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Terai H, Miki S, Yamashita T, Makise K, Wang Z. Demonstration of single-flux-quantum readout operation for superconducting single-photon detectors. Appl Phys Lett. 2010;97(11):3.
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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Saunders DJ, Jones SJ, Wiseman HM, Pryde GJ. Experimental EPR-steering using Bell-local states. Nat Phys. 2010;6(11):845–9.
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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Saffman M. Quantum computing: A quantum telecom link. Nat Phys. 2010;6(11):838–9.
Abstract: Converting data-carrying photons to telecommunication wavelengths enables distribution of quantum information over long distances.
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Raussendorf R. Quantum computing: Shaking up ground states. Nat Phys. 2010;6(11):840–1.
Abstract: Measurement-based quantum computation with an Affleck-Kennedy-Lieb-Tasaki state is experimentally realized for the first time.
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Ozhegov RV, Gorshkov KN, Okunev OV, Gol’tsman GN. Superconducting hot-electron bolometer mixer as element of thermal imager matrix. Tech Phys Lett. 2010;36(11):1006–8.
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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Shangina EL, Smirnov KV, Morozov DV, Kovalyuk VV, Gol’tsman GN, Verevkin AA, et al. Frequency bandwidth and conversion loss of a semiconductor heterodyne receiver with phonon cooling of two-dimensional electrons. Semicond. 2010;44(11):1427–9.
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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Maingault L, Tarkhov M, Florya I, Semenov A, Espiau de Lamaëstre R, Cavalier P, et al. Spectral dependency of superconducting single photon detectors. J Appl Phys. 2010;107(11):116103 (1 to 3).
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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Tret’yakov IV, Ryabchun SA, Kaurova NS, Larionov PA, Lobastova AA, Voronov BM, et al. Optimum absorbed heterodyne power for superconducting NbN hot-electron bolometer mixer. Tech Phys Lett. 2010;36(12):1103–5.
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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Toyabe S, Sagawa T, Ueda M, Muneyuki E, Sano M. Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality. Nat Phys. 2010;6(12):988–92.
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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Home J. Quantum entanglement: Watching correlations disappear. Nat Phys. 2010;6(12):938–9.
Abstract: Engineered decoherence enables tracking of multipartite entanglement as a quantum state decays.
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