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Author Hanneke, D.; Home, J. P.; Jost, J. D.; Amini, J. M.; Leibfried, D.; Wineland, D. J.
Title Realization of a programmable two-qubit quantum processor Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 1 Pages 13-16
Keywords fromIPMRAS
Abstract The universal quantum computer is a device capable of simulating any physical system and represents a major goal for the field of quantum information science. In the context of quantum information, `universal' refers to the ability to carry out arbitrary unitary transformations in the system's computational space. Combining arbitrary single-quantum-bit (qubit) gates with an entangling two-qubit gate provides a set of gates capable of achieving universal control of any number of qubits, provided that these gates can be carried out repeatedly and between arbitrary pairs of qubits. Although gate sets have been demonstrated in several technologies, they have so far been tailored towards specific tasks, forming a small subset of all unitary operators. Here we demonstrate a quantum processor that can be programmed with 15 classical inputs to realize arbitrary unitary transformations on two qubits, which are stored in trapped atomic ions. Using quantum state and process tomography, we characterize the fidelity of our implementation for 160 randomly chosen operations. This universal control is equivalent to simulating any pairwise interaction between spin-1/2 systems. A programmable multiqubit register could form a core component of a large-scale quantum processor, and the methods used here are suitable for such a device.
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Call Number RPLAB @ gujma @ Serial 801
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Author Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I.
Title Concentration dependence of the intermediate frequency bandwidth of submillimeter heterodyne AlGaAs/GaAs nanostructures Type Journal Article
Year 2010 Publication Bull. Russ. Acad. Sci. Phys. Abbreviated Journal Bull. Russ. Acad. Sci. Phys.
Volume 74 Issue (up) 1 Pages 100-102
Keywords 2DEG AlGaAs/GaAs heterostructures, THz heterodyne detectors, IF bandwidth
Abstract The concentration dependence of the intermediate frequency bandwidth of heterodyne AlGaAs/GaAs detectors with 2D electron gas is measured using submillimeter spectroscopy with high time resolution at T= 4.2 K. The intermediate frequency bandwidth f3dBfalls from 245 to 145 MHz with increasing concentration of 2D electrons n s = (1.6-6.6) × 10[su11] cm-2. The dependence f3dB ≈ n s – 0.04±is observed in the studied concentration range; this dependence is determined by electron scattering by the deformation potential of acoustic phonons and piezoelectric scattering.
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ISSN 1062-8738 ISBN Medium
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Notes Approved no
Call Number Serial 1217
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Author Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim
Title Hacking commercial quantum cryptography systems by tailored bright illumination Type Journal Article
Year 2010 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 4 Issue (up) 10 Pages 686 - 689
Keywords quantum cryptography, hacking, QKD, APD
Abstract The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built of off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies.
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Call Number RPLAB @ gujma @ Serial 657
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Author Шангина, Е. Л.; Смирнов, К. В.; Морозов, Д. В.; Ковалюк, В. В.; Гольцман, Г. Н.; Веревкин, А. А.; Торопов, А. И.
Title Полоса и потери преобразования полупроводникового смесителя с фононным каналом охлаждения двумерных электронов Type Journal Article
Year 2010 Publication Физика и техника полупроводников Abbreviated Journal
Volume 44 Issue (up) 11 Pages 1475-1478
Keywords 2DEG, AlGaAs/GaAs heterostructures mixers
Abstract Методом субмиллиметровой спектроскопии с высоким временным разрешением измерены температурная и концентрационная зависимости полосы преобразования смесителей терагерцового диапазона AlGaAs/GaAs на разогреве двумерных электронов с фононным каналом их охлаждения. Полоса преобразования на уровне 3 дБ (f3 dB) при 4.2 K при изменении концентрации ns варьируется в пределах 150-250 МГц в соответствии со степенным законом f3 dB propto ns-0.5, что соответствует доминирующему механизму рассеяния на пьезоэлектрических фононах. Минимальное значение коэффициента потерь преобразования полупроводникового смесителя достигается в структурах с высокой подвижностью носителей mu>3·105 см2/В·с при 4.2 K.
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Notes Duplicated as 1216 Approved no
Call Number RPLAB @ gujma @ Serial 702
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Author Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M.
Title Quantum noise in a terahertz hot electron bolometer mixer Type Journal Article
Year 2010 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume 96 Issue (up) 11 Pages 111113-(1-3)
Keywords HEB mixer, quantum limit, quantum noise, vacuum box, THz, Terahertz
Abstract We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The beta-factor (the quantum efficiency of the HEB) obtained experimentally agrees reasonably well with the calculated value.
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Call Number Serial 624
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Author Terai, Hirotaka; Miki, Shigehito; Yamashita, Taro; Makise, Kazumasa; Wang, Zhen
Title Demonstration of single-flux-quantum readout operation for superconducting single-photon detectors Type Journal Article
Year 2010 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume 97 Issue (up) 11 Pages 3
Keywords SSPD
Abstract A readout circuit using superconducting single-flux-quantum (SFQ) circuits has been developed to realize an independently addressable array of superconducting single-photon detectors (SSPDs). We tested the SFQ readout circuits by connecting with SSPDs. The error rates of readout circuits were below 10–5 for input signal amplitude of greater than 18.2 μA. Detection efficiencies (DEs) for single-photon incidents were measured both with and without the connection of a readout circuit. The observed DEs traced almost the same curves regardless of the connection of the readout circuit, except that the SSPD is likely to latch by connecting the readout circuit.
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Call Number RPLAB @ gujma @ Serial 654
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Author Saunders, D. J.; Jones, S. J.; Wiseman, H. M.; Pryde, G. J.
Title Experimental EPR-steering using Bell-local states Type Journal Article
Year 2010 Publication Nat. Phys. Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 11 Pages 845-849
Keywords fromIPMRAS
Abstract The concept of `steering' was introduced in 1935 by Schrödinger as a generalization of the EPR (Einstein-Podolsky-Rosen) paradox. It has recently been formalized as a quantum-information task with arbitrary bipartite states and measurements, for which the existence of entanglement is necessary but not sufficient. Previous experiments in this area have been restricted to an approach that followed the original EPR argument in considering only two different measurement settings per side. Here we demonstrate experimentally that EPR-steering occurs for mixed entangled states that are Bell local (that is, that cannot possibly demonstrate Bell non-locality). Unlike the case of Bell inequalities, increasing the number of measurement settings beyond two-we use up to six-significantly increases the robustness of the EPR-steering phenomenon to noise.
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Notes Approved no
Call Number RPLAB @ gujma @ Serial 808
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Author Saffman, Mark
Title Quantum computing: A quantum telecom link Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 11 Pages 838-839
Keywords fromIPMRAS
Abstract Converting data-carrying photons to telecommunication wavelengths enables distribution of quantum information over long distances.
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Call Number RPLAB @ gujma @ Serial 833
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Author Raussendorf, Robert
Title Quantum computing: Shaking up ground states Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 11 Pages 840-841
Keywords fromIPMRAS
Abstract Measurement-based quantum computation with an Affleck-Kennedy-Lieb-Tasaki state is experimentally realized for the first time.
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Call Number RPLAB @ gujma @ Serial 834
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Author Ozhegov, R. V.; Gorshkov, K. N.; Okunev, O. V.; Gol’tsman, G. N.
Title Superconducting hot-electron bolometer mixer as element of thermal imager matrix Type Journal Article
Year 2010 Publication Tech. Phys. Lett. Abbreviated Journal Tech. Phys. Lett.
Volume 36 Issue (up) 11 Pages 1006-1008
Keywords HEB mixers
Abstract The possibility of using a matrix of sensitive elements on a 12-mm-diameter hyperhemispherical lens in a thermal imager operating in the terahertz range has been studied. Dimensions of a lens region acceptable for arrangement of the matrix, in which the receiver noise temperature varies within 16% of the mean value, are determined to be 3.3% of the lens diameter. Deviations of the main lobe of the directivity pattern are evaluated, which amount to ±1.25° relative to the direction toward the optimum position of a mixer. The fluctuation sensitivity of the receiver measured in experiment is 0.5 K at a frequency of 300 GHz.
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ISSN 1063-7850 ISBN Medium
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Notes Approved no
Call Number Serial 1390
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Author Shangina, E. L.; Smirnov, K. V.; Morozov, D. V.; Kovalyuk, V. V.; Gol’tsman, G. N.; Verevkin, A. A.; Toropov, A. I.
Title Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons Type Journal Article
Year 2010 Publication Semicond. Abbreviated Journal Semicond.
Volume 44 Issue (up) 11 Pages 1427-1429
Keywords 2DEG, AlGaAs/GaAs heterostructures mixers
Abstract The temperature and concentration dependences of the frequency bandwidth of terahertz heterodyne AlGaAs/GaAs detectors based on hot electron phenomena with phonon cooling of two-dimensional electrons have been measured by submillimeter spectroscopy with a high time resolution. At a temperature of 4.2 K, the frequency bandwidth at a level of 3 dB (f 3 dB) is varied from 150 to 250 MHz with a change in the concentration n s according to the power law f 3dB ∝ n −0.5 s due to the dominant contribution of piezoelectric phonon scattering. The minimum conversion loss of the semiconductor heterodyne detector is obtained in structures with a high carrier mobility (μ > 3 × 105 cm2 V−1 s−1 at 4.2 K).
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ISSN 1063-7826 ISBN Medium
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Notes Полоса и потери преобразования полупроводникового смесителя с фононным каналом охлаждения двумерных электронов Approved no
Call Number Serial 1216
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Author Maingault, L.; Tarkhov, M.; Florya, I.; Semenov, A.; Espiau de Lamaëstre, R.; Cavalier, P.; Gol’tsman, G.; Poizat, J.-P.; Villégier, J.-C.
Title Spectral dependency of superconducting single photon detectors Type Journal Article
Year 2010 Publication J. Appl. Phys. Abbreviated Journal J. Appl. Phys.
Volume 107 Issue (up) 11 Pages 116103 (1 to 3)
Keywords NbN SSPD, SNSPD
Abstract We investigate the effect of varying both incoming optical wavelength and width of NbN nanowires on the superconducting single photon detectors (SSPD) detection efficiency. The SSPD are current biased close to critical value and temperature fixed at 4.2 K, far from transition. The experimental results are found to verify with a good accuracy predictions based on the “hot spot model,” whose size scales with the absorbed photon energy. With larger optical power inducing multiphoton detection regime, the same scaling law remains valid, up to the three-photon regime. We demonstrate the validity of applying a limited number of measurements and using such a simple model to reasonably predict any SSPD behavior among a collection of nanowire device widths at different photon wavelengths. These results set the basis for designing efficient single photon detectors operating in the infrared (2–5 μm range).

This work was supported by European projects FP6 STREP “SINPHONIA” (Contract No. NMP4-CT-2005-16433) and IP “QAP” (Contract No. 15848).
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ISSN 0021-8979 ISBN Medium
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Notes Approved no
Call Number Serial 1392
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Author Tret’yakov, I. V.; Ryabchun, S. A.; Kaurova, N. S.; Larionov, P. A.; Lobastova, A. A.; Voronov, B. M.; Finkel, M. I.; Gol’tsman, G. N.
Title Optimum absorbed heterodyne power for superconducting NbN hot-electron bolometer mixer Type Journal Article
Year 2010 Publication Tech. Phys. Lett. Abbreviated Journal Tech. Phys. Lett.
Volume 36 Issue (up) 12 Pages 1103-1105
Keywords NbN HEB mixer
Abstract Absorbed heterodyne power has been measured in a low-noise broadband hot-electron bolometer (HEB) mixer for the terahertz range, operating on the effect of electron heating in the resistive state of an ultrathin superconducting NbN film. It is established that the optimum absorbed heterodyne power for the HEB mixer operating at 2.5 THz is about 100 nW.
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ISSN 1063-7850 ISBN Medium
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Notes Approved no
Call Number Serial 1389
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Author Toyabe, Shoichi; Sagawa, Takahiro; Ueda, Masahito; Muneyuki, Eiro; Sano, Masaki
Title Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 12 Pages 988-992
Keywords fromIPMRAS
Abstract In 1929, Leo Szilard invented a feedback protocol in which a hypothetical intelligence called Maxwell's demon pumps heat from an isothermal environment and transduces it to work. After an intense controversy that lasted over eighty years; it was finally clarified that the demon's role does not contradict the second law of thermodynamics, implying that we can convert information to free energy in principle. Nevertheless, experimental demonstration of this information-to-energy conversion has been elusive. Here, we demonstrate that a nonequilibrium feedback manipulation of a Brownian particle based on information about its location achieves a Szilard-type information-energy conversion. Under real-time feedback control, the particle climbs up a spiral-stairs-like potential exerted by an electric field and obtains free energy larger than the amount of work performed on it. This enables us to verify the generalized Jarzynski equality, or a new fundamental principle of “information-heat engine” which converts information to energy by feedback control.
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Call Number RPLAB @ gujma @ Serial 831
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Author Home, Jonathan
Title Quantum entanglement: Watching correlations disappear Type Journal Article
Year 2010 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 6 Issue (up) 12 Pages 938-939
Keywords fromIPMRAS
Abstract Engineered decoherence enables tracking of multipartite entanglement as a quantum state decays.
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Call Number RPLAB @ gujma @ Serial 832
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