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Author Steudle, Gesine A.; Schietinger, Stefan; Höckel, David; Dorenbos, Sander N.; Zadeh, Iman E.; Zwiller, Valery; Benson, Oliver doi  openurl
  Title Measuring the quantum nature of light with a single source and a single detector Type Journal Article
  Year 2012 Publication Phys. Rev. A Abbreviated Journal  
  Volume 86 Issue 5 Pages 053814  
  Keywords SSPD, SNSPD, saturation count rates, dead time, dynamic range  
  Abstract An elementary experiment in optics consists of a light source and a detector. Yet, if the source generates nonclassical correlations such an experiment is capable of unambiguously demonstrating the quantum nature of light. We realized such an experiment with a defect center in diamond and a superconducting detector. Previous experiments relied on more complex setups, such as the Hanbury Brown and Twiss configuration, where a beam splitter directs light to two photodetectors, creating the false impression that the beam splitter is a fundamentally required element. As an additional benefit, our results provide a simplification of the widely used photon-correlation techniques.  
  Address  
  Corporate Author Thesis  
  Publisher American Physical Society Place of Publication Editor  
  Language Summary Language Original Title  
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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1089  
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Author De Luca, M.; Gupta, H.; Neufeld, D.; Gerin, M.; Teyssier, D.; Drouin, B. J.; Pearson, J. C.; Lis, D. C.; Monje, R.; Phillips, T. G.; Goicoechea, J. R.; Godard, B.; Falgarone, E.; Coutens, A.; Bell, T. A. doi  openurl
  Title Herschel/HIFI discovery of HCL+ in the interstellar medium Type Journal Article
  Year 2012 Publication Astrophys. J. Lett. Abbreviated Journal  
  Volume 751 Issue 2 Pages L37  
  Keywords HEB mixer applications, HIFI, Herschel  
  Abstract The radical ion HCl+, a key intermediate in the chlorine chemistry of the interstellar gas, has been identified for the first time in the interstellar medium with the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared. The ground-state rotational transition of H35Cl+, 2Π3/2 J = 5/2-3/2, showing Λ-doubling and hyperfine structure, is detected in absorption toward the Galactic star-forming regions W31C (G10.6-0.4) and W49N. The complex interstellar absorption features are modeled by convolving in velocity space the opacity profiles of other molecular tracers toward the same sources with the fine and hyperfine structure of HCl+. This structure is derived from a combined analysis of optical data from the literature and new laboratory measurements of pure rotational transitions, reported in the accompanying Letter by Gupta et al. The models reproduce well the interstellar absorption, and the frequencies inferred from the astronomical observations are in exact agreement with those calculated using spectroscopic constants derived from the laboratory data. The detection of H37Cl+ toward W31C, with a column density consistent with the expected 35Cl/37Cl isotopic ratio, provides additional evidence for the identification. A comparison with the chemically related molecules HCl and H2Cl+ yields an abundance ratio of unity with both species (HCl+ : H2Cl+ : HCl ~ 1). These observations also yield the unexpected result that HCl+ accounts for 3%-5% of the gas-phase chlorine toward W49N and W31C, values several times larger than the maximum fraction (~1%) predicted by chemical models.  
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  Notes Approved no  
  Call Number Serial 1092  
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Author Swetz, D. S.; Bennett, D. A.; Irwin, K. D.; Schmidt, D. R.; Ullom, J. N. doi  openurl
  Title Current distribution and transition width in superconducting transition-edge sensors Type Journal Article
  Year 2012 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 101 Issue Pages 242603  
  Keywords  
  Abstract Present models of the superconducting-to-normal transition in transition-edge sensors (TESs) do not describe the current distribution within a biased TES. This distribution is complicated by normal-metal features that are integral to TES design. We present a model with one free parameter that describes the evolution of the current distribution with bias. To probe the current distribution experimentally, we fabricated TES devices with different current return geometries. Devices where the current return geometry mirrors current flow within the device have sharper transitions, thus allowing for a direct test of the current-flow model.Measurements from these devices show that current meanders through a TES low in the resistivetransition but flows across the normal-metal features by 40% of the normal-state resistance. Comparison of transition sharpness between device designs reveals that self-induced magnetic fields play an important role in determining the width of the superconducting transition.  
  Address TES, current distribution  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Recommended by Klapwijk Approved no  
  Call Number Serial 930  
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Author Smirnov, A. V.; Baryshev, A. M.; de Bernardis, P.; Vdovin, V. F.; Gol'tsman, G. N.; Kardashev, N. S.; Kuz'min, L. S.; Koshelets, V. P.; Vystavkin, A. N.; Lobanov, Yu. V.; Ryabchun, S. A.; Finkel, M. I.; Khokhlov, D. R. doi  openurl
  Title The current stage of development of the receiving complex of the millimetron space observatory Type Journal Article
  Year 2012 Publication Radiophys. Quant. Electron. Abbreviated Journal Radiophys. Quant. Electron.  
  Volume 54 Issue 8 Pages 557-568  
  Keywords Millimetron space observatory, HEB applications  
  Abstract We present an overview of the state of the onboard receiving complex of the Millimetron space observatory in the development phase of its preliminary design. The basic parameters of the onboard equipment planned to create and required for astrophysical observations are considered. A review of coherent and incoherent detectors, which are central to each receiver of the observatory, is given. Their characteristics and limiting parameters feasible at the present level of technology are reported.  
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  Notes Approved no  
  Call Number Serial 1079  
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Author Bulaevskii, L. N.; Graf, Matthias J.; Kogan, V. G. openurl 
  Title Vortex-assisted photon counts and their magnetic field dependence in single-photon superconducting detectors Type Journal Article
  Year 2012 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 85 Issue 1 Pages 9  
  Keywords SSPD; SNSPD; single-vortex crossing; normal-state belt  
  Abstract We argue that photon counts in a superconducting nanowire single-photon detector (SNSPD) are caused by the transition from a current-biased metastable superconducting state to the normal state. Such a transition is triggered by vortices crossing the thin and narrow superconducting strip from one edge to another due to the Lorentz force. Detector counts in SNSPDs may be caused by three processes: (a) a single incident photon with sufficient energy to break enough Cooper pairs to create a normal-state belt across the entire width of the strip (direct photon count), (b) thermally induced single-vortex crossing in the absence of photons (dark count), which at high-bias currents releases the energy sufficient to trigger the transition to the normal state in a belt across the whole width of the strip, and (c) a single incident photon of insufficient energy to create a normal-state belt but initiating a subsequent single-vortex crossing, which provides the rest of the energy needed to create the normal-state belt (vortex-assisted single-photon count). We derive the current dependence of the rate of vortex-assisted photon counts. The resulting photon count rate has a plateau at high currents close to the critical current and drops as a power law with high exponent at lower currents. While the magnetic field perpendicular to the film plane does not affect the formation of hot spots by photons, it causes the rate of vortex crossings (with or without photons) to increase. We show that by applying a magnetic field one may characterize the energy barrier for vortex crossings and identify the origin of dark counts and vortex-assisted photon counts.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 733  
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Author Knee, George C.; Simmons, Stephanie; Gauger, Erik M.; Morton, John J. L.; Riemann, Helge; Abrosimov, Nikolai V.; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei M.; Thewalt, Mike L. W.; Briggs, G. Andrew D.; Benjamin, Simon C. openurl 
  Title Violation of a Leggett–Garg inequality with ideal non-invasive measurements Type Journal Article
  Year 2012 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 3 Issue 606 Pages 6  
  Keywords fromIPMRAS  
  Abstract The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 767  
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Author Smith, Devin H.; Gillett, Geoff; de Almeida, Marcelo P.; Branciard, Cyril; Fedrizzi, Alessandro; Weinhold, Till J.; Lita, Adriana; Calkins, Brice; Gerrits, Thomas; Wiseman, Howard M.; Nam, Sae Woo; White, Andrew G. openurl 
  Title Conclusive quantum steering with superconducting transition-edge sensors Type Journal Article
  Year 2012 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 3 Issue 625 Pages 6  
  Keywords fromIPMRAS  
  Abstract Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date, all experimental tests with single-photon states have relied on post selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this 'detection loophole' by combining a highly efficient source of entangled photon pairs with superconducting transition-edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 s.d.s. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 768  
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Author Ghali, Mohsen; Ohtani1, Keita; Ohno, Yuzo; Ohno, Hideo openurl 
  Title Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field Type Journal Article
  Year 2012 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 3 Issue 661 Pages 6  
  Keywords fromIPMRAS  
  Abstract Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton-exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72 ± 0.05.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 769  
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Author Grotz, Bernhard; Hauf, Moritz V.; Dankerl, Markus; Naydenov, Boris; Pezzagna, Sébastien; Meijer, Jan; Jelezko, Fedor; Wrachtrup, Jörg; Stutzmann, Martin; Reinhard, Friedemann; Garrido, Jose A. openurl 
  Title Charge state manipulation of qubits in diamond Type Journal Article
  Year 2012 Publication Nature Communications Abbreviated Journal Nat. Comm.  
  Volume 3 Issue 729 Pages 6  
  Keywords fromIPMRAS  
  Abstract The nitrogen-vacancy (NV) centre in diamond is a promising candidate for a solid-state qubit. However, its charge state is known to be unstable, discharging from the qubit state NV- into the neutral state NV0 under various circumstances. Here we demonstrate that the charge state can be controlled by an electrolytic gate electrode. This way, single centres can be switched from an unknown non-fluorescent state into the neutral charge state NV0, and the population of an ensemble of centres can be shifted from NV0 to NV-. Numerical simulations confirm the manipulation of the charge state to be induced by the gate-controlled shift of the Fermi level at the diamond surface. This result opens the way to a dynamic control of transitions between charge states and to explore hitherto inaccessible states, such as NV+.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 770  
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Author Gao, Jie; McMillan, James F.; Wong, Chee Wei openurl 
  Title Nanophotonics: Remote on-chip coupling Type Journal Article
  Year 2012 Publication Nature Photonics Abbreviated Journal Nat. Photon.  
  Volume 6 Issue 1 Pages 7-8  
  Keywords fromIPMRAS  
  Abstract Scientists have demonstrated strongly coupled photon states between two distant high-Q photonic crystal cavities connected by a photonic crystal waveguide. Remote dynamic control over the coupled states could aid the development of delay lines, optical buffers and qubit operations in both classical and quantum information processing.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 779  
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