to 22 kcounts/s optical saturation rates from a single silicon vacancy center while preserving the single photon emission and the optically induced electron-spin polarization properties. Our study demonstrates silicon carbide as a readily available platform for scalable quantum photonics architecture relying on single photon sources and qubits.

  8. Scalable Quantum Photonics with Single Color Centers in Silicon Carbide

    Science.gov (United States)

    Radulaski, Marina; Widmann, Matthias; Niethammer, Matthias; Zhang, Jingyuan Linda; Lee, Sang-Yun; Rendler, Torsten; Lagoudakis, Konstantinos G.; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Wrachtrup, Jörg; Vučković, Jelena

    2017-03-01

    Silicon carbide is a promising platform for single photon sources, quantum bits (qubits) and nanoscale sensors based on individual color centers. Towards this goal, we develop a scalable array of nanopillars incorporating single silicon vacancy centers in 4H-SiC, readily available for efficient interfacing with free-space objective and lensed-fibers. A commercially obtained substrate is irradiated with 2 MeV electron beams to create vacancies. Subsequent lithographic process forms 800 nm tall nanopillars with 400-1,400 nm diameters. We obtain high collection efficiency, up to 22 kcounts/s optical saturation rates from a single silicon vacancy center, while preserving the single photon emission and the optically induced electron-spin polarization properties. Our study demonstrates silicon carbide as a readily available platform for scalable quantum photonics architecture relying on single photon sources and qubits.

  9. Quantum non demolition measurement of a single nuclear spin in a room temperature solid

    Energy Technology Data Exchange (ETDEWEB)

    Neumann, Phillip; Beck, Johannes; Steiner, Matthias; Rathgen, Helmut; Rempp, Florian; Zarrabi, Navid; Dolde, Florian; Jelezko, Fedor; Wrachtrup, Joerg [Universitaet Stuttgart (Germany); Hemmer, Philip [A and M University, Texas (United States)

    2010-07-01

    The measurement process and its interpretation are in the focus of quantum mechanics since its early days. Today's ability to isolate single quantum objects allows experimental demonstration of former ''gedankenexperiments'' like measurement induced quantum state collaps. Rapidly growing quantum technologies explore fundamental aspects of measurements in quantum computing, however for solid state systems such experiments require operation at very low temperatures. Here we show that projective quantum measurement can be performed on a single nuclear spin in diamond under ambient conditions. Using quantum non demolition (QND) readout we are able to detect quantum jumps and the quantum Zeno effect emphasising the addressability of fundamental questions of quantum mechanics in solids. Single shot measurements with fidelities exceeding 0.9 enable efficient state initialization, quantum error correction and entanglement pumping that is crucial for quantum information processing including measurement based schemes and distributed quantum networks.

  10. Quantum teleportation via noisy bipartite and tripartite accelerating quantum states: beyond the single mode approximation

    Science.gov (United States)

    Zounia, M.; Shamirzaie, M.; Ashouri, A.

    2017-09-01

    In this paper quantum teleportation of an unknown quantum state via noisy maximally bipartite (Bell) and maximally tripartite (Greenberger-Horne-Zeilinger (GHZ)) entangled states are investigated. We suppose that one of the observers who would receive the sent state accelerates uniformly with respect to the sender. The interactions of the quantum system with its environment during the teleportation process impose noises. These (unital and nonunital) noises are: phase damping, phase flip, amplitude damping and bit flip. In expressing the modes of the Dirac field used as qubits, in the accelerating frame, the so-called single mode approximation is not imposed. We calculate the fidelities of teleportation, and discuss their behaviors using suitable plots. The effects of noise, acceleration and going beyond the single mode approximation are discussed. Although the Bell states bring higher fidelities than GHZ states, the global behaviors of the two quantum systems with respect to some noise types, and therefore their fidelities, are different.

  11. Single-Atom Gating of Quantum State Superpositions

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-04-28

    The ultimate miniaturization of electronic devices will likely require local and coherent control of single electronic wavefunctions. Wavefunctions exist within both physical real space and an abstract state space with a simple geometric interpretation: this state space - or Hilbert space - is spanned by mutually orthogonal state vectors corresponding to the quantized degrees of freedom of the real-space system. Measurement of superpositions is akin to accessing the direction of a vector in Hilbert space, determining an angle of rotation equivalent to quantum phase. Here we show that an individual atom inside a designed quantum corral1 can control this angle, producing arbitrary coherent superpositions of spatial quantum states. Using scanning tunnelling microscopy and nanostructures assembled atom-by-atom we demonstrate how single spins and quantum mirages can be harnessed to image the superposition of two electronic states. We also present a straightforward method to determine the atom path enacting phase rotations between any desired state vectors. A single atom thus becomes a real-space handle for an abstract Hilbert space, providing a simple technique for coherent quantum state manipulation at the spatial limit of condensed matter.

  12. Single-ion quantum lock-in amplifier.

    Science.gov (United States)

    Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Keselman, Anna; Ozeri, Roee

    2011-05-05

    Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor. ©2011 Macmillan Publishers Limited. All rights reserved

  13. Quantum delayed-choice experiment with a single neutral atom.

    Science.gov (United States)

    Li, Gang; Zhang, Pengfei; Zhang, Tiancai

    2017-10-01

    We present a proposal to implement a quantum delayed-choice (QDC) experiment with a single neutral atom, such as a rubidium or cesium atom. In our proposal, a Ramsey interferometer is adopted to observe the wave-like or particle-like behaviors of a single atom depending on the existence or absence of the second π/2-rotation. A quantum-controlled π/2-rotation on target atom is realized through a Rydberg-Rydberg interaction by another ancilla atom. It shows that a heavy neutral atom can also have a morphing behavior between the particle and the wave. The realization of the QDC experiment with such heavy neutral atoms not only is significant to understand the Bohr's complementarity principle in matter-wave and matter-particle domains but also has great potential on the quantum information process with neutral atoms.

  14. Resonance fluorescence and quantum interference of a single NV center

    Science.gov (United States)

    Ma, Yong-Hong; Zhang, Xue-Feng; Wu, E.

    2017-11-01

    The detection of a single nitrogen-vacancy center in diamond has attracted much interest, since it is expected to lead to innovative applications in various domains of quantum information, including quantum metrology, information processing and communications, as well as in various nanotechnologies, such as biological and subdiffraction limit imaging, and tests of entanglement in quantum mechanics. We propose a novel scheme of a single NV center coupled with a multi-mode superconducting microwave cavity driven by coherent fields in squeezed vacuum. We numerically investigate the spectra in-phase quadrature and out-of-phase quadrature for different driving regimes with or without detunings. It shows that the maximum squeezing can be obtained for optimal Rabi fields. Moreover, with the same parameters, the maximum squeezing is greatly increased when the detunings are nonzero compared to the resonance case.

  15. Single-passage read-out of atomic quantum memory

    DEFF Research Database (Denmark)

    Fiurasek, J; Sherson, J; Opatrny, T

    2005-01-01

    Retrieving quantum information, collective atomic spin systems, quantum memory Udgivelsesdato: 17 Feb.......Retrieving quantum information, collective atomic spin systems, quantum memory Udgivelsesdato: 17 Feb....

  16. Rapid single flux quantum logic in high temperature superconductor technology

    NARCIS (Netherlands)

    Shunmugavel, K.

    2006-01-01

    A Josephson junction is the basic element of rapid single flux quantum logic (RSFQ) circuits. A high operating speed and low power consumption are the main advantages of RSFQ logic over semiconductor electronic circuits. To realize complex RSFQ circuits in HTS technology one needs a reproducible

  17. Coherent excitonic nonlinearity versus inhomogeneous broadening in single quantum wells

    DEFF Research Database (Denmark)

    Langbein, Wolfgang Werner; Borri, Paola; Hvam, Jørn Märcher

    1998-01-01

    The coherent response of excitons in semiconductor nanostructures, as measured in four wave mixing (FWM) experiments, depends strongly on the inhomogeneous broadening of the exciton transition. We investigate GaAs-AlGaAs single quantum wells (SQW) of 4 nm to 25 nm well width. Two main mechanisms ...

  18. Deep-submicron CMOS Single Photon Detectors and Quantum Effects

    NARCIS (Netherlands)

    Karami, M.A.

    2011-01-01

    Quantum parasitic effects and miniaturization of Single Photon Avalanche Diodes in deep-submicron technologies have been studied in this thesis in detail. Tunneling noise and Random Telegraph Signal (RTS) noise have been the main two parasitic effects addressed comprehensively. While the fundamental

  19. Advances in single quantum dot-based nanosensors.

    Science.gov (United States)

    Hu, Juan; Wang, Zi-Yue; Li, Chen-Chen; Zhang, Chun-Yang

    2017-12-14

    Single-molecule detection provides a simple and ultrasensitive platform to quantify target molecules by simply counting the individual fluorescence signals. Quantum dots (QDs) are novel semiconductor nanocrystals with distinct characteristics of high brightness, large Stokes shift and broad absorption spectra, high molar extinction coefficients, high quantum yield, good photostability and long fluorescence lifetime. The combination of single-molecule detection with QDs enables the development of single QD-based nanosensors with extremely high sensitivity. Single QD-based nanosensors may be divided into two categories based on single QD burst coincidence detection and single QD-fluorescence resonance energy transfer (FRET) detection, and have significant advantages of high signal-to-noise ratio, high sensitivity, rapidity, and low sample consumption. The single QD-based nanosensors have the capability of directly detecting low-abundance species without the need for nucleic acid amplification, and may elucidate a variety of biological and biochemical phenomena in real time using single QD tracking. In this review, we summarize the recent advances in single QD-based nanosensors and their applications for sensitive detection of DNAs, microRNAs, proteins, enzymes, small molecules and viruses. We highlight the challenges and future direction of single QD-based nanosensors as well.

  20. Superconducting Single-Photon Detectors for Integrated Quantum Optics

    OpenAIRE

    Kahl, Oliver

    2016-01-01

    This thesis reports on the implementation and characterization of a fully integrated single-photon detector. Several detector circuits are realized and it is shown that the detectors exhibit supreme detection performance over a wide optical spectrum. The detectors' scalability is showcased by the parallel operation of multiple detectors within a single integrated circuit. These demonstrations are essential for future developments in integrated quantum optics.

  1. Optical properties of bimodally distributed InAs quantum dots grown on digital AlAs0.56Sb0.44 matrix for use in intermediate band solar cells

    Science.gov (United States)

    Debnath, Mukul C.; Liang, Baolai; Laghumavarapu, Ramesh B.; Wang, Guodong; Das, Aparna; Juang, Bor-Chau; Huffaker, Diana L.

    2017-06-01

    High-quality InAs quantum dots (QDs) with nominal thicknesses of 5.0-8.0 monolayers were grown on a digital AlAs0.56Sb0.44 matrix lattice-matched to the InP(001) substrate. All QDs showed bimodal size distribution, and their optical properties were investigated by photoluminescence (PL) and time-resolved PL measurements. Power dependent PL exhibited a linear relationship between the peak energy and the cube root of the excitation power for both the small QD family (SQDF) and the large QD family (LQDF), which is attributed to the type-II transition. The PL intensity, peak energy, and carrier lifetime of SQDF and LQDF showed very sensitive at high temperature. Above 125 K, the PL intensity ratio increased continuously between LQDF and SQDF, the peak energy shifted anomalously in SQDF, and the longer carrier radiative lifetime (≥3.0 ns at 77 K) reduced rapidly in SQDF and slowly in LQDF. These results are ascribed to thermally activated carrier escape from SQDF into the wetting layer, which then relaxed into LQDF with low-localized energy states.

  2. Quantum Information Science with Single Atoms and Photons

    Science.gov (United States)

    Kimble, H. J.

    2003-03-01

    Cavity quantum electrodynamics (QED) offers powerful possibilities for the deterministic control of atom-photon interactions quantum by quantum [1]. Indeed, modern experiments in cavity QED have achieved the exceptional circumstance of strong coupling, for which single quanta can profoundly impact the dynamics of the atom-cavity system. The diverse accomplishments of this field set the stage for advances into yet broader frontiers in quantum information science for which cavity QED offers unique advantages, including the creation of quantum networks [2]. The primary technical challenge on the road toward such scientific goals is the need to trap and localize atoms within a cavity in a setting suitable for strong coupling. Two separate experiments in our group have achieved significant milestones in this quest, namely the real-time trapping and tracking of single atoms in cavity QED [3-5]. In one experiment, an atom is trapped by an auxiliary field that functions as a far-detuned dipole-force trap (FORT) [3,4], with trap lifetime 3s, which should be compared to the nanosecond time scale for internal dynamics of the atom-cavity system. In a second experiment, we rely upon light forces at the single-photon level to trap a single atom within the cavity mode [5]. As illustrated by the movies available at http://www.its.caltech.edu/ qoptics/atomorbits/, these reconstructions reveal single atoms bound in orbit by the mechanical forces associated with single photons, and realize a new form of microscopy. Over the duration of the observation, the sensitivity is near the standard quantum limit for sensing the motion of a Cesium atom. This work is supported by the NSF, by the Caltech MURI for Quantum Networks administered by the ARO, and by the ONR. 1. For a review, see contributions in the Special Issue of Physica Scripta T76 (1998). 2. J. I. Cirac, S. J. van Enk, P. Zoller, H. J. Kimble, and H. Mabuchi, Physica Scripta T76, 223 (1998). 3. J. Ye, D. W. Vernooy, and H. J

  3. Quantum optics with quantum dots in photonic nanowires

    DEFF Research Database (Denmark)

    We will review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices.......We will review recent studies performed on InAs quantum dots embedded in GaAs photonic wires, which highlight the strong interest of the photonic wire geometry for quantum optics experiments and quantum optoelectronic devices....

  4. A Single Molecule Investigation of the Photostability of Quantum Dots

    DEFF Research Database (Denmark)

    Christensen, Eva Arnspang; Kulatunga, Pasad; Lagerholm, B. Christoffer

    2012-01-01

    Quantum dots (QDs) are very attractive probes for multi-color fluorescence applications. We report here however that single QDs that are subject to continuous blue excitation from a 100W mercury arc lamp will undergo a continuous blue-switching of the emission wavelength eventually reaching a per...... is especially detrimental for multi-color single molecule applications, as we regularly observe spectral blue-shifts of 50 nm, or more even after only ten seconds of illumination.......Quantum dots (QDs) are very attractive probes for multi-color fluorescence applications. We report here however that single QDs that are subject to continuous blue excitation from a 100W mercury arc lamp will undergo a continuous blue-switching of the emission wavelength eventually reaching...

  5. Single-atom based coherent quantum interference device structure.

    Science.gov (United States)

    Naydenov, Borislav; Rungger, Ivan; Mantega, Mauro; Sanvito, Stefano; Boland, John J

    2015-05-13

    We describe the fabrication, operation principles, and simulation of a coherent single-atom quantum interference device (QID) structure on Si(100) controlled by the properties of single atoms. The energy and spatial distribution of the wave functions associated with the device are visualized by scanning tunneling spectroscopy and the amplitude and phase of the evanescent wave functions that couple into the quantum well states are directly measured, including the action of an electrostatic gate. Density functional theory simulations were employed to simulate the electronic structure of the device structure, which is in excellent agreement with the measurements. Simulations of device transmission demonstrate that our coherent single-atom QID can have ON-OFF ratios in excess of 10(3) with potentially minimal power dissipation.

  6. Vacuum Rabi spectra of a single quantum emitter.

    Science.gov (United States)

    Ota, Yasutomo; Ohta, Ryuichi; Kumagai, Naoto; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2015-04-10

    We report the observation of the vacuum Rabi splitting of a single quantum emitter by measuring its direct spontaneous emission into free space. We use a semiconductor quantum dot inside a photonic crystal nanocavity, in conjunction with an appropriate cavity design and filtering with a polarizer and an aperture, enabling the extraction of the inherently weak emitter's signal. The emitter's vacuum Rabi spectra exhibit clear differences from those measured by detecting the cavity photon leakage. Moreover, we observe an asymmetric vacuum Rabi spectrum induced by interference between the emitter and cavity detection channels. Our observations lay the groundwork for accessing various cavity quantum electrodynamics phenomena that manifest themselves only in the emitter's direct spontaneous emission.

  7. Reconstructing quantum states from single-party information

    Science.gov (United States)

    Schilling, Christian; Benavides-Riveros, Carlos L.; Vrana, Péter

    2017-11-01

    The possible compatibility of density matrices for single-party subsystems is described by linear constraints on their respective spectra. Whenever some of those quantum marginal constraints are saturated, the total quantum state has a specific, simplified structure. We prove that these remarkable global implications of extremal local information are stable; i.e., they hold approximately for spectra close to the boundary of the allowed region. Application of this general result to fermionic quantum systems allows us to characterize natural extensions of the Hartree-Fock ansatz and to quantify their accuracy by resorting to one-particle information, only: The fraction of the correlation energy not recovered by such an ansatz can be estimated from above by a simple geometric quantity in the occupation number picture.

  8. Quantum optics with quantum dots in photonic nanowires

    DEFF Research Database (Denmark)

    Claudon, Julien; Munsch, Matthieu; Bleuse, Joel

    2012-01-01

    Besides microcavities and photonic crystals, photonic nanowires have recently emerged as a novel resource for solidstate quantum optics. We will review recent studies which demonstrate an excellent control over the spontaneous emission of InAs quantum dots (QDs) embedded in single-mode Ga......As photonic wires. On the basic side, we have demonstrated a strong inhibition (x 1/16) of QD SpE in thin wires (d0.95 for d~λ/n), and polarization control in elliptical nanowires. A single QD in a photonic wire is thus an attractive system to explore the physics of the "one-dimensional atom" and build novel...

  9. Quantum Otto engine using a single ion and a single thermal bath

    Science.gov (United States)

    Biswas, Asoka; Chand, Suman

    2016-05-01

    Quantum heat engines employ a quantum system as the working fluid, that gives rise to large work efficiency, beyond the limit for classical heat engines. Existing proposals for implementing quantum heat engines require that the system interacts with the hot bath and the cold bath (both modelled as a classical system) in an alternative fashion and therefore assumes ability to switch off the interaction with the bath during a certain stage of the heat-cycle. However, it is not possible to decouple a quantum system from its always-on interaction with the bath without use of complex pulse sequences. It is also hard to identify two different baths at two different temperatures in quantum domain, that sequentially interact with the system. Here, we show how to implement a quantum Otto engine without requiring to decouple the bath in a sequential manner. This is done by considering a single thermal bath, coupled to a single trapped ion. The electronic degree of freedom of the ion is chosen as a two-level working fluid while the vibrational degree of freedom plays the role of the cold bath. Measuring the electronic state mimics the release of heat into the cold bath. Thus, our model is fully quantum and exhibits very large work efficiency, asymptotically close to unity.

  10. High performance superluminescent diode with InAs quantum-dashes and chirped AlGaInAs barriers active region

    KAUST Repository

    Khan, Mohammed Zahed Mustafa

    2013-01-01

    The demonstration of high power, ultra-low ripple superluminescent diode using multiple quantum-dash-in-a-well layers with variable barrier thickness is reported. The device exhibits >20 mW power, < 0.3dB ripple, and > 80 nm 3dB bandwidth at ~1.55 μm.

  11. Manipulating single electron spins and coherence in quantum dots

    Science.gov (United States)

    Awschalom, David

    2008-05-01

    The non-destructive detection of a single electron spin in a quantum dot (QD) is demonstrated using a time- averaged magneto-optical Kerr rotation measurementootnotetextJ. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006).. This technique provides a means to directly probe the spin off- resonance, thus minimally disturbing the system. Furthermore, the ability to sequentially initialize, manipulate, and read out the state of a qubit, such as an electron spin in a quantum dot, is necessary for virtually any scheme for quantum information processing. In addition to the time-averaged measurements, we have extended the single dot KR technique into the time domain with pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin stateootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Nature Physics 3, 770 (2007).. The dot is formed by interface fluctuations of a GaAs quantum well and embedded in a diode structure to allow controllable gating/charging of the QD. To enhance the small single spin signal, the QD is positioned within a vertical optical cavity. Observations of coherent single spin precession in an applied magnetic field allow a direct measurement of the electron g-factor and transverse spin lifetime. These measurements reveal information about the relevant spin decoherence mechanisms, while also providing a sensitive probe of the local nuclear spin environment. Finally, we have recently eveloped a scheme for high speed all-optical manipulation of the spin state that enables multiple operations within the coherence timeootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, accepted for publication (2008).. The results represent progress toward the control and coupling of single spins and photons for quantum information processingootnotetextS. Ghosh, W.H. Wang, F. M. Mendoza, R. C

  12. Realization of a Cascaded Quantum System: Heralded Absorption of a Single Photon Qubit by a Single-Electron Charged Quantum Dot.

    Science.gov (United States)

    Delteil, Aymeric; Sun, Zhe; Fält, Stefan; Imamoğlu, Atac

    2017-04-28

    Photonic losses pose a major limitation for the implementation of a quantum state transfer between nodes of a quantum network. A measurement that heralds a successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate the heralded absorption of a single photonic qubit, generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 m away. The transfer of quantum information to the spin degree of freedom takes place upon the emission of a photon; for a properly chosen or prepared quantum dot, the detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for the realization of quantum information protocols based on cascaded quantum systems.

  13. Real-time single-molecule imaging of quantum interference.

    Science.gov (United States)

    Juffmann, Thomas; Milic, Adriana; Müllneritsch, Michael; Asenbaum, Peter; Tsukernik, Alexander; Tüxen, Jens; Mayor, Marcel; Cheshnovsky, Ori; Arndt, Markus

    2012-03-25

    The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514 AMU and 1,298 AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics.

  14. Single quantum dot controls a plasmonic cavity's scattering and anisotropy.

    Science.gov (United States)

    Hartsfield, Thomas; Chang, Wei-Shun; Yang, Seung-Cheol; Ma, Tzuhsuan; Shi, Jinwei; Sun, Liuyang; Shvets, Gennady; Link, Stephan; Li, Xiaoqin

    2015-10-06

    Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices.

  15. Development of Integrated Single Flux Quantum - Superconducting Qubit Circuits

    Science.gov (United States)

    Leonard, Edward, Jr.; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Hutchings, Matthew; Nelson, Jj; Plourde, Britton; McDermott, Robert

    Significant theoretical and experimental progress has been made in recent years towards a scalable superconducting quantum circuit architecture. Here we present a first attempt to integrate classical control elements from the single flux quantum (SFQ) digital logic family with a superconducting transom qubit on a single chip. The SFQ driving circuit is fabricated in a six-layer high-Jc Nb/Al-AlOx/Nb junction process while the transmon qubit is subsequently formed using submicron Al-AlOx-Al junctions grown by double-angle evaporation. We investigate sources of decoherence associated with the more complex fabrication process and describe first attempts to perform coherent qubit manipulations using resonant trains of SFQ pulses.

  16. Multi-group dynamic quantum secret sharing with single photons

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hongwei [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Ma, Haiqiang, E-mail: hqma@bupt.edu.cn [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Wei, Kejin [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Yang, Xiuqing [School of Science, Beijing Jiaotong University, Beijing 100044 (China); Qu, Wenxiu; Dou, Tianqi; Chen, Yitian; Li, Ruixue; Zhu, Wu [School of Science and State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2016-07-15

    In this letter, we propose a novel scheme for the realization of single-photon dynamic quantum secret sharing between a boss and three dynamic agent groups. In our system, the boss can not only choose one of these three groups to share the secret with, but also can share two sets of independent keys with two groups without redistribution. Furthermore, the security of communication is enhanced by using a control mode. Compared with previous schemes, our scheme is more flexible and will contribute to a practical application. - Highlights: • A multi-group dynamic quantum secret sharing with single photons scheme is proposed. • Any one of the groups can be chosen to share secret through controlling the polarization of photons. • Two sets of keys can be shared simultaneously without redistribution.

  17. Single cell magnetic imaging using a quantum diamond microscope

    Science.gov (United States)

    Park, H.; Weissleder, R.; Yacoby, A.; Lukin, M. D.; Lee, H.; Walsworth, R. L.; Connolly, C. B.

    2015-01-01

    We apply a quantum diamond microscope to detection and imaging of immunomagnetically labeled cells. This instrument uses nitrogen-vacancy (NV) centers in diamond for correlated magnetic and fluorescence imaging. Our device provides single-cell resolution and two orders of magnitude larger field of view (~1 mm2) than previous NV imaging technologies, enabling practical applications. To illustrate, we quantify cancer biomarkers expressed by rare tumor cells in a large population of healthy cells. PMID:26098019

  18. Quantum optics with single nanodiamonds flying over gold films: Towards a Robust quantum plasmonics

    Energy Technology Data Exchange (ETDEWEB)

    Mollet, O.; Drezet, A.; Huant, S. [Institut Néel, CNRS and Université Joseph Fourier, BP 166, F-38042 Grenoble (France)

    2013-12-04

    A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.

  19. High-Sensitivity Charge Detection with a Single-Lead Quantum Dot for Scalable Quantum Computation

    Science.gov (United States)

    House, Matthew; Bartlett, Ian; Pakkiam, Prasanna; Koch, Matthias; Peretz, Eldad; van der Heijden, Joost; Kobayashi, Takashi; Rogge, Sven; Simmons, Michelle

    We report the development of a high sensitivity semiconductor charge sensor based on a quantum dot coupled to a single lead, designed to minimize the geometric requirements of a charge sensor for scalable quantum computing architectures. The quantum dot is fabricated in Si:P using atomic precision lithography and its charge transitions are measured with rf reflectometry. A second quantum dot with two leads placed 42 nm away serves as both a charge for the sensor to measure and as a conventional rf single electron transistor (rf-SET) with which to make a comparison of the charge detection sensitivity. We demonstrate sensitivity equivalent to an integration time of 550 ns to detect a single charge with a signal-to-noise ratio of 1, compared with an integration time of 55 ns for the rf-SET. This level of sensitivity is suitable for fast (Communication Technology (Project No. CE110001027) and the U.S. Army Research Office under Contract No. W911NF-13-1-0024.

  20. Measurable quantum geometric phase from a rotating single spin.

    Science.gov (United States)

    Maclaurin, D; Doherty, M W; Hollenberg, L C L; Martin, A M

    2012-06-15

    We demonstrate that the internal magnetic states of a single nitrogen-vacancy defect, within a rotating diamond crystal, acquire geometric phases. The geometric phase shift is manifest as a relative phase between components of a superposition of magnetic substates. We demonstrate that under reasonable experimental conditions a phase shift of up to four radians could be measured. Such a measurement of the accumulation of a geometric phase, due to macroscopic rotation, would be the first for a single atom-scale quantum system.

  1. Probing into hybrid organic-molecule and InAs quantum-dots nanosystem with multistacked dots-in-a-well units

    DEFF Research Database (Denmark)

    Chen, Miaoxiang Max; Kobashi, Kazufumi

    2012-01-01

    Hybridizing air-stable organic-molecules with advanced III-V semiconductor quantum-dots (QDs) structures can be utilized to create a new generation of biochemical sensing devices. In order to enhance their optical performances, the active regions in these QDs structures commonly consist...... the system. Because of the complexity of the energy-levels in the QDs structure due to the existing surface QDs and DWELLs, selective excitation wavelengths (400, 633, and 885 nm, respectively) with different photo-energies are used to exactly analyze the complete charging mechanism in these QDs. A clear...

  2. On-Chip Single-Plasmon Nanocircuit Driven by a Self-Assembled Quantum Dot.

    Science.gov (United States)

    Wu, Xiaofei; Jiang, Ping; Razinskas, Gary; Huo, Yongheng; Zhang, Hongyi; Kamp, Martin; Rastelli, Armando; Schmidt, Oliver G; Hecht, Bert; Lindfors, Klas; Lippitz, Markus

    2017-07-12

    Quantum photonics holds great promise for future technologies such as secure communication, quantum computation, quantum simulation, and quantum metrology. An outstanding challenge for quantum photonics is to develop scalable miniature circuits that integrate single-photon sources, linear optical components, and detectors on a chip. Plasmonic nanocircuits will play essential roles in such developments. However, for quantum plasmonic circuits, integration of stable, bright, and narrow-band single photon sources in the structure has so far not been reported. Here we present a plasmonic nanocircuit driven by a self-assembled GaAs quantum dot. Through a planar dielectric-plasmonic hybrid waveguide, the quantum dot efficiently excites narrow-band single plasmons that are guided in a two-wire transmission line until they are converted into single photons by an optical antenna. Our work demonstrates the feasibility of fully on-chip plasmonic nanocircuits for quantum optical applications.

  3. Quantum efficiency of a single microwave photon detector based on a semiconductor double quantum dot

    Science.gov (United States)

    Wong, Clement H.; Vavilov, Maxim G.

    2017-01-01

    Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we consider a double quantum dot (DQD) capacitively coupled to a superconducting resonator that is driven by the microwave field of a superconducting transmission line. We analyze the DQD current response using input-output theory and show that the resonator-coupled DQD is a sensitive microwave single photon detector. Using currently available experimental parameters of DQD-resonator coupling and dissipation, including the effects of 1 /f charge noise and phonon noise, we determine the parameter regime for which incident photons are completely absorbed and near-unit ≳98 % efficiency can be achieved. We show that this regime can be reached by using very high quality resonators with quality factor Q ≃105 .

  4. Lecture demonstrations of interference and quantum erasing with single photons

    Science.gov (United States)

    Dimitrova, T. L.; Weis, A.

    2009-07-01

    Single-photon interference is a beautiful manifestation of the wave-particle duality of light and the double-slit Gedankenexperiment is a standard lecture example for introducing quantum mechanical reality. Interference arises only if each photon can follow several (classical) paths from the source to the detector, and if one does not have the possibility to determine which specific path the photon has taken. Attaching a specific label to the photon traveling along a specific path destroys the interference. However, in some cases those labels can be erased from the photon between leaving the apparatus and being detected, by which interference can be restored, a phenomenon called quantum erasing. We present lecture demonstration experiments that illustrate the wave-particle duality of light and the phenomenon of quantum erasing. Both experiments are first shown with strong light and, in a second step, on a photon-by-photon basis. The smooth transition from the quantum to the classical case can be shown in real time by varying the incident light intensity.

  5. Multi-Color Single Particle Tracking with Quantum Dots

    DEFF Research Database (Denmark)

    Christensen, Eva Arnspang; Brewer, J. R.; Lagerholm, B. C.

    2012-01-01

    Quantum dots (QDs) have long promised to revolutionize fluorescence detection to include even applications requiring simultaneous multi-species detection at single molecule sensitivity. Despite the early promise, the unique optical properties of QDs have not yet been fully exploited in e. g....... multiplex single molecule sensitivity applications such as single particle tracking (SPT). In order to fully optimize single molecule multiplex application with QDs, we have in this work performed a comprehensive quantitative investigation of the fluorescence intensities, fluorescence intensity fluctuations...... further show that there is only a small size advantage in using blue-shifted QDs in biological applications because of the additional size of the water-stabilizing surface coat. Extending previous work, we finally also show that parallel four color multicolor (MC)-SPT with QDs is possible at an image...

  6. Single-shot work extraction in quantum thermodynamics revisited

    Science.gov (United States)

    Wang, Shang-Yung

    2018-01-01

    We revisit the problem of work extraction from a system in contact with a heat bath to a work storage system, and the reverse problem of state formation from a thermal system state in single-shot quantum thermodynamics. A physically intuitive and mathematically simple approach using only elementary majorization theory and matrix analysis is developed, and a graphical interpretation of the maximum extractable work, minimum work cost of formation, and corresponding single-shot free energies is presented. This approach provides a bridge between two previous methods based respectively on the concept of thermomajorization and a comparison of subspace dimensions. In addition, a conceptual inconsistency with regard to general work extraction involving transitions between multiple energy levels of the work storage system is clarified and resolved. It is shown that an additional contribution to the maximum extractable work in those general cases should be interpreted not as work extracted from the system, but as heat transferred from the heat bath. Indeed, the additional contribution is an artifact of a work storage system (essentially a suspended ‘weight’ that can be raised or lowered) that does not truly distinguish work from heat. The result calls into question the common concept that a work storage system in quantum thermodynamics is simply the quantum version of a suspended weight in classical thermodynamics.

  7. A novel high-efficiency single-mode quantum dot single photon source

    DEFF Research Database (Denmark)

    Gerard, J.M.; Gregersen, Niels; Nielsen, Torben Roland

    2008-01-01

    We present a novel single-mode single photon source exploiting the emission of a semiconductor quantum dot (QD) located inside a photonic wire. Besides an excellent coupling (>95%) of QD spontaneous emission to the fundamental guided mode [1], we show that a single photon collection efficiency...... above 80% within a 0.5 numerical aperture can be achieved using a bottom Bragg mirror and a tapering of the nanowire tip. Because this photon collection strategy does not exploit the Purcell effect, it could also be efficiently applied to broadband single photon emitters such as F-centers in diamond....

  8. Deterministic Secure Quantum Communication with Collective Detection Using Single Photons

    Science.gov (United States)

    Huang, Wei; Wen, Qiao-Yan; Liu, Bin; Gao, Fei; Chen, Hui

    2012-09-01

    Two novel single-photon deterministic secure quantum communication (DSQC) schemes with collective detection are proposed. One is a two-party DSQC, the other is a DSQC network. In these two schemes, only single-photon source and single-photon measurements are required, which makes the schemes more feasible with present techniques. Apart from this, a detection strategy called collective detection is utilized in our schemes, in which the detection is taken only once after the whole process of particle transmission. Such detection strategy improves the efficiencies of our protocols and also reduces the cost of realization as the message sender only need to perform unitary operations in the whole communication. What's more, the efficiencies of qubits and source capacity are both high since almost all the states can be used to transmit message except the ones used for eavesdropping check and each single photon can carry one bit of information. Finally, we prove the security of the our protocols by using the theorems on quantum operation discrimination.

  9. Operation of an InAs quantum-dot embedded GaAs photonic crystal slab waveguide laser by using two-photon pumping for photonics integrated circuits

    Directory of Open Access Journals (Sweden)

    H. Oda

    2016-06-01

    Full Text Available The development of small sized laser operating above room temperature is important in the realization of optical integrated circuits. Recently, micro-lasers consisting of photonic crystals (PhCs and whispering gallery mode cavities have been demonstrated. Optically pumped laser devices could be easily designed using photonic crystal-slab waveguides (PhC-WGs with an air-bridge type structure. In this study, we observe lasing at 1.3μm from two-photon pumped InAs-quantum-dots embedded GaAs PhC-WGs above room temperature. This type of compact laser shows promise as a new light source in ultra-compact photonics integrated circuits.

  10. Coherent control of ground state excitons in the nonlinear regime within an ensemble of self-assembled InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Moldaschl, Thomas; Mueller, Thomas; Golka, Sebastian; Parz, Wolfgang; Strasser, Gottfried; Unterrainer, Karl [Photonics Institute and Center for Micro- and Nanostructures, Vienna University of Technology (Austria)

    2009-04-15

    In this work femtosecond spectral hole burning spectroscopy is used to resonantly excite ground state excitons in an ensemble of self-assembled InAs/GaAs quantum dots with a strong pump pulse. Two fundamental coherent nonlinear effects are observed with the aid of the intrinsic time- and frequency resolution of the setup: The low temperature Rabi oscillation of the two-level system associated with the excitonic ground state transition and the observation of two-photon absorption in the surrounding GaAs crystal matrix. The emergence of the latter effect also infers the existence of charged excitons in the nominally undoped QD sample, backed up by the observation of additional spectral holes next to the excitonic transitions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Operation of an InAs quantum-dot embedded GaAs photonic crystal slab waveguide laser by using two-photon pumping for photonics integrated circuits

    Energy Technology Data Exchange (ETDEWEB)

    Oda, H., E-mail: h-oda@photon.chitose.ac.jp; Yamanaka, A. [Chitose Institute of Science and Technology, 758-65 Chitose 066-8655 (Japan); Ozaki, N. [Faculty of Systems Engineering, Wakayama University, Wakayama 640-8510 (Japan); Ikeda, N.; Sugimoto, Y. [National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8561 (Japan)

    2016-06-15

    The development of small sized laser operating above room temperature is important in the realization of optical integrated circuits. Recently, micro-lasers consisting of photonic crystals (PhCs) and whispering gallery mode cavities have been demonstrated. Optically pumped laser devices could be easily designed using photonic crystal-slab waveguides (PhC-WGs) with an air-bridge type structure. In this study, we observe lasing at 1.3μm from two-photon pumped InAs-quantum-dots embedded GaAs PhC-WGs above room temperature. This type of compact laser shows promise as a new light source in ultra-compact photonics integrated circuits.

  12. Probing silicon quantum dots by single-dot techniques

    Science.gov (United States)

    Sychugov, Ilya; Valenta, Jan; Linnros, Jan

    2017-02-01

    Silicon nanocrystals represent an important class of non-toxic, heavy-metal free quantum dots, where the high natural abundance of silicon is an additional advantage. Successful development in mass-fabrication, starting from porous silicon to recent advances in chemical and plasma synthesis, opens up new possibilities for applications in optoelectronics, bio-imaging, photovoltaics, and sensitizing areas. In this review basic physical properties of silicon nanocrystals revealed by photoluminescence spectroscopy, lifetime, intensity trace and electrical measurements on individual nanoparticles are summarized. The fabrication methods developed for accessing single Si nanocrystals are also reviewed. It is concluded that silicon nanocrystals share many of the properties of direct bandgap nanocrystals exhibiting sharp emission lines at low temperatures, on/off blinking, spectral diffusion etc. An analysis of reported results is provided in comparison with theory and with direct bandgap material quantum dots. In addition, the role of passivation and inherent interface/matrix defects is discussed.

  13. Quantum Dot Platform for Single-Cell Molecular Profiling

    Science.gov (United States)

    Zrazhevskiy, Pavel S.

    In-depth understanding of the nature of cell physiology and ability to diagnose and control the progression of pathological processes heavily rely on untangling the complexity of intracellular molecular mechanisms and pathways. Therefore, comprehensive molecular profiling of individual cells within the context of their natural tissue or cell culture microenvironment is essential. In principle, this goal can be achieved by tagging each molecular target with a unique reporter probe and detecting its localization with high sensitivity at sub-cellular resolution, primarily via microscopy-based imaging. Yet, neither widely used conventional methods nor more advanced nanoparticle-based techniques have been able to address this task up to date. High multiplexing potential of fluorescent probes is heavily restrained by the inability to uniquely match probes with corresponding molecular targets. This issue is especially relevant for quantum dot probes---while simultaneous spectral imaging of up to 10 different probes is possible, only few can be used concurrently for staining with existing methods. To fully utilize multiplexing potential of quantum dots, it is necessary to design a new staining platform featuring unique assignment of each target to a corresponding quantum dot probe. This dissertation presents two complementary versatile approaches towards achieving comprehensive single-cell molecular profiling and describes engineering of quantum dot probes specifically tailored for each staining method. Analysis of expanded molecular profiles is achieved through augmenting parallel multiplexing capacity with performing several staining cycles on the same specimen in sequential manner. In contrast to other methods utilizing quantum dots or other nanoparticles, which often involve sophisticated probe synthesis, the platform technology presented here takes advantage of simple covalent bioconjugation and non-covalent self-assembly mechanisms for straightforward probe

  14. Realization of Microwave Quantum Circuits Using Hybrid Superconducting Semiconducting Nanowire Josephson Elements

    NARCIS (Netherlands)

    De Lange, G.; Van Heck, B.; Bruno, A.; Van Woerkom, D.J.; Geresdi, A.; Plissard, S.R.; Bakkers, E.P.A.M.; Akhmerov, A.R.; Di Carlo, L.

    2015-01-01

    We report the realization of quantum microwave circuits using hybrid superconductor-semiconductor Josephson elements comprised of InAs nanowires contacted by NbTiN. Capacitively shunted single elements behave as transmon circuits with electrically tunable transition frequencies. Two-element circuits

  15. Investigating and Improving Student Understanding of Quantum Mechanics in the Context of Single Photon Interference

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2017-01-01

    Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the…

  16. Quantum-Sequencing: Fast electronic single DNA molecule sequencing

    Science.gov (United States)

    Casamada Ribot, Josep; Chatterjee, Anushree; Nagpal, Prashant

    2014-03-01

    A major goal of third-generation sequencing technologies is to develop a fast, reliable, enzyme-free, high-throughput and cost-effective, single-molecule sequencing method. Here, we present the first demonstration of unique ``electronic fingerprint'' of all nucleotides (A, G, T, C), with single-molecule DNA sequencing, using Quantum-tunneling Sequencing (Q-Seq) at room temperature. We show that the electronic state of the nucleobases shift depending on the pH, with most distinct states identified at acidic pH. We also demonstrate identification of single nucleotide modifications (methylation here). Using these unique electronic fingerprints (or tunneling data), we report a partial sequence of beta lactamase (bla) gene, which encodes resistance to beta-lactam antibiotics, with over 95% success rate. These results highlight the potential of Q-Seq as a robust technique for next-generation sequencing.

  17. Tunable single-mode slot waveguide quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Bo; Tao, Jin; Quan Zeng, Yong [NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, 637553 Singapore (Singapore); Hui Li, Xiao [NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wu, Sheng [Power Energy and Environmental Research Institute, Covina, California, 91722 (United States); Jie Wang, Qi, E-mail: qjwang@ntu.edu.sg [NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); CDPT, Centre for Disruptive Photonic Technologies, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)

    2014-05-19

    We report experimental demonstration of tunable, monolithic, single-mode quantum cascade lasers (QCLs) at ∼10 μm with a two-section etched slot structure. A single-mode tuning range of 77 cm{sup −1} (785 nm), corresponding to ∼7.8% of the relative tuning range, was realized with a ∼20 dB side mode suppression ratio within the whole tuning range. Compared with integrated distributed feedback QCLs, our devices have the advantages of easy fabrication and a broader tuning range. Further theoretical analyses and numerical simulations show that it is possible to achieve a broad continuous tuning range by optimizing the slot structures. The proposed slot-waveguide design could provide an alternative but simple approach to the existing tuning schemes for realizing broadly continuous tunable single-mode QCLs.

  18. High power and single mode quantum cascade lasers.

    Science.gov (United States)

    Bismuto, Alfredo; Bidaux, Yves; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Rochat, Michel; Muller, Antoine; Bonzon, Christopher; Faist, Jerome

    2016-05-16

    We present a single mode quantum cascade laser with nearly 1 W optical power. A buried distributed feedback reflector is used on the back section for wavelength selection. The laser is 6 mm long, 3.5 μm wide, mounted episide-up and the laser facets are left uncoated. Laser emission is centered at 4.68 μm. Single-mode operation with a side mode suppression ratio of more than 30 dB is obtained in whole range of operation. Farfield measurements prove a symmetric, single transverse-mode emission in TM00-mode with typical divergences of 41° and 33° in the vertical and horizontal direction respectively. This work shows the potential for simple fabrication of high power lasers compatible with standard DFB processing.

  19. Quantum Probability Cancellation Due to a Single-Photon State

    Science.gov (United States)

    Ou, Z. Y.

    1996-01-01

    When an N-photon state enters a lossless symmetric beamsplitter from one input port, the photon distribution for the two output ports has the form of Bernouli Binormial, with highest probability at equal partition (N/2 at one outport and N/2 at the other). However, injection of a single photon state at the other input port can dramatically change the photon distribution at the outputs, resulting in zero probability at equal partition. Such a strong deviation from classical particle theory stems from quantum probability amplitude cancellation. The effect persists even if the N-photon state is replaced by an arbitrary state of light. A special case is the coherent state which corresponds to homodyne detection of a single photon state and can lead to the measurement of the wave function of a single photon state.

  20. Can a quantum state over time resemble a quantum state at a single time?

    Science.gov (United States)

    Horsman, Dominic; Heunen, Chris; Pusey, Matthew F; Barrett, Jonathan; Spekkens, Robert W

    2017-09-01

    The standard formalism of quantum theory treats space and time in fundamentally different ways. In particular, a composite system at a given time is represented by a joint state, but the formalism does not prescribe a joint state for a composite of systems at different times. If there were a way of defining such a joint state, this would potentially permit a more even-handed treatment of space and time, and would strengthen the existing analogy between quantum states and classical probability distributions. Under the assumption that the joint state over time is an operator on the tensor product of single-time Hilbert spaces, we analyse various proposals for such a joint state, including one due to Leifer and Spekkens, one due to Fitzsimons, Jones and Vedral, and another based on discrete Wigner functions. Finding various problems with each, we identify five criteria for a quantum joint state over time to satisfy if it is to play a role similar to the standard joint state for a composite system: that it is a Hermitian operator on the tensor product of the single-time Hilbert spaces; that it represents probabilistic mixing appropriately; that it has the appropriate classical limit; that it has the appropriate single-time marginals; that composing over multiple time steps is associative. We show that no construction satisfies all these requirements. If Hermiticity is dropped, then there is an essentially unique construction that satisfies the remaining four criteria.

  1. Simple Atomic Quantum Memory Suitable for Semiconductor Quantum Dot Single Photons

    Science.gov (United States)

    Wolters, Janik; Buser, Gianni; Horsley, Andrew; Béguin, Lucas; Jöckel, Andreas; Jahn, Jan-Philipp; Warburton, Richard J.; Treutlein, Philipp

    2017-08-01

    Quantum memories matched to single photon sources will form an important cornerstone of future quantum network technology. We demonstrate such a memory in warm Rb vapor with on-demand storage and retrieval, based on electromagnetically induced transparency. With an acceptance bandwidth of δ f =0.66 GHz , the memory is suitable for single photons emitted by semiconductor quantum dots. In this regime, vapor cell memories offer an excellent compromise between storage efficiency, storage time, noise level, and experimental complexity, and atomic collisions have negligible influence on the optical coherences. Operation of the memory is demonstrated using attenuated laser pulses on the single photon level. For a 50 ns storage time, we measure ηe2 e 50 ns=3.4 (3 )% end-to-end efficiency of the fiber-coupled memory, with a total intrinsic efficiency ηint=17 (3 )%. Straightforward technological improvements can boost the end-to-end-efficiency to ηe 2 e≈35 %; beyond that, increasing the optical depth and exploiting the Zeeman substructure of the atoms will allow such a memory to approach near unity efficiency. In the present memory, the unconditional read-out noise level of 9 ×10-3 photons is dominated by atomic fluorescence, and for input pulses containing on average μ1=0.27 (4 ) photons, the signal to noise level would be unity.

  2. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    Energy Technology Data Exchange (ETDEWEB)

    Baart, T. A.; Vandersypen, L. M. K. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Eendebak, P. T. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 155, 2600 AD Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)

    2016-05-23

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  3. Optimised quantum hacking of superconducting nanowire single-photon detectors

    Science.gov (United States)

    Tanner, Michael G.; Makarov, Vadim; Hadfield, Robert H.

    2014-03-01

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

  4. Lateral photocurrent spreading in single quantum well infrared photodetectors

    OpenAIRE

    Ershov, Maxim

    1998-01-01

    Lateral physical effects in single quantum well infrared photodetectors (SQWIPs) under non-uniform illumination over detector area are considered. These effects are due mainly to the in-plane transport of the photoinduced charge in the QW. The length of the lateral photocurrent spreading is determined by the in-plane conductivity of the carriers in the QW and characteristic time of the QW recharging, and can be as large as 10-10000 mkm. Closed-form analytical expressions for SQWIP responsivit...

  5. Controlled synthesis of InAs wires, dot and twin-dot array configurations by cleaved edge overgrowth

    Energy Technology Data Exchange (ETDEWEB)

    Uccelli, Emanuele; Bichler, Max; Nuernberger, Simon; Abstreiter, Gerhard; Morral, Anna Fontcuberta i [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany)

    2008-01-30

    We present experimental results on the controlled synthesis of InAs ordered nanostructures with three different grades of complexity: nanowires, quantum dot arrays, and double quantum dot arrays. A model for the diffusion of In adatoms on (110) surfaces explains the observed ordering and establishes general criteria for the optimized fabrication of the three different InAs nanostructure configurations, as a function of the growth conditions. These results are important for the use of ordered InAs nanostructures in future optoelectronic applications.

  6. Realization of electrically tunable single quantum dot nanocavities

    Energy Technology Data Exchange (ETDEWEB)

    Hofbauer, Felix Florian Georg

    2009-03-15

    We investigated the design, fabrication and optical investigation of electrically tunable single quantum dot-photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light matter interaction. We demonstrate that the quantum confined Stark effect can be employed to quickly and reversibly switch the dot-cavity coupling, simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by up to {proportional_to}4 meV relative to the nanocavity mode, before the emission quenches due to carrier tunneling escape from the dots. We directly probe spontaneous emission, irreversible polariton decay and the statistics of the emitted photons from a single-dot nanocavity in the weak and strong coupling regimes. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime and electrical control of zero dimensional polaritons is demonstrated for the first time. The structures investigated are p-i-n photodiodes consisting of an 180nm thick free-standing GaAs membrane into which a two dimensional photonic crystal is formed by etching a triangular lattice of air holes. Low mode volume nanocavities (V{sub mode}<1.6 ({lambda}/n){sup 3}) are realized by omitting 3 holes in a line to form L3 cavities and a single layer of InGaAs self-assembled quantum dots is embedded into the midpoint of the membrane. The nanocavities are electrically contacted via 35 nm thick p- and n-doped contact layers in the GaAs membrane. In the weak coupling regime, time resolved spectroscopy reveals a {proportional_to}7 x shortening of the spontaneous emission lifetime as the dot is tuned through the nanocavity mode, due to the Purcell effect. Upon strongly detuning the same quantum dot transition from the nanocavity mode we observe an additional {proportional_to}8 x lengthening of the spontaneous emission lifetime. These observations unequivocally highlight two regimes of dot

  7. Frequency Conversion of Single Photons: Physics, Devices, and Applications

    Science.gov (United States)

    2012-07-01

    89 6.7 Rabi oscillations in photon counts for downconverted quantum dot single photons...dot, and show that the photon statistics of the quantum dot emission are preserved. Additionally, through the observation of Rabi oscillations in the...InAs is grown by molecular beam epitaxy (MBE, [119]) on a GaAs substrate, due to the lattice mismatch between InAs and GaAs, after the growth of a

  8. Single-atom gating and magnetic interactions in quantum corrals

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Anh T.; Kim, Eugene H.; Ulloa, Sergio E.

    2017-04-01

    Single-atom gating, achieved by manipulation of adatoms on a surface, has been shown in experiments to allow precise control over superposition of electronic states in quantum corrals. Using a Green's function approach, we demonstrate theoretically that such atom gating can also be used to control the coupling between magnetic degrees of freedom in these systems. Atomic gating enables control not only on the direct interaction between magnetic adatoms, but also over superpositions of many-body states which can then control long distance interactions. We illustrate this effect by considering the competition between direct exchange between magnetic impurities and the Kondo screening mediated by the host electrons, and how this is affected by gating. These results suggest that both magnetic and nonmagnetic single-atom gating may be used to investigate magnetic impurity systems with tailored interactions, and may allow the control of entanglement of different spin states.

  9. Single-particle spectroscopic measurements of fluorescent graphene quantum dots.

    Science.gov (United States)

    Xu, Qinfeng; Zhou, Qi; Hua, Zheng; Xue, Qi; Zhang, Chunfeng; Wang, Xiaoyong; Pan, Dengyu; Xiao, Min

    2013-12-23

    We have performed the first single-particle spectroscopic measurements on individual graphene quantum dots (GQDs) and revealed several intriguing fluorescent phenomena that are otherwise hidden in the optical studies of ensemble GQDs. First, despite noticeable differences in the size and the number of layers from particle to particle, all of the GQDs studied possess almost the same spectral lineshapes and peak positions. Second, GQDs with more layers are normally brighter emitters but are associated with shorter fluorescent lifetimes. Third, the fluorescent spectrum of GQDs was red-shifted upon being aged in air, possibly due to the water desorption effect. Finally, the missing emission of single photons and stable fluorescence without any intermittent behavior were observed from individual GQDs.

  10. Single donor electronics and quantum functionalities with advanced CMOS technology.

    Science.gov (United States)

    Jehl, Xavier; Niquet, Yann-Michel; Sanquer, Marc

    2016-03-16

    Recent progresses in quantum dots technology allow fundamental studies of single donors in various semiconductor nanostructures. For the prospect of applications figures of merits such as scalability, tunability, and operation at relatively large temperature are of prime importance. Beyond the case of actual dopant atoms in a host crystal, similar arguments hold for small enough quantum dots which behave as artificial atoms, for instance for single spin control and manipulation. In this context, this experimental review focuses on the silicon-on-insulator devices produced within microelectronics facilities with only very minor modifications to the current industrial CMOS process and tools. This is required for scalability and enabled by shallow trench or mesa isolation. It also paves the way for real integration with conventional circuits, as illustrated by a nanoscale device coupled to a CMOS circuit producing a radio-frequency drive on-chip. At the device level we emphasize the central role of electrostatics in etched silicon nanowire transistors, which allows to understand the characteristics in the full range from zero to room temperature.

  11. Imaging Few-Electron Double Quantum Dots in InAs/InP Nanowires

    Science.gov (United States)

    Trodahl, Halvar J.; Boyd, Erin E.; Bleszynski, Ania; Westervelt, R. M.; Froberg, Linus E.; Samuelson, Lars

    2007-03-01

    InAs quantum dots formed in InAs/InP nanowire heterostructures are attractive candidates for nanoelectronics, spintronics and quantum information processing. Tunnel-coupled double InAs dots defined by InP barriers can be grown using chemical beam epitaxy; each dot can be small enough to hold just a few electrons. It is difficult to lithographically define gates small enough to individually address each dot. With use of a liquid-He cooled scanning probe microscope (SPM), the Coulomb blockade conductance of a single InAs quantum dot in an InAs/InP nanowire has been imaged, using the SPM tip as a movable gate [1]. This approach can individually tune the charge on each InAs dot in an InAs/InP nanowire. We plan to use this technique to investigate tunnel-coupled InAs double dots. [1] A. Bleszynski et al., 28th Int. Conf. on the Physics of Semiconductors, 2006.

  12. Quantum Correlations between Single Telecom Photons and a Multimode On-Demand Solid-State Quantum Memory

    Directory of Open Access Journals (Sweden)

    Alessandro Seri

    2017-05-01

    Full Text Available Quantum correlations between long-lived quantum memories and telecom photons that can propagate with low loss in optical fibers are an essential resource for the realization of large-scale quantum information networks. Significant progress has been realized in this direction with atomic and solid-state systems. Here, we demonstrate quantum correlations between a telecom photon and a multimode on-demand solid state quantum memory. This is achieved by mapping a correlated single photon onto a spin collective excitation in a Pr^{3+}:Y_{2}SiO_{5} crystal for a controllable time. The stored single photons are generated by cavity-enhanced spontaneous parametric down-conversion and heralded by their partner photons at telecom wavelength. These results represent the first demonstration of a multimode on-demand solid state quantum memory for external quantum states of light. They provide an important resource for quantum repeaters and pave the way for the implementation of quantum information networks with distant solid state quantum nodes.

  13. Quantum Correlations between Single Telecom Photons and a Multimode On-Demand Solid-State Quantum Memory

    Science.gov (United States)

    Seri, Alessandro; Lenhard, Andreas; Rieländer, Daniel; Gündoǧan, Mustafa; Ledingham, Patrick M.; Mazzera, Margherita; de Riedmatten, Hugues

    2017-04-01

    Quantum correlations between long-lived quantum memories and telecom photons that can propagate with low loss in optical fibers are an essential resource for the realization of large-scale quantum information networks. Significant progress has been realized in this direction with atomic and solid-state systems. Here, we demonstrate quantum correlations between a telecom photon and a multimode on-demand solid state quantum memory. This is achieved by mapping a correlated single photon onto a spin collective excitation in a Pr3 +:Y2SiO5 crystal for a controllable time. The stored single photons are generated by cavity-enhanced spontaneous parametric down-conversion and heralded by their partner photons at telecom wavelength. These results represent the first demonstration of a multimode on-demand solid state quantum memory for external quantum states of light. They provide an important resource for quantum repeaters and pave the way for the implementation of quantum information networks with distant solid state quantum nodes.

  14. Storing single photons emitted by a quantum memory on a highly excited Rydberg state.

    Science.gov (United States)

    Distante, Emanuele; Farrera, Pau; Padrón-Brito, Auxiliadora; Paredes-Barato, David; Heinze, Georg; de Riedmatten, Hugues

    2017-01-19

    Strong interaction between two single photons is a long standing and important goal in quantum photonics. This would enable a new regime of nonlinear optics and unlock several applications in quantum information science, including photonic quantum gates and deterministic Bell-state measurements. In the context of quantum networks, it would be important to achieve interactions between single photons from independent photon pairs storable in quantum memories. So far, most experiments showing nonlinearities at the single-photon level have used weak classical input light. Here we demonstrate the storage and retrieval of a paired single photon emitted by an ensemble quantum memory in a strongly nonlinear medium based on highly excited Rydberg atoms. We show that nonclassical correlations between the two photons persist after retrieval from the Rydberg ensemble. Our result is an important step towards deterministic photon-photon interactions, and may enable deterministic Bell-state measurements with multimode quantum memories.

  15. Investigating and improving student understanding of quantum mechanics in the context of single photon interference

    Directory of Open Access Journals (Sweden)

    Emily Marshman

    2017-04-01

    Full Text Available Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the abstract quantum theory and concrete laboratory settings and have the potential to help students develop a solid grasp of the foundational issues in quantum mechanics. Here we describe students’ conceptual difficulties with these topics in the context of Mach-Zehnder interferometer experiments with single photons and how the difficulties found in written surveys and individual interviews were used as a guide in the development of a Quantum Interactive Learning Tutorial (QuILT. The QuILT uses an inquiry-based approach to learning and takes into account the conceptual difficulties found via research to help upper-level undergraduate and graduate students learn about foundational quantum mechanics concepts using the concrete quantum optics context. It strives to help students learn the basics of quantum mechanics in the context of single photon experiment, develop the ability to apply fundamental quantum principles to experimental situations in quantum optics, and explore the differences between classical and quantum ideas in a concrete context. We discuss the findings from in-class evaluations suggesting that the QuILT was effective in helping students learn these abstract concepts.

  16. Investigating and improving student understanding of quantum mechanics in the context of single photon interference

    Science.gov (United States)

    Marshman, Emily; Singh, Chandralekha

    2017-06-01

    Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the abstract quantum theory and concrete laboratory settings and have the potential to help students develop a solid grasp of the foundational issues in quantum mechanics. Here we describe students' conceptual difficulties with these topics in the context of Mach-Zehnder interferometer experiments with single photons and how the difficulties found in written surveys and individual interviews were used as a guide in the development of a Quantum Interactive Learning Tutorial (QuILT). The QuILT uses an inquiry-based approach to learning and takes into account the conceptual difficulties found via research to help upper-level undergraduate and graduate students learn about foundational quantum mechanics concepts using the concrete quantum optics context. It strives to help students learn the basics of quantum mechanics in the context of single photon experiment, develop the ability to apply fundamental quantum principles to experimental situations in quantum optics, and explore the differences between classical and quantum ideas in a concrete context. We discuss the findings from in-class evaluations suggesting that the QuILT was effective in helping students learn these abstract concepts.

  17. Ab Initio Quantum Chemical Design of Single Supermolecule Photoactive Machines and Molecular Logical Devices

    National Research Council Canada - National Science Library

    Tamulis, Arvydas

    2001-01-01

    ...: The contractor will investigate quantum mechanical design of light-driven, single supermolecular logically-controlled machines and molecular computing devices based on fullerene and photoactive...

  18. Tuning single GaAs quantum dots in resonance with a rubidium vapor

    NARCIS (Netherlands)

    Akopian, N.; Perinetti, U.; Wang, L.; Rastelli, A.; Schmidt, O.G.; Zwiller, V.

    2010-01-01

    We study single GaAs quantum dots with optical transitions that can be brought into resonance with the widely used D2 transitions of rubidium atoms. We achieve resonance by Zeeman or Stark shifting the quantum dot levels. We discuss an energy stabilization scheme based on the absorption of quantum

  19. Experimental realization of highly efficient broadband coupling of single quantum dots to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian

    2008-01-01

    We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. From these measurements -factors of up to 0...

  20. Near-unity efficiency, single-photon sources based on tapered photonic nanowires

    DEFF Research Database (Denmark)

    Bleuse, Joël; Munsch, Mathieu; Claudon, Julien

    2012-01-01

    Single-photon emission from excitons in InAs Quantum Dots (QD) embedded in GaAs Tapered Photonic Wires (TPW) already demonstrated a 0.72 collection efficiency, with TPWs were the apex is the sharp end of the cone. Going to alternate designs, still based on the idea of the adiabatic deconfinement...

  1. Single photon response in GaAs quantum transport devices for photon-spin quantum state transfer

    Energy Technology Data Exchange (ETDEWEB)

    Kutsuwa, T. [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012 (Japan); Arai, K. [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012 (Japan); ERATO-JST, Semiconductor Spintronics, Project, JST (Japan); Shigyo, H.; Kinjo, H.; Edamatsu, K. [Research Institute of Electrical Communication, Tohoku University, Sendai (Japan); Ono, K. [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012 (Japan); Low Temperature Physics Laboratory, RIKEN, Saitama (Japan); Mitsumori, Y.; Kosaka, H. [CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012 (Japan); Research Institute of Electrical Communication, Tohoku University, Sendai (Japan)

    2006-07-01

    Quantum information can be stored and manipulated by an electron spin if its state was faithfully transferred from messenger photon qubit. Such a quantum state transfer needs to have a function of conversion from photon polarization to electron spin state and flagging the safe conversion without destroying the spin state. We have achieved single photon response by using a quantum dot as an electron trap and a quantum point contact as a charge sensor on GaAs/AlGaAs-based modulation doped structure. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Single photon emission and quantum ring-cavity coupling in InAs/GaAs quantum rings

    Energy Technology Data Exchange (ETDEWEB)

    Gallardo, E; Nowak, A K; Sanvitto, D; Meulen, H P van der; Calleja, J M [Departamento de Fisica de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); MartInez, L J; Prieto, I; Alija, A R; Granados, D; Taboada, A G; GarcIa, J M; Postigo, P A [Instituto de Microelectronica de Madrid, Centro Nacional de MicrotecnologIa, CSIC, Isaac Newton 8, PTM Tres Cantos, E-28760 Madrid (Spain); Sarkar, D, E-mail: eva.gallardo@uam.e [Department of Physics and Astronomy, University of Sheffield, S3 7RH (United Kingdom)

    2010-02-01

    Different InAs/GaAs quantum rings embedded in a photonic crystal microcavity are studied by quantum correlation measurements. Single photon emission, with g{sup (2)}(0) values around 0.3, is demonstrated for a quantum ring not coupled to the microcavity. Characteristic rise-times are found to be longer for excitons than for biexcitons, resulting in the time asymmetry of the exciton-biexciton cross-correlation. No antibunching is observed in another quantum ring weakly coupled to the microcavity.

  3. Quantum correlations of helicity entangled states in non-inertial frames beyond single mode approximation

    Energy Technology Data Exchange (ETDEWEB)

    Harsij, Zeynab, E-mail: z.harsij@ph.iut.ac.ir; Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir

    2014-12-15

    A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation. - Highlights: • The helicity entangled states here are observer independent in non-inertial frames. • It is explicitly shown that Quantum Discord for these states is observer independent. • Geometric Quantum Discord is also not affected by acceleration increase. • Extending to beyond single mode does not change the degree of entanglement. • Beyond single mode approximation the degree of Quantum Discord is also preserved.

  4. Efficient fiber-coupled single-photon sources based on quantum dots

    DEFF Research Database (Denmark)

    Daveau, Raphaël Sura

    This thesis presents the study of solid-state quantum emitters in two dierent forms. The rst part of the thesis deals with quantum dot based single-photon sources with an emphasis on ecient photon extraction into an optical ber. The second part of the thesis covers a theoretical study of optical...... refrigeration with coupled quantum wells. Many photonic quantum information processing applications would benet from a highbrightness, ber-coupled source of triggered single photons. This thesis presents a study of such sources based on quantum dots coupled to unidirectional photonic-crystal waveguide devices...

  5. Multi-state discrimination below the quantum noise limit at the single-photon level

    Science.gov (United States)

    Ferdinand, A. R.; DiMario, M. T.; Becerra, F. E.

    2017-10-01

    Measurements approaching the ultimate quantum limits of sensitivity are central in quantum information processing, quantum metrology, and communication. Quantum measurements to discriminate multiple states at the single-photon level are essential for optimizing information transfer in low-power optical communications and quantum communications, and can enhance the capabilities of many quantum information protocols. Here, we theoretically investigate and experimentally demonstrate the discrimination of multiple coherent states of light with sensitivities surpassing the quantum noise limit (QNL) at the single-photon level under realistic conditions of loss and noise based on strategies implementing globally-optimized adaptive measurements with single photon counting and displacement operations. These discrimination strategies can provide realistic advantages to enhance information transfer at low powers, and are compatible with photon number resolving detection, which provides robustness at high powers, thus allowing for surpassing the QNL at arbitrary input power levels under realistic conditions.

  6. A triple quantum dot in a single-wall carbon nanotube

    DEFF Research Database (Denmark)

    Grove-Rasmussen, Kasper; Jørgensen, Henrik Ingerslev; Hayashi, T.

    2008-01-01

    A top-gated single-wall carbon nanotube is used to define three coupled quantum dots in series between two electrodes. The additional electron number on each quantum dot is controlled by top-gate voltages allowing for current measurements of single, double, and triple quantum dot stability diagrams....... Simulations using a capacitor model including tunnel coupling between neighboring dots captures the observed behavior with good agreement. Furthermore, anticrossings between indirectly coupled levels and higher order cotunneling are discussed. Udgivelsesdato: April...

  7. A single molecule investigation of the photostability of quantum dots.

    Directory of Open Access Journals (Sweden)

    Eva Christensen Arnspang

    Full Text Available Quantum dots (QDs are very attractive probes for multi-color fluorescence imaging in biological applications because of their immense brightness and reported extended photostability. We report here however that single QDs, suitable for biological applications, that are subject to continuous blue excitation from a conventional 100 W mercury arc lamp will undergo a continuous blue-switching of the emission wavelength eventually reaching a permanent dark, photobleached state. We further show that β-mercaptoethanol has a dual stabilizing effect on the fluorescence emission of QDs: 1 by increasing the frequency of time that a QD is in its fluorescent state, and 2 by decreasing the photobleaching rate. The observed QD color spectral switching is especially detrimental for multi-color single molecule applications, as we regularly observe spectral blue-shifts of 50 nm, or more even after only ten seconds of illumination. However, of significant importance for biological applications, we find that even small, biologically compatible, concentrations (25 µM of β-mercaptoethanol has a significant stabilizing effect on the emission color of QDs, but that greater amounts are required to completely abolish the spectral blue shifting or to minimize the emission intermittency of QDs.

  8. Experimental Adiabatic Quantum Factorization under Ambient Conditions Based on a Solid-State Single Spin System.

    Science.gov (United States)

    Xu, Kebiao; Xie, Tianyu; Li, Zhaokai; Xu, Xiangkun; Wang, Mengqi; Ye, Xiangyu; Kong, Fei; Geng, Jianpei; Duan, Changkui; Shi, Fazhan; Du, Jiangfeng

    2017-03-31

    The adiabatic quantum computation is a universal and robust method of quantum computing. In this architecture, the problem can be solved by adiabatically evolving the quantum processor from the ground state of a simple initial Hamiltonian to that of a final one, which encodes the solution of the problem. Adiabatic quantum computation has been proved to be a compatible candidate for scalable quantum computation. In this Letter, we report on the experimental realization of an adiabatic quantum algorithm on a single solid spin system under ambient conditions. All elements of adiabatic quantum computation, including initial state preparation, adiabatic evolution (simulated by optimal control), and final state read-out, are realized experimentally. As an example, we found the ground state of the problem Hamiltonian S_{z}I_{z} on our adiabatic quantum processor, which can be mapped to the factorization of 35 into its prime factors 5 and 7.

  9. Single-photon non-linear optics with a quantum dot in a waveguide.

    Science.gov (United States)

    Javadi, A; Söllner, I; Arcari, M; Hansen, S Lindskov; Midolo, L; Mahmoodian, S; Kiršanskė, G; Pregnolato, T; Lee, E H; Song, J D; Stobbe, S; Lodahl, P

    2015-10-23

    Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.

  10. Photonic transistor and router using a single quantum-dot-confined spin in a single-sided optical microcavity.

    Science.gov (United States)

    Hu, C Y

    2017-03-28

    The future Internet is very likely the mixture of all-optical Internet with low power consumption and quantum Internet with absolute security guaranteed by the laws of quantum mechanics. Photons would be used for processing, routing and com-munication of data, and photonic transistor using a weak light to control a strong light is the core component as an optical analogue to the electronic transistor that forms the basis of modern electronics. In sharp contrast to previous all-optical tran-sistors which are all based on optical nonlinearities, here I introduce a novel design for a high-gain and high-speed (up to terahertz) photonic transistor and its counterpart in the quantum limit, i.e., single-photon transistor based on a linear optical effect: giant Faraday rotation induced by a single electronic spin in a single-sided optical microcavity. A single-photon or classical optical pulse as the gate sets the spin state via projective measurement and controls the polarization of a strong light to open/block the photonic channel. Due to the duality as quantum gate for quantum information processing and transistor for optical information processing, this versatile spin-cavity quantum transistor provides a solid-state platform ideal for all-optical networks and quantum networks.

  11. Photonic transistor and router using a single quantum-dot-confined spin in a single-sided optical microcavity

    Science.gov (United States)

    Hu, C. Y.

    2017-03-01

    The future Internet is very likely the mixture of all-optical Internet with low power consumption and quantum Internet with absolute security guaranteed by the laws of quantum mechanics. Photons would be used for processing, routing and com-munication of data, and photonic transistor using a weak light to control a strong light is the core component as an optical analogue to the electronic transistor that forms the basis of modern electronics. In sharp contrast to previous all-optical tran-sistors which are all based on optical nonlinearities, here I introduce a novel design for a high-gain and high-speed (up to terahertz) photonic transistor and its counterpart in the quantum limit, i.e., single-photon transistor based on a linear optical effect: giant Faraday rotation induced by a single electronic spin in a single-sided optical microcavity. A single-photon or classical optical pulse as the gate sets the spin state via projective measurement and controls the polarization of a strong light to open/block the photonic channel. Due to the duality as quantum gate for quantum information processing and transistor for optical information processing, this versatile spin-cavity quantum transistor provides a solid-state platform ideal for all-optical networks and quantum networks.

  12. Quantum photonics hybrid integration platform

    Energy Technology Data Exchange (ETDEWEB)

    Murray, E.; Floether, F. F. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Ellis, D. J. P.; Meany, T.; Bennett, A. J., E-mail: anthony.bennet@crl.toshiba.co.uk; Shields, A. J. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Lee, J. P. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Engineering Department, University of Cambridge, 9 J. J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Griffiths, J. P.; Jones, G. A. C.; Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-10-26

    Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single-photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to a SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO{sub 2} cladding. A tuneable Mach Zehnder interferometer (MZI) modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single-photon nature of the emission was verified using the on-chip MZI as a beamsplitter in a Hanbury Brown and Twiss measurement.

  13. Quantum photonics hybrid integration platform

    CERN Document Server

    Murray, Eoin; Meany, Thomas; Flother, Frederick F; Lee, James P; Griffiths, Jonathan P; Jones, Geb A C; Farrer, Ian; Ritchie, David A; Bennet, Anthony J; Shields, Andrew J

    2015-01-01

    Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to an SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO2 cladding. A tuneable Mach Zehnder modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single photon nature of the emission was veri?ed by an on-chip Hanbury Brown and Twiss measurement.

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

    Science.gov (United States)

    Tang, Jian-Shun; Zhou, Zong-Quan; Wang, Yi-Tao; Li, Chuan-Feng; Guo, Guang-Can

    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 scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devices.

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2015-10-15

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

  17. Optical studies on a single GaAs laterally coupled quantum dot in comparison with an uncoupled quantum dot

    Science.gov (United States)

    Kim, Heedae; Song, Jin Dong

    2018-01-01

    We performed spectroscopy studies on a single GaAs laterally coupled quantum dot and an uncoupled quantum dot. Photoluminescence spectra confirmed the presence of optical coupling in the coupled quantum dot through dipole-dipole interactions. The optical coupling was investigated in terms of the integrated photoluminescence intensities and redshift of emission energies as the excitation power was increased. The excitation intensity was increased with linearly polarized light in the lateral coupling direction 1 1 bar 0 , which resulted in excitons X1 and X2 of the coupled quantum dot showing a clear photoluminescence peak shift to lower energy with drastically different power factors. These results were obtained by integrating the PL spectrum and comparing it to that of a single quantum dot. We also found that the decay rates of X1 and X2 in the coupled quantum dot increased significantly as a consequence of overlap of electron and hole wavefunctions extended via optical coupling in individual dots of the coupled quantum dot system.

  18. Single photon emission from site-controlled InGaN/GaN quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei; Hill, Tyler A.; Deng, Hui, E-mail: dengh@umich.edu [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109 (United States); Teng, Chu-Hsiang; Lee, Leung-Kway; Ku, Pei-Cheng, E-mail: peicheng@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States)

    2013-11-04

    Single photon emission was observed from site-controlled InGaN/GaN quantum dots. The single-photon nature of the emission was verified by the second-order correlation function up to 90 K, the highest temperature to date for site-controlled quantum dots. Micro-photoluminescence study on individual quantum dots showed linearly polarized single exciton emission with a lifetime of a few nanoseconds. The dimensions of these quantum dots were well controlled to the precision of state-of-the-art fabrication technologies, as reflected in the uniformity of their optical properties. The yield of optically active quantum dots was greater than 90%, among which 13%–25% exhibited single photon emission at 10 K.

  19. Online evolution reconstruction from a single measurement record with random time intervals for quantum communication

    Science.gov (United States)

    Zhou, Hua; Su, Yang; Wang, Rong; Zhu, Yong; Shen, Huiping; Pu, Tao; Wu, Chuanxin; Zhao, Jiyong; Zhang, Baofu; Xu, Zhiyong

    2017-10-01

    Online reconstruction of a time-variant quantum state from the encoding/decoding results of quantum communication is addressed by developing a method of evolution reconstruction from a single measurement record with random time intervals. A time-variant two-dimensional state is reconstructed on the basis of recovering its expectation value functions of three nonorthogonal projectors from a random single measurement record, which is composed from the discarded qubits of the six-state protocol. The simulated results prove that our method is robust to typical metro quantum channels. Our work extends the Fourier-based method of evolution reconstruction from the version for a regular single measurement record with equal time intervals to a unified one, which can be applied to arbitrary single measurement records. The proposed protocol of evolution reconstruction runs concurrently with the one of quantum communication, which can facilitate the online quantum tomography.

  20. Efficiency and Coherence of Quantum-Dot Single-Photon Sources

    DEFF Research Database (Denmark)

    Madsen, Marta Arcari

    in a Hong-Ou-Mandel experiment. Finally, we demonstrate that a coherent quantum dot coupled to a photonic crystal waveguide is not only a promising single-photon source, but also a highly nonlinear system sensitive at the single-photon level. By performing resonant transmission measurements through...... on this result, we improved the design of the photonic crystal waveguide, and we characterized in detail the efficiency of the device and the coherence of the emitted single photons. We investigate the decoherence mechanisms affecting the quantum dots by performing resonance fluorescence experiments on emitters...... of a single charge. A very high degree of coherence can be achieved by embedding quantum dots in electrically gated samples. We show that a single quantum dot behaves like a nearly-ideal two-level system in a sample with electrical gates, and single photons emitted up to 1 μs apart show indistinguishability...

  1. Semiconductor Quantum Rods as Single Molecule FluorescentBiological Labels

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua; Gu, Weiwei; Boussert, Benjamine; Koski, Kristie; Gerion, Daniele; Manna, Liberato; Le Gros, Mark; Larabell, Carolyn; Alivisatos, A. Paul

    2006-05-29

    In recent years, semiconductor quantum dots have beenapplied with great advantage in a wide range of biological imagingapplications. The continuing developments in the synthesis of nanoscalematerials and specifically in the area of colloidal semiconductornanocrystals have created an opportunity to generate a next generation ofbiological labels with complementary or in some cases enhanced propertiescompared to colloidal quantum dots. In this paper, we report thedevelopment of rod shaped semiconductor nanocrystals (quantum rods) asnew fluorescent biological labels. We have engineered biocompatiblequantum rods by surface silanization and have applied them fornon-specific cell tracking as well as specific cellular targeting. Theproperties of quantum rods as demonstrated here are enhanced sensitivityand greater resistance for degradation as compared to quantum dots.Quantum rods have many potential applications as biological labels insituations where their properties offer advantages over quantumdots.

  2. Quantum optics. All-optical routing of single photons by a one-atom switch controlled by a single photon.

    Science.gov (United States)

    Shomroni, Itay; Rosenblum, Serge; Lovsky, Yulia; Bechler, Orel; Guendelman, Gabriel; Dayan, Barak

    2014-08-22

    The prospect of quantum networks, in which quantum information is carried by single photons in photonic circuits, has long been the driving force behind the effort to achieve all-optical routing of single photons. We realized a single-photon-activated switch capable of routing a photon from any of its two inputs to any of its two outputs. Our device is based on a single atom coupled to a fiber-coupled, chip-based microresonator. A single reflected control photon toggles the switch from high reflection (R ~ 65%) to high transmission (T ~ 90%), with an average of ~1.5 control photons per switching event (~3, including linear losses). No additional control fields are required. The control and target photons are both in-fiber and practically identical, making this scheme compatible with scalable architectures for quantum information processing. Copyright © 2014, American Association for the Advancement of Science.

  3. Single qudit realization of the Deutsch algorithm using superconducting many-level quantum circuits

    Science.gov (United States)

    Kiktenko, E. O.; Fedorov, A. K.; Strakhov, A. A.; Man'ko, V. I.

    2015-07-01

    Design of a large-scale quantum computer has paramount importance for science and technologies. We investigate a scheme for realization of quantum algorithms using noncomposite quantum systems, i.e., systems without subsystems. In this framework, n artificially allocated "subsystems" play a role of qubits in n-qubits quantum algorithms. With focus on two-qubit quantum algorithms, we demonstrate a realization of the universal set of gates using a d = 5 single qudit state. Manipulation with an ancillary level in the systems allows effective implementation of operators from U(4) group via operators from SU(5) group. Using a possible experimental realization of such systems through anharmonic superconducting many-level quantum circuits, we present a blueprint for a single qudit realization of the Deutsch algorithm, which generalizes previously studied realization based on the virtual spin representation (Kessel et al., 2002 [9]).

  4. Heralded quantum gates for atomic systems assisted by the scattering of photons off single emitters

    Science.gov (United States)

    Song, Guo-Zhu; Liu, Qian; Qiu, Jing; Yang, Guo-Jian; Alzahrani, Faris; Hobiny, Aatef; Deng, Fu-Guo; Zhang, Mei

    2017-12-01

    Quantum logic gates are essential in quantum information processing. Here, we propose three heralded schemes for universal quantum gates, including the controlled-NOT, Toffoli, and Fredkin gates on atomic systems, assisted by the scattering of photons off single emitters in one-dimensional waveguides. Interestingly, our schemes can turn faulty scattering processes of photons off atoms into the detection of the photon polarization. Furthermore, auxiliary atomic qubits are not needed and only one photon medium is adopted. With current technology, we discuss the feasibility of these universal quantum gates, concluding that they are feasible and scalable in solid-state quantum systems. We provide a different method for realizing universal quantum gates, and it may be useful in quantum information processing in the future.

  5. Pure Gaussian states from quantum harmonic oscillator chains with a single local dissipative process

    Science.gov (United States)

    Ma, Shan; Woolley, Matthew J.; Petersen, Ian R.; Yamamoto, Naoki

    2017-03-01

    We study the preparation of entangled pure Gaussian states via reservoir engineering. In particular, we consider a chain consisting of (2\\aleph +1) quantum harmonic oscillators where the central oscillator of the chain is coupled to a single reservoir. We then completely parametrize the class of (2\\aleph +1) -mode pure Gaussian states that can be prepared by this type of quantum harmonic oscillator chain. This parametrization allows us to determine the steady-state entanglement properties of such quantum harmonic oscillator chains.

  6. Single-quadrature continuous-variable quantum key distribution

    DEFF Research Database (Denmark)

    Gehring, Tobias; Jacobsen, Christian Scheffmann; Andersen, Ulrik Lund

    2016-01-01

    Most continuous-variable quantum key distribution schemes are based on the Gaussian modulation of coherent states followed by continuous quadrature detection using homodyne detectors. In all previous schemes, the Gaussian modulation has been carried out in conjugate quadratures thus requiring two...... commercialization of continuous-variable quantum key distribution, provided that the low noise requirement can be achieved....

  7. High-resolution photoluminescence studies of single semiconductor quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis

    2000-01-01

    Semiconductor quantum dots, especially those formed by self-organized growth, are considered a promising material system for future optical devices [1] and the optical properties of quantum dot ensembles have been investigated in detail over the past years. Recently, considerable interest has dev...

  8. Single-Photon Technologies Based on Quantum-Dots in Photonic Crystals

    DEFF Research Database (Denmark)

    Lehmann, Tau Bernstorff

    In this thesis, the application of semiconductor quantum-dots in photonic crystals is explored as aresource for single-photon technology.Two platforms based on photonic crystals, a cavity and a waveguide, are examined as platformssingle-photon sources. Both platforms demonstrate strong single......-photons from a quantum-dot are routed on timescalesof the exciton lifetime. Using active demultiplexing a three-fold single-photon state is generated at anextracted rate of 2:03 ±0:49 Hz.An on-chip power divider integrated with a quantum-dot is investigated. Correlation measurementof the photon statistic...... veries the single-photon nature of the quantum-dot. Furthermore correlationmeasurement between the outputs of the power divider conrms the passive separation of the singlephotonemission.A scheme for post-emission entanglement generation between single-photons from an efficientsource is discussed...

  9. Quantum dot-micropillars: a bright source of coherent single photons

    DEFF Research Database (Denmark)

    Unsleber, Sebastian; He, Yu-Ming; Maier, Sebastian

    2016-01-01

    We present the efficient generation of coherent single photons based on quantum dots in micropillars. We utilize a scalable lithography scheme leading to quantum dot-micropillar devices with 74% extraction efficiency. Via pulsed strict resonant pumping, we show an indistinguishability...

  10. QUANTUM CRYPTOGRAPHY SYSTEM WITH A SINGLE PHOTON SOURCE BASED ON THE SPONTANEOUS PARAMETRIC SCATTERING EFFECT

    Directory of Open Access Journals (Sweden)

    V. I. Egorov

    2012-01-01

    Full Text Available A scheme of a single photon source for quantum informatics applications based on the spontaneous parametric scattering effect is proposed and a quantum cryptography setup using it is presented. The system is compared to the alternative ones that operate with attenuated classic light.

  11. A heterogeneous III-V/silicon integration platform for on-chip quantum photonic circuits with single quantum dot devices

    CERN Document Server

    Davanco, Marcelo; Sapienza, Luca; Zhang, Chen-Zhao; Cardoso, Jose Vinicius De Miranda; Verma, Varun; Mirin, Richard; Nam, Sae Woo; Liu, Liu; Srinivasan, Kartik

    2016-01-01

    Photonic integration is an enabling technology for photonic quantum science, offering greater scalability, stability, and functionality than traditional bulk optics. Here, we describe a scalable, heterogeneous III-V/silicon integration platform to produce Si$_3$N$_4$ photonic circuits incorporating GaAs-based nanophotonic devices containing self-assembled InAs/GaAs quantum dots. We demonstrate pure singlephoton emission from individual quantum dots in GaAs waveguides and cavities - where strong control of spontaneous emission rate is observed - directly launched into Si$_3$N$_4$ waveguides with > 90 % efficiency through evanescent coupling. To date, InAs/GaAs quantum dots constitute the most promising solidstate triggered single-photon sources, offering bright, pure and indistinguishable emission that can be electrically and optically controlled. Si$_3$N$_4$ waveguides offer low-loss propagation, tailorable dispersion and high Kerr nonlinearities, desirable for linear and nonlinear optical signal processing d...

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

    Science.gov (United States)

    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.

  13. Quantum ion-acoustic oscillations in single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Khan, S.A. [Kyoto Univ., Katsura (Japan). Graduate School of Engineering; Quaid-i-Azam Univ., Islamabad (Pakistan). National Centre for Physics; Iqbal, Z. [University of Management and Technology, Sialkot (Pakistan); Wazir, Z. [Riphah International Univ., Islamabad (Pakistan). Dept. of Basic Sciences; Rehman, Aman ur [Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad (Pakistan)

    2016-08-01

    Quantum ion-acoustic oscillations in single-walled carbon nanotubes are studied by employing a quantum hydrodynamics model. The dispersion equation is obtained by Fourier transformation, which exhibits the existence of quantum ion-acoustic wave affected by change of density balance due to presence of positive or negative heavy species as stationary ion clusters and wave potential at equilibrium. The numerical results are presented, and the role of quantum degeneracy, nanotube geometry, electron exchange-correlation effects, and concentration and polarity of heavy species on wave dispersion is pointed out for typical systems of interest.

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

    Science.gov (United States)

    Owari, Masaki; Kato, Go; Hayashi, Masahito

    2018-01-01

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

  15. Quantum interference in a single anisotropic quantum dot near hyperbolic metamaterials.

    Science.gov (United States)

    Sun, Lu; Jiang, Chun

    2016-04-04

    We theoretically demonstrate an anisotropic quantum vacuum created by a judiciously designed hyperbolic metamaterial. An electric dipole located nearby shows strong orientation dependence in the decay rate. With a proper arrangement of the ellipsoid-shaped CdSe/ZnSe quantum dot relative to the Ag/TiO2 metamaterial, the anisotropies of quantum vacuum and quantum dot are harnessed to achieve an extraordinary quantum interference between radiative decay channels of orthogonal transitions. The ratio between cross damping term and spontaneous decay rate, Γij/Γii, which never exceeds unity in previously reported works reaches 1.04 in our numerical results. The corresponding evolution of excited state population in quantum dot is also dramatically modified.

  16. Hybrid confocal Raman fluorescence microscopy on single cells using semiconductor quantum dots

    NARCIS (Netherlands)

    van Manen, H.J.; Otto, Cornelis

    2007-01-01

    We have overcome the traditional incompatibility of Raman microscopy with fluorescence microscopy by exploiting the optical properties of semiconductor fluorescent quantum dots (QDs). Here we present a hybrid Raman fluorescence spectral imaging approach for single-cell microscopy applications. We

  17. Quantum cascade laser infrared spectroscopy of single cancer cells

    KAUST Repository

    Patel, Imran

    2017-03-27

    Quantum cascade laser infrared spectroscopy is a next generation novel imaging technique allowing high resolution spectral imaging of cells. We show after spectral pre-processing, identification of different cancer cell populations within minutes.

  18. Exciton dephasing in single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis

    2000-01-01

    . The homogeneous and inhomogeneous broadening of InGaAs quantum dot luminescence is of central importance for the potential application of this material system in optoelectronic devices. Recent measurements of MOCVD-grown InAs/InGaAs quantum dots indicate a large homogeneous broadening at room temperature due......The homogeneous linewidth of excitonic transitions is a parameter of fundamental physical importance. In self-assembled quantum dot systems, a strong inhomogeneous broadening due to dot size fluctuations masks the homogeneous linewidth associated with transitions between individual states...... to fast dephasing. We present an investigation of the low-temperature homogeneous linewidth of individual PL lines from MBE-grown In0.5Ga0.5As/GaAs quantum dots....

  19. Single-photon sources for quantum technologies - Results of the joint research project SIQUTE

    DEFF Research Database (Denmark)

    Kück, S.; López, M.; Rodiek, B.

    2017-01-01

    In this presentation, the results of the joint research project “Single-Photon Sources for Quantum Technologies” (SIQUTE) [1] will be presented. The focus will be on the development of absolutely characterized single-photon sources, on the realization of an efficient waveguide-based single...

  20. Quantum resource theories in the single-shot regime

    Science.gov (United States)

    Gour, Gilad

    2017-06-01

    One of the main goals of any resource theory such as entanglement, quantum thermodynamics, quantum coherence, and asymmetry, is to find necessary and sufficient conditions that determine whether one resource can be converted to another by the set of free operations. Here we find such conditions for a large class of quantum resource theories which we call affine resource theories. Affine resource theories include the resource theories of athermality, asymmetry, and coherence, but not entanglement. Remarkably, the necessary and sufficient conditions can be expressed as a family of inequalities between resource monotones (quantifiers) that are given in terms of the conditional min-entropy. The set of free operations is taken to be (1) the maximal set (i.e., consists of all resource nongenerating quantum channels) or (2) the self-dual set of free operations (i.e., consists of all resource nongenerating maps for which the dual map is also resource nongenerating). As an example, we apply our results to quantum thermodynamics with Gibbs preserving operations, and several other affine resource theories. Finally, we discuss the applications of these results to resource theories that are not affine and, along the way, provide the necessary and sufficient conditions that a quantum resource theory consists of a resource destroying map.

  1. DESIGN METHODOLOGIES AND TOOLS FOR SINGLE-FLUX QUANTUM LOGIC CIRCUITS

    Science.gov (United States)

    2017-10-01

    DESIGN METHODOLOGIES AND TOOLS FOR SINGLE-FLUX QUANTUM LOGIC CIRCUITS UNIVERSITY OF SOUTHERN CALIFORNIA OCTOBER 2017 FINAL...Directorate This report is published in the interest of scientific and technical information exchange, and its publication does not constitute the...SUBTITLE DESIGN METHODOLOGIES AND TOOLS FOR SINGLE-FLUX QUANTUM LOGIC CIRCUITS 5a. CONTRACT NUMBER FA8750-15-C-0203 5b. GRANT NUMBER N/A 5c. PROGRAM

  2. Highly anisotropic decay rate of single quantum dots in photonic crystal membranes

    DEFF Research Database (Denmark)

    Wang, Qin; Stobbe, Søren; Nielsen, Henri Thyrrestrup

    2010-01-01

    We measured the variation of spontaneous emission rates with polarization for self-assembled single quantum-dots in photonic crystal membranes, and obtained a maximum anisotropy factor of 6 between decay rates of the two nondegenerate bright states.......We measured the variation of spontaneous emission rates with polarization for self-assembled single quantum-dots in photonic crystal membranes, and obtained a maximum anisotropy factor of 6 between decay rates of the two nondegenerate bright states....

  3. On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits.

    Science.gov (United States)

    Elshaari, Ali W; Zadeh, Iman Esmaeil; Fognini, Andreas; Reimer, Michael E; Dalacu, Dan; Poole, Philip J; Zwiller, Val; Jöns, Klaus D

    2017-08-30

    Quantum light plays a pivotal role in modern science and future photonic applications. Since the advent of integrated quantum nanophotonics different material platforms based on III-V nanostructures-, colour centers-, and nonlinear waveguides as on-chip light sources have been investigated. Each platform has unique advantages and limitations; however, all implementations face major challenges with filtering of individual quantum states, scalable integration, deterministic multiplexing of selected quantum emitters, and on-chip excitation suppression. Here we overcome all of these challenges with a hybrid and scalable approach, where single III-V quantum emitters are positioned and deterministically integrated in a complementary metal-oxide-semiconductor-compatible photonic circuit. We demonstrate reconfigurable on-chip single-photon filtering and wavelength division multiplexing with a foot print one million times smaller than similar table-top approaches, while offering excitation suppression of more than 95 dB and efficient routing of single photons over a bandwidth of 40 nm. Our work marks an important step to harvest quantum optical technologies' full potential.Combining different integration platforms on the same chip is currently one of the main challenges for quantum technologies. Here, Elshaari et al. show III-V Quantum Dots embedded in nanowires operating in a CMOS compatible circuit, with controlled on-chip filtering and tunable routing.

  4. Observation of entanglement between a quantum dot spin and a single photon.

    Science.gov (United States)

    Gao, W B; Fallahi, P; Togan, E; Miguel-Sanchez, J; Imamoglu, A

    2012-11-15

    Entanglement has a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen-vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin-photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.

  5. Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit

    CERN Document Server

    Santhosh, Kotni; Chuntonov, Lev; Haran, Gilad

    2015-01-01

    The strong interaction of individual quantum emitters with resonant cavities is of fundamental interest for understanding light matter interactions, as well as for quantum information processing and quantum communication applications. Plasmonic cavities hold the promise of attaining the strong coupling regime even under ambient conditions and within subdiffraction volumes. Recent experiments revealed strong coupling between individual plasmonic structures and multiple organic molecules, but so far strong coupling at the limit of a single quantum emitter has not been reported. Here we demonstrate vacuum Rabi splitting, a manifestation of strong coupling, using silver bowtie plasmonic cavities loaded with semiconductor quantum dots (QDs). A transparency dip is observed in the scattering spectra of individual bowties with one to a few QDs in their gaps. Rabi splitting values as high as 180 meV are registered with a single QD. These observations are verified by polarization-dependent experiments and validated by ...

  6. Simultaneous Teleportation of Arbitrary Two-qubit and Two Arbitrary Single-qubit States Using A Single Quantum Resource

    Science.gov (United States)

    Choudhury, Binayak S.; Dhara, Arpan

    2017-09-01

    In this paper we present a teleportation protocol by which the multitask of transfer of a two-qubit and two single-qubit quantum states is performed simultaneously with the help of a single entangled channel. The protocol is under the supervision of a controller. There are three pairs of senders and receivers who are connected among themselves along with the controller by a single entangled state. The teleportation protocol is perfect.

  7. Two-message quantum-Arthur-Merlin game with single-qubit measurements

    Science.gov (United States)

    Morimae, Tomoyuki

    2016-06-01

    We show that the class quantum-Arthur-Merlin (QAM) does not change even if the verifier's ability is restricted to only single-qubit measurements. To show the result, we use the idea of measurement-based quantum computing: the verifier, who can do only single-qubit measurements, can test the graph state sent from the prover and use it for his measurement-based quantum computing. Inspired by this construction, we also introduce a problem which we call stabilizer state optimization, and show that it is QMA-complete.

  8. Extracting quantum work statistics and fluctuation theorems by single-qubit interferometry.

    Science.gov (United States)

    Dorner, R; Clark, S R; Heaney, L; Fazio, R; Goold, J; Vedral, V

    2013-06-07

    We propose an experimental scheme to verify the quantum nonequilibrium fluctuation relations using current technology. Specifically, we show that the characteristic function of the work distribution for a nonequilibrium quench of a general quantum system can be extracted by Ramsey interferometry of a single probe qubit. Our scheme paves the way for the full characterization of nonequilibrium processes in a variety of quantum systems, ranging from single particles to many-body atomic systems and spin chains. We demonstrate our idea using a time-dependent quench of the motional state of a trapped ion, where the internal pseudospin provides a convenient probe qubit.

  9. Temperature dependence of the single photon emission from interface-fluctuation GaN quantum dots.

    Science.gov (United States)

    Le Roux, F; Gao, K; Holmes, M; Kako, S; Arita, M; Arakawa, Y

    2017-11-23

    The temperature dependent single photon emission statistics of interface-fluctuation GaN quantum dots are reported. Quantum light emission is confirmed at temperatures up to ~77 K, by which point the background emission degrades the emission purity and results in a measured g(2) (0) in excess of 0.5. A discussion on the extent of the background contamination is also given through comparison to extensive data taken under various ambient and experimental conditions, revealing that the quantum dots themselves are emitting single photons with high purity.

  10. Quantum nonlinear optics with single photons enabled by strongly interacting atoms.

    Science.gov (United States)

    Peyronel, Thibault; Firstenberg, Ofer; Liang, Qi-Yu; Hofferberth, Sebastian; Gorshkov, Alexey V; Pohl, Thomas; Lukin, Mikhail D; Vuletić, Vladan

    2012-08-02

    The realization of strong nonlinear interactions between individual light quanta (photons) is a long-standing goal in optical science and engineering, being of both fundamental and technological significance. In conventional optical materials, the nonlinearity at light powers corresponding to single photons is negligibly weak. Here we demonstrate a medium that is nonlinear at the level of individual quanta, exhibiting strong absorption of photon pairs while remaining transparent to single photons. The quantum nonlinearity is obtained by coherently coupling slowly propagating photons to strongly interacting atomic Rydberg states in a cold, dense atomic gas. Our approach paves the way for quantum-by-quantum control of light fields, including single-photon switching, all-optical deterministic quantum logic and the realization of strongly correlated many-body states of light.

  11. Quantum nonlinear optics with single photons enabled by strongly interacting atoms

    DEFF Research Database (Denmark)

    Peyronel, Thibault; Firstenberg, Ofer; Liang, Qi Yu

    2012-01-01

    The realization of strong nonlinear interactions between individual light quanta (photons) is a long-standing goal in optical science and engineering, being of both fundamental and technological significance. In conventional optical materials, the nonlinearity at light powers corresponding...... to single photons is negligibly weak. Here we demonstrate a medium that is nonlinear at the level of individual quanta, exhibiting strong absorption of photon pairs while remaining transparent to single photons. The quantum nonlinearity is obtained by coherently coupling slowly propagating photons...... to strongly interacting atomic Rydberg states in a cold, dense atomic gas. Our approach paves the way for quantum-by-quantum control of light fields, including single-photon switching, all-optical deterministic quantum logic and the realization of strongly correlated many-body states of light....

  12. Scanning gate imaging of two coupled quantum dots in single-walled carbon nanotubes.

    Science.gov (United States)

    Zhou, Xin; Hedberg, James; Miyahara, Yoichi; Grutter, Peter; Ishibashi, Koji

    2014-12-12

    Two coupled single wall carbon nanotube quantum dots in a multiple quantum dot system were characterized by using a low temperature scanning gate microscopy (SGM) technique, at a temperature of 170 mK. The locations of single wall carbon nanotube quantum dots were identified by taking the conductance images of a single wall carbon nanotube contacted by two metallic electrodes. The single electron transport through single wall carbon nanotube multiple quantum dots has been observed by varying either the position or voltage bias of a conductive atomic force microscopy tip. Clear hexagonal patterns were observed in the region of the conductance images where only two sets of overlapping conductance rings are visible. The values of coupling capacitance over the total capacitance of the two dots, C(m)/C(1(2)) have been extracted to be 0.21 ∼ 0.27 and 0.23 ∼ 0.28, respectively. In addition, the interdot coupling (conductance peak splitting) has also been confirmed in both conductance image measurement and current-voltage curves. The results show that a SGM technique enables spectroscopic investigation of coupled quantum dots even in the presence of unexpected multiple quantum dots.

  13. Single-hidden-layer feed-forward quantum neural network based on Grover learning.

    Science.gov (United States)

    Liu, Cheng-Yi; Chen, Chein; Chang, Ching-Ter; Shih, Lun-Min

    2013-09-01

    In this paper, a novel single-hidden-layer feed-forward quantum neural network model is proposed based on some concepts and principles in the quantum theory. By combining the quantum mechanism with the feed-forward neural network, we defined quantum hidden neurons and connected quantum weights, and used them as the fundamental information processing unit in a single-hidden-layer feed-forward neural network. The quantum neurons make a wide range of nonlinear functions serve as the activation functions in the hidden layer of the network, and the Grover searching algorithm outstands the optimal parameter setting iteratively and thus makes very efficient neural network learning possible. The quantum neuron and weights, along with a Grover searching algorithm based learning, result in a novel and efficient neural network characteristic of reduced network, high efficient training and prospect application in future. Some simulations are taken to investigate the performance of the proposed quantum network and the result show that it can achieve accurate learning. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates.

    Science.gov (United States)

    Birowosuto, M D; Zhang, G; Yokoo, A; Takiguchi, M; Notomi, M

    2014-05-19

    We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO(2)), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive-index materials of Si. Experimentally, the inhibition factor ζ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO(2) and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.

  15. High-density 1.54 μm InAs/InGaAlAs/InP(100) based quantum dots with reduced size inhomogeneity

    Science.gov (United States)

    Banyoudeh, Saddam; Reithmaier, Johann Peter

    2015-09-01

    Self-assembled InAs quantum dots (QDs) were grown by solid source molecular beam epitaxy. The impact of the growth parameters like the growth temperature of the InGaAlAs nucleation layer, V/III ratio and growth rate during growth of QD layers were carefully investigated by using atomic force microscopy and photoluminescence spectroscopy. The excellent size uniformity of InAs QDs grown on InP substrates are verified by narrow photoluminescence line widths of 17 meV for single QD layers and 26 meV for stacked QD layers, respectivaly. Both values measured at 10 K.

  16. Efficient data processing and quantum phenomena : Single-particle systems

    NARCIS (Netherlands)

    de Raedt, H.A.; De Raedt, K.; Michielsen, K; Miyashita, S

    2006-01-01

    We study the relation between the acquisition and analysis of data and quantum theory using a probabilistic and deterministic model for photon polarizers. We introduce criteria for efficient processing of data and then use these criteria to demonstrate that efficient processing of the data contained

  17. No-go theorem for passive single-rail linear optical quantum computing.

    Science.gov (United States)

    Wu, Lian-Ao; Walther, Philip; Lidar, Daniel A

    2013-01-01

    Photonic quantum systems are among the most promising architectures for quantum computers. It is well known that for dual-rail photons effective non-linearities and near-deterministic non-trivial two-qubit gates can be achieved via the measurement process and by introducing ancillary photons. While in principle this opens a legitimate path to scalable linear optical quantum computing, the technical requirements are still very challenging and thus other optical encodings are being actively investigated. One of the alternatives is to use single-rail encoded photons, where entangled states can be deterministically generated. Here we prove that even for such systems universal optical quantum computing using only passive optical elements such as beam splitters and phase shifters is not possible. This no-go theorem proves that photon bunching cannot be passively suppressed even when extra ancilla modes and arbitrary number of photons are used. Our result provides useful guidance for the design of optical quantum computers.

  18. Quantum-dot spin-photon entanglement via frequency downconversion to telecom wavelength.

    Science.gov (United States)

    De Greve, Kristiaan; Yu, Leo; McMahon, Peter L; Pelc, Jason S; Natarajan, Chandra M; Kim, Na Young; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Kamp, Martin; Höfling, Sven; Hadfield, Robert H; Forchel, Alfred; Fejer, M M; Yamamoto, Yoshihisa

    2012-11-15

    Long-distance quantum teleportation and quantum repeater technologies require entanglement between a single matter quantum bit (qubit) and a telecommunications (telecom)-wavelength photonic qubit. Electron spins in III-V semiconductor quantum dots are among the matter qubits that allow for the fastest spin manipulation and photon emission, but entanglement between a single quantum-dot spin qubit and a flying (propagating) photonic qubit has yet to be demonstrated. Moreover, many quantum dots emit single photons at visible to near-infrared wavelengths, where silica fibre losses are so high that long-distance quantum communication protocols become difficult to implement. Here we demonstrate entanglement between an InAs quantum-dot electron spin qubit and a photonic qubit, by frequency downconversion of a spontaneously emitted photon from a singly charged quantum dot to a wavelength of 1,560 nanometres. The use of sub-10-picosecond pulses at a wavelength of 2.2 micrometres in the frequency downconversion process provides the necessary quantum erasure to eliminate which-path information in the photon energy. Together with previously demonstrated indistinguishable single-photon emission at high repetition rates, the present technique advances the III-V semiconductor quantum-dot spin system as a promising platform for long-distance quantum communication.

  19. Efficient single-photon frequency conversion in the microwave domain using superconducting quantum circuits

    Science.gov (United States)

    Jia, W. Z.; Wang, Y. W.; Liu, Yu-xi

    2017-11-01

    We present an approach to achieve efficient single-photon frequency conversion in the microwave domain based on coherent control in superconducting quantum circuits, which consist of a driven artificial atom coupled to a semi-infinite transmission line. Using the full quantum-mechanical method, we analyze the single-photon scattering process in this system and find that single-photon frequency up- or down-conversion with efficiency close to unity can be achieved by adjusting the parameters of the control field applied to the artificial atom. We further show that our approach is experimentally feasible in currently available superconducting flux qubit circuits.

  20. Photon antibunching from a single lithographically defined InGaAs/GaAs quantum dot.

    Science.gov (United States)

    Verma, V B; Stevens, Martin J; Silverman, K L; Dias, N L; Garg, A; Coleman, J J; Mirin, R P

    2011-02-28

    We demonstrate photon antibunching from a single lithographically defined quantum dot fabricated by electron beam lithography, wet chemical etching, and overgrowth of the barrier layers by metalorganic chemical vapor deposition. Measurement of the second-order autocorrelation function indicates g(2)(0)=0.395±0.030, below the 0.5 limit necessary for classification as a single photon source.

  1. Frequency Stabilization of a Single Mode Terahertz Quantum Cascade Laser to the Kilohertz Level

    Science.gov (United States)

    2009-04-27

    Frequency stabilization of a single mode terahertz quantum cascade laser to the kilohertz level 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...primarily in a single-longitudinal mode (SLM) up to a bias voltage of 3.7 V and a multi-lodgitudinal mode ( MLM ) at higher voltages. It was mounted in a

  2. Highly efficient photonic nanowire single-photon sources for quantum information applications

    DEFF Research Database (Denmark)

    Gregersen, Niels; Claudon, J.; Munsch, M.

    2013-01-01

    Within the emerging field of optical quantum information processing, the current challenge is to construct the basic building blocks for the quantum computing and communication systems. A key component is the singlephoton source (SPS) capable of emitting single photons on demand. Ideally, the SPS...... must feature near-unity efficiency, where the efficiency is defined as the number of detected photons per trigger, the probability g(2)(τ=0) of multi-photon emission events should be 0 and the emitted photons are required to be indistinguishable. An optically or electrically triggered quantum light...... emitter, e.g. a nitrogen-vacancy center or a semiconductor quantum dot (QD), embedded in a solid-state semiconductor host material appears as an attractive platform for generating such single photons. However, for a QD in bulk material, the large index contrast at the semiconductor-air interface leads...

  3. Double-slit experiment with single wave-driven particles and its relation to quantum mechanics

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Madsen, Jacob; Reichelt, Christian Günther

    2015-01-01

    even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes...... results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schro......¨dinger equation with a source term originating from a localized particle that generates a wave while being simultaneously guided by it. We show that the ensuing particle-wave dynamics can capture some characteristics of quantum mechanics such as orbital quantization. However, the particle-wave dynamics can...

  4. Tunable single-photon multi-channel quantum router based on an optomechanical system

    Science.gov (United States)

    Ma, Peng-Cheng; Yan, Lei-Lei; Zhang, Jian; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang

    2018-01-01

    Routing of photons plays a key role in optical communication networks and quantum networks. Although the quantum routing of signals has been investigated for various systems, both in theory and experiment, the general form of a quantum router with multi-output terminals still needs to be explored. Here, we propose an experimentally accessible tunable single-photon multi-channel routing scheme using an optomechanics cavity which is Coulomb coupled to a nanomechanical resonator. The router can extract single photons from the coherent input signal and directly modulate them into three different output channels. More importantly, the two output signal frequencies can be selected by adjusting the Coulomb coupling strength. For application purposes, we justify that there is insignificant influence from the vacuum and thermal noises on the performance of the router under cryogenic conditions. Our proposal may pave a new avenue towards multi-channel routers and quantum networks.

  5. Site-resolved imaging of single atoms with a Faraday quantum gas microscope

    CERN Document Server

    Yamamoto, Ryuta; Kato, Kohei; Kuno, Takuma; Sakura, Yuto; Takahashi, Yoshiro

    2016-01-01

    We successfully demonstrate a quantum gas microscopy using the Faraday effect which has an inherently non-destructive nature. The observed Faraday rotation angle reaches 3.0(2) degrees for a single atom. We reveal the non-destructive feature of this Faraday imaging method by comparing the detuning dependence of the Faraday signal strength with that of the photon scattering rate. We determine the atom distribution with deconvolution analysis. We also demonstrate the absorption and the dark field Faraday imaging, and reveal the different shapes of the point spread functions for these methods, which are fully explained by theoretical analysis. Our result is an important first step towards an ultimate quantum non-demolition site-resolved imaging and furthermore opens up the possibilities for quantum feedback control of a quantum many-body system with a single-site resolution.

  6. Single-Particle Quantum Dynamics in a Magnetic Lattice

    Energy Technology Data Exchange (ETDEWEB)

    Venturini, Marco

    2001-02-01

    We study the quantum dynamics of a spinless charged-particle propagating through a magnetic lattice in a transport line or storage ring. Starting from the Klein-Gordon equation and by applying the paraxial approximation, we derive a Schroedinger-like equation for the betatron motion. A suitable unitary transformation reduces the problem to that of a simple harmonic oscillator. As a result we are able to find an explicit expression for the particle wavefunction.

  7. Quantum-Dot Single-Photon Sources for Entanglement Enhanced Interferometry.

    Science.gov (United States)

    Müller, M; Vural, H; Schneider, C; Rastelli, A; Schmidt, O G; Höfling, S; Michler, P

    2017-06-23

    Multiphoton entangled states such as "N00N states" have attracted a lot of attention because of their possible application in high-precision, quantum enhanced phase determination. So far, N00N states have been generated in spontaneous parametric down-conversion processes and by mixing quantum and classical light on a beam splitter. Here, in contrast, we demonstrate superresolving phase measurements based on two-photon N00N states generated by quantum dot single-photon sources making use of the Hong-Ou-Mandel effect on a beam splitter. By means of pulsed resonance fluorescence of a charged exciton state, we achieve, in postselection, a quantum enhanced improvement of the precision in phase uncertainty, higher than prescribed by the standard quantum limit. An analytical description of the measurement scheme is provided, reflecting requirements, capability, and restraints of single-photon emitters in optical quantum metrology. Our results point toward the realization of a real-world quantum sensor in the near future.

  8. Impact of the dark path on quantum dot single photon emitters in small cavities

    Science.gov (United States)

    Kamide, Kenji; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2014-10-01

    Incoherent pumping in quantum dots can create a biexciton state through two paths: via the formation of bright or dark exciton states. The latter, dark-pumping path is shown to enhance the probability of two-photon simultaneous emission and hence increase g(2)(0) by a factor ∝1/γS, due to the slow spin relaxation rate γS in quantum dots. The existence of the dark path is shown to impose a limitation on the single photon emission process, especially in nanocavities which exhibit a large exciton-cavity coupling and a Purcell enhancement for fast quantum telecommunications.

  9. Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot

    Directory of Open Access Journals (Sweden)

    Moskalenko ES

    2010-01-01

    Full Text Available Abstract Individual InAs/GaAs quantum dots are studied by micro-photoluminescence. By varying the strength of an applied external magnetic field and/or the temperature, it is demonstrated that the charge state of a single quantum dot can be tuned. This tuning effect is shown to be related to the in-plane electron and hole transport, prior to capture into the quantum dot, since the photo-excited carriers are primarily generated in the barrier.

  10. Quantum criticality out of equilibrium: steady state in a magnetic single-electron transistor.

    Science.gov (United States)

    Kirchner, Stefan; Si, Qimiao

    2009-11-13

    Quantum critical systems out of equilibrium are of extensive interest, but are difficult to study theoretically. We consider here the steady-state limit of a single-electron transistor with ferromagnetic leads. In equilibrium (i.e., bias voltage V = 0), this system features a continuous quantum phase transition with a critical destruction of the Kondo effect. We construct an exact quantum Boltzmann treatment in a dynamical large-N limit, and determine the universal scaling functions of both the nonlinear conductance and fluctuation-dissipation ratios. We also elucidate the decoherence properties as encoded in the local spin response.

  11. Integration of fiber-tip cavities in single-ion traps for quantum sensing

    Science.gov (United States)

    Horak, Peter; Podoliak, Nina; Takahashi, Hiroki; Keller, Matthias

    2017-04-01

    We investigate geometries for efficient coupling of single ions to fiber-coupled light fields for applications in quantum sensing, quantum metrology, and quantum information processing. Specifically, we discuss the integration of fiber-tip microcavities into radio-frequency ion traps. The distortions of the trapping fields induced by the presence of the optical fibers are simulated for a range of ion trap geometries and the most promising arrangements are identified. Finally, we investigate the use of fiber-tip microcavities with non-spherical mirrors for enhanced ion-light coupling at the center of the trap by appropriate shaping of the cavity modes.

  12. Channel analysis for single photon underwater free space quantum key distribution.

    Science.gov (United States)

    Shi, Peng; Zhao, Shi-Cheng; Gu, Yong-Jian; Li, Wen-Dong

    2015-03-01

    We investigate the optical absorption and scattering properties of underwater media pertinent to our underwater free space quantum key distribution (QKD) channel model. With the vector radiative transfer theory and Monte Carlo method, we obtain the attenuation of photons, the fidelity of the scattered photons, the quantum bit error rate, and the sifted key generation rate of underwater quantum communication. It can be observed from our simulations that the most secure single photon underwater free space QKD is feasible in the clearest ocean water.

  13. Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes.

    Science.gov (United States)

    Gong, Su-Hyun; Kim, Je-Hyung; Ko, Young-Ho; Rodriguez, Christophe; Shin, Jonghwa; Lee, Yong-Hee; Dang, Le Si; Zhang, Xiang; Cho, Yong-Hoon

    2015-04-28

    The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter-light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield on-chip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing.

  14. Fault tolerant filtering and fault detection for quantum systems driven by fields in single photon states

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Qing, E-mail: qing.gao.chance@gmail.com; Dong, Daoyi, E-mail: daoyidong@gmail.com; Petersen, Ian R., E-mail: i.r.petersen@gmai.com [School of Engineering and Information Technology, University of New South Wales, Canberra, ACT 2600 (Australia); Rabitz, Herschel, E-mail: hrabitz@princeton.edu [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    2016-06-15

    The purpose of this paper is to solve the fault tolerant filtering and fault detection problem for a class of open quantum systems driven by a continuous-mode bosonic input field in single photon states when the systems are subject to stochastic faults. Optimal estimates of both the system observables and the fault process are simultaneously calculated and characterized by a set of coupled recursive quantum stochastic differential equations.

  15. Compact transmission system using single-sideband modulation of light for quantum cryptography.

    Science.gov (United States)

    Duraffourg, L; Merolla, J M; Goedgebuer, J P; Mazurenko, Y; Rhodes, W T

    2001-09-15

    We report a new transmission that can be used for quantum key distribution. The system uses single-sideband-modulated light in an implementation of the BB84 quantum cryptography protocol. The system is formed by two integrated unbalanced Mach-Zehnder interferometers and is based on interference between phase-modulated sidebands in the spectral domain. Experiments show that high interference visibility can be obtained.

  16. High-Dimensional Single-Photon Quantum Gates: Concepts and Experiments

    Science.gov (United States)

    Babazadeh, Amin; Erhard, Manuel; Wang, Feiran; Malik, Mehul; Nouroozi, Rahman; Krenn, Mario; Zeilinger, Anton

    2017-11-01

    Transformations on quantum states form a basic building block of every quantum information system. From photonic polarization to two-level atoms, complete sets of quantum gates for a variety of qubit systems are well known. For multilevel quantum systems beyond qubits, the situation is more challenging. The orbital angular momentum modes of photons comprise one such high-dimensional system for which generation and measurement techniques are well studied. However, arbitrary transformations for such quantum states are not known. Here we experimentally demonstrate a four-dimensional generalization of the Pauli X gate and all of its integer powers on single photons carrying orbital angular momentum. Together with the well-known Z gate, this forms the first complete set of high-dimensional quantum gates implemented experimentally. The concept of the X gate is based on independent access to quantum states with different parities and can thus be generalized to other photonic degrees of freedom and potentially also to other quantum systems.

  17. High-Dimensional Single-Photon Quantum Gates: Concepts and Experiments.

    Science.gov (United States)

    Babazadeh, Amin; Erhard, Manuel; Wang, Feiran; Malik, Mehul; Nouroozi, Rahman; Krenn, Mario; Zeilinger, Anton

    2017-11-03

    Transformations on quantum states form a basic building block of every quantum information system. From photonic polarization to two-level atoms, complete sets of quantum gates for a variety of qubit systems are well known. For multilevel quantum systems beyond qubits, the situation is more challenging. The orbital angular momentum modes of photons comprise one such high-dimensional system for which generation and measurement techniques are well studied. However, arbitrary transformations for such quantum states are not known. Here we experimentally demonstrate a four-dimensional generalization of the Pauli X gate and all of its integer powers on single photons carrying orbital angular momentum. Together with the well-known Z gate, this forms the first complete set of high-dimensional quantum gates implemented experimentally. The concept of the X gate is based on independent access to quantum states with different parities and can thus be generalized to other photonic degrees of freedom and potentially also to other quantum systems.

  18. Joint remote control of an arbitrary single-qubit state by using a multiparticle entangled state as the quantum channel

    Science.gov (United States)

    Lv, Shu-Xin; Zhao, Zheng-Wei; Zhou, Ping

    2018-01-01

    We present a scheme for joint remote implementation of an arbitrary single-qubit operation following some ideas in one-way quantum computation. All the senders share the information of implemented quantum operation and perform corresponding single-qubit measurements according to their information of implemented operation. An arbitrary single-qubit operation can be implemented upon the remote receiver's quantum system if the receiver cooperates with all the senders. Moreover, we study the protocol of multiparty joint remote implementation of an arbitrary single-qubit operation with many senders by using a multiparticle entangled state as the quantum channel.

  19. Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State

    Directory of Open Access Journals (Sweden)

    A. M. Kaufman

    2012-11-01

    Full Text Available We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.

  20. Linewidth statistics of single InGaAs quantum dot photolumincescence lines

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

    2000-01-01

    of linewidths is not significantly influenced by small variations in the quantum dot confinement potential. We claim that the wider transition lines are broadened by local electric field fluctuations while narrower lines are homogeneously broadened by acoustic-phonon interactions. The width of narrow single......We have used photoluminescence spectroscopy with high spatial and spectral resolution to measure the linewidths of single emission lines from In0.5Ga0.5As/GaAs self-assembled quantum dots. At 10 K, we find a broad, asymmetric distribution of linewidths with a maximum at 50 mu eV. The distribution...

  1. Superconducting Qubit with Integrated Single Flux Quantum Controller Part I: Theory and Fabrication

    Science.gov (United States)

    Beck, Matthew; Leonard, Edward, Jr.; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

    As the size of quantum processors grow, so do the classical control requirements. The single flux quantum (SFQ) Josephson digital logic family offers an attractive route to proximal classical control of multi-qubit processors. Here we describe coherent control of qubits via trains of SFQ pulses. We discuss the fabrication of an SFQ-based pulse generator and a superconducting transmon qubit on a single chip. Sources of excess microwave loss stemming from the complex multilayer fabrication of the SFQ circuit are discussed. We show how to mitigate this loss through judicious choice of process workflow and appropriate use of sacrificial protection layers. Present address: IBM T.J. Watson Research Center.

  2. Superconducting Qubit with Integrated Single Flux Quantum Controller Part II: Experimental Characterization

    Science.gov (United States)

    Leonard, Edward, Jr.; Beck, Matthew; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

    We describe the characterization of a single flux quantum (SFQ) pulse generator cofabricated with a superconducting quantum circuit on a single chip. Resonant trains of SFQ pulses are used to induce coherent qubit rotations on the Bloch sphere. We describe the SFQ drive characteristics of the qubit at the fundamental transition frequency and at subharmonics (ω01 / n , n = 2 , 3 , 4 , ⋯). We address the issue of quasiparticle poisoning due to the proximal SFQ pulse generator, and we characterize the fidelity of SFQ-based rotations using randomized benchmarking. Present address: IBM T.J. Watson Research Center.

  3. Optical holonomic single quantum gates with a geometric spin under a zero field

    Science.gov (United States)

    Sekiguchi, Yuhei; Niikura, Naeko; Kuroiwa, Ryota; Kano, Hiroki; Kosaka, Hideo

    2017-04-01

    The realization of fast fault-tolerant quantum gates on a single spin is the core requirement for solid-state quantum-information processing. As polarized light shows geometric interference, spin coherence is also geometrically controlled with light via the spin-orbit interaction. Here, we show that a geometric spin in a degenerate subspace of a spin-1 electronic system under a zero field in a nitrogen vacancy centre in diamond allows implementation of optical non-adiabatic holonomic quantum gates. The geometric spin under quasi-resonant light exposure undergoes a cyclic evolution in the spin-orbit space, and acquires a geometric phase or holonomy that results in rotations about an arbitrary axis by any angle defined by the light polarization and detuning. This enables universal holonomic quantum gates with a single operation. We demonstrate a complete set of Pauli quantum gates using the geometric spin preparation and readout techniques. The new scheme opens a path to holonomic quantum computers and repeaters.

  4. Copenhagen's single system premise prevents a unified view of integer and fractional quantum Hall effect

    CERN Document Server

    Post, E J

    1999-01-01

    This essay presents conclusive evidence of the impermissibility of Copenhagen's single system interpretation of the Schroedinger process. The latter needs to be viewed as a tool exclusively describing phase and orientation randomized ensembles and is not be used for isolated single systems. Asymptotic closeness of single system and ensemble behavior and the rare nature of true single system manifestations have prevented a definitive identification of this Copenhagen deficiency over the past three quarter century. Quantum uncertainty so becomes a basic trade mark of phase and orientation disordered ensembles. The ensuing void of usable single system tools opens a new inquiry for tools without statistical connotations. Three, in part already known, period integrals here identified as flux, charge and action counters emerge as diffeo-4 invariant tools fully compatible with the demands of the general theory of relativity. The discovery of the quantum Hall effect has been instrumental in forcing a distinction betw...

  5. Live cell imaging of single genomic loci with quantum dot-labeled TALEs.

    Science.gov (United States)

    Ma, Yingxin; Wang, Mingxiu; Li, Wei; Zhang, Zhiping; Zhang, Xiaowei; Tan, Tianwei; Zhang, Xian-En; Cui, Zongqiang

    2017-05-08

    Single genomic loci are often related to specific cellular functions, genetic diseases, or pathogenic infections. Visualization of single genomic loci in live human cells is currently of great interest, yet it remains challenging. Here, we describe a strategy for live cell imaging of single genomic loci by combining transcription activator-like effectors (TALEs) with a quantum dot labelling technique. We design and select a pair of TALEs that specifically target HIV-1 proviral DNA sequences, and use bioorthogonal ligation reactions to label them with different colour quantum dots (QDs). These QD-labelled TALEs are able to enter the cell nucleus to provide fluorescent signals to identify single gene loci. Based on the co-localization of the pair of different coloured QD-labelled TALEs, we determine and map single-copy HIV-1 provirus loci in human chromosomes in live host cells.

  6. Self-assembly of InAs ring complexes on InP substrates by droplet epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Noda, T.; Mano, T.; Jo, M.; Kawazu, T. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakaki, H. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan)

    2012-09-15

    We report the self-assembly of InAs ring complexes on InP (100) substrates by droplet epitaxy. Single-ring, ring-disk complex, and concentric double-ring structures were formed by controlling the As beam flux and substrate temperature. A clear photoluminescence signal was detected in a sample where InAs rings were embedded in InGaAs.

  7. Geometry dependent transport properties of undoped InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Guenel, H. Yusuf; Bloemers, Christian; Sladek, Kamil; Penz, Andreas; Hardtdegen, Hilde; Lenk, Steffi; Schubert, Juergen; Schaepers, Thomas; Gruetzmacher, Detlev [Institute of Bio- and Nanosystems (IBN-1) and JARA-Fundamentals of Future Information Technology, Research Centre Juelich GmbH, 52425 Juelich (Germany); Luysberg, Martina [Institute of Solid State Research and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forchungszentrum Juelich, 52425 Juelich (Germany)

    2010-07-01

    In recent time nanowire (NW) structures attracted much attention, for electronics, optoelectronics and fundamental quantum properties. On account of different application purposes basic transport properties are crucially important at room temperature as well as low temperatures. In this respect InAs NWs are particularly important due to the low band gap and high carrier concentration. We characterized the basic transport parameters of undoped InAs NWs at room temperature, which were grown on GaAs(001) substrate by MOVPE without catalyst. The NWs that we used in this work had diameters ranging from 25 nm to 200 nm and lengths up to 3.5 {mu}m. Basic transport parameters, such as carrier concentration and mobility, were determined by using two- and four-terminal measurement configuration. The carrier concentration could be controlled by a SiO{sub 2} -isolated back-gate structure. By analyzing the transfer characteristics of the NW FET, we observed very good gate controllability.

  8. Site-resolved imaging of single atoms with a Faraday quantum gas microscope

    Science.gov (United States)

    Yamamoto, Ryuta; Kobayashi, Jun; Kato, Kohei; Kuno, Takuma; Sakura, Yuto; Takahashi, Yoshiro

    2017-09-01

    We demonstrate a quantum gas microscope based on the Faraday effect that does not require a stochastic spontaneous emission process. We reveal the dispersive feature of this Faraday-imaging method by comparing the detuning dependence of the Faraday signal with that of the photon scattering rate. In addition, we determine the atom distribution through a deconvolution analysis, demonstrate absorption and dark-field Faraday imaging, and reveal the various shapes of the point spread functions for these methods, which are fully explained by a theoretical analysis. The results constitute an important first step toward ultimate quantum nondemolition site-resolved imaging and open the way to quantum feedback control of a quantum many-body system with single-site resolution.

  9. Double-slit experiment with single wave-driven particles and its relation to quantum mechanics.

    Science.gov (United States)

    Andersen, Anders; Madsen, Jacob; Reichelt, Christian; Rosenlund Ahl, Sonja; Lautrup, Benny; Ellegaard, Clive; Levinsen, Mogens T; Bohr, Tomas

    2015-07-01

    In a thought-provoking paper, Couder and Fort [Phys. Rev. Lett. 97, 154101 (2006)] describe a version of the famous double-slit experiment performed with droplets bouncing on a vertically vibrated fluid surface. In the experiment, an interference pattern in the single-particle statistics is found even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes place between different classical paths with precise amplitude and phase relations. In the double-slit experiment with walking droplets, these relations are lost since one of the paths is singled out by the droplet. To support our conclusions, we have carried out our own double-slit experiment, and our results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schrödinger equation with a source term originating from a localized particle that generates a wave while being simultaneously guided by it. We show that the ensuing particle-wave dynamics can capture some characteristics of quantum mechanics such as orbital quantization. However, the particle-wave dynamics can not reproduce quantum mechanics in general, and we show that the single-particle statistics for our model in a double-slit experiment with an additional splitter plate differs qualitatively from that of quantum mechanics.

  10. Electronic and optical properties of InAs/InP self-assembled quantum dots on patterned substrates

    Science.gov (United States)

    Sheng, Weidong; Hawrylak, Pawel

    2006-05-01

    We present atomistic theory of electronic and optical properties of a single InAs quantum dot grown on a pyramidal InP nanotemplate. The shape and size of the dot is assumed to follow the nanotemplate shape and size. The electron and valence hole single particle states are calculated using atomistic effective-bond-orbital model with second nearest-neighbor interactions. The electronic calculations are coupled to separately calculated strain distribution via Bir-Pikus Hamiltonian. The optical properties of InAs dots embedded in InP pyramids are calculated by solving the many-exciton Hamiltonian for interacting electron and hole complexes using the configuration-interaction method. The effect of quantum-dot geometry on the optical spectra is investigated by a comparison between dots of different shapes.

  11. Molecular engineering with artificial atoms: designing a material platform for scalable quantum spintronics and photonics

    Science.gov (United States)

    Doty, Matthew F.; Ma, Xiangyu; Zide, Joshua M. O.; Bryant, Garnett W.

    2017-09-01

    Self-assembled InAs Quantum Dots (QDs) are often called "artificial atoms" and have long been of interest as components of quantum photonic and spintronic devices. Although there has been substantial progress in demonstrating optical control of both single spins confined to a single QD and entanglement between two separated QDs, the path toward scalable quantum photonic devices based on spins remains challenging. Quantum Dot Molecules, which consist of two closely-spaced InAs QDs, have unique properties that can be engineered with the solid state analog of molecular engineering in which the composition, size, and location of both the QDs and the intervening barrier are controlled during growth. Moreover, applied electric, magnetic, and optical fields can be used to modulate, in situ, both the spin and optical properties of the molecular states. We describe how the unique photonic properties of engineered Quantum Dot Molecules can be leveraged to overcome long-standing challenges to the creation of scalable quantum devices that manipulate single spins via photonics.

  12. 27Al-27Al double-quantum single-quantum MAS NMR: Applications to the structural characterization of microporous materials.

    Science.gov (United States)

    Martineau-Corcos, Charlotte; Dědeček, Jiri; Taulelle, Francis

    In this paper, we review and illustrate applications, reported in the literature or used in our group, of 27Al-27Al double-quantum single-quantum (DQ-SQ) MAS NMR experiments for the structural characterization of Al-containing microporous solids, namely zeolites, aluminophosphates and metal-organic frameworks. Information regarding the periodic frameworks or the localization of the various aluminum species in the materials are obtained from the analysis of the two-dimensional NMR spectra, which allows getting local structural details sometimes inaccessible from other characterization technique. An application of 27Al-27Al of the DQ-SQ experiment for the detection of aluminum pairing in zeolite is shown. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, X. T.; Zhang, Y.; Liu, X. G., E-mail: liuxuguang@tyut.edu.cn [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, F.; Wang, Y. L.; Yang, Y. Z., E-mail: yyztyut@126.com [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Taiyuan 030024 (China); Research Center on Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China)

    2015-11-23

    Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation light source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.

  14. Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission

    Directory of Open Access Journals (Sweden)

    Fuster D

    2010-01-01

    Full Text Available Abstract In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 108 cm−2 to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

  15. Single-step fabrication of quantum funnels via centrifugal colloidal casting of nanoparticle films.

    KAUST Repository

    Kim, Jin Young

    2015-07-13

    Centrifugal casting of composites and ceramics has been widely employed to improve the mechanical and thermal properties of functional materials. This powerful method has yet to be deployed in the context of nanoparticles--yet size-effect tuning of quantum dots is among their most distinctive and application-relevant features. Here we report the first gradient nanoparticle films to be constructed in a single step. By creating a stable colloid of nanoparticles that are capped with electronic-conduction-compatible ligands we were able to leverage centrifugal casting for thin-films devices. This new method, termed centrifugal colloidal casting, is demonstrated to form films in a bandgap-ordered manner with efficient carrier funnelling towards the lowest energy layer. We constructed the first quantum-gradient photodiode to be formed in a single deposition step and, as a result of the gradient-enhanced electric field, experimentally measured the highest normalized detectivity of any colloidal quantum dot photodetector.

  16. Kondo blockade due to quantum interference in single-molecule junctions.

    Science.gov (United States)

    Mitchell, Andrew K; Pedersen, Kim G L; Hedegård, Per; Paaske, Jens

    2017-05-11

    Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm.

  17. Kondo blockade due to quantum interference in single-molecule junctions

    Science.gov (United States)

    Mitchell, Andrew K.; Pedersen, Kim G. L.; Hedegård, Per; Paaske, Jens

    2017-05-01

    Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm.

  18. Single-step fabrication of quantum funnels via centrifugal colloidal casting of nanoparticle films

    Science.gov (United States)

    Kim, Jin Young; Adinolfi, Valerio; Sutherland, Brandon R.; Voznyy, Oleksandr; Kwon, S. Joon; Kim, Tae Wu; Kim, Jeongho; Ihee, Hyotcherl; Kemp, Kyle; Adachi, Michael; Yuan, Mingjian; Kramer, Illan; Zhitomirsky, David; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    Centrifugal casting of composites and ceramics has been widely employed to improve the mechanical and thermal properties of functional materials. This powerful method has yet to be deployed in the context of nanoparticles—yet size–effect tuning of quantum dots is among their most distinctive and application-relevant features. Here we report the first gradient nanoparticle films to be constructed in a single step. By creating a stable colloid of nanoparticles that are capped with electronic-conduction-compatible ligands we were able to leverage centrifugal casting for thin-films devices. This new method, termed centrifugal colloidal casting, is demonstrated to form films in a bandgap-ordered manner with efficient carrier funnelling towards the lowest energy layer. We constructed the first quantum-gradient photodiode to be formed in a single deposition step and, as a result of the gradient-enhanced electric field, experimentally measured the highest normalized detectivity of any colloidal quantum dot photodetector. PMID:26165185

  19. Vacuum Rabi splitting in a plasmonic cavity at the single quantum emitter limit.

    Science.gov (United States)

    Santhosh, Kotni; Bitton, Ora; Chuntonov, Lev; Haran, Gilad

    2016-06-13

    The strong interaction of individual quantum emitters with resonant cavities is of fundamental interest for understanding light-matter interactions. Plasmonic cavities hold the promise of attaining the strong coupling regime even under ambient conditions and within subdiffraction volumes. Recent experiments revealed strong coupling between individual plasmonic structures and multiple organic molecules; however, strong coupling at the limit of a single quantum emitter has not been reported so far. Here we demonstrate vacuum Rabi splitting, a manifestation of strong coupling, using silver bowtie plasmonic cavities loaded with semiconductor quantum dots (QDs). A transparency dip is observed in the scattering spectra of individual bowties with one to a few QDs, which are directly counted in their gaps. A coupling rate as high as 120 meV is registered even with a single QD, placing the bowtie-QD constructs close to the strong coupling regime. These observations are verified by polarization-dependent experiments and validated by electromagnetic calculations.

  20. Quantum key distribution and 1 Gbps data encryption over a single fibre

    Energy Technology Data Exchange (ETDEWEB)

    Eraerds, P; Walenta, N; Gisin, N; Zbinden, H [Group of Applied Physics-Optique, University of Geneva, Rue de l' Ecole-de-Medecine 20, 1205 Geneva (Switzerland); Legre, M, E-mail: patrick.eraerds@unige.c, E-mail: nino.walenta@unige.c [idQuantique SA, Chemin de la Marbrerie 3, 1227, Geneva (Switzerland)

    2010-06-15

    We perform quantum key distribution (QKD) over a single fibre in the presence of four classical channels in a C-band dense wavelength division multiplexing (DWDM) configuration using a commercial QKD system. The classical channels are used for key distillation and 1 Gbps encrypted communication, rendering the entire system independent of any other communication channel than a single dedicated fibre. We successfully distil secret keys over fibre spans of up to 50 km. The separation between the quantum channel at 1551.72 nm and the nearest classical channel is only 200 GHz, while the classical channels are all separated by 100 GHz. In addition to that, we discuss possible improvements and alternative configurations, e.g. whether it is advantageous to choose the quantum channel at 1310 nm or to opt for a pure C-band (1530-1565 nm) configuration.

  1. Single photoelectron trapping, storage, and detection in a one-electron quantum dot

    Science.gov (United States)

    Rao, Deepak Sethu; Szkopek, Thomas; Robinson, Hans Daniel; Yablonovitch, Eli; Jiang, Hong-Wen

    2005-12-01

    There has been considerable progress in electrostatically emptying, and refilling, quantum dots with individual electrons. Typically the quantum dot is defined by electrostatic gates on a GaAs /AlyGa1-yAs modulation-doped heterostructure. We report the filling of such a quantum dot by a single photoelectron, originating from an individual photon. The electrostatic dot can be emptied and reset in a controlled fashion before the arrival of each photon. The trapped photoelectron is detected by a point contact transistor integrated adjacent to the electrostatic potential trap. Each stored photoelectron causes a persistent negative step in the transistor channel current. Such a controllable, benign, single photoelectron detector could allow for information transfer between flying photon qubits and stored electron qubits.

  2. Quantum Stirling heat engine and refrigerator with single and coupled spin systems

    Science.gov (United States)

    Huang, Xiao-Li; Niu, Xin-Ya; Xiu, Xiao-Ming; Yi, Xue-Xi

    2014-02-01

    We study the reversible quantum Stirling cycle with a single spin or two coupled spins as the working substance. With the single spin as the working substance, we find that under certain conditions the reversed cycle of a heat engine is NOT a refrigerator, this feature holds true for a Stirling heat engine with an ion trapped in a shallow potential as its working substance. The efficiency of quantum Stirling heat engine can be higher than the efficiency of the Carnot engine, but the performance coefficient of the quantum Stirling refrigerator is always lower than its classical counterpart. With two coupled spins as the working substance, we find that a heat engine can turn to a refrigerator due to the increasing of the coupling constant, this can be explained by the properties of the isothermal line in the magnetic field-entropy plane.

  3. Single-step fabrication of quantum funnels via centrifugal colloidal casting of nanoparticle films

    Science.gov (United States)

    Kim, Jin Young; Adinolfi, Valerio; Sutherland, Brandon R.; Voznyy, Oleksandr; Kwon, S. Joon; Kim, Tae Wu; Kim, Jeongho; Ihee, Hyotcherl; Kemp, Kyle; Adachi, Michael; Yuan, Mingjian; Kramer, Illan; Zhitomirsky, David; Hoogland, Sjoerd; Sargent, Edward H.

    2015-07-01

    Centrifugal casting of composites and ceramics has been widely employed to improve the mechanical and thermal properties of functional materials. This powerful method has yet to be deployed in the context of nanoparticles--yet size-effect tuning of quantum dots is among their most distinctive and application-relevant features. Here we report the first gradient nanoparticle films to be constructed in a single step. By creating a stable colloid of nanoparticles that are capped with electronic-conduction-compatible ligands we were able to leverage centrifugal casting for thin-films devices. This new method, termed centrifugal colloidal casting, is demonstrated to form films in a bandgap-ordered manner with efficient carrier funnelling towards the lowest energy layer. We constructed the first quantum-gradient photodiode to be formed in a single deposition step and, as a result of the gradient-enhanced electric field, experimentally measured the highest normalized detectivity of any colloidal quantum dot photodetector.

  4. Bright single photon source based on self-aligned quantum dot–cavity systems

    DEFF Research Database (Denmark)

    Maier, Sebastian; Gold, Peter; Forchel, Alfred

    2014-01-01

    We report on a quasi-planar quantum-dot-based single-photon source that shows an unprecedented high extraction efficiency of 42% without complex photonic resonator geometries or post-growth nanofabrication. This very high efficiency originates from the coupling of the photons emitted by a quantum...... dot to a Gaussian shaped nanohill defect that naturally arises during epitaxial growth in a self-aligned manner. We investigate the morphology of these defects and characterize the photonic operation mechanism. Our results show that these naturally arising coupled quantum dot-defects provide a new...... avenue for efficient (up to 42% demonstrated) and pure (g2(0) value of 0.023) single-photon emission....

  5. Women Fellows of INAE | Women in Science | Initiatives | Indian ...

    Indian Academy of Sciences (India)

    Women Fellows of INAE. INAE - Indian National Academy of Engineering. Ms. Alpa Sheth Civil Engineering. Prof. Bharathi Bhat Electronics & Communication Engineering. Prof. Dipanwita Roy Chowdhury Computer Engineering and Information Technology. Prof. Kamala Krithivasan Computer Engineering and Information ...

  6. Multiparameter estimation with single photons—linearly-optically generated quantum entanglement beats the shotnoise limit

    Science.gov (United States)

    You, Chenglong; Adhikari, Sushovit; Chi, Yuxi; LaBorde, Margarite L.; Matyas, Corey T.; Zhang, Chenyu; Su, Zuen; Byrnes, Tim; Lu, Chaoyang; Dowling, Jonathan P.; Olson, Jonathan P.

    2017-12-01

    It was suggested in (Motes et al 2015 Phys. Rev. Lett. 114 170802) that optical networks with relatively inexpensive overheads—single photon Fock states, passive optical elements, and single photon detection—can show significant improvements over classical strategies for single-parameter estimation, when the number of modes in the network is small (n< 7). A similar case was made in (Humphreys et al 2013 Phys. Rev. Lett. 111 070403) for multi-parameter estimation, where measurement is instead made using photon-number resolving detectors. In this paper, we analytically compute the quantum Cramér–Rao bound to show these networks can have a constant-factor quantum advantage in multi-parameter estimation for even large number of modes. Additionally, we provide a simplified measurement scheme using only single-photon (on–off) detectors that is capable of approximately obtaining this sensitivity for a small number of modes.

  7. Quantum detector tomography of a time-multiplexed superconducting nanowire single-photon detector at telecom wavelengths

    NARCIS (Netherlands)

    Natarajan, C.M.; Zhang, L.; Coldenstrodt-Ronge, H.; Donati, G.; Dorenbos, S.N.; Zwiller, V.; Walmsley, I.A.; Hadfield, R.H.

    2013-01-01

    Superconducting nanowire single-photon detectors (SNSPDs) are widely used in telecom wavelength optical quantum information science applications. Quantum detector tomography allows the positive-operator-valued measure (POVM) of a single-photon detector to be determined. We use an all-fiber telecom

  8. The photonic nanowire: an emerging platform for highly efficient single-photon sources for quantum information applications

    DEFF Research Database (Denmark)

    Gregersen, Niels; Munsch, Mathieu; Malik, Nitin S.

    2013-01-01

    Efficient coupling between a localized quantum emitter and a well defined optical channel represents a powerful route to realize single-photon sources and spin-photon interfaces. The tailored fiber-like photonic nanowire embedding a single quantum dot has recently demonstrated an appealing...

  9. Simulation of a quantum NOT gate for a single qutrit system

    Indian Academy of Sciences (India)

    A three-level system based an a three-level atom interacting with a detuned cavity is considered. Because of the fact that the three-level atom defines a total normalized state composed of superposition of three different single-level states, it is assumed that such a system implements a qutrit. In order to achieve a quantum ...

  10. Quantum dot resonant tunneling diode single photon detector with aluminum oxide aperture defined tunneling area

    DEFF Research Database (Denmark)

    Li, H.W.; Kardynal, Beata; Ellis, D.J.P.

    2008-01-01

    Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality res...

  11. Quantum interference effects at room temperature in OPV-based single-molecule junctions

    NARCIS (Netherlands)

    Arroyo Rodriguez, C.; Frisenda, R.; Moth-Poulsen, K.; Seldenthuis, J.S.; Bjornholm, T.; Van der Zant, H.S.

    2013-01-01

    Interference effects on charge transport through an individual molecule can lead to a notable modulation and suppression on its conductance. In this letter, we report the observation of quantum interference effects occurring at room temperature in single-molecule junctions based on

  12. Generating single photons at gigahertz modulation-speed using electrically controlled quantum dot microlenses

    Energy Technology Data Exchange (ETDEWEB)

    Schlehahn, A.; Schmidt, R.; Hopfmann, C.; Schulze, J.-H.; Strittmatter, A.; Heindel, T., E-mail: tobias.heindel@tu-berlin.de; Reitzenstein, S. [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Gantz, L.; Schmidgall, E. R.; Gershoni, D. [The Physics Department and the Solid State Institute, Technion-Israel Institute of Technology, 32000 Haifa (Israel)

    2016-01-11

    We report on the generation of single-photon pulse trains at a repetition rate of up to 1 GHz. We achieve this speed by modulating the external voltage applied on an electrically contacted quantum dot microlens, which is optically excited by a continuous-wave laser. By modulating the photoluminescence of the quantum dot microlens using a square-wave voltage, single-photon emission is triggered with a response time as short as (281 ± 19) ps, being 6 times faster than the radiative lifetime of (1.75 ± 0.02) ns. This large reduction in the characteristic emission time is enabled by a rapid capacitive gating of emission from the quantum dot, which is placed in the intrinsic region of a p-i-n-junction biased below the onset of electroluminescence. Here, since our circuit acts as a rectifying differentiator, the rising edge of the applied voltage pulses triggers the emission of single photons from the optically excited quantum dot. The non-classical nature of the photon pulse train generated at GHz-speed is proven by intensity autocorrelation measurements with g{sup (2)}(0) = 0.3 ± 0.1. Our results combine optical excitation with fast electrical gating and thus show promise for the generation of indistinguishable single photons at rates exceeding the limitations set by the intrinsic radiative lifetime.

  13. Generating single photons at gigahertz modulation-speed using electrically controlled quantum dot microlenses

    Science.gov (United States)

    Schlehahn, A.; Schmidt, R.; Hopfmann, C.; Schulze, J.-H.; Strittmatter, A.; Heindel, T.; Gantz, L.; Schmidgall, E. R.; Gershoni, D.; Reitzenstein, S.

    2016-01-01

    We report on the generation of single-photon pulse trains at a repetition rate of up to 1 GHz. We achieve this speed by modulating the external voltage applied on an electrically contacted quantum dot microlens, which is optically excited by a continuous-wave laser. By modulating the photoluminescence of the quantum dot microlens using a square-wave voltage, single-photon emission is triggered with a response time as short as (281 ± 19) ps, being 6 times faster than the radiative lifetime of (1.75 ± 0.02) ns. This large reduction in the characteristic emission time is enabled by a rapid capacitive gating of emission from the quantum dot, which is placed in the intrinsic region of a p-i-n-junction biased below the onset of electroluminescence. Here, since our circuit acts as a rectifying differentiator, the rising edge of the applied voltage pulses triggers the emission of single photons from the optically excited quantum dot. The non-classical nature of the photon pulse train generated at GHz-speed is proven by intensity autocorrelation measurements with g(2)(0) = 0.3 ± 0.1. Our results combine optical excitation with fast electrical gating and thus show promise for the generation of indistinguishable single photons at rates exceeding the limitations set by the intrinsic radiative lifetime.

  14. Single atom doping for quantum device development in diamond and silicon

    NARCIS (Netherlands)

    Weis, C.D.; Schuh, A.; Batra, A.; Persaud, A.; Rangelow, I.W.; Bokor, J.; Lo, C.C.; Cabrini, S.; Sideras-Haddad, E.; Fuchs, G.D.; Hanson, R.; Awschalom, D.D.; Schenkel, T.

    2008-01-01

    The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species, and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in

  15. Multiparty Quantum English Auction Scheme Using Single Photons as Message Carrier

    Science.gov (United States)

    Liu, Ge; Zhang, Jian-Zhong; Xie, Shu-Cui

    2017-11-01

    In this paper, a secure and economic multiparty english auction protocol using the single photons as message carrier of bids is proposed. In order to achieve unconditional security, fairness, undeniability and so on, we adopt the decoy photon checking technique and quantum encryption algorithm. Analysis result shows that our protocol satisfies all the characteristics of traditional english auction, meanwhile, it can resist malicious attacks.

  16. Microwave testing of high-Tc based direct current to a single flux quantum converter

    DEFF Research Database (Denmark)

    Kaplunenko, V. K.; Fischer, Gerd Michael; Ivanov, Z. G.

    1994-01-01

    Design, simulation, and experimental investigations of a direct current to a single flux quantum converter loaded with a Josephson transmission line and driven by an external 70 GHz microwave oscillator are reported. The test circuit includes nine YBaCuO Josephson junctions aligned on the grain...

  17. Highly anisotropic decay rates of single quantum dots in photonic crystal membranes

    DEFF Research Database (Denmark)

    Wang, Qin; Stobbe, Søren; Nielsen, Henri Thyrrestrup

    2010-01-01

    We have measured the variation of the spontaneous emission rate with polarization for self-assembled single quantum dots in two-dimensional photonic crystal membranes. We observe a maximum anisotropy factor of 6 between the decay rates of the two bright exciton states. This large anisotropy...

  18. Experimental demonstration of highly anisotropic decay rates of single quantum dots inside photonic crystals

    DEFF Research Database (Denmark)

    Wang, Qin; Stobbe, Søren; Nielsen, Henri Thyrrestrup

    We have systematically measured the variation of the spontaneous emission rate with polarization for self-assembled single quantum dots in two-dimensional photonic crystal membranes and obtained a maximum anisotropy factor of 6 between the decay rates of the two nondegenerate bright exciton states....

  19. Self-exothermic reaction prompted synthesis of single-layered graphene quantum dots at room temperature.

    Science.gov (United States)

    Chen, Bin Bin; Li, Rong Sheng; Liu, Meng Li; Zhang, Hong Zhi; Huang, Cheng Zhi

    2017-05-02

    The easy fabrication of single-layered graphene quantum dots (s-GQDs) still faces challenge. Herein, we report an efficient route to fabricate s-GQDs within 5 min at room temperature by introducing a simple self-exothermic reaction. The as-prepared s-GQDs can specifically bind with aluminium ions to produce an aggregation-induced emission enhancement effect.

  20. Spin Echo of a Single Electron Spin in a Quantum Dot

    NARCIS (Netherlands)

    Koppens, F.H.L.; Nowack, K.C.; Vandersypen, L.M.K.

    2008-01-01

    We report a measurement of the spin-echo decay of a single electron spin confined in a semiconductor quantum dot. When we tip the spin in the transverse plane via a magnetic field burst, it dephases in 37 ns due to the Larmor precession around a random effective field from the nuclear spins in the

  1. Homogeneous linewidth of single InGaAs quantum dot photoluminescence

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Langbein, Wolfgang; Jensen, Jacob Riis

    2000-01-01

    We have used m-photoluminescence spectroscopy with a spectral resolution of 20 meV to measure homogeneous linewidths of single emission lines within an inhomogeneously broadened ensemble of In0.5Ga0.5As/GaAs self-assembled quantum dots. At 10K, a distribution of linewidths peaking around 50 me...

  2. Extraction of the beta-factor for single quantum dots coupled to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Nielsen, Henri Thyrrestrup; Sapienza, Luca; Lodahl, Peter

    2010-01-01

    We present measurements of the β-factor, describing the coupling efficiency of light emitted by single InAs/GaAs semiconductor quantum dots into a photonic crystal waveguide mode. The β-factor is evaluated by means of time resolved frequency-dependent photoluminescence spectroscopy. The emission...

  3. In-plane commensurate GaN/AlN junctions: Single-layer composite structures, single and multiple quantum wells and quantum dots

    Science.gov (United States)

    Onen, A.; Kecik, D.; Durgun, E.; Ciraci, S.

    2017-04-01

    In-plane composite structures constructed of the stripes or core/shells of single-layer GaN and AlN, which are joined commensurately, display a diversity of electronic properties that can be tuned by the size of their constituents. In heterostructures, the dimensionality of the electrons changes from two dimensional (2D) to one dimensional (1D) upon their confinements in wide constituent stripes, leading to the type-I band alignment and hence multiple quantum well structure in the direct space. The δ doping of one wide stripe by another narrow stripe results in local narrowing or widening of the band gap. A single quantum well structure is acquired from the finite-size AlN-GaN-AlN junctions. In a patterned array of GaN/AlN core/shells, the dimensionality of the electronic states is reduced from two dimensional to zero dimensional, forming multiple quantum dots in large GaN cores, while 2D electrons propagate in multiply connected AlN shell as if they are in a supercrystal. A consistent and detailed discussion of the effects of confinement in momentum and direct spaces is provided. As a result of confinement, the variation of the band gap in the direct space is found to be rather different from the edges of the conduction and valence bands inferred from the band edges of constituent 2D single-layer GaN and AlN. Even if all the results in this study pertain to the free-standing single-layer composite structures, the effects of the different substrates over which these composites can grow are examined in detail. This study unveils the potential of composite structures in designing novel nanomaterials. These predictions are obtained from first-principles calculations based on density functional theory on 2D GaN and AlN compound semiconductors which were synthesized recently.

  4. Influence of quantum dot labels on single molecule movement in the plasma membrane

    DEFF Research Database (Denmark)

    Clausen, Mathias P.; Lagerholm, B. Christoffer

    2011-01-01

    Single particle tracking results are very dependent on the probe that is used. In this study we have investigated the influence that functionalized quantum dots (QDs) have on the recorded movement in single molecule tracking experiments of plasma membrane species in live cells. Potential issues...... for simultaneous investigations of different plasma membrane species in order to discriminate the effect of the label from differences in movement of the target molecules....

  5. Strong photo-absorption by a single quantum wire in waveguide-transmission spectroscopy

    OpenAIRE

    Takahashi, Yasushi; Hayamizu, Yuhei; Itoh, Hirotake; Yoshita, Masahiro; Akiyama, Hidefumi; Pfeiffer, Loren N.; West, Ken W.

    2005-01-01

    We measured the absorption spectrum of a single T-shaped, 14x6 nm lateral-sized quantum wire embedded in an optical waveguide using waveguide-transmission spectroscopy at 5 K. In spite of its small volume, the one-dimensional-exciton ground state shows a large absorption coefficient of 80 /cm, or a 98 % absorption probability for a single pass of the 500-um-long waveguide.

  6. Quantum non-demolition detection of single microwave photons in a circuit

    Science.gov (United States)

    Johnson, B. R.; Reed, M. D.; Houck, A. A.; Schuster, D. I.; Bishop, Lev S.; Ginossar, E.; Gambetta, J. M.; Dicarlo, L.; Frunzio, L.; Girvin, S. M.; Schoelkopf, R. J.

    2010-09-01

    Thorough control of quantum measurement is key to the development of quantum information technologies. Many measurements are destructive, removing more information from the system than they obtain. Quantum non-demolition (QND) measurements allow repeated measurements that give the same eigenvalue. They could be used for several quantum information processing tasks such as error correction, preparation by measurement and one-way quantum computing. Achieving QND measurements of photons is especially challenging because the detector must be completely transparent to the photons while still acquiring information about them. Recent progress in manipulating microwave photons in superconducting circuits has increased demand for a QND detector that operates in the gigahertz frequency range. Here we demonstrate a QND detection scheme that measures the number of photons inside a high-quality-factor microwave cavity on a chip. This scheme maps a photon number, n, onto a qubit state in a single-shot by means of qubit-photon logic gates. We verify the operation of the device for n=0 and 1 by analysing the average correlations of repeated measurements, and show that it is 90% QND. It differs from previously reported detectors because its sensitivity is strongly selective to chosen photon number states. This scheme could be used to monitor the state of a photon-based memory in a quantum computer.

  7. Temporal Purity and Quantum Interference of Single Photons from Two Independent Cold Atomic Ensembles.

    Science.gov (United States)

    Qian, Peng; Gu, Zhenjie; Cao, Rong; Wen, Rong; Ou, Z Y; Chen, J F; Zhang, Weiping

    2016-07-01

    The temporal purity of single photons is crucial to the indistinguishability of independent photon sources for the fundamental study of the quantum nature of light and the development of photonic technologies. Currently, the technique for single photons heralded from time-frequency entangled biphotons created in nonlinear crystals does not guarantee the temporal-quantum purity, except using spectral filtering. Nevertheless, an entirely different situation is anticipated for narrow-band biphotons with a coherence time far longer than the time resolution of a single-photon detector. Here we demonstrate temporally pure single photons with a coherence time of 100 ns, directly heralded from the time-frequency entangled biphotons generated by spontaneous four-wave mixing in cold atomic ensembles, without any supplemented filters or cavities. A near-perfect purity and indistinguishability are both verified through Hong-Ou-Mandel quantum interference using single photons from two independent cold atomic ensembles. The time-frequency entanglement provides a route to manipulate the pure temporal state of the single-photon source.

  8. Constructions of secure entanglement channels assisted by quantum dots inside single-sided optical cavities

    Science.gov (United States)

    Heo, Jino; Kang, Min-Sung; Hong, Chang-Ho; Choi, Seong-Gon; Hong, Jong-Phil

    2017-08-01

    We propose quantum information processing schemes to generate and swap entangled states based on the interactions between flying photons and quantum dots (QDs) confined within optical cavities for quantum communication. To produce and distribute entangled states (Bell and Greenberger-Horne-Zeilinger [GHZ] states) between the photonic qubits of flying photons of consumers (Alice and Bob) and electron-spin qubits of a provider (trust center, or TC), the TC employs the interactions of the QD-cavity system, which is composed of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, the TC constructs an entanglement channel (Bell state and 4-qubit GHZ state) to link one consumer with another through entanglement swapping, which can be realized to exploit a probe photon with interactions of the QD-cavity systems and single-qubit measurements without Bell state measurement, for quantum communication between consumers. Consequently, the TC, which has quantum nodes (QD-cavity systems), can accomplish constructing the entanglement channel (authenticated channel) between two separated consumers from the distributions of entangled states and entanglement swapping. Furthermore, our schemes using QD-cavity systems, which are feasible with a certain probability of success and high fidelity, can be experimentally implemented with technology currently in use.

  9. Preparation and coherent manipulation of pure quantum states of a single molecular ion

    Science.gov (United States)

    Chou, Chin-Wen; Kurz, Christoph; Hume, David B.; Plessow, Philipp N.; Leibrandt, David R.; Leibfried, Dietrich

    2017-05-01

    Laser cooling and trapping of atoms and atomic ions has led to advances including the observation of exotic phases of matter, the development of precision sensors and state-of-the-art atomic clocks. The same level of control in molecules could also lead to important developments such as controlled chemical reactions and sensitive probes of fundamental theories, but the vibrational and rotational degrees of freedom in molecules pose a challenge for controlling their quantum mechanical states. Here we use quantum-logic spectroscopy, which maps quantum information between two ion species, to prepare and non-destructively detect quantum mechanical states in molecular ions. We develop a general technique for optical pumping and preparation of the molecule into a pure initial state. This enables us to observe high-resolution spectra in a single ion (CaH+) and coherent phenomena such as Rabi flopping and Ramsey fringes. The protocol requires a single, far-off-resonant laser that is not specific to the molecule, so many other molecular ions, including polyatomic species, could be treated using the same methods in the same apparatus by changing the molecular source. Combined with the long interrogation times afforded by ion traps, a broad range of molecular ions could be studied with unprecedented control and precision. Our technique thus represents a critical step towards applications such as precision molecular spectroscopy, stringent tests of fundamental physics, quantum computing and precision control of molecular dynamics.

  10. Preparation and coherent manipulation of pure quantum states of a single molecular ion.

    Science.gov (United States)

    Chou, Chin-Wen; Kurz, Christoph; Hume, David B; Plessow, Philipp N; Leibrandt, David R; Leibfried, Dietrich

    2017-05-10

    Laser cooling and trapping of atoms and atomic ions has led to advances including the observation of exotic phases of matter, the development of precision sensors and state-of-the-art atomic clocks. The same level of control in molecules could also lead to important developments such as controlled chemical reactions and sensitive probes of fundamental theories, but the vibrational and rotational degrees of freedom in molecules pose a challenge for controlling their quantum mechanical states. Here we use quantum-logic spectroscopy, which maps quantum information between two ion species, to prepare and non-destructively detect quantum mechanical states in molecular ions. We develop a general technique for optical pumping and preparation of the molecule into a pure initial state. This enables us to observe high-resolution spectra in a single ion (CaH+) and coherent phenomena such as Rabi flopping and Ramsey fringes. The protocol requires a single, far-off-resonant laser that is not specific to the molecule, so many other molecular ions, including polyatomic species, could be treated using the same methods in the same apparatus by changing the molecular source. Combined with the long interrogation times afforded by ion traps, a broad range of molecular ions could be studied with unprecedented control and precision. Our technique thus represents a critical step towards applications such as precision molecular spectroscopy, stringent tests of fundamental physics, quantum computing and precision control of molecular dynamics.

  11. Growth and anisotropic transport properties of self-assembled InAs nanostructures in InP

    Energy Technology Data Exchange (ETDEWEB)

    Bierwagen, O.

    2007-12-20

    Self-assembled InAs nanostructures in InP, comprising quantum wells, quantum wires, and quantum dots, are studied in terms of their formation and properties. In particular, the structural, optical, and anisotropic transport properties of the nanostructures are investigated. The focus is a comprehending exploration of the anisotropic in-plane transport in large ensembles of laterally coupled InAs nanostructures. The self-assembled Stranski-Krastanov growth of InAs nanostructures is studied by gas-source molecular beam epitaxy on both nominally oriented and vicinal InP(001). Optical polarization of the interband transitions arising from the nanostructure type is demonstrated by photoluminescence and transmission spectroscopy. The experimentally convenient four-contact van der Pauw Hall measurement of rectangularly shaped semiconductors, usually applied to isotropic systems, is extended to yield the anisotropic transport properties. Temperature dependent transport measurements are performed in large ensembles of laterally closely spaced nanostructures. The transport of quantum wire-, quantum dash- and quantum dot containing samples is highly anisotropic with the principal axes of conductivity aligned to the <110> directions. The direction of higher mobility is [ anti 110], which is parallel to the direction of the quantum wires. In extreme cases, the anisotropies exceed 30 for electrons, and 100 for holes. The extreme anisotropy for holes is due to diffusive transport through extended states in the [ anti 110], and hopping transport through laterally localized states in the [110] direction, within the same sample. A novel 5-terminal electronic switching device based on gate-controlled transport anisotropy is proposed. The gate-control of the transport anisotropy in modulation-doped, self-organized InAs quantum wires embedded in InP is demonstrated. (orig.)

  12. Novel single photon sources for new generation of quantum communications

    Science.gov (United States)

    2017-06-13

    state single photon sources that was published in Nature Photonics in October 2016. 15. SUBJECT TERMS diamond color center, diamond, AOARD 16. SECURITY...06/2017 PI and Co-PI information: Igor Aharonovich, igor.aharonovich@uts.edu.au, University of Technology Sydney, School of Mathematical and...manipulation of a silicon vacancy color cent er in a nanodiamond. We demonstrate ultra fast coherent control of a photon, that make s this defect

  13. Probing quantum confinement within single core-multishell nanowires

    OpenAIRE

    Martínez-Criado, Gema; Homs, Alejandro; Alén, Benito; Sans, Juan Ángel; Segura-Ruiz, Jaime; Molina-Sánchez, Alejandro; Susini, Jean; Yoo, Jinkyoung; Yi, J. G. C.

    2012-01-01

    Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-r...

  14. Current-phase relations of few-mode InAs nanowire Josephson junctions

    Science.gov (United States)

    Spanton, Eric M.; Deng, Mingtang; Vaitiekėnas, Saulius; Krogstrup, Peter; Nygård, Jesper; Marcus, Charles M.; Moler, Kathryn A.

    2017-12-01

    Gate-tunable semiconductor nanowires with superconducting leads have great potential for quantum computation and as model systems for mesoscopic Josephson junctions. The supercurrent, I, versus the phase, φ, across the junction is called the current-phase relation (CPR). It can reveal not only the amplitude of the critical current, but also the number of modes and their transmission. We measured the CPR of many individual InAs nanowire Josephson junctions, one junction at a time. Both the amplitude and shape of the CPR varied between junctions, with small critical currents and skewed CPRs indicating few-mode junctions with high transmissions. In a gate-tunable junction, we found that the CPR varied with gate voltage: near the onset of supercurrent, we observed behaviour consistent with resonant tunnelling through a single, highly transmitting mode. The gate dependence is consistent with modelled subband structure that includes an effective tunnelling barrier due to an abrupt change in the Fermi level at the boundary of the gate-tuned region. These measurements of skewed, tunable, few-mode CPRs are promising both for applications that require anharmonic junctions and for Majorana readout proposals.

  15. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  16. Computing with a single qubit faster than the computation quantum speed limit

    Science.gov (United States)

    Sinitsyn, Nikolai A.

    2018-02-01

    The possibility to save and process information in fundamentally indistinguishable states is the quantum mechanical resource that is not encountered in classical computing. I demonstrate that, if energy constraints are imposed, this resource can be used to accelerate information-processing without relying on entanglement or any other type of quantum correlations. In fact, there are computational problems that can be solved much faster, in comparison to currently used classical schemes, by saving intermediate information in nonorthogonal states of just a single qubit. There are also error correction strategies that protect such computations.

  17. Coherent interaction of a metallic structure with a single quantum emitter: from super absorption to cloaking

    CERN Document Server

    Chen, Xue-Wen; Agio, Mario

    2012-01-01

    We provide a general theoretical platform based on quantized radiation in absorptive and inhomogeneous media for investigating the coherent interaction of light with metallic structures in the immediate vicinity of quantum emitters. In the case of a very small metallic cluster, we demonstrate extreme regimes where a single emitter can either counteract or enhance particle absorption by three orders of magnitude. For larger structures, we show that an emitter can eliminate both scattering and absorption and cloak a plasmonic antenna. We provide physical interpretations of our results and discuss their applications in active metamaterials and quantum plasmonics.

  18. Terahertz Absorption of (In,Ga)As Quantum Post Nanostructures

    Science.gov (United States)

    Morris, C. M.; Stehr, D.; Allen, D. G.; He, J.; Krenner, H. J.; Pryor, C.; Petroff, P. M.; Sherwin, M. S.

    2008-03-01

    Quantum posts (QPs) are a new kind of self-assembled semiconductor nanostructure created by vertical stacking of self-assembled InAs quantum dots into roughly cylindrical In rich regions embedded in a GaAs matrix.^2 These structures have potential applications for THz quantum information processing,^1 THz generation, and THz detection. For a single electron trapped in a 40 nm high QP, the orbital transition between the ground and first excited state is predicted to occur near 1 THz.^2 Voltage controlled electron loading of QPs is measured by capacitance-voltage spectroscopy. Terahertz absorption spectroscopy of electrons in quantum post samples is demonstrated as a function of electron loading. ^1 M. S. Sherwin, A. Imamoglu and C. Montroy, PRA 60, 3508 (1999) ^2 J. He et al, Nanoletters 7, 802 (2007)

  19. Controlled Rephasing of Single Collective Spin Excitations in a Cold Atomic Quantum Memory.

    Science.gov (United States)

    Albrecht, Boris; Farrera, Pau; Heinze, Georg; Cristiani, Matteo; de Riedmatten, Hugues

    2015-10-16

    We demonstrate active control of inhomogeneous dephasing and rephasing for single collective atomic spin excitations (spin waves) created by spontaneous Raman scattering in a quantum memory based on cold 87Rb atoms. The control is provided by a reversible external magnetic field gradient inducing an inhomogeneous broadening of the atomic hyperfine levels. We demonstrate experimentally that active rephasing preserves the single photon nature of the retrieved photons. Finally, we show that the control of the inhomogeneous dephasing enables the creation of time-separated spin waves in a single ensemble followed by a selective read-out in time. This is an important step towards the implementation of a functional temporally multiplexed quantum repeater node.

  20. Electron confinement and correlation in double quantum well single charge electrometers

    Science.gov (United States)

    Gyure, Mark F.; Caflisch, Russel E.; Anderson, Chris; Robinson, Hans D.; Croke, Edward T.; Yablonovitch, Eli

    2002-03-01

    Single electron transistors and other related device concepts have been proposed for use in a variety of quantum information processing applications. Central to the application of these devices is not only single electron confinement and sensitivity, but the ability to discriminate between the singlet and triplet states for indirect measurement of electron spin. In this talk, we will describe theoretical and numerical results for a new device based on InGaAs/InP double quantum well structures (see related talk by H.D. Robinson et al) that demonstrate that single electron confinement is achievable in this structure. In addition, we will discuss properties related to spin readout such as the the singlet-triplet energy splitting of two-electron states as well as the role of electron correlation effects in this device.

  1. Dissecting contact mechanics from quantum interference in single-molecule junctions of stilbene derivatives.

    Science.gov (United States)

    Aradhya, Sriharsha V; Meisner, Jeffrey S; Krikorian, Markrete; Ahn, Seokhoon; Parameswaran, Radha; Steigerwald, Michael L; Nuckolls, Colin; Venkataraman, Latha

    2012-03-14

    Electronic factors in molecules such as quantum interference and cross-conjugation can lead to dramatic modulation and suppression of conductance in single-molecule junctions. Probing such effects at the single-molecule level requires simultaneous measurements of independent junction properties, as conductance alone cannot provide conclusive evidence of junction formation for molecules with low conductivity. Here, we compare the mechanics of the conducting para-terminated 4,4'-di(methylthio)stilbene and moderately conducting 1,2-bis(4-(methylthio)phenyl)ethane to that of insulating meta-terminated 3,3'-di(methylthio)stilbene single-molecule junctions. We simultaneously measure force and conductance across single-molecule junctions and use force signatures to obtain independent evidence of junction formation and rupture in the meta-linked cross-conjugated molecule even when no clear low-bias conductance is measured. By separately quantifying conductance and mechanics, we identify the formation of atypical 3,3'-di(methylthio)stilbene molecular junctions that are mechanically stable but electronically decoupled. While theoretical studies have envisaged many plausible systems where quantum interference might be observed, our experiments provide the first direct quantitative study of the interplay between contact mechanics and the distinctively quantum mechanical nature of electronic transport in single-molecule junctions. © 2012 American Chemical Society

  2. Weak link nanobridges as single flux quantum elements

    Science.gov (United States)

    Shelly, Connor D.; See, Patrick; Ireland, Jane; Romans, Ed J.; Williams, Jonathan M.

    2017-09-01

    This paper investigates the feasibility of using weak link nanobridges as Josephson junction elements for the purpose of creating Josephson circuits. We demonstrate the development of a single-step electron beam lithography procedure to fabricate niobium nanobridges with dimensions down to 40 {nm}× 100 {nm}. The single-step process facilitates fabrication that is scalable to complex circuits that require many junctions. We measure the IV-characteristics (IVC) of the nanobridges between temperatures of 4.2 and 9 {{K}} and find agreement with numerical simulations and the analytical resistively shunted junction (RSJ) model. Furthermore, we investigate the behaviour of the nanobridges under rf irradiation and observe the characteristic microwave-induced Shapiro steps. Our simulated IVC under rf irradiation using both the RSJ model and circuit simulator JSIM are in agreement with the experimental data. As a potential use of nanobridges in circuits requiring many junctions, we investigate the theoretical performance of a nanobridge-based Josephson comparator circuit using JSIM.

  3. Quantum yield in polymer wrapped single walled carbon nanotubes: a computational model

    Science.gov (United States)

    Djokić, Dejan M.; Goswami, Aranya

    2017-11-01

    Quantum yield in polymer wrapped single walled carbon nanotubes (SWCNTs) has been computationally investigated using a 2D model of exciton decay with non-radiative channels due to the diffusive motion across the nanotube surface. Beside the role of SWCNT’s ends as the exciton quenchers, we have considered the influence of the wrapping polymer through its chemistry and wrapping angle. The model has been solved exactly for zero-angle wrapping, a particular case when the polymer interfaces the nanotube along its axis. The general case has been treated numerically and it has been concluded that the wrapping angle has no relevant influence upon the quantum yield values which are of experimental interest. A wide range of quantum yield values computed in the present contribution can be helpful in understanding potentially available photoluminescence data of SWCNTs wrapped with a variety of polymer families.

  4. Conditioned spin and charge dynamics of a single-electron quantum dot

    Science.gov (United States)

    Greplova, Eliska; Laird, Edward A.; Briggs, G. Andrew D.; Mølmer, Klaus

    2017-11-01

    In this article we describe the incoherent and coherent spin and charge dynamics of a single-electron quantum dot. We use a stochastic master equation to model the state of the system, as inferred by an observer with access to only the current signal through a quantum point contact, acting as a charge sensor. Measurements obtained during an interval of time contribute, by a past quantum state analysis, to our knowledge about the system at any time t within that interval. Such analysis permits precise estimation of physical parameters and we propose and test a modification of the classical Baum-Welch parameter reestimation method to systems driven by both coherent and incoherent processes.

  5. Single-mode quantum cascade lasers employing a candy-cane shaped monolithic coupled cavity

    Science.gov (United States)

    Liu, Peter Q.; Sladek, Kamil; Wang, Xiaojun; Fan, Jen-Yu; Gmachl, Claire F.

    2011-12-01

    We demonstrate single-mode quantum cascade lasers emitting at ˜4.5 μm by employing a monolithic "candy-cane" shaped coupled-cavity consisting of a straight section connecting at one end to a spiral section. The fabrication process is identical to those for simple Fabry-Perot-type ridge lasers. Continuously tunable single-mode emission across ˜8 cm-1 with side mode suppression ratio up to ˜25 dB and a single-mode operating current range of more than 70% above the threshold current is achieved when the lasers are operated in pulsed-mode from 80 K to 155 K.

  6. Equivalence relations for the classical capacity of single-mode Gaussian quantum channels.

    Science.gov (United States)

    Schäfer, Joachim; Karpov, Evgueni; García-Patrón, Raúl; Pilyavets, Oleg V; Cerf, Nicolas J

    2013-07-19

    We prove the equivalence of an arbitrary single-mode Gaussian quantum channel and a newly defined fiducial channel preceded by a phase shift and followed by a Gaussian unitary operation. This equivalence implies that the energy-constrained classical capacity of any single-mode Gaussian channel can be calculated based on this fiducial channel, which is furthermore simply realizable with a beam splitter, two identical single-mode squeezers, and a two-mode squeezer. In a large domain of parameters, we also provide an analytical expression for the Gaussian classical capacity, exploiting its additivity, and prove that the classical capacity cannot exceed it by more than 1/ln2 bits.

  7. Quantum Simulation of Single-Qubit Thermometry Using Linear Optics.

    Science.gov (United States)

    Mancino, Luca; Sbroscia, Marco; Gianani, Ilaria; Roccia, Emanuele; Barbieri, Marco

    2017-03-31

    Standard thermometry employs the thermalization of a probe with the system of interest. This approach can be extended by incorporating the possibility of using the nonequilibrium states of the probe and the presence of coherence. Here, we illustrate how these concepts apply to the single-qubit thermometer introduced by Jevtic et al. [Phys. Rev. A 91, 012331 (2015)PLRAAN1050-294710.1103/PhysRevA.91.012331] by performing a simulation of the qubit-environment interaction in a linear-optical device. We discuss the role of the coherence and how this affects the usefulness of nonequilibrium conditions. The origin of the observed behavior is traced back to how the coherence affects the propensity to thermalization. We discuss this aspect by considering the availability function.

  8. Simple intrinsic defects in InAs :

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Peter Andrew

    2013-03-01

    This Report presents numerical tables summarizing properties of intrinsic defects in indium arsenide, InAs, as computed by density functional theory using semi-local density functionals, intended for use as reference tables for a defect physics package in device models.

  9. Realization of Microwave Quantum Circuits Using Hybrid Superconducting-Semiconducting Nanowire Josephson Elements.

    Science.gov (United States)

    de Lange, G; van Heck, B; Bruno, A; van Woerkom, D J; Geresdi, A; Plissard, S R; Bakkers, E P A M; Akhmerov, A R; DiCarlo, L

    2015-09-18

    We report the realization of quantum microwave circuits using hybrid superconductor-semiconductor Josephson elements comprised of InAs nanowires contacted by NbTiN. Capacitively shunted single elements behave as transmon circuits with electrically tunable transition frequencies. Two-element circuits also exhibit transmonlike behavior near zero applied flux but behave as flux qubits at half the flux quantum, where nonsinusoidal current-phase relations in the elements produce a double-well Josephson potential. These hybrid Josephson elements are promising for applications requiring microwave superconducting circuits operating in a magnetic field.

  10. Single ion impact detection and scanning probe aligned ion implantation for quantum bit formation

    Energy Technology Data Exchange (ETDEWEB)

    Weis, Christoph D.

    2011-10-04

    Quantum computing and quantum information processing is a promising path to replace classical information processing via conventional computers which are approaching fundamental physical limits. Instead of classical bits, quantum bits (qubits) are utilized for computing operations. Due to quantum mechanical phenomena such as superposition and entanglement, a completely different way of information processing is achieved, enabling enhanced performance for certain problem sets. Various proposals exist on how to realize a quantum bit. Among them are electron or nuclear spins of defect centers in solid state systems. Two such candidates with spin degree of freedom are single donor atoms in silicon and nitrogen vacancy (NV) defect centers in diamond. Both qubit candidates possess extraordinary qualities which makes them promising building blocks. Besides certain advantages, the qubits share the necessity to be placed precisely in their host materials and device structures. A commonly used method is to introduce the donor atoms into the substrate materials via ion implantation. For this, focused ion beam systems can be used, or collimation techniques as in this work. A broad ion beam hits the back of a scanning probe microscope (SPM) cantilever with incorporated apertures. The high resolution imaging capabilities of the SPM allows the non destructive location of device areas and the alignment of the cantilever and thus collimated ion beam spot to the desired implant locations. In this work, this technique is explored, applied and pushed forward to meet necessary precision requirements. The alignment of the ion beam to surface features, which are sensitive to ion impacts and thus act as detectors, is demonstrated. The technique is also used to create NV center arrays in diamond substrates. Further, single ion impacts into silicon device structures are detected which enables deliberate single ion doping.

  11. Flux qubit interaction with rapid single-flux quantum logic circuits: Control and readout

    Science.gov (United States)

    Klenov, N. V.; Kuznetsov, A. V.; Soloviev, I. I.; Bakurskiy, S. V.; Denisenko, M. V.; Satanin, A. M.

    2017-07-01

    We present the results of an analytical study and numerical simulation of the dynamics of a superconducting three-Josephson-junction (3JJ) flux qubit magnetically coupled with rapid single-flux quantum (RSFQ) logic circuit, which demonstrate the fundamental possibility of implementing the simplest logic operations at picosecond times, as well as rapid non-destructive readout. It is shown that when solving optimization problems, the qubit dynamics can be conveniently interpreted as a precession of the magnetic moment vector around the direction of the magnetic field. In this case, the role of magnetic field components is played by combinations of the Hamiltonian matrix elements, and the role of the magnetic moment is played by the Bloch vector. Features of the 3JJ qubit model are discussed during the analysis of how the qubit is affected by exposure to a short control pulse, as are the similarities between the Bloch and Landau-Lifshitz-Gilbert equations. An analysis of solutions to the Bloch equations made it possible to develop recommendations for the use of readout RSFQ circuits in implementing an optimal interface between the classical and quantum parts of the computer system, as well as to justify the use of single-quantum logic in order to control superconducting quantum circuits on a chip.

  12. `Kondo Blockade' due to quantum interference in single-molecule transistors

    Science.gov (United States)

    Mitchell, Andrew; Pedersen, Kim; Hedegaard, Per; Paaske, Jens

    Molecular electronics offers unique scientific and technological possibilities resulting from both the nanometer scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule transistors: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. In this talk I discuss recent progress in unifying these phenomena within an exact theoretical framework, showing how quantum interference leads to new types of Kondo-mediated transport beyond the standard single-orbital paradigm. Conductance can be strongly enhanced by the Kondo effect, but can take a different universal form from that of magnetic impurities or quantum dots. By contrast, we prove that a quantum interference node in exchange cotunneling leads to a novel `Kondo Blockade' mechanism, resulting in an exact node in the total conductance at low temperatures. Analytic results are supported by full numerical renormalization group calculations for simple molecular junctions where efficient transistor function is predicted, exploiting gate-controllable tuning between Kondo resonance and Kondo blockade.

  13. Probing correlated quantum many-body systems at the single-particle level

    Energy Technology Data Exchange (ETDEWEB)

    Endres, Manuel

    2013-02-27

    The detection of correlation and response functions plays a crucial role in the experimental characterization of quantum many-body systems. In this thesis, we present novel techniques for the measurement of such functions at the single-particle level. Specifically, we show the single-atom- and single-site-resolved detection of an ultracold quantum gas in an optical lattice. The quantum gas is described by the Bose-Hubbard model, which features a zero temperature phase transition from a superfluid to a Mott-insulating state, a paradigm example of a quantum phase transition. We used the aforementioned detection techniques to study correlation and response properties across the superfluid-Mott-insulator transition. The single-atom sensitivity of our method is achieved by fluorescence detection of individual atoms with a high signal-to-noise ratio. A high-resolution objective collects the fluorescence light and yields in situ 'snapshots' of the quantum gas that allow for a single-site-resolved reconstruction of the atomic distribution. This allowed us to measure two-site and non-local correlation-functions across the superfluid-Mott-insulator transition. Non-local correlation functions are based on the information of an extended region of the system and play an important role for the characterization of low-dimensional quantum phases. While non-local correlation functions were so far only theoretical tools, our results show that they are actually experimentally accessible. Furthermore, we used a new thermometry scheme, based on the counting of individual thermal excitations, to measure the response of the system to lattice modulation. Using this method, we studied the excitation spectrum of the system across the two-dimensional superfluid-Mott-insulator transition. In particular, we detected a 'Higgs' amplitude mode in the strongly-interacting superfluid close to the transition point where the system is described by an effectively Lorentz

  14. Doubly resonant photonic antenna for single infrared quantum dot imaging at telecommunication wavelengths

    CERN Document Server

    Xie, Zhihua; Mivelle, Mathieu; Salut, Roland; Merolla, Jean-Marc; Grosjean, Thierry

    2016-01-01

    Colloidal Quantum dots (CQDs) are nowadays one of the cornerstones of modern photonics as they have led to the emergence of new optoelectronic and biomedical technologies. However, the full characterization of these quantum emitters is currently restricted to the visible wavelengths and it remains a key challenge to optically probe single CQDs operating in the infrared spectral domain which is targeted by a growing number of applications. Here, we report the first experimental detection and imaging at room temperature of single infrared CQDs operating at telecommunication wavelengths. Imaging was done with a doubly resonant bowtie nano-aperture antenna (BNA) written at the end of a fiber nanoprobe, whose resonances spectrally fit the CQD absorption and emission wavelengths. Direct near-field characterization of PbS CQDs reveal individual nanocrystals with a spatial resolution of 75 nm (lambda/20) together with their intrinsic 2D dipolar free-space emission properties and exciton dynamics (blinking phenomenon)...

  15. Toward quantum state tomography of a single polariton state of an atomic ensemble

    DEFF Research Database (Denmark)

    Christensen, S.L.; Béguin, J.B.; Sørensen, H.L.

    2013-01-01

    We present a proposal and a feasibility study for the creation and quantum state tomography of a single polariton state of an atomic ensemble. The collective non-classical and non-Gaussian state of the ensemble is generated by detection of a single forward-scattered photon. The state is subsequen...... the feasibility of the proposed method for the detection of a non-classical and non-Gaussian state of the mesoscopic atomic ensemble. This work represents the first attempt at hybrid discrete-continuous variable quantum state processing with atomic memories....... is subsequently characterized by atomic state tomography performed using strong dispersive light-atom interaction followed by a homodyne measurement on the transmitted light. The proposal is backed by preliminary experimental results showing projection noise limited sensitivity and a simulation demonstrating...

  16. Surface acoustic wave regulated single photon emission from a coupled quantum dot-nanocavity system

    CERN Document Server

    Weiß, Matthias; Reichert, Thorsten; Finley, Jonathan J; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J

    2016-01-01

    A coupled quantum dot--nanocavity system in the weak coupling regime of cavity quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a $f_{\\rm SAW}\\simeq800\\,\\mathrm{MHz}$ surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function $g^{(2)}$. All relevant frequencies of our experiment are faithfully identified in the Fourier transform of $g^{(2)}$, demonstrating high fidelity regulation of the stream of single photons emitted by the system. The implemented scheme can be directly extended to strongly coupled systems and acoustically drives non-adiabatic entangling quantum gates based on Landau-Zener transitions.

  17. Modulation of nonradiative processes of single colloidal quantum dots by glycerol passivation

    Science.gov (United States)

    Xu, Hao; Gan, Zhixing

    2017-11-01

    The radiative and nonradiative processes play predominant roles in the fluorescence performance of single colloidal quantum dots (QDs). In our report, we found that glycerol, a rarely studied chemical for CdSe core-shell QDs, would substantially modulate the nonradiative processes of single QDs. More specifically, the presence of glycerol would passivate the surface traps of single QDs, partly suppressing QD blinking. Simultaneously, glycerol would activate the defect states contributing to the nonradiative pathways, resulting in a shortened fluorescence lifetime and weakened fluorescence intensity. Additionally, glycerol could also stabilize single QDs, rendering enhanced chemical stability and photo stability of single QDs. As far as we know, this is a pioneering work studying on the impact of glycerol on fluorescence properties of CdSe core-shell QDs.

  18. Room-temperature near-field reflection spectroscopy of single quantum wells

    DEFF Research Database (Denmark)

    Langbein, Wolfgang Werner; Hvam, Jørn Marcher; Madsen, Steen

    1997-01-01

    . This technique suppresses efficiently the otherwise dominating far-field background and reduces topographic artifacts. We demonstrate its performance on a thin, strained near-surface CdS/ZnS single quantum well at room temperature. The optical structure of these topographically flat samples is due to Cd......S thickness fluctuations, and is observed to be uncorrelated within the spatial resolution of the instrument....

  19. Scattering of a vortex pair by a single quantum vortex in a Bose–Einstein condensate

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, L. A., E-mail: smirnov-lev@allp.sci-nnov.ru; Smirnov, A. I., E-mail: smirnov@appl.sci-nnov.ru; Mironov, V. A. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2016-01-15

    We analyze the scattering of vortex pairs (the particular case of 2D dark solitons) by a single quantum vortex in a Bose–Einstein condensate with repulsive interaction between atoms. For this purpose, an asymptotic theory describing the dynamics of such 2D soliton-like formations in an arbitrary smoothly nonuniform flow of a ultracold Bose gas is developed. Disregarding the radiation loss associated with acoustic wave emission, we demonstrate that vortex–antivortex pairs can be put in correspondence with quasiparticles, and their behavior can be described by canonical Hamilton equations. For these equations, we determine the integrals of motion that can be used to classify various regimes of scattering of vortex pairs by a single quantum vortex. Theoretical constructions are confirmed by numerical calculations performed directly in terms of the Gross–Pitaevskii equation. We propose a method for estimating the radiation loss in a collision of a soliton-like formation with a phase singularity. It is shown by direct numerical simulation that under certain conditions, the interaction of vortex pairs with a core of a single quantum vortex is accompanied by quite intense acoustic wave emission; as a result, the conditions for applicability of the asymptotic theory developed here are violated. In particular, it is visually demonstrated by a specific example how radiation losses lead to a transformation of a vortex–antivortex pair into a vortex-free 2D dark soliton (i.e., to the annihilation of phase singularities).

  20. Detecting correlations in deterministically prepared quantum states with single-atom imaging

    Science.gov (United States)

    Bergschneider, Andrea; Klinkhamer, Vincent M.; Becher, Jan Hendrik; Bommer, Philine L.; Niedermayer, Justin F.; Zuern, Gerhard; Preiss, Philipp M.; Jochim, Selim

    2017-04-01

    We deterministically prepare quantum states consisting of few fermions in single and double-well potentials. Here we report on a new imaging scheme for 6Lithium with which we detect the correlations of the quantum state on a single-atom level and with spin resolution. The detection method uses fluorescence imaging at high magnetic field where the optical transitions for the used hyperfine states are almost closed. With a high-resolution objective we image about 15 scattered photons per atom on an EMCCD camera. This is sufficient to identify and locate single atoms in our imaging plane. We can perform this scheme in situ or after an expansion in time-of-flight and additionally resolve the spin by subsequently adressing the different hyperfine states. By combining this scheme with our deterministic preparation, we measure the two-point momentum correlations to probe the spatial symmetry of the two-particle wavefunction. The high contrast and the scalability of the detection technique allows us to go beyond measuring two-point correlations and characterize many-body quantum states.

  1. Single-step fabrication of scalable multimode quantum resources using four-wave mixing with a spatially structured pump

    Science.gov (United States)

    Wang, Hailong; Fabre, Claude; Jing, Jietai

    2017-05-01

    Multimode quantum resources or states, in which quantum correlations are shared and distributed among multiple parties, are important not only for fundamental tests of quantum effects but also for their numerous possible applications in quantum technologies, such as quantum imaging and quantum metrology. Here we demonstrate the single-step fabrication of a multimode quantum resource from four-wave mixing (FWM) process in hot Rb vapor using a spatially structured pump, which consists of a coherent combination of two tilted pump beams. During this FWM process, one probe beam is amplified, three conjugate and two new probe beams are generated. The measured degrees of the intensity squeezing for the four-beam case and six-beam case are around -4.1 ±0.1 dB and -4.7 ±0.1 dB, respectively. The generated multiple quantum correlated beams are naturally separated with distinct directions, which is crucial for sending them out to quantum nodes at different locations in quantum communication. Our scheme is compact, simple, phase insensitive, and easily scalable to larger number of quantum-correlated modes.

  2. Quantum interference effects at room temperature in OPV-based single-molecule junctions

    DEFF Research Database (Denmark)

    Arroyo, Carlos R.; Frisenda, Riccardo; Moth-Poulsen, Kasper

    2013-01-01

    Interference effects on charge transport through an individual molecule can lead to a notable modulation and suppression on its conductance. In this letter, we report the observation of quantum interference effects occurring at room temperature in single-molecule junctions based on oligo(3......)-phenylenevinylene (OPV3) derivatives, in which the central benzene ring is coupled to either para- or meta-positions. Using the break-junction technique, we find that the conductance for a single meta-OPV3 molecule wired between gold electrodes is one order of magnitude smaller than that of a para-OPV3 molecule...

  3. Single photon quantum non-demolition measurements in the presence of inhomogeneous broadening

    Energy Technology Data Exchange (ETDEWEB)

    Greentree, Andrew D; Hollenberg, L C L; Prawer, S [Centre for Quantum Computer Technology, School of Physics, University of Melbourne, Melbourne, VIC 3010 (Australia); Beausoleil, R G [Hewlett-Packard Laboratories, 1501 Page Mill Rd, Palo Alto, CA 94304-1123 (United States); Munro, W J; Spiller, T P [Hewlett-Packard Laboratories, Filton Road, Stoke Gifford, Bristol BS34 8QZ (United Kingdom); Nemoto, Kae [National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430 (Japan)], E-mail: andrew.greentree@ph.unimelb.edu.au

    2009-09-15

    Electromagnetically induced transparency (EIT) has often been proposed for generating nonlinear optical effects at the single photon level; in particular, as a means to effect a quantum non-demolition measurement of a single-photon field. Previous treatments have usually considered homogeneously broadened samples, but realizations in any medium will have to contend with inhomogeneous broadening. Here we reappraise an earlier scheme (Munro et al 2005 Phys. Rev. A 71 033819) with respect to inhomogeneities and show an alternative mode of operation that is preferred in an inhomogeneous environment. We further show the implications of these results on a potential implementation in diamond-containing nitrogen-vacancy colour centres.

  4. Single photon quantum non-demolition measurements in the presence of inhomogeneous broadening

    Science.gov (United States)

    Greentree, Andrew D.; Beausoleil, R. G.; Hollenberg, L. C. L.; Munro, W. J.; Nemoto, Kae; Prawer, S.; Spiller, T. P.

    2009-09-01

    Electromagnetically induced transparency (EIT) has often been proposed for generating nonlinear optical effects at the single photon level; in particular, as a means to effect a quantum non-demolition measurement of a single-photon field. Previous treatments have usually considered homogeneously broadened samples, but realizations in any medium will have to contend with inhomogeneous broadening. Here we reappraise an earlier scheme (Munro et al 2005 Phys. Rev. A 71 033819) with respect to inhomogeneities and show an alternative mode of operation that is preferred in an inhomogeneous environment. We further show the implications of these results on a potential implementation in diamond-containing nitrogen-vacancy colour centres.

  5. Super-Resolution Definition of Coordinates of Single Semiconductor Nanocrystal (Quantum Dot): Luminescence Intensity Dependence

    Science.gov (United States)

    Eremchev, M. Yu.; Eremchev, I. Yu.; Naumov, A. V.

    2015-09-01

    In this research a relation between the accuracy of restoration of the single quantum dots (QD) CdSe/CdS/ZnS cross-cut coordinates and luminescence intensity was investigated. It was shown that the limit of the accuracy of determining the coordinates of a single QD for a considerable total amount of registered photons approaches its limiting value that is comparable to the size of the QD. It also means that the installation used in the research is mechanically stable enough to reach the limiting values of determination accuracy of point emitters coordinates.

  6. Super-Resolution Definition of Coordinates of Single Semiconductor Nanocrystal (Quantum Dot: Luminescence Intensity Dependence

    Directory of Open Access Journals (Sweden)

    Eremchev M. Yu.

    2015-01-01

    Full Text Available In this research a relation between the accuracy of restoration of the single quantum dots (QD CdSe/CdS/ZnS cross-cut coordinates and luminescence intensity was investigated. It was shown that the limit of the accuracy of determining the coordinates of a single QD for a considerable total amount of registered photons approaches its limiting value that is comparable to the size of the QD. It also means that the installation used in the research is mechanically stable enough to reach the limiting values of determination accuracy of point emitters coordinates.

  7. Thermally-fluctuated single-flux-quantum pulse intervals reflected in input-output characteristics of a double-flux-quantum amplifier

    Science.gov (United States)

    Mizugaki, Yoshinao; Urai, Yoshiaki; Shimada, Hiroshi

    2017-07-01

    A double-flux-quantum amplifier (DFQA) is a voltage multiplier of quantum accuracy, which we have employed at the final stage of a single-flux-quantum (SFQ) digital-to-analog converter (DAC). We recently found that experimental input-output (IO) characteristics of DFQAs were always slightly different from numerical results assuming ideally-periodic SFQ pulse trains. That is, experimental IO characteristics obtained using an over-biasing method were gradually deteriorated near their maximum operation voltages. Numerical simulation including the over-biasing method at a finite temperature suggested that the difference was likely to be attributed to thermally-fluctuated intervals of input SFQ pulses.

  8. Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies.

    Science.gov (United States)

    Tettamanzi, Giuseppe Carlo; Hile, Samuel James; House, Matthew Gregory; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y

    2017-03-28

    The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

  9. Cavity enhanced telecom heralded single photons for spin-wave solid state quantum memories

    Science.gov (United States)

    Rieländer, Daniel; Lenhard, Andreas; Mazzera, Margherita; de Riedmatten, Hugues

    2016-12-01

    We report on a source of heralded narrowband (≈ 3 MHz) single photons compatible with solid-state spin-wave quantum memories based on praseodymium doped crystals. Widely non-degenerate narrow-band photon pairs are generated using cavity enhanced down conversion. One photon from the pair is at telecom wavelengths and serves as heralding signal, while the heralded single photon is at 606 nm, resonant with an optical transition of Pr3+:Y2SiO5. The source offers a heralding efficiency of 28% and a generation rate exceeding 2000 pairs mW-1 in a single-mode. The single photon nature of the heralded field is confirmed by a direct antibunching measurement, with a measured antibunching parameter down to 0.010(4). Moreover, we investigate in detail photon cross- and autocorrelation functions proving non-classical correlations between the two photons. The results presented in this paper offer prospects for the demonstration of single photon spin-wave storage in an on-demand solid state quantum memory, heralded by a telecom photon.

  10. A quantum circuit rule for interference effects in single-molecule electrical junctions.

    Science.gov (United States)

    Manrique, David Zsolt; Huang, Cancan; Baghernejad, Masoud; Zhao, Xiaotao; Al-Owaedi, Oday A; Sadeghi, Hatef; Kaliginedi, Veerabhadrarao; Hong, Wenjing; Gulcur, Murat; Wandlowski, Thomas; Bryce, Martin R; Lambert, Colin J

    2015-03-03

    A quantum circuit rule for combining quantum interference effects in the conductive properties of oligo(phenyleneethynylene) (OPE)-type molecules possessing three aromatic rings was investigated both experimentally and theoretically. Molecules were of the type X-Y-X, where X represents pyridyl anchors with para (p), meta (m) or ortho (o) connectivities and Y represents a phenyl ring with p and m connectivities. The conductances GXmX (GXpX) of molecules of the form X-m-X (X-p-X), with meta (para) connections in the central ring, were predominantly lower (higher), irrespective of the meta, para or ortho nature of the anchor groups X, demonstrating that conductance is dominated by the nature of quantum interference in the central ring Y. The single-molecule conductances were found to satisfy the quantum circuit rule Gppp/Gpmp=Gmpm/Gmmm. This demonstrates that the contribution to the conductance from the central ring is independent of the para versus meta nature of the anchor groups.

  11. Single-photon test of hyper-complex quantum theories using a metamaterial.

    Science.gov (United States)

    Procopio, Lorenzo M; Rozema, Lee A; Wong, Zi Jing; Hamel, Deny R; O'Brien, Kevin; Zhang, Xiang; Dakić, Borivoje; Walther, Philip

    2017-04-21

    In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although this has so far proven sufficient to predict experimental results, there is no theoretical reason to choose them over real numbers or generalizations of complex numbers, that is, hyper-complex numbers. Experiments performed to date have proven that real numbers are insufficient, but the need for hyper-complex numbers remains an open question. Here we experimentally probe hyper-complex quantum theories, studying one of their deviations from complex quantum theory: the non-commutativity of phases. We do so by passing single photons through a Sagnac interferometer containing both a metamaterial with a negative refractive index, and a positive phase shifter. To accomplish this we engineered a fishnet metamaterial to have a negative refractive index at 780 nm. We show that the metamaterial phase commutes with other phases with high precision, allowing us to place limits on a particular prediction of hyper-complex quantum theories.

  12. Analysis of decoherence mechanisms in a single-atom quantum memory

    Science.gov (United States)

    Koerber, Matthias; Langenfeld, Stefan; Morin, Olivier; Neuzner, Andreas; Ritter, Stephan; Rempe, Gerhard

    2017-04-01

    While photons are ideal for the transmission of quantum information, they require dedicated memories for long-term storage. The challenge for such a photonic quantum memory is the combination of an efficient light-matter interface with a low-decoherence encoding. To increase the time before the quantum information is lost, a thorough analysis of the relevant decoherence mechanisms is indispensable. Our optical quantum memory consists of a single rubidium atom trapped in a two dimensional optical lattice in a high-finesse Fabry-Perot-type optical resonator. The qubit is initially stored in a superposition of Zeeman states, making magnetic field fluctuations the dominant source of decoherence. The impact to this type of noise is greatly reduced by transferring the qubit into a subspace less susceptible to magnetic field fluctuations. In this configuration, the achievable coherence times are no longer limited by those fluctuations, but decoherence mechanisms induced by the trapping beams pose a new limit. We will discuss the origin and magnitude of the relevant effects and strategies for possible resolutions.

  13. Physics colloquium: Single-electron counting in quantum metrology and in statistical mechanics

    CERN Multimedia

    Geneva University

    2011-01-01

    GENEVA UNIVERSITY Ecole de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 Genève 4 Tél.: (022) 379 62 73 Fax: (022) 379 69 92olé   Lundi 17 octobre 2011 17h00 - Ecole de Physique, Auditoire Stueckelberg PHYSICS COLLOQUIUM « Single-electron counting in quantum metrology and in statistical mechanics » Prof. Jukka Pekola Low Temperature Laboratory, Aalto University Helsinki, Finland   First I discuss the basics of single-electron tunneling and its potential applications in metrology. My main focus is in developing an accurate source of single-electron current for the realization of the unit ampere. I discuss the principle and the present status of the so-called single- electron turnstile. Investigation of errors in transporting electrons one by one has revealed a wealth of observations on fundamental phenomena in mesoscopic superconductivity, including individual Andreev...

  14. Single-Step Multicolor Fluorescence In Situ Hybridization Using Semiconductor Quantum Dot–DNA Conjugates

    Science.gov (United States)

    Bentolila, Laurent A.; Weiss, Shimon

    2011-01-01

    We report a rapid method for the direct multicolor imaging of multiple subnuclear genetic sequences using novel quantum dot-based fluorescence in situ hybridization (FISH) probes (QD–FISH). Short DNA oligonucleotides were attached on QDs and used in a single hybridization/detection step of target sites in situ. QD–FISH probes penetrate both intact interphase nuclei and metaphase chromosomes and showed good targeting of dense chromatin domains with minimal steric hindrances. We further demonstrated that QD’s broad absorption spectra allowed different colored probes specific for distinct subnuclear genetic sequences to be simultaneously excited with a single excitation wavelength and imaged free of chromatic aberrations in a single exposure. Thus, these results demonstrate that QD–FISH probes are very effective in multicolor FISH applications. This work also documents new possibilities of using QD–FISH probes detection down to the single molecule level. PMID:16679564

  15. Hybrid Double Quantum Dots

    DEFF Research Database (Denmark)

    Sherman, D.; Yodh, J. S.; Albrecht, S. M.

    2016-01-01

    Epitaxial semiconductor-superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density. Here, we investigate double-quantum-dot devices made from InA...... that the individual dots host weakly hybridized Majorana modes....

  16. Sulfur Doping of InAs

    Science.gov (United States)

    2015-06-04

    results were also observed with co-implantation of gallium with selenium , which sits on the group-V site [10]. Consequently, the sulfur dose was...wavelength equivalent to the plasma frequency to >4 µm. Glazov and co-workers studied several alternative n-type dopants (sulfur, selenium , and...Wafers were then ion-implanted with varying sulfur doses at peak concentration depths of 50 nm, providing ~100 nm of sulfur-doped InAs. This was

  17. Highly polarized electrically driven single-photon emission from a non-polar InGaN quantum dot

    Science.gov (United States)

    Kocher, C. C.; Puchtler, T. J.; Jarman, J. C.; Zhu, T.; Wang, T.; Nuttall, L.; Oliver, R. A.; Taylor, R. A.

    2017-12-01

    Nitride quantum dots are well suited for the deterministic generation of single photons at high temperatures. However, this material system faces the challenge of large in-built fields, decreasing the oscillator strength and possible emission rates considerably. One solution is to grow quantum dots on a non-polar plane; this gives the additional advantage of strongly polarized emission along one crystal direction. This is highly desirable for future device applications, as is electrical excitation. Here, we report on electroluminescence from non-polar InGaN quantum dots. The emission from one of these quantum dots is studied in detail and found to be highly polarized with a degree of polarization of 0.94. Single-photon emission is achieved under excitation with a constant current giving a g(2 )(0 ) correlation value of 0.18. The quantum dot electroluminescence persists up to temperatures as high as 130 K.

  18. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    Science.gov (United States)

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-07

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging".

  19. Electrically injected GaAsBi/GaAs single quantum well laser diodes

    Science.gov (United States)

    Liu, Juanjuan; Pan, Wenwu; Wu, Xiaoyan; Cao, Chunfang; Li, Yaoyao; Chen, Xiren; Zhang, Yanchao; Wang, Lijuan; Yan, Jinyi; Zhang, Dongliang; Song, Yuxin; Shao, Jun; Wang, Shumin

    2017-11-01

    We present electrically injected GaAs/GaAsBi single quantum well laser diodes (LDs) emitting at a record long wavelength of 1141 nm at room temperature grown by molecular beam epitaxy. The LDs have excellent device performances with internal quantum efficiency of 86%, internal loss of 10 cm-1 and transparency current density of 196 A/cm2. The LDs can operate under continuous-wave mode up to 273 K. The characteristic temperature are extracted to be 125 K in the temperature range of 77˜150 K, and reduced to 90 K in the range of 150˜273 K. The temperature coefficient of 0.3 nm/K is extracted in the temperature range of 77˜273 K.

  20. Interaction induced dephasing of excitons in wide ZnSe/ZnMgSe single quantum wells

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Schätz, A.; Maier, R.

    1998-01-01

    . Polarization-dependent measurements identify a biexcition formation of the 11h exciton showing a binding energy of E-BX = 3.5 +/- 0.5 meV. The measurements also indicate, that the third-order polarization is strongly influenced by interaction-induced processes. We show, that excitation-induced dephasing gives......The dephasing of excitons in wide ZnSe/Zn0.94Mg0.06Se single quantum wells (SQW) is investigated by spectrally resolved, time integrated four-wave mixing (FWM). Simultaneous excitation of Is center-of-mass quantized heavy-hole and light-hole excition states leads to pronounced quantum beats...

  1. Quantum dot-like excitonic behavior in individual single walled-carbon nanotubes

    Science.gov (United States)

    Wang, Xu; Alexander-Webber, Jack A.; Jia, Wei; Reid, Benjamin P. L.; Stranks, Samuel D.; Holmes, Mark J.; Chan, Christopher C. S.; Deng, Chaoyong; Nicholas, Robin J.; Taylor, Robert A.

    2016-11-01

    Semiconducting single-walled carbon nanotubes are one-dimensional materials with great prospects for applications such as optoelectronic and quantum information devices. Yet, their optical performance is hindered by low fluorescent yield. Highly mobile excitons interacting with quenching sites are attributed to be one of the main non-radiative decay mechanisms that shortens the exciton lifetime. In this paper we report on time-integrated photoluminescence measurements on individual polymer wrapped semiconducting carbon nanotubes. An ultra narrow linewidth we observed demonstrates intrinsic exciton dynamics. Furthermore, we identify a state filling effect in individual carbon nanotubes at cryogenic temperatures as previously observed in quantum dots. We propose that each of the CNTs is segmented into a chain of zero-dimensional states confined by a varying local potential along the CNT, determined by local environmental factors such as the amount of polymer wrapping. Spectral diffusion is also observed, which is consistent with the tunneling of excitons between these confined states.

  2. Quantum dot-like excitonic behavior in individual single walled-carbon nanotubes.

    Science.gov (United States)

    Wang, Xu; Alexander-Webber, Jack A; Jia, Wei; Reid, Benjamin P L; Stranks, Samuel D; Holmes, Mark J; Chan, Christopher C S; Deng, Chaoyong; Nicholas, Robin J; Taylor, Robert A

    2016-11-16

    Semiconducting single-walled carbon nanotubes are one-dimensional materials with great prospects for applications such as optoelectronic and quantum information devices. Yet, their optical performance is hindered by low fluorescent yield. Highly mobile excitons interacting with quenching sites are attributed to be one of the main non-radiative decay mechanisms that shortens the exciton lifetime. In this paper we report on time-integrated photoluminescence measurements on individual polymer wrapped semiconducting carbon nanotubes. An ultra narrow linewidth we observed demonstrates intrinsic exciton dynamics. Furthermore, we identify a state filling effect in individual carbon nanotubes at cryogenic temperatures as previously observed in quantum dots. We propose that each of the CNTs is segmented into a chain of zero-dimensional states confined by a varying local potential along the CNT, determined by local environmental factors such as the amount of polymer wrapping. Spectral diffusion is also observed, which is consistent with the tunneling of excitons between these confined states.

  3. Waveguide integrated superconducting single-photon detectors with high internal quantum efficiency at telecom wavelengths.

    Science.gov (United States)

    Kahl, Oliver; Ferrari, Simone; Kovalyuk, Vadim; Goltsman, Gregory N; Korneev, Alexander; Pernice, Wolfram H P

    2015-06-10

    Superconducting nanowire single-photon detectors (SNSPDs) provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, compatibility with an integrated optical platform is a crucial requirement for applications in emerging quantum photonic technologies. Here we present SNSPDs embedded in nanophotonic integrated circuits which achieve internal quantum efficiencies close to unity at 1550 nm wavelength. This allows for the SNSPDs to be operated at bias currents far below the critical current where unwanted dark count events reach milli-Hz levels while on-chip detection efficiencies above 70% are maintained. The measured dark count rates correspond to noise-equivalent powers in the 10(-19) W/Hz(-1/2) range and the timing jitter is as low as 35 ps. Our detectors are fully scalable and interface directly with waveguide-based optical platforms.

  4. Interplay between quantum interference and conformational fluctuations in single-molecule break junctions.

    Science.gov (United States)

    Berritta, Marco; Manrique, David Zs; Lambert, Colin J

    2015-01-21

    We theoretically explored the combined role of conformational fluctuations and quantum interference in determining the electrical conductance of single-molecule break junctions. In particular we computed the conductance of a family of methylsulfide-functionalized trans-α,ω-diphenyloligoene molecules, with terminal phenyl rings containing meta or para linkages, for which (at least in the absence of fluctuations) destructive interference in the former is expected to decrease their electrical conductance compared with the latter. We compared the predictions of density functional theory (DFT), in which fluctuational effects are absent, with results for the conformationally-averaged conductance obtained from an ensemble of conformations obtained from classical molecular dynamics. We found that junctions formed from these molecules exhibit distinct transport regimes during junction evolution and the signatures of quantum interference in these molecules survive the effect of conformational fluctuations. Furthermore, the agreement between theory and experiment is significantly improved by including conformational averaging.

  5. Strong coupling and stimulated emission in single parabolic quantum well microcavity for terahertz cascade

    Energy Technology Data Exchange (ETDEWEB)

    Tzimis, A.; Savvidis, P. G. [Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Crete (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Trifonov, A. V.; Ignatiev, I. V. [Spin Optics Laboratory, State University of Saint-Petersburg, 1 Ulianovskaya, 198504 St. Petersburg (Russian Federation); Christmann, G.; Tsintzos, S. I. [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Hatzopoulos, Z. [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, 71110 Heraklion, Crete (Greece); Department of Physics, University of Crete, 71003 Heraklion, Crete (Greece); Kavokin, A. V. [Spin Optics Laboratory, State University of Saint-Petersburg, 1 Ulianovskaya, 198504 St. Petersburg (Russian Federation); School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-09-07

    We report observation of strong light-matter coupling in an AlGaAs microcavity (MC) with an embedded single parabolic quantum well. The parabolic potential is achieved by varying aluminum concentration along the growth direction providing equally spaced energy levels, as confirmed by Brewster angle reflectivity from a reference sample without MC. It acts as an active region of the structure which potentially allows cascaded emission of terahertz (THz) light. Spectrally and time resolved pump-probe spectroscopy reveals characteristic quantum beats whose frequencies range from 0.9 to 4.5 THz, corresponding to energy separation between relevant excitonic levels. The structure exhibits strong stimulated nonlinear emission with simultaneous transition to weak coupling regime. The present study highlights the potential of such devices for creating cascaded relaxation of bosons, which could be utilized for THz emission.

  6. Manipulation of dynamic nuclear spin polarization in single quantum dots by photonic environment engineering

    Science.gov (United States)

    Fong, C. F.; Ota, Y.; Iwamoto, S.; Arakawa, Y.

    2017-06-01

    Optically induced dynamic nuclear spin polarization (DNP) in a semiconductor quantum dot (QD) requires many cycles of excitation of spin polarized carriers and carrier recombination. As such, the radiative lifetime of the exciton containing the electron becomes one of the limiting factors of DNP. In principle, changing the radiative lifetime of the exciton will affect DNP and thus the nuclear spin polarization. Here, we demonstrate the manipulation of DNP in single QDs through the engineering of the photonic environment using two-dimensional photonic crystals. We find that the achievable degree of nuclear spin polarization can be controlled through the modification of exciton radiative lifetime. Our results show the promise of achieving a higher degree of nuclear spin polarization via photonic environment engineering, with implications on spin-based quantum information processing.

  7. Coherent properties of single quantum dot transitions and single photon emission

    Energy Technology Data Exchange (ETDEWEB)

    Ester, Patrick

    2008-04-23

    In this work, the properties and the different dephasing mechanisms of single QD transitions are analyzed. In addition, some applications are presented which arise due to the properties of the confined exciton. The isolation of a single QD out of the ensemble is achieved via near field shadow masks, which restricts excitation and QD luminescence to a single QD. The integration of a QD-layer into a diode structure allows for an analysis of various dephasing mechanisms of a confined electron hole pair. The single QD is characterized regarding the energy of nearly all possible transitions, e.g. the ground state, excited states, charged states, multiple occupations, and phonon assisted absorptions. A very important issue in this content is the voltage dependence of the transition energy and thereby the ability of tunneling processes of charge carriers in and out of the QD. The QD-states, which are subject of investigation here, are the single exciton ground state, the first excited state (p-shell), and the (GaAs-) LO (longitudinal optical) phonon assisted absorption. By applying a suitable voltage, the resonantly excited ground state exciton is able to decay by a tunneling process, which reflects the transition energy in the photocurrent spectra. The p-shell transition decays by a relaxation process into the ground state, followed by an optical recombination process. The phonon assisted absorption differs from the p-shell transition. The resonant excitation energy fits to the exciton ground state energy plus the energy of a GaAs LO phonon. In this case, the single exciton (ground state) is generated as well as a GaAs LO phonon. These three states are investigated in different respects, such as different applied voltages, excitation polarizations, excitation intensities, and coherent properties. The LO-assisted absorption shows also a saturation behavior. The exciton in the QD is able to interfere with the second laser pulse due to the storage of the phase information

  8. Quantum Otto engine of a two-level atom with single-mode fields

    Science.gov (United States)

    Wang, Jianhui; Wu, Zhaoqi; He, Jizhou

    2012-04-01

    We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.

  9. Basic concepts of quantum interference and electron transport in single-molecule electronics.

    Science.gov (United States)

    Lambert, C J

    2015-02-21

    This tutorial outlines the basic theoretical concepts and tools which underpin the fundamentals of phase-coherent electron transport through single molecules. The key quantity of interest is the transmission coefficient T(E), which yields the electrical conductance, current-voltage relations, the thermopower S and the thermoelectric figure of merit ZT of single-molecule devices. Since T(E) is strongly affected by quantum interference (QI), three manifestations of QI in single-molecules are discussed, namely Mach-Zehnder interferometry, Breit-Wigner resonances and Fano resonances. A simple MATLAB code is provided, which allows the novice reader to explore QI in multi-branched structures described by a tight-binding (Hückel) Hamiltonian. More generally, the strengths and limitations of materials-specific transport modelling based on density functional theory are discussed.

  10. Timing discriminator based on single-flux-quantum circuit toward high time-resolved photon detection

    Science.gov (United States)

    Miyajima, Shigeyuki; Miki, Shigehito; Yabuno, Masahiro; Yamashita, Taro; Terai, Hirotaka

    2017-12-01

    We propose a new time discriminating method based on a single-flux quantum (SFQ) circuit to realize a high time-resolved single-photon detection scheme that uses a superconducting nanowire single-photon detector (SSPD). The timing discriminator consists of an SFQ comparator and an interface circuit for converting the output signals of an SSPD into SFQ pulses. Prior to connecting with the SSPD, we evaluated the timing jitters of the SFQ timing discriminator itself by applying external electrical pulses. The timing jitters of the SFQ timing discriminator were found to be dominated by the timing jitters in the interface circuit. However, it was estimated to be below 10 ps even with an input pulse amplitude of 20 μA, which is close to the typical output amplitude of the SSPD.

  11. Electrically driven quantum dot-micropillar single photon source with 34% overall efficiency

    Science.gov (United States)

    Heindel, T.; Schneider, C.; Lermer, M.; Kwon, S. H.; Braun, T.; Reitzenstein, S.; Höfling, S.; Kamp, M.; Forchel, A.

    2010-01-01

    We report on triggered single photon emission from low mode volume electrically driven quantum dot-micropillar cavities at repetition rates of up to 220 MHz. Due to an optimized layout of the doped planar microcavity and an advanced lateral current injection scheme, highly efficient single photon sources are realized. While g(2)(0)-values as low as 0.13±0.05 and a Purcell factor of 4 are observed for a 2.0 μm diameter micropillar, single photon emission at a rate of (35±7) MHz and an overall efficiency of (34±7)% are demonstrated for a 3.0 μm device.

  12. Quantum

    CERN Document Server

    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.

  13. High-dimensional quantum key distribution with the entangled single-photon-added coherent state

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yang [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Bao, Wan-Su, E-mail: 2010thzz@sina.com [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Bao, Hai-Ze; Zhou, Chun; Jiang, Mu-Sheng; Li, Hong-Wei [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2017-04-25

    High-dimensional quantum key distribution (HD-QKD) can generate more secure bits for one detection event so that it can achieve long distance key distribution with a high secret key capacity. In this Letter, we present a decoy state HD-QKD scheme with the entangled single-photon-added coherent state (ESPACS) source. We present two tight formulas to estimate the single-photon fraction of postselected events and Eve's Holevo information and derive lower bounds on the secret key capacity and the secret key rate of our protocol. We also present finite-key analysis for our protocol by using the Chernoff bound. Our numerical results show that our protocol using one decoy state can perform better than that of previous HD-QKD protocol with the spontaneous parametric down conversion (SPDC) using two decoy states. Moreover, when considering finite resources, the advantage is more obvious. - Highlights: • Implement the single-photon-added coherent state source into the high-dimensional quantum key distribution. • Enhance both the secret key capacity and the secret key rate compared with previous schemes. • Show an excellent performance in view of statistical fluctuations.

  14. Single InGaAs quantum dots embedded in electrically active photonic crystal nanocavities

    Energy Technology Data Exchange (ETDEWEB)

    Hofbauer, Felix; Kaniber, Michael; Bichler, Max; Boehm, Gerhard; Abstreiter, Gerhard; Finley, Jonathan [Walter Schottky Institut, Am Coulombwall 3, TU Muenchen, 85748 Garching (Germany)

    2007-07-01

    We present investigations of the coupling of single InGaAs quantum dots (QDs) to both extended and strongly localised optical modes in electrical contacted 2D photonic crystal (PC) nanostructures. The samples investigated consist of an 180 nm thick, free-standing GaAs membrane into which a PC is formed by etching a triangular lattice of air holes. Low mode-volume (V (<{lambda}/n){sup 3}) and high-Q ({proportional_to}2000) cavities are introduced by single missing hole defects. Embedding the QDs into the intrinsic region of a p-i-n diode enables us to apply static electric fields to QDs in the cavity and control the energy detuning between the dot and cavity using the quantum confined Stark effect. The active PC nanocavities were studied using spatially resolved luminescence and photocurrent absorption spectroscopy. Quenching of the PL is observed for fields>50 kV/cm due to carrier tunneling escape from the dots that occurs over timescales faster than the radiative lifetime. By measuring the PL quenching as a function of position on the PC and nanocavity we electrically probe the local density of photonic states via a shift of the threshold voltage. Also investigations of the exciton lifetime and PL intensity of single QDs as a function of spectral detuning from the cavity mode are made.

  15. Shell thickness dependent photoinduced hole transfer in hybrid conjugated polymer/quantum dot nanocomposites: from ensemble to single hybrid level.

    Science.gov (United States)

    Xu, Zhihua; Hine, Corey R; Maye, Mathew M; Meng, Qingping; Cotlet, Mircea

    2012-06-26

    Photoinduced hole transfer is investigated in inorganic/organic hybrid nanocomposites of colloidal CdSe/ZnS quantum dots and a cationic conjugated polymer, poly(9,9'-bis(6-N,N,N-trimethylammoniumhexyl)fluorene-alt-phenylene, in solution and in solid thin film, and down to the single hybrid level and is assessed to be a dynamic quenching process. We demonstrate control of hole transfer rate in these quantum dot/conjugated polymer hybrids by using a series of core/shell quantum dots with varying shell thickness, for which a clear exponential dependency of the hole transfer rate vs shell thickness is observed, for both solution and thin-film situations. Furthermore, we observe an increase of hole-transfer rate from solution to film and correlate this with changes in quantum dot/polymer interfacial morphology affecting the hole transfer rate, namely, the donor-acceptor distance. Single particle spectroscopy experiments reveal fluctuating dynamics of hole transfer at the single conjugated polymer/quantum dot interface and an increased heterogeneity in the hole-transfer rate with the increase of the quantum dot's shell thickness. Although hole transfer quenches the photoluminescence intensity of quantum dots, it causes little or no effect on their blinking behavior over the time scales probed here.

  16. Microscopic theory of indistinguishable single-photon emission from a quantum dot coupled to a cavity: The role of non-Markovian phonon-induced decoherence

    DEFF Research Database (Denmark)

    Nielsen, Per Kær; Lodahl, Peter; Jauho, Antti-Pekka

    2013-01-01

    We study the fundamental limit on single-photon indistinguishability imposed by decoherence due to phonon interactions in semiconductor quantum dot-cavity quantum electrodynamics systems. Employing an exact diagonalization approach we find large differences compared to standard methods. An import......We study the fundamental limit on single-photon indistinguishability imposed by decoherence due to phonon interactions in semiconductor quantum dot-cavity quantum electrodynamics systems. Employing an exact diagonalization approach we find large differences compared to standard methods...

  17. High frequency modulation capabilities and quasi single-sideband emission from a quantum cascade laser.

    Science.gov (United States)

    Hangauer, Andreas; Spinner, Georg; Nikodem, Michal; Wysocki, Gerard

    2014-09-22

    Both intensity- (IM) and frequency-modulation (FM) behavior of a directly modulated quantum cascade laser (QCL) are measured from 300 Hz to 1.7 GHz. Quantitative measurements of tuning coefficients has been performed and the transition from thermal- to electronic-tuning is clearly observed. A very specific FM behavior of QCLs has been identified which allows for optical quasi single sideband (SSB) modulation through current injection and has not been observed in directly modulated semiconductor lasers before. This predestines QCLs in applications where SSB is required, such as telecommunication or high speed spectroscopy. The experimental procedure and theoretical modeling for data extraction is discussed.

  18. The Relation between Structure and Quantum Interference in Single Molecule Junctions

    DEFF Research Database (Denmark)

    Markussen, Troels; Stadler, Robert; Thygesen, Kristian Sommer

    2010-01-01

    Quantum interference (QI) of electron pathways has recently attracted increased interest as an enabling tool for single-molecule electronic devices. Although various molecular systems have been shown to exhibit QI effects and a number of methods have been proposed for its analysis, simple...... guidelines linking the molecular structure to QI effects in the phase-coherent transport regime have until now been lacking. In the present work we demonstrate that QI in aromatic molecules is intimately related to the topology of the molecule’s π system and establish a simple graphical scheme to predict...

  19. Protonation tuning of quantum interference in azulene-type single-molecule junctions.

    Science.gov (United States)

    Yang, Guogang; Sangtarash, Sara; Liu, Zitong; Li, Xiaohui; Sadeghi, Hatef; Tan, Zhibing; Li, Ruihao; Zheng, Jueting; Dong, Xiaobiao; Liu, Junyang; Yang, Yang; Shi, Jia; Xiao, Zongyuan; Zhang, Guanxin; Lambert, Colin; Hong, Wenjing; Zhang, Deqing

    2017-11-01

    The protonation of azulene derivatives with quantum interference effects is studied by the conductance measurements of single-molecule junctions. Three azulene derivatives with different connectivities are synthesized and reacted with trifluoroacetic acid to form the protonated states. It is found that the protonated azulene molecular junctions produce more than one order of magnitude higher conductance than the neutral states, while the molecules with destructive interference show more significant changes. These experimental observations are supported by our recently-developed parameter free theory of connectivity, which suggests that the largest conductance change occurs when destructive interference near the Fermi energy in the neutral state is alleviated by protonation.

  20. Fock-Darwin spectrum of a single InAs/GaAs quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Babinski, A. [Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Grenoble High Magnetic Field Laboratory, CNRS, BP-166, 38042 Grenoble Cedex 9 (France); Potemski, M. [Grenoble High Magnetic Field Laboratory, CNRS, BP-166, 38042 Grenoble Cedex 9 (France); Raymond, S.; Lapointe, J.; Wasilewski, Z.R. [Institute for Microstructural Sciences, NRC, Ottawa, K1A 0R6 (Canada)

    2006-07-01

    Magnetospectroscopic study of a highly excited single InAs/GaAs quantum dot is reported. Optical emission from the s- and p-shells is identified and investigated in magnetic fields up to 20T. The zero-field splitting and the Zeeman orbital splitting of the p-shell-related emission lines in magnetic field are observed. The evolution of spectra in magnetic field resembles a classical Fock-Darwin energy diagram, although effects of the electron-electron interaction and asymmetry of localizing potential can be clearly observed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Quantum Heisenberg antiferromagnetic chains with exchange and single-ion anisotropies

    Energy Technology Data Exchange (ETDEWEB)

    Peters, D; Selke, W [Institut fuer Theoretische Physik, RWTH Aachen University and JARA-SIM, 52056 Aachen (Germany); McCulloch, I P, E-mail: selke@physik.rwth-aachen.d [Department of Physics, University of Queensland, Brisbane, QLD 4072 (Australia)

    2010-01-01

    Using density matrix renormalization group calculations, ground state properties of the spin-1 Heisenberg chain with exchange and quadratic single-ion anisotropies in an external field are studied, for special choices of the two kinds of anisotropies. In particular, the phase diagram includes antiferromagnetic, spin-liquid (or spin-flop), IS2, and supersolid (or biconical) phases. Especially, new features of the spin-liquid and supersolid phases are discussed. Properties of the quantum chains are compared to those of corresponding classical spin chains.

  2. Indistinguishable and efficient single photons from a quantum dot in a planar nanobeam waveguide

    DEFF Research Database (Denmark)

    Kirsanské, Gabija; Nielsen, Henri Thyrrestrup; Daveau, Raphaël Sura

    2017-01-01

    We demonstrate a high-purity source of indistinguishable single photons using a quantum dot embedded in a nanophotonic waveguide. The source features a near-unity internal coupling efficiency and the collected photons are efficiently coupled off chip by implementing a taper that adiabatically...... allows pinpointing the residual decoherence processes, notably the effect of phonon broadening. Strict resonant excitation is implemented as well as another means of suppressing photon jitter, and the additional complexity of suppressing the excitation laser source is addressed. The paper opens a clear...

  3. Mapping the Local Density of Optical States of a Photonic Crystal with Single Quantum Dots

    DEFF Research Database (Denmark)

    Wang, Qin; Stobbe, Søren; Lodahl, Peter

    2011-01-01

    We use single self-assembled InGaAs quantum dots as internal probes to map the local density of optical states of photonic crystal membranes. The employed technique separates contributions from nonradiative recombination and spin-flip processes by properly accounting for the role of the exciton...... fine structure. We observe inhibition factors as high as 70 and compare our results to local density of optical states calculations available from the literature, thereby establishing a quantitative understanding of photon emission in photonic crystal membranes. © 2011 American Physical Society....

  4. Asymmetry of single-particle hole states in a strained Ge/Si double quantum dot

    Science.gov (United States)

    Yakimov, A. I.; Bloshkin, A. A.; Dvurechenskii, A. V.

    2008-10-01

    A six-band kṡp formalism was used to study single-particle hole states of two vertically aligned pyramidal Ge quantum dots embedded in Si and separated by a distance tSi . The elastic strain due to the lattice mismatch between Ge and Si was included into the problem via Bir-Pikus Hamiltonian. The three-dimensional spatial strain distribution was obtained by finite element method. We found that at small interdot separation (tSi3.5nm , σAS becomes the ground state of the system, replacing σS .

  5. Passive states as optimal inputs for single-jump lossy quantum channels

    Science.gov (United States)

    De Palma, Giacomo; Mari, Andrea; Lloyd, Seth; Giovannetti, Vittorio

    2016-06-01

    The passive states of a quantum system minimize the average energy among all the states with a given spectrum. We prove that passive states are the optimal inputs of single-jump lossy quantum channels. These channels arise from a weak interaction of the quantum system of interest with a large Markovian bath in its ground state, such that the interaction Hamiltonian couples only consecutive energy eigenstates of the system. We prove that the output generated by any input state ρ majorizes the output generated by the passive input state ρ0 with the same spectrum of ρ . Then, the output generated by ρ can be obtained applying a random unitary operation to the output generated by ρ0. This is an extension of De Palma et al. [IEEE Trans. Inf. Theory 62, 2895 (2016)], 10.1109/TIT.2016.2547426, where the same result is proved for one-mode bosonic Gaussian channels. We also prove that for finite temperature this optimality property can fail already in a two-level system, where the best input is a coherent superposition of the two energy eigenstates.

  6. A Single-Step Electrochemical Synthesis of Luminescent WS2 Quantum Dots.

    Science.gov (United States)

    Valappil, Manila O; Anil, Athira; Shaijumon, Manikoth; Pillai, Vijayamohanan K; Alwarappan, Subbiah

    2017-07-06

    Transition-metal dichalcogenide quantum dots (TMDQDs) with few layers are in the forefront of recent research on tailored 2D layered materials owing to their unique band structure. Such quantum dots (QDs) draw wide interest as potential candidates for components in optoelectronic devices. Although a few attempts towards single step synthesis of MoS2 QDs have been demonstrated, limited methods are available for WS2 QDs. Herein, we demonstrate a one-step electrochemical synthesis of luminescent WS2 QDs from their bulk material. This is achieved by a synergistic effect of perchlorate intercalation in non-aqueous electrolyte and the applied electric field. The average size of the WS2 QDs is 3  ±1 nm (N=102) with few layers. The QDs show a higher photoluminescence (PL) quantum efficiency (5 %) and exhibit an excitation wavelength-dependent photoluminescence. This unprecedented electrochemical avenue offers a strategy to synthesize size tunable WS2 nanostructures, which have been systematically investigated by various characterization techniques such as transmission electron microscopy (TEM), photoluminescence and UV/Vis spectroscopies, and X-ray diffraction (XRD). Time-dependent TEM investigations revealed that time plays a vital role in this electrochemical transformation. This electrochemical transformation provides a facile method to obtain WS2 QDs from their bulk counterpart, which is expected to have a greater impact on the design and development of nanostructures derived from 2D materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Blinking effect and the use of quantum dots in single molecule spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Rombach-Riegraf, Verena; Oswald, Peter; Bienert, Roland; Petersen, Jan [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany); Domingo, M.P. [Instituto de Carboquimica (CSIC), Miguel Luesma 4, 50018 Zaragoza (Spain); Pardo, Julian [Grupo Apoptosis, Inmunidad y Cancer, Departamento Bioquimica y Biologia Molecular y Celular, Fac. Ciencias, Universidad de Zaragoza, Zaragoza (Spain); Fundacion Aragon I-D (ARAID), Gobierno de Aragon, Zaragoza (Spain); Immune Effector Cells Group, Aragon Health Research Institute (IIS Aragon), Biomedical Research Centre of Aragon (CIBA) Fundacion Aragon I-D - ARAID, Gobierno de Aragon, Zaragoza (Spain); Graeber, P. [Albert-Ludwigs-Universitaet Freiburg, Institut fuer Physikalische Chemie, Albertstrasse 23a, 79104 Freiburg (Germany); Galvez, E.M., E-mail: eva@icb.csic.es [Instituto de Carboquimica (CSIC), Miguel Luesma 4, 50018 Zaragoza (Spain); Immune Effector Cells Group, Aragon Health Research Institute (IIS Aragon), Biomedical Research Centre of Aragon (CIBA) Fundacion Aragon I-D - ARAID, Gobierno de Aragon, Zaragoza (Spain)

    2013-01-04

    Highlights: Black-Right-Pointing-Pointer It is possible to eliminate the blinking effect of a water-soluble QD. Black-Right-Pointing-Pointer We provide a direct method to study protein function and dynamics at the single level. Black-Right-Pointing-Pointer QD, potent tool for single molecule studies of biochemical and biological processes. -- Abstract: Luminescent semiconductor nanocrystals (quantum dots, QD) have unique photo-physical properties: high photostability, brightness and narrow size-tunable fluorescence spectra. Due to their unique properties, QD-based single molecule studies have become increasingly more popular during the last years. However QDs show a strong blinking effect (random and intermittent light emission), which may limit their use in single molecule fluorescence studies. QD blinking has been widely studied and some hypotheses have been done to explain this effect. Here we summarise what is known about the blinking effect in QDs, how this phenomenon may affect single molecule studies and, on the other hand, how the 'on'/'off' states can be exploited in diverse experimental settings. In addition, we present results showing that site-directed binding of QD to cysteine residues of proteins reduces the blinking effect. This option opens a new possibility of using QDs to study protein-protein interactions and dynamics by single molecule fluorescence without modifying the chemical composition of the solution or the QD surface.

  8. Dependence of Internal Crystal Structures of InAs Nanowires on Electrical Characteristics of Field Effect Transistors

    Science.gov (United States)

    Han, Sangmoon; Choi, Ilgyu; Lee, Kwanjae; Lee, Cheul-Ro; Lee, Seoung-Ki; Hwang, Jeongwoo; Chung, Dong Chul; Kim, Jin Soo

    2018-02-01

    We report on the dependence of internal crystal structures on the electrical properties of a catalyst-free and undoped InAs nanowire (NW) formed on a Si(111) substrate by metal-organic chemical vapor deposition. Cross-sectional transmission electron microscopy images, obtained from four different positions of a single InAs NW, indicated that the wurtzite (WZ) structure with stacking faults was observed mostly in the bottom region of the NW. Vertically along the InAs NW, the amount of stacking faults decreased and a zinc-blende (ZB) structure was observed. At the top of the NW, the ZB structure was prominently observed. The resistance and resistivity of the top region of the undoped InAs NW with the ZB structure were measured to be 121.5 kΩ and 0.19 Ω cm, respectively, which are smaller than those of the bottom region with the WZ structure, i.e., 251.8 kΩ and 0.39 Ω cm, respectively. The reduction in the resistance of the top region of the NW is attributed to the improvement in the crystal quality and the change in the ZB crystal structure. For a field effect transistor with an undoped InAs NW channel, the drain current versus drain-source voltage characteristic curves under various negative gate-source voltages were successfully observed at room temperature.

  9. Quantum transport in nanowire-based hybrid devices

    Energy Technology Data Exchange (ETDEWEB)

    Guenel, Haci Yusuf

    2013-05-08

    the Andreev reflection of quasiparticles at single interface, by suppressing the superconductivity of Al with small magnetic fields, as well as at double interface for zero magnetic field. The junction geometry was further changed by replacing the InAs nanowire with the InAs tube. In this case the GaAs/InAs core/shell tubular nanowires were contacted by two superconducting Nb electrodes. For this junction geometry we have demonstrated the interference of phase conjugated electron-hole pairs in the presence of coaxial magnetic. The effect of temperature, constant dc bias current and gate voltage on the magnetoresistance oscillations were examined. In the last part of this thesis, we have fabricated and characterized the single crystal Au nanowire-based proximity superconducting quantum interference device (SQUID).

  10. Weak localization and spin splitting in inversion layers on p -type InAs

    Science.gov (United States)

    Schierholz, Christopher; Matsuyama, Toru; Merkt, Ulrich; Meier, Guido

    2004-12-01

    We report on the magnetoconductivity of quasi-two-dimensional electron systems in inversion layers on p -type InAs single crystals. In low magnetic fields pronounced features of weak localization and antilocalization are observed. They are almost perfectly described by the theory of Iordanskii, Lyanda-Geller, and Pikus. This allows us to determine the spin splitting and the Rashba parameter of the ground electric subband as a function of the electron density.

  11. Heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Song, Guo-Zhu; Zhang, Mei; Ai, Qing; Yang, Guo-Jian [Department of Physics, Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875 (China); Alsaedi, Ahmed; Hobiny, Aatef [NAAM-Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Deng, Fu-Guo, E-mail: fgdeng@bnu.edu.cn [Department of Physics, Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875 (China); NAAM-Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia)

    2017-03-15

    We propose a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We show the details by implementing nonlocal entanglement generation, entanglement swapping, and entanglement purification modules with atoms in waveguides, and discuss the feasibility of the repeater with currently achievable technology. In our scheme, the faulty events can be discarded by detecting the polarization of the photons. That is, our protocols are accomplished with a fidelity of 100% in principle, which is advantageous for implementing realistic long-distance quantum communication. Moreover, additional atomic qubits are not required, but only a single-photon medium. Our scheme is scalable and attractive since it can be realized in solid-state quantum systems. With the great progress on controlling atom-waveguide systems, the repeater may be very useful in quantum information processing in the future.

  12. Heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides

    Science.gov (United States)

    Song, Guo-Zhu; Zhang, Mei; Ai, Qing; Yang, Guo-Jian; Alsaedi, Ahmed; Hobiny, Aatef; Deng, Fu-Guo

    2017-03-01

    We propose a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We show the details by implementing nonlocal entanglement generation, entanglement swapping, and entanglement purification modules with atoms in waveguides, and discuss the feasibility of the repeater with currently achievable technology. In our scheme, the faulty events can be discarded by detecting the polarization of the photons. That is, our protocols are accomplished with a fidelity of 100% in principle, which is advantageous for implementing realistic long-distance quantum communication. Moreover, additional atomic qubits are not required, but only a single-photon medium. Our scheme is scalable and attractive since it can be realized in solid-state quantum systems. With the great progress on controlling atom-waveguide systems, the repeater may be very useful in quantum information processing in the future.

  13. Functionalized vertical InAs nanowire arrays for gas sensing

    NARCIS (Netherlands)

    Offermans, P.; Crego-Calama, M.; Brongersma, S.H.

    2012-01-01

    Vertical InAs nanowires are contacted in situ using an air-bridge construction and functionalized with a metalloporphyrin (Hemin). The response of bare and functionalized vertical InAs nanowire arrays to ppb-level concentrations of NO2 and NO is demonstrated. Hemin enhances the response to NO

  14. Implementation of single-photon quantum routing and decoupling using a nitrogen-vacancy center and a whispering-gallery-mode resonator-waveguide system.

    Science.gov (United States)

    Cao, Cong; Duan, Yu-Wen; Chen, Xi; Zhang, Ru; Wang, Tie-Jun; Wang, Chuan

    2017-07-24

    Quantum router is a key element needed for the construction of future complex quantum networks. However, quantum routing with photons, and its inverse, quantum decoupling, are difficult to implement as photons do not interact, or interact very weakly in nonlinear media. In this paper, we investigate the possibility of implementing photonic quantum routing based on effects in cavity quantum electrodynamics, and present a scheme for single-photon quantum routing controlled by the other photon using a hybrid system consisting of a single nitrogen-vacancy (NV) center coupled with a whispering-gallery-mode resonator-waveguide structure. Different from the cases in which classical information is used to control the path of quantum signals, both the control and signal photons are quantum in our implementation. Compared with the probabilistic quantum routing protocols based on linear optics, our scheme is deterministic and also scalable to multiple photons. We also present a scheme for single-photon quantum decoupling from an initial state with polarization and spatial-mode encoding, which can implement an inverse operation to the quantum routing. We discuss the feasibility of our schemes by considering current or near-future techniques, and show that both the schemes can operate effectively in the bad-cavity regime. We believe that the schemes could be key building blocks for future complex quantum networks and large-scale quantum information processing.

  15. Doubly Resonant Photonic Antenna for Single Infrared Quantum Dot Imaging at Telecommunication Wavelengths.

    Science.gov (United States)

    Xie, Zhihua; Lefier, Yannick; Suarez, Miguel Angel; Mivelle, Mathieu; Salut, Roland; Merolla, Jean-Marc; Grosjean, Thierry

    2017-04-12

    Colloidal quantum dots (CQDs) have drawn strong interest in the past for their high prospects in scientific, medical, and industrial applications. However, the full characterization of these quantum emitters is currently restricted to the visible wavelengths, and it remains a key challenge to optically probe single CQDs operating in the infrared spectral domain, which is targeted by a growing number of applications. Here, we report the first experimental detection and imaging at room temperature of single infrared CQDs operating at telecommunication wavelengths. Imaging was done with a doubly resonant bowtie nanoaperture antenna (BNA) written at the end of a fiber nanoprobe, whose resonances spectrally fit the CQD absorption and emission wavelengths. Direct near-field characterization of PbS CQDs reveal individual nanocrystals with a spatial resolution of 75 nm (λ/20) together with their intrinsic 2D dipolar free-space emission properties and exciton dynamics (blinking phenomenon). Because the doubly resonant BNA is strongly transmissive at both the CQD absorption and the emission wavelengths, we are able to perform all-fiber nanoimaging with a standard 20% efficiency InGaAs avalanche photodiode (APD). The detection efficiency is predicted to be 3000 fold larger than with a conventional circular aperture tip of the same transmission area. Double resonance BNA fiber probes thus offer the possibility of exploring extreme light-matter interaction in low band gap CQDs with current plug-and-play detection techniques, opening up new avenues in the fields of infrared light-emitting devices, photodetectors, telecommunications, bioimaging, and quantum information technology.

  16. Noncovalent Attachment of PbS Quantum Dots to Single- and Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Anirban Das

    2014-01-01

    Full Text Available Attachment of PbS quantum dots (QD to single-walled carbon nanotubes (SWNT and multiwalled carbon nanotubes (MWCNT is described; wherein commercially obtained PbS-QD of size 2.7 nm, stabilized by oleic acid, are added to a suspension of single- or multiwalled carbon nanotubes (CNT prefunctionalized noncovalently with 1,2-benzenedimethanethiol (1,2-BDMT in ethanol. The aromatic part of 1,2-BDMT attaches to the CNT by π-π stacking interactions, noncovalently functionalizing the CNT. The thiol part of the 1,2-BDMT on the functionalized CNT replaces oleic acid on the surface of the QD facilitating the noncovalent attachment of the QD to the CNT. The composites were characterized by TEM and FTIR spectroscopy. Quenching of NIR fluorescence of the PbS-QD on attachment to the carbon nanotubes (CNT was observed, indicating FRET from the QD to the CNT.

  17. HIGH-SPEED SINGLE QUANTUM DOT IMAGING OF IN LIVE CELLS REVEAL HOP DIFFUSION

    DEFF Research Database (Denmark)

    Lagerholm, B. Christoffer; Clausen, Mathias P.

    2011-01-01

    Ultra high-speed single particle tracking (image frame rates 40-50 kHz) experiments with 40 nm gold particles has indicated that lipids and proteins in the plasma membrane undergo hop-diffusion between nanometer sized compartments (Fujiwara et al. (2002) J Cell Biol. 157:1071-81). These findings...... have yet to be independently confirmed. In this work, we show that high-speed single particle tracking with quantum dots (QDs) and using a standard wide-field fluorescence microscope and an EMCCD is possible at image acquisition rates of up to ~2000 Hz. The spatial precision in these experiments is ~40...... nm (as determined from the standard deviation of repeated position measurements of an immobile QD on a cell). Using this system, we show that membrane proteins and lipids, which have been exogenously labeled with functionalized QDs, show examples of three types of motion in the plasma membrane...

  18. Quantum interference effects at room temperature in OPV-based single-molecule junctions.

    Science.gov (United States)

    Arroyo, Carlos R; Frisenda, Riccardo; Moth-Poulsen, Kasper; Seldenthuis, Johannes S; Bjørnholm, Thomas; van der Zant, Herre Sj

    2013-05-16

    Interference effects on charge transport through an individual molecule can lead to a notable modulation and suppression on its conductance. In this letter, we report the observation of quantum interference effects occurring at room temperature in single-molecule junctions based on oligo(3)-phenylenevinylene (OPV3) derivatives, in which the central benzene ring is coupled to either para- or meta-positions. Using the break-junction technique, we find that the conductance for a single meta-OPV3 molecule wired between gold electrodes is one order of magnitude smaller than that of a para-OPV3 molecule. Theoretical calculations confirm the occurrence of constructive and destructive interference in the para- and meta-OPV3 molecules respectively, which arises from the phase difference of the transmission coefficients through the molecular orbitals.

  19. Surface acoustic wave regulated single photon emission from a coupled quantum dot–nanocavity system

    Energy Technology Data Exchange (ETDEWEB)

    Weiß, M.; Kapfinger, S.; Wixforth, A.; Krenner, H. J., E-mail: hubert.krenner@physik.uni-augsburg.de [Lehrstuhl für Experimentalphysik 1 and Augsburg Centre for Innovative Technologies (ACIT), Universität Augsburg, Universitätsstr. 1, 86159 Augsburg (Germany); Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München (Germany); Reichert, T.; Finley, J. J. [Walter Schottky Institut and Physik Department E24, TU München, Am Coulombwall 4, 85748 Garching (Germany); Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München (Germany); Kaniber, M. [Walter Schottky Institut and Physik Department E24, TU München, Am Coulombwall 4, 85748 Garching (Germany)

    2016-07-18

    A coupled quantum dot–nanocavity system in the weak coupling regime of cavity-quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a f{sub SAW} ≃ 800 MHz surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function, g{sup (2)}. All relevant frequencies of our experiment are faithfully identified in the Fourier transform of g{sup (2)}, demonstrating high fidelity regulation of the stream of single photons emitted by the system.

  20. Particle tracking single protein-functionalized quantum dot diffusion and binding at silica surfaces.

    Science.gov (United States)

    Rife, Jack C; Long, James P; Wilkinson, John; Whitman, Lloyd J

    2009-04-09

    We evaluate commercial QD585 and QD605 streptavidin-functionalized quantum dots (QDs) for single-particle tracking microscopy at surfaces using total internal reflectance fluorescence and measure single QD diffusion and nonspecific binding at silica surfaces in static and flow conditions. The QD diffusion coefficient on smooth, near-ideal, highly hydroxylated silica surfaces is near bulk-solution diffusivity, as expected for repulsive surfaces, but many QD trajectories on rougher, less-than-ideal surfaces or regions display transient adsorptions. We attribute the binding to defect sites or adsorbates, possibly in conjunction with protein conformation changes, and estimate binding energies from the transient adsorption lifetimes. We also assess QD parameters relevant to tracking, including hydrodynamic radius, charge state, signal levels, blinking reduction with reducing solutions, and photoinduced blueing and bleaching.

  1. Quantum dash based single section mode locked lasers for photonic integrated circuits.

    Science.gov (United States)

    Joshi, Siddharth; Calò, Cosimo; Chimot, Nicolas; Radziunas, Mindaugas; Arkhipov, Rostislav; Barbet, Sophie; Accard, Alain; Ramdane, Abderrahim; Lelarge, Francois

    2014-05-05

    We present the first demonstration of an InAs/InP Quantum Dash based single-section frequency comb generator designed for use in photonic integrated circuits (PICs). The laser cavity is closed using a specifically designed Bragg reflector without compromising the mode-locking performance of the self pulsating laser. This enables the integration of single-section mode-locked laser in photonic integrated circuits as on-chip frequency comb generators. We also investigate the relations between cavity modes in such a device and demonstrate how the dispersion of the complex mode frequencies induced by the Bragg grating implies a violation of the equi-distance between the adjacent mode frequencies and, therefore, forbids the locking of the modes in a classical Bragg Device. Finally we integrate such a Bragg Mirror based laser with Semiconductor Optical Amplifier (SOA) to demonstrate the monolithic integration of QDash based low phase noise sources in PICs.

  2. A nanocryotron comparator can connect single-flux-quantum circuits to conventional electronics

    Science.gov (United States)

    Zhao, Qing-Yuan; McCaughan, Adam N.; Dane, Andrew E.; Berggren, Karl K.; Ortlepp, Thomas

    2017-04-01

    Integration with conventional electronics offers a straightforward and economical approach to upgrading existing superconducting technologies, such as scaling up superconducting detectors into large arrays and combining single flux quantum (SFQ) digital circuits with semiconductor logic gates and memories. However, direct output signals from superconducting devices (e.g., Josephson junctions) are usually not compatible with the input requirements of conventional devices (e.g., transistors). Here, we demonstrate the use of a single three-terminal superconducting-nanowire device, called the nanocryotron (nTron), as a digital comparator to combine SFQ circuits with mature semiconductor circuits such as complementary metal oxide semiconductor (CMOS) circuits. Since SFQ circuits can digitize output signals from general superconducting devices and CMOS circuits can interface existing CMOS-compatible electronics, our results demonstrate the feasibility of a general architecture that uses an nTron as an interface to realize a ‘super-hybrid’ system consisting of superconducting detectors, superconducting quantum electronics, CMOS logic gates and memories, and other conventional electronics.

  3. Electronic and optical properties of single excitons and biexcitons in type-II quantum dot nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Koc, Fatih, E-mail: fatih.koc@msn.com [Department of Physics, Faculty of Sciences, Selcuk University, 42075 Konya (Turkey); Sahin, Mehmet, E-mail: mehmet.sahin@agu.edu.tr, E-mail: mehsahin@gmail.com [Department of Physics, Faculty of Sciences, Selcuk University, 42075 Konya (Turkey); Department of Material Science and Nanotechnology Engineering, Abdullah Gül University, Kayseri (Turkey)

    2014-05-21

    In this study, a detailed investigation of the electronic and optical properties (i.e., binding energies, absorption wavelength, overlap of the electron-hole wave functions, recombination oscillator strength, etc.) of an exciton and a biexciton in CdTe/CdSe core/shell type-II quantum dot heterostructures has been carried out in the frame of the single band effective mass approximation. In order to determine the electronic properties, we have self-consistently solved the Poisson-Schrödinger equations in the Hartree approximation. We have considered all probable Coulomb interaction effects on both energy levels and also on the corresponding wave functions for both single exciton and biexciton. In addition, we have taken into account the quantum mechanical exchange-correlation effects in the local density approximation between same kinds of particles for biexciton. Also, we have examined the effect of the ligands and dielectric mismatch on the electronic and optical properties. We have used a different approximation proposed by Sahin and Koc [Appl. Phys. Lett. 102, 183103 (2013)] for the recombination oscillator strength of the biexciton for bound and unbound cases. The results obtained have been presented comparatively as a function of the shell thicknesses and probable physical reasons in behind of the results have been discussed in a detail.

  4. Inside Perovskites: Quantum Luminescence from Bulk Cs4PbBr6 Single Crystals

    KAUST Repository

    de Bastiani, Michele

    2017-08-01

    Zero-dimensional perovskite-related structures (0D-PRS) are a new frontier of perovskite-based materials. 0D-PRS, commonly synthesized in powder form, manifest distinctive optical properties such as strong photoluminescence (PL), narrow emission linewidth, and high exciton binding energy. These properties make 0D-PRS compelling for several types of optoelectronic applications, including phosphor screens and electroluminescent devices. However, it would not be possible to rationally design the chemistry and structure of these materials, without revealing the origins of their optical behaviour, which is contradictory to the well-studied APbX3 perovskites. In this work, we synthesize single crystals of Cs4PbBr6 0D-PRS, and investigated the origins of their unique optical and electronic properties. The crystals exhibit a PL quantum yield higher than 40%, the highest reported for perovskite-based single crystals. Time-resolved and temperature dependent PL studies, supported by DFT calculations, and structural analysis, elucidate an emissive behaviour reminiscent of a quantum confined structure rather than a typical bulk perovskite material.

  5. Quantum statistics of a single-atom Scovil-Schulz-DuBois heat engine

    Science.gov (United States)

    Li, Sheng-Wen; Kim, Moochan B.; Agarwal, Girish S.; Scully, Marlan O.

    2017-12-01

    We study the statistics of the lasing output from a single-atom quantum heat engine, which was originally proposed by Scovil and Schulz-DuBois [H. E. D. Scovil and E. O. Schulz-DuBois, Phys. Rev. Lett. 2, 262 (1959), 10.1103/PhysRevLett.2.262]. In this heat engine model, a single three-level atom is coupled with an optical cavity and is in contact with a hot and a cold heat bath together. We derive a fully quantum laser equation for this heat engine model and obtain the photon number distribution both below and above the lasing threshold. With the increase of the hot bath temperature, the population is inverted and lasing light comes out. However, we notice that if the hot bath temperature keeps increasing, the atomic decay rate is also enhanced, which weakens the lasing gain. As a result, another critical point appears at a very high temperature of the hot bath, after which the output light become thermal radiation again. To avoid this double-threshold behavior, we introduce a four-level heat engine model, where the atomic decay rate does not depend on the hot bath temperature. In this case, the lasing threshold is much easier to achieve and the double-threshold behavior disappears.

  6. Single-step colloidal quantum dot films for infrared solar harvesting

    KAUST Repository

    Kiani, Amirreza

    2016-11-01

    Semiconductors with bandgaps in the near- to mid-infrared can harvest solar light that is otherwise wasted by conventional single-junction solar cell architectures. In particular, colloidal quantum dots (CQDs) are promising materials since they are cost-effective, processed from solution, and have a bandgap that can be tuned into the infrared (IR) via the quantum size effect. These characteristics enable them to harvest the infrared portion of the solar spectrum to which silicon is transparent. To date, IR CQD solar cells have been made using a wasteful and complex sequential layer-by-layer process. Here, we demonstrate ∼1 eV bandgap solar-harvesting CQD films deposited in a single step. By engineering a fast-drying solvent mixture for metal iodide-capped CQDs, we deposited active layers greater than 200 nm in thickness having a mean roughness less than 1 nm. We integrated these films into infrared solar cells that are stable in air and exhibit power conversion efficiencies of 3.5% under illumination by the full solar spectrum, and 0.4% through a simulated silicon solar cell filter.

  7. Water drops kinematic analysis: the classic-quantum and single-multiparticle viewpoints

    Science.gov (United States)

    Wrachien, Daniele; Lorenzini, Giulio

    2013-03-01

    One of the most challenging modelling problems in science is that of a particle crossing a gaseous mean. In sprinkler irrigation this applies to a water droplet travelling from the nozzle to the ground. The challenge mainly refers to the intense difficulty in writing and solving the system of governing equations for such complicate process, where many non-linearities occur when describing the relations and dependences among one influential parameter and another. The problem becomes even more complicate when not just a single droplet alone is assessed but a multi-droplet system is accounted for as, in addition to the inter-parameter dependencies, it is also observed an inter-droplet reciprocal affection, mainly due to electrical interactions between the hydrogen and the oxygen atoms of the different water molecules. An alternative to traditional classic approaches to analyse water droplet dynamics in sprinkler irrigation have been recently proposed in the form of a quantum approach, but the whole classic-quantum and single-droplet versus multi-droplet alternatives need to be discussed and pinpointed and these are among the main aims of the present paper which focuses on the theoretical part of the issue, thus highlighting the new perspectives of a deeper comprehension in the spray flow related phenomena.

  8. Multiphoton imaging of tumor biomarkers with conjugates of single-domain antibodies and quantum dots.

    Science.gov (United States)

    Hafian, Hilal; Sukhanova, Alyona; Turini, Marc; Chames, Patrick; Baty, Daniel; Pluot, Michel; Cohen, Jacques H M; Nabiev, Igor; Millot, Jean-Marc

    2014-11-01

    An ideal multiphoton fluorescent nanoprobe should combine a nanocrystal with the largest possible two-photon absorption cross section (TPACS) and the smallest highly specific recognition molecules bound in an oriented manner. CdSe/ZnS quantum dots (QDs) conjugated to 13-kDa single-domain antibodies (sdAbs) derived from camelid IgG or streptavidin have been used as efficient two-photon excitation (TPE) probes for carcinoembryonic antigen (CEA) imaging on normal human appendix and colon carcinoma tissue. The TPACS for some conjugates was higher than 49,000 GM (Goeppert-Mayer units), considerably exceeding that of organic dyes being close to the theoretical value of 50,000 GM calculated for CdSe QDs. The ratio of sdAb-QD emission to the autofluorescence for 800 nm TPE was 40 times higher than that for 457.9 nm one-photon excitation. TPE ensures a clear discrimination of CEA-overexpressing tumor areas from normal tissue. Oriented sdAb-QD conjugates are bright specific labels for detecting low concentrations of antigens using multiphoton microscopy. This study demonstrates carcinoembryonic antigen imaging on normal human appendix and colon carcinoma tissue utilizing CdSe/ZnS quantum dots conjugated to streptavidin or to 13-kDa single-domain antibodies as efficient two-photon excitation probes. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Spin relaxation in submonolayer and monolayer InAs structures grown in a GaAs matrix

    Science.gov (United States)

    Yang, Chunlei; Cui, Xiaodong; Shen, Shun-Qing; Xu, Zhongying; Ge, Weikun

    2009-07-01

    Electron-spin dynamics in InAs/GaAs heterostructures consisting of a single layer of InAs (1/3-1 monolayer) embedded in (001) and (311)A GaAs matrix was studied by means of time-resolved Kerr rotation spectroscopy. The spin-relaxation time of the submonolayer InAs samples is significantly enhanced, compared with that of the monolayer InAs sample. The electron-spin-relaxation time and the effective g factor in submonolayer samples were found to be strongly dependent on the photogenerated carrier density. The contribution from both the D’yakonov-Perel’ mechanism and Bir-Aronov-Pikus mechanism are discussed to interpret the temperature dependence of spin decoherence at various carrier densities.

  10. Quantum trajectories for a system interacting with environment in a single-photon state: Counting and diffusive processes

    Science.gov (United States)

    DÄ browska, Anita; Sarbicki, Gniewomir; Chruściński, Dariusz

    2017-11-01

    We derived quantum trajectories for a system interacting with the environment prepared in a continuous mode single-photon state as the limit of a discrete filtering model with an environment defined as a series of independent qubits prepared initially in the entangled state being an analog of a continuous mode state. The environment qubits interact with the quantum system and they are subsequently measured. The initial correlation between the bath qubits is the source of the non-Markovianity. The conditional evolutions of the quantum system for the limit of the continuous in time observations together with the formulas for the photon counting probabilities are given.

  11. Single nanoparticle imaging and characterization of different phospholipid-encapsulated quantum dot micelles.

    Science.gov (United States)

    Liu, Jianbo; Yang, Xiaohai; Wang, Kemin; He, Yan; Zhang, Pengfei; Ji, Haining; Jian, Lixin; Liu, Wei

    2012-07-17

    Phospholipid quantum dot (QD) micelles have been extensively used as fluorescent tags in single nanoparticle imaging for biomedical imaging. In this work, the microscopic structures and photophysical properties of the phospholipid QD micelles were studied at the single nanoparticle level. Two commonly used types of phospholipid QD micelles were prepared and tested both on a solid-phase surface and in liquid phase, including 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-encapsulated QD micelles (DSPE-QDMs) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000]-encapsulated QD micelles (PEG-DSPE-QDMs). Their fluorescence intensities and diffusion trajectories were determined by a total internal reflection fluorescence-based single nanoparticle imaging platform and comparatively analyzed carefully. It was demonstrated that DSPE-QDMs possessed a comparably wider intensity distribution and lower diffusion coefficient than that of PEG-DSPE-QDMs. PEG-DSPE-QDMs exhibited an obvious fluorescent intermittence. The results suggested that for most of the DSPE-QDMs, more than one QD were encapsulated in a single micelle. On the other hand, only one QD was embedded in a single micelle of PEG-DSPE-QDMs for most of the cases. Such variances suggested that phospholipids play a key role in the fabrication of the QD micelles. This work provides a useful foundation for their further biomedical applications.

  12. Poisson-distributed electron-transfer dynamics from single quantum dots to C60 molecules.

    Science.gov (United States)

    Song, Nianhui; Zhu, Haiming; Jin, Shengye; Zhan, Wei; Lian, Tianquan

    2011-01-25

    Functional quantum dot (QD)-based nanostructures are often constructed through the self-assembly of QDs with binding partners (molecules or other nanoparticles), a process that leads to a statistical distribution of the number of binding partners. Using single QD fluorescence spectroscopy, we probe this distribution and its effect on the function (electron-transfer dynamics) in QD-C60 complexes. Ensemble-averaged transient absorption and fluorescence decay as well as single QD fluorescence decay measurements show that the QD exciton emission was quenched by electron transfer from the QD to C60 molecules and the electron-transfer rate increases with the C60-to-QD ratio. The electron-transfer rate of single QD-C60 complexes fluctuates with time and varies among different QDs. The standard deviation increases linearly with the average of electron-transfer rates of single QD-C60 complexes, and the distributions of both quantities obey Poisson statistics. The observed distributions of single QD-C60 complexes and ensemble-averaged fluorescence decay kinetics can be described by a model that assumes a Poisson distribution of the number of adsorbed C60 molecules per QD. Our findings suggest that, in self-assembled QD nanostructures, the statistical distribution of the number of adsorbed partners can dominate the distributions of the averages and standard deviation of their interfacial dynamical properties.

  13. Low-Temperature Single Carbon Nanotube Spectroscopy of sp3 Quantum Defects

    Energy Technology Data Exchange (ETDEWEB)

    Blackburn, Jeffrey L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Ihly, Rachelle R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); He, Xiaowei [Los Alamos National Laboratory; Gifford, Brendan J. [Los Alamos National Laboratory; Hartmann, Nicolai F. [Los Alamos National Laboratory; Ma, Xuedan [Los Alamos National Laboratory; Kilina, Svetlana V. [North Dakota State University; Luo, Yue [Stevens Institute of Technology; Shayan, Kamran [Stevens Institute of Technology; Strauf, Stefan [Stevens Institute of Technology; Tretiak, Sergei [Los Alamos National Laboratory; Doorn, Stephen K. [Los Alamos National Laboratory; Htoon, Han [Los Alamos National Laboratory

    2017-09-28

    Aiming to unravel the relationship between chemical configuration and electronic structure of sp3 defects of aryl-functionalized (6,5) single-walled carbon nanotubes (SWCNTs), we perform low-temperature single nanotube photoluminescence (PL) spectroscopy studies and correlate our observations with quantum chemistry simulations. We observe sharp emission peaks from individual defect sites that are spread over an extremely broad, 1000-1350 nm, spectral range. Our simulations allow us to attribute this spectral diversity to the occurrence of six chemically and energetically distinct defect states resulting from topological variation in the chemical binding configuration of the monovalent aryl groups. Both PL emission efficiency and spectral line width of the defect states are strongly influenced by the local dielectric environment. Wrapping the SWCNT with a polyfluorene polymer provides the best isolation from the environment and yields the brightest emission with near-resolution limited spectral line width of 270 ueV, as well as spectrally resolved emission wings associated with localized acoustic phonons. Pump-dependent studies further revealed that the defect states are capable of emitting single, sharp, isolated PL peaks over 3 orders of magnitude increase in pump power, a key characteristic of two-level systems and an important prerequisite for single-photon emission with high purity. These findings point to the tremendous potential of sp3 defects in development of room temperature quantum light sources capable of operating at telecommunication wavelengths as the emission of the defect states can readily be extended to this range via use of larger diameter SWCNTs.

  14. Gating of high-mobility InAs metamorphic heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Shabani, J. [California NanoSystems Institute, University of California, Santa Barbara, California 93106 (United States); McFadden, A. P. [Department of Electrical Engineering, University of California, Santa Barbara, California 93106 (United States); Shojaei, B. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Palmstrøm, C. J. [California NanoSystems Institute, University of California, Santa Barbara, California 93106 (United States); Department of Electrical Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Department, University of California, Santa Barbara, California 93106 (United States)

    2014-12-29

    We investigate the performance of gate-defined devices fabricated on high mobility InAs metamorphic heterostructures. We find that heterostructures capped with In{sub 0.75}Ga{sub 0.25}As often show signs of parallel conduction due to proximity of their surface Fermi level to the conduction band minimum. Here, we introduce a technique that can be used to estimate the density of this surface charge that involves cool-downs from room temperature under gate bias. We have been able to remove the parallel conduction under high positive bias, but achieving full depletion has proven difficult. We find that by using In{sub 0.75}Al{sub 0.25}As as the barrier without an In{sub 0.75}Ga{sub 0.25}As capping, a drastic reduction in parallel conduction can be achieved. Our studies show that this does not change the transport properties of the quantum well significantly. We achieved full depletion in InAlAs capped heterostructures with non-hysteretic gating response suitable for fabrication of gate-defined mesoscopic devices.

  15. Transformation of self-assembled InAs/InP quantum dots into quantum rings without capping.

    Science.gov (United States)

    Sormunen, Jaakko; Riikonen, Juha; Mattila, Marco; Tiilikainen, Jouni; Sopanen, Markku; Lipsanen, Harri

    2005-08-01

    Transformation of self-assembled InAs quantum dots (QDs) on InP(100) into quantum rings (QRs) is studied. In contrast to the typical approach to III--V semiconductor QR growth, the QDs are not capped to form rings. Atomic force micrographs reveal a drastic change from InAs QDs into rings after a growth interruption in tertiarybutylphosphine ambient. Strain energy relief in the InAs QD is discussed and a mechanism for dot-to-ring transformation by As/P exchange reactions is proposed.

  16. Tuning InP self-assembled quantum structures to telecom wavelength: A versatile original InP(As) nanostructure "workshop"

    Science.gov (United States)

    Mura, E. E.; Gocalinska, A.; Juska, G.; Moroni, S. T.; Pescaglini, A.; Pelucchi, E.

    2017-03-01

    The influence of hydride exposure on previously unreported self-assembled InP(As) nanostructures is investigated, showing an unexpected morphological variability with growth parameters, and producing a large family of InP(As) nanostructures by metalorganic vapour phase epitaxy, from dome and ring-like structures to double dot in a ring ensembles. Moreover, preliminary microphotoluminescence data are indicating the capped rings system as an interesting candidate for single quantum emitters at telecom wavelengths, potentially becoming a possible alternative to InAs QDs for quantum technology and telecom applications.

  17. Operation of a quantum dot in the finite-state machine mode: Single-electron dynamic memory

    Energy Technology Data Exchange (ETDEWEB)

    Klymenko, M. V. [Department of Chemistry, University of Liège, B4000 Liège (Belgium); Klein, M. [The Fritz Haber Center for Molecular Dynamics and the Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Levine, R. D. [The Fritz Haber Center for Molecular Dynamics and the Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Crump Institute for Molecular Imaging and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095 (United States); Remacle, F., E-mail: fremacle@ulg.ac.be [Department of Chemistry, University of Liège, B4000 Liège (Belgium); The Fritz Haber Center for Molecular Dynamics and the Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

    2016-07-14

    A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states corresponds to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters, thereby demonstrating that the device can operate as a dynamic single electron memory.

  18. Entanglement and quantum phase transition in a mixed-spin Heisenberg chain with single-ion anisotropy

    Science.gov (United States)

    Solano-Carrillo, E.; Franco, R.; Silva-Valencia, J.

    2011-06-01

    We study the ground-state and thermal entanglement in the mixed-spin (S,s)=(1,1/2) Heisenberg chain with single-ion anisotropy D using exact diagonalization of small clusters. In this system, a quantum phase transition is revealed to occur at the value D=0, which is the bifurcation point for the global ground state; that is, when the single-ion anisotropy energy is positive, the ground state is unique, whereas when it is negative, the ground state becomes doubly degenerate and the system has the ferrimagnetic long-range order. Using the negativity as a measure of entanglement, we find that a pronounced dip in this quantity, taking place just at the bifurcation point, serves to signal the quantum phase transition. Moreover, we show that the single-ion anisotropy helps to improve the characteristic temperatures above which the quantum behavior disappears.

  19. Strained-layer InGaAs/GaAs/AlGaAs single quantum well lasers with high internal quantum efficiency

    Science.gov (United States)

    Larsson, Anders; Cody, Jeffrey; Lang, Robert J.

    1989-01-01

    Low threshold current density strained-layer In(0.2)Ga(0.8)As/GaAs/AlGaAs single quantum well lasers, emitting at 980 nm, have been grown by molecular beam epitaxy. Contrary to what has been reported for broad-area lasers with pseudomorphic InGaAs active layers grown by metalorganic chemical vapor deposition, these layers exhibit a high internal quantum efficiency (about 90 percent). The maximum external differential quantum efficiency is 70 percent, limited by an anomalously high internal loss possibly caused by a large lateral spreading of the optical mode. In addition, experimental results supporting the theoretically predicted strain-induced reduction of the valence-band nonparabolicity and density of states are presented.

  20. Solid-phase single molecule biosensing using dual-color colocalization of fluorescent quantum dot nanoprobes

    Science.gov (United States)

    Liu, Jianbo; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Liu, Wei; Wang, Dong

    2013-10-01

    The development of solid-phase surface-based single molecule imaging technology has attracted significant interest during the past decades. Here we demonstrate a sandwich hybridization method for highly sensitive detection of a single thrombin protein at a solid-phase surface based on the use of dual-color colocalization of fluorescent quantum dot (QD) nanoprobes. Green QD560-modified thrombin binding aptamer I (QD560-TBA I) were deposited on a positive poly(l-lysine) assembled layer, followed by bovine serum albumin blocking. It allowed the thrombin protein to mediate the binding of the easily detectable red QD650-modified thrombin binding aptamer II (QD650-TBA II) to the QD560-TBA I substrate. Thus, the presence of the target thrombin can be determined based on fluorescent colocalization measurements of the nanoassemblies, without target amplification or probe separation. The detection limit of this assay reached 0.8 pM. This fluorescent colocalization assay has enabled single molecule recognition in a separation-free detection format, and can serve as a sensitive biosensing platform that greatly suppresses the nonspecific adsorption false-positive signal. This method can be extended to other areas such as multiplexed immunoassay, single cell analysis, and real time biomolecule interaction studies.The development of solid-phase surface-based single molecule imaging technology has attracted significant interest during the past decades. Here we demonstrate a sandwich hybridization method for highly sensitive detection of a single thrombin protein at a solid-phase surface based on the use of dual-color colocalization of fluorescent quantum dot (QD) nanoprobes. Green QD560-modified thrombin binding aptamer I (QD560-TBA I) were deposited on a positive poly(l-lysine) assembled layer, followed by bovine serum albumin blocking. It allowed the thrombin protein to mediate the binding of the easily detectable red QD650-modified thrombin binding aptamer II (QD650-TBA II) to

  1. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis

    DEFF Research Database (Denmark)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas

    2017-01-01

    Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanis...... fabricated junctions in radial nanowire heterostructures.......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism....... Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show...

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

    National Research Council Canada - National Science Library

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

    2015-01-01

    .... Among these protocols, the elimination of multiple photons (or multiple photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate...

  3. A study of transport suppression in an undoped AlGaAs/GaAs quantum dot single-electron transistor

    DEFF Research Database (Denmark)

    See, A. M.; Klochan, O.; Micolich, P.

    2013-01-01

    We report a study of transport blockade features in a quantum dot single-electron transistor, based on an undoped AlGaAs/GaAs heterostructure. We observe suppression of transport through the ground state of the dot, as well as negative differential conductance at finite source-drain bias. The tem......We report a study of transport blockade features in a quantum dot single-electron transistor, based on an undoped AlGaAs/GaAs heterostructure. We observe suppression of transport through the ground state of the dot, as well as negative differential conductance at finite source-drain bias...

  4. Quantum detector tomography of a time-multiplexed superconducting nanowire single-photon detector at telecom wavelengths.

    Science.gov (United States)

    Natarajan, Chandra M; Zhang, Lijian; Coldenstrodt-Ronge, Hendrik; Donati, Gaia; Dorenbos, Sander N; Zwiller, Val; Walmsley, Ian A; Hadfield, Robert H

    2013-01-14

    Superconducting nanowire single-photon detectors (SNSPDs) are widely used in telecom wavelength optical quantum information science applications. Quantum detector tomography allows the positive-operator-valued measure (POVM) of a single-photon detector to be determined. We use an all-fiber telecom wavelength detector tomography test bed to measure detector characteristics with respect to photon flux and polarization, and hence determine the POVM. We study the SNSPD both as a binary detector and in an 8-bin, fiber based, Time-Multiplexed (TM) configuration at repetition rates up to 4 MHz. The corresponding POVMs provide an accurate picture of the photon number resolving capability of the TM-SNSPD.

  5. Single atom cavity quantum electrodynamics with non-transversally polarized light fields

    Energy Technology Data Exchange (ETDEWEB)

    Junge, Christian; O' Shea, Danny; Volz, Juergen; Rauschenbeutel, Arno [Vienna Center for Quantum Science and Technology, TU Wien, Atominstitut, Stadionallee 2, A-1020 Wien (Austria)

    2013-07-01

    Whispering-gallery-mode (WGM) microresonators are versatile devices for enhancing light-matter interaction. They combine ultra high quality factors and small mode volumes with near lossless in- and out-coupling of light via tapered fiber couplers. Here, we report on a cavity quantum electrodynamics (CQED) experiment in which single {sup 85}Rb atoms interact in the strong coupling regime with a WGM in an ultra high-Q bottle microresonator. We present optical transmission spectra of our system that fundamentally deviate from the predictions of the established theoretical model for CQED in ring resonators. We identify the non-transversal character of the field of WGMs as the origin of this discrepancy. Excellent agreement is found between our data and the predictions of an extended theoretical model that accounts for the full vectorial description of the WGMs. Our studies demonstrate that the non-transversal character of WGMs allows one to realize a paradigmatic quantum system that is ideally suited for basic studies as well as for technological applications.

  6. Position dependent optical coupling between single quantum dots and photonic crystal nanocavities

    Energy Technology Data Exchange (ETDEWEB)

    Kuruma, K.; Takamiya, D. [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Ota, Y.; Kakuda, M. [Institute of Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Iwamoto, S.; Arakawa, Y. [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Nano Quantum Information Electronics, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

    2016-08-15

    We demonstrate precise and quick detection of the positions of quantum dots (QDs) embedded in two-dimensional photonic crystal nanocavities. We apply this technique to investigate the QD position dependence of the optical coupling between the QD and the nanocavity. We use a scanning electron microscope (SEM) operating at a low acceleration voltage to detect surface bumps induced by the QDs buried underneath. This enables QD detection with a sub-10 nm precision. We then experimentally measure the vacuum Rabi spectra to extract the optical coupling strengths (gs) between single QDs and cavities, and compare them to the values estimated by a combination of the SEM-measured QD positions and electromagnetic cavity field simulations. We found a highly linear relationship between the local cavity field intensities and the QD-cavity gs, suggesting the validity of the point dipole approximation used in the estimation of the gs. The estimation using SEM has a small standard deviation of ±6.2%, which potentially enables the high accuracy prediction of g prior to optical measurements. Our technique will play a key role for deeply understanding the interaction between QDs and photonic nanostructures and for advancing QD-based cavity quantum electrodynamics.

  7. The giant acoustic atom - a single quantum system with a deterministic time delay

    Science.gov (United States)

    Guo, Lingzhen; Grimsmo, Arne; Frisk Kockum, Anton; Pletyukhov, Mikhail; Johansson, Göran

    2017-04-01

    We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. Furthermore, we find the short-time dynamics of the giant atom for arbitrary drive strength by a numerically exact method for open quantum systems with a finite-time-delay feedback loop. L. G. acknowledges financial support from Carl-Zeiss Stiftung (0563-2.8/508/2).

  8. Photoluminescence Study of Plasma-Induced Damage of GaInN Single Quantum Well

    Science.gov (United States)

    Izumi, Shouichiro; Minami, Masaki; Kamada, Michiru; Tatsumi, Tetsuya; Yamaguchi, Atsushi A.; Ishikawa, Kenji; Hori, Masaru; Tomiya, Shigetaka

    2013-08-01

    Plasma-induced damage (PID) due to Cl2/SiCl4/Ar plasma etching of the GaN capping layer (CAP)/GaInN single quantum well (SQW)/GaN structure was investigated by conventional photoluminescence (PL), transmission electron microscopy (TEM), and time-resolved and temperature-dependent photoluminescence (TRPL). SQW PL intensity remained constant initially, although plasma etching of the CAP layer proceeded, but when the etching thickness reached a certain amount (˜60 nm above the SQW), PL intensity started to decrease sharply. On the other hand, TEM observations show that the physical damage (structural damage) was limited to the topmost surface region. These findings can be explained by the results of TRPL studies, which revealed that there exist two different causes of PID. One is an increase in the number of nonradiative recombination centers, which mainly affects the PL intensity. The other is an increase in the quantum level fluctuation owing mainly to physical damage.

  9. Modeling satellite-Earth quantum channel downlinks with adaptive-optics coupling to single-mode fibers

    Science.gov (United States)

    Gruneisen, Mark T.; Flanagan, Michael B.; Sickmiller, Brett A.

    2017-10-01

    The efficient coupling of photons from a free-space quantum channel into a single-mode optical fiber (SMF) has important implications to quantum network concepts involving SMF interfaces to quantum detectors, atomic systems, integrated photonics and direct coupling to a fiber network. Propagation through atmospheric turbulence however leads to wavefront errors that degrade mode-matching with SMFs. In a free-space quantum channel, this leads to photon losses in proportion to the severity of the aberration. This is particularly problematic for satellite-Earth quantum channels where atmospheric turbulence can lead to significant wavefront errors. This report considers propagation from a transmitter in low-Earth orbit to a terrestrial ground station and evaluates the efficiency with which photons couple either through a circular field stop or into a SMF situated in the focal plane of the optical receiver. The effects of atmospheric turbulence on the quantum channel are calculated numerically and quantified through the quantum bit error rate and secure key generation rates in a decoy-state BB84 protocol. Numerical simulations include the statistical nature of Kolmogorov turbulence, sky radiance, and an adaptive optics system under closed loop control.

  10. Quantum dots: lasers and amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Bimberg, Dieter; Ledentsov, Nikolai [Institut fuer Festkoerperphysik, PN5-2, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 (Germany)

    2003-06-25

    Continuous wave room-temperature output power of {approx} 3 W for edge emitters and of 1.2 mW for vertical-cavity surface-emitting lasers is realized for GaAs-based devices using InAs quantum dots (QDs) operating at 1.3 {mu}m. Characteristic temperatures up to 170 K below 330 K are realized. Simultaneously, differential efficiency exceeds 80% for these devices. Lasers emitting up to 12 W at 1140-1160 nm are useful as pump sources for Tm{sup 3+}-doped fibres for frequency up-conversion to 470 nm. Both types of lasers show transparency current densities of 6 A cm{sup -2} per dot layer, {eta}{sub int} = 98% and {alpha}{sub i} around 1.5 cm{sup -1}. Long operation lifetimes (above 3000 h at 50 deg C heatsink temperature at 1.5 W CW) and improved radiation hardness as compared to quantum well (QW) devices are manifested. Cut-off frequencies of about 10 GHz at 1100 nm and 6 GHz at 1300 nm and low {alpha} factors resulting in reduced filamentation and improved M{sup 2} values in single-mode operation are realized. Quantum dot semiconductor optical amplifiers (QD SOAs) demonstrate gain recovery times of 120-140 fs, 4-7 times faster than bulk/QW SOAs. The breakthrough became possible due to the development of self-organized growth in QD technology. (topical review)

  11. Single-ion quantum Otto engine with always-on bath interaction

    Science.gov (United States)

    Chand, Suman; Biswas, Asoka

    2017-06-01

    We demonstrate how the reciprocating heat cycle of a quantum Otto engine (QOE) can be implemented using a single ion and an always-on thermal environment. The internal degree of freedom of the ion is chosen as the working fluid, while the motional degree of freedom can be used as the cold bath. We show, that by adiabatically changing the local magnetic field, the work efficiency can be asymptotically made unity. We propose a projective measurement of the internal state of the ion that mimics the release of heat from the working fluid during the engine cycle. In our proposal, the coupling to the hot and the cold baths need not be switched off and on in an alternate fashion during the engine cycle, unlike other existing proposals of QOE. This renders the proposal experimentally feasible using the available tapped-ion engineering technology.

  12. The relation between structure and quantum interference in single molecule junctions.

    Science.gov (United States)

    Markussen, Troels; Stadler, Robert; Thygesen, Kristian S

    2010-10-13

    Quantum interference (QI) of electron pathways has recently attracted increased interest as an enabling tool for single-molecule electronic devices. Although various molecular systems have been shown to exhibit QI effects and a number of methods have been proposed for its analysis, simple guidelines linking the molecular structure to QI effects in the phase-coherent transport regime have until now been lacking. In the present work we demonstrate that QI in aromatic molecules is intimately related to the topology of the molecule's π system and establish a simple graphical scheme to predict the existence of QI-induced transmission antiresonances. The generality of the scheme, which is exact for a certain class of tight-binding models, is proved by a comparison to first-principles transport calculations for 10 different configurations of anthraquinone as well as a set of cross-conjugated molecular wires.

  13. Single electron phenomena in InP /InGaAs quantum point contacts

    Science.gov (United States)

    Bandaru, Prabhakar; Robinson, Hans; Kosaka, Hideo; Yablonovitch, Eli; Jiang, Hong-Wen

    2002-03-01

    InP based heterostructures have the advantages over those based on GaAs, in that (a) the bandgap wavelengths are in the range 1.3-1.55 microns, suitable for light transmission through fibers, (b) there is a greater tunability range of the electromagnetic Lande g-factors, important for spintronic applications, and (c) growth on InP substrates is more flexible as InP is lattice matched both to InGaAs and AlInAs. We report here on our results in Quantum Point Contacts (QPCs) fabricated in InP/InGaAs heterostructures, of relevance to single electron phenomena. Several features of the conductance quantization in QPCs such as the Random Telegraph Signal (RTS) noise and resonant tunneling peaks are analyzed with respect to the (a) the length and width of the channel, (b) the nature of the impurities, (d) magnetic field, (e) bias voltage, and (f) temperature.

  14. Phase locking of a semiconductor double-quantum-dot single-atom maser

    Science.gov (United States)

    Liu, Y.-Y.; Hartke, T. R.; Stehlik, J.; Petta, J. R.

    2017-11-01

    We experimentally study the phase stabilization of a semiconductor double-quantum-dot (DQD) single-atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output field demonstrate that the maser can be phase locked to an external cavity drive, with a resulting phase noise L =-99 dBc/Hz at a frequency offset of 1.3 MHz. The injection locking range, and the phase of the maser output relative to the injection locking input tone are in good agreement with Adler's theory. Furthermore, the electrically tunable DQD energy level structure allows us to rapidly switch the gain medium on and off, resulting in an emission spectrum that resembles a frequency comb. The free running frequency comb linewidth is ≈8 kHz and can be improved to less than 1 Hz by operating the comb in the injection locked regime.

  15. Two-photon interference at telecom wavelengths for time-bin-encoded single photons from quantum-dot spin qubits.

    Science.gov (United States)

    Yu, Leo; Natarajan, Chandra M; Horikiri, Tomoyuki; Langrock, Carsten; Pelc, Jason S; Tanner, Michael G; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Höfling, Sven; Kamp, Martin; Hadfield, Robert H; Fejer, Martin M; Yamamoto, Yoshihisa

    2015-11-24

    Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911 nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances.

  16. Linear optical quantum metrology with single photons: exploiting spontaneously generated entanglement to beat the shot-noise limit.

    Science.gov (United States)

    Motes, Keith R; Olson, Jonathan P; Rabeaux, Evan J; Dowling, Jonathan P; Olson, S Jay; Rohde, Peter P

    2015-05-01

    Quantum number-path entanglement is a resource for supersensitive quantum metrology and in particular provides for sub-shot-noise or even Heisenberg-limited sensitivity. However, such number-path entanglement has been thought to be resource intensive to create in the first place--typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feedforward, which are difficult to implement. Very recently, arising from the study of quantum random walks with multiphoton walkers, as well as the study of the computational complexity of passive linear optical interferometers fed with single-photon inputs, it has been shown that such passive linear optical devices generate a superexponentially large amount of number-path entanglement. A logical question to ask is whether this entanglement may be exploited for quantum metrology. We answer that question here in the affirmative by showing that a simple, passive, linear-optical interferometer--fed with only uncorrelated, single-photon inputs, coupled with simple, single-mode, disjoint photodetection--is capable of significantly beating the shot-noise limit. Our result implies a pathway forward to practical quantum metrology with readily available technology.

  17. Electrical control of spontaneous emission and strong coupling for a single quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Laucht, A; Hofbauer, F; Hauke, N; Angele, J; Kaniber, M; Boehm, G; Amann, M-C; Finley, J J [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, D-85748 Garching (Germany); Stobbe, S; Lodahl, P [DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DTU-Building 345V, DK-2800 Kgs Lyngby (Denmark)], E-mail: finley@wsi.tum.de

    2009-02-15

    We report the design, fabrication and optical investigation of electrically tunable single quantum dots-photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light-matter interaction. Unlike previous studies where the dot-cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, we demonstrate that the quantum-confined Stark effect can be employed to quickly and reversibly switch the dot-cavity coupling simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by {approx}4 meV relative to the nanocavity mode before the emission quenches due to carrier tunneling escape. This range is much larger than the typical linewidth of the high-Q cavity modes ({approx}100 {mu}eV) allowing us to explore and contrast regimes where the dots couple to the cavity or decay by spontaneous emission into the two-dimensional photonic bandgap. In the weak-coupling regime, we show that the dot spontaneous emission rate can be tuned using a gate voltage, with Purcell factors {>=}7. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime, and electrical control of zero-dimensional polaritons is demonstrated for the highest-Q cavities (Q{>=}12 000). Vacuum Rabi splittings up to {approx}120 {mu}eV are observed, larger than the linewidths of either the decoupled exciton ({gamma}{<=}40 {mu}eV) or cavity mode. These observations represent a voltage switchable optical nonlinearity at the single photon level, paving the way towards on-chip dot-based nano-photonic devices that can be integrated with passive optical components.

  18. Electrical control of spontaneous emission and strong coupling for a single quantum dot

    Science.gov (United States)

    Laucht, A; Hofbauer, F; Hauke, N; Angele, J; Stobbe, S; Kaniber, M; Böhm, G; Lodahl, P; Amann, M-C; Finley, J J

    2009-02-01

    We report the design, fabrication and optical investigation of electrically tunable single quantum dots—photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light-matter interaction. Unlike previous studies where the dot-cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, we demonstrate that the quantum-confined Stark effect can be employed to quickly and reversibly switch the dot-cavity coupling simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by ~4 meV relative to the nanocavity mode before the emission quenches due to carrier tunneling escape. This range is much larger than the typical linewidth of the high-Q cavity modes (~100 μeV) allowing us to explore and contrast regimes where the dots couple to the cavity or decay by spontaneous emission into the two-dimensional photonic bandgap. In the weak-coupling regime, we show that the dot spontaneous emission rate can be tuned using a gate voltage, with Purcell factors >=7. New information is obtained on the nature of the dot-cavity coupling in the weak coupling regime, and electrical control of zero-dimensional polaritons is demonstrated for the highest-Q cavities (Q>=12 000). Vacuum Rabi splittings up to ~120 μeV are observed, larger than the linewidths of either the decoupled exciton (γ<=40 μeV) or cavity mode. These observations represent a voltage switchable optical nonlinearity at the single photon level, paving the way towards on-chip dot-based nano-photonic devices that can be integrated with passive optical components.

  19. Spin-polarized transport through a quantum ring with an embedded protein-like single-helical molecule

    Science.gov (United States)

    Wang, Xiao; Wu, Hai-Na; Gong, Wei-Jiang

    2017-04-01

    We investigate the spin-polarized electron transport through a quantum ring whose arms are embedded by one protein-like single-helical molecule and one quantum dot, respectively. It is found that the inter-arm quantum interference leads to the enhancement of the spin polarization in this structure. Moreover, when local magnetic flux is applied through the ring, the spin polarization in the electron transport process, including the polarization strength and direction, can be further adjusted. Next in the finite-bias case, the spin polarization is also apparent and can be tuned by changing the magnetic flux or the dot level. This work provides a new scheme to manipulate the spin transport based on the single-helical molecule.

  20. High-power single-element pseudomorphic InGaAs/GaAs/AlGaAs single quantum well lasers for pumping Er-doped fiber amplifiers

    Science.gov (United States)

    Larsson, A.; Forouhar, S.; Cody, J.; Lang, R. J.; Andrekson, P. A.

    1991-01-01

    A 980-nm-ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well laser with a maximum single-ended output power of 240 mW from a facet-coated device is fabricated from a graded-index separate-confinement heterostructure grown by molecular-beam epitaxy. The laser oscillates in the fundamental spatial mode, allowing 22 percent coupling efficiency into a 1.55-micron single-mode optical fiber. Life testing at an output power of 30 mW per facet from uncoated devices reveals a superior reliability to GaAs/AlGaAs quantum-well lasers but also the need for protective facet coatings for long term reliability at power levels required for pumping Er-doped fiber amplifiers.