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Author Pernice, W.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G. N.; Sergienko, A. V.; Tang, H. X. url  openurl
  Title High speed and high efficiency travelling wave single-photon detectors embedded in nanophotonic circuits Type Miscellaneous
  Year 2012 Publication arXiv Abbreviated Journal arXiv  
  Volume 1108.5299 Issue Pages 1-23  
  Keywords optical waveguides, waveguide SSPD, guantum photonics, jitter, detection efficiency  
  Abstract Ultrafast, high quantum efficiency single photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. High photon detection efficiency is essential for scalable measurement-based quantum computation, quantum key distribution, and loophole-free Bell experiments. However, imperfect modal matching and finite photon absorption rates have usually limited the maximum attainable detection efficiency of single photon detectors. Here we demonstrate a superconducting nanowire detector atop nanophotonic waveguides which allows us to drastically increase the absorption length for incoming photons. When operating the detectors close to the critical current we achieve high on-chip single photon detection efficiency up to 91% at telecom wavelengths, with uncertainty dictated by the variation of the waveguide photon flux. We also observe remarkably low dark count rates without significant compromise of detection efficiency. Furthermore, our detectors are fully embedded in a scalable silicon photonic circuit and provide ultrashort timing jitter of 18ps. Exploiting this high temporal resolution we demonstrate ballistic photon transport in silicon ring resonators. The direct implementation of such a detector with high quantum efficiency, high detection speed and low jitter time on chip overcomes a major barrier in integrated quantum photonics.  
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  Notes Approved no  
  Call Number (up) Serial 845  
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Author Shurakov, Alexander; Tong, Edward; Blundell, Raymond; Gol'tsman, Gregory openurl 
  Title Microwave stabilization of HEB mixer by a microchip controller Type Conference Article
  Year 2012 Publication IEEE MTT-S international microwave symposium digest Abbreviated Journal  
  Volume Issue Pages 1-3  
  Keywords HEB mixer stability, microwave injection, Allan variance, Allan time  
  Abstract The stability of a Hot Electron Bolometer (HEB) mixer can be improved by the use of microwave injection. In this article we report a refinement of this approach. We introduce a microchip controller to facilitate the implementation of the stabilization scheme, and demonstrate that the feedback loop effectively suppresses drifts in the HEB bias current, leading to an improvement in the receiver stability. The measured Allan time of the mixer's IF output power is increased to > 10 s.  
  Address Montreal, QC, Canada  
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  Notes Approved no  
  Call Number (up) Serial 857  
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Author Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. openurl 
  Title Evanescent states and nonequilibrium in driven superconducting nanowires Type Journal Article
  Year 2012 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 85 Issue Pages 224503(1-10)  
  Keywords Al HEB, Al superconducting nanowire, global state, bimodal state, quasiclassical kinetic equations, Usadel equation  
  Abstract We study the nonlinear response of current transport in a superconducting diffusive nanowire between normal reservoirs. We demonstrate theoretically and experimentally the existence of two different superconducting states appearing when the wire is driven out of equilibrium by an applied bias, called the global and bimodal superconducting states. The different states are identified by using two-probe measurements of the wire, and measurements of the local density of states with tunneling probes. The analysis is performed within the framework of the quasiclassical kinetic equations for diffusive superconductors.  
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  Notes Approved no  
  Call Number (up) Serial 898  
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Author Pütz, P.; Honingh, C. E.; Jacobs, K.; Justen, M.; Schultz, M.; Stutzki, J. openurl 
  Title Terahertz hot electron bolometer waveguide mixers for GREAT Type Journal Article
  Year 2012 Publication Astron. Astrophys. Abbreviated Journal A&A  
  Volume 542 Issue Pages L2  
  Keywords HEB mixer, applications  
  Abstract Context. Supplementing the publications based on the first-light observations with the German REceiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. This Letter complements the GREAT instrument Letter and focuses on the mixers itself.

Aims. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given.

Methods. Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss.

Results. Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. We show that our niobium-titanium-nitride (NbTiN) material HEBs on silicon nitride (SiN) membrane substrates have an intermediate frequency (IF) noise roll-off frequency above 2.8 GHz, which does not limit the current receiver IF bandwidth. Our mixer technology development efforts culminate in the first successful operation of a waveguide-based HEB mixer at 2.5 THz and deployment for radioastronomy. A significant contribution to the success of GREAT is made by technological development, thorough characterization and performance optimization of the mixer and its IF interface for receiver operation on SOFIA. In particular, the development of an optimized mixer IF interface contributes to the low passband ripple and excellent stability, which GREAT demonstrated during its initial successful astronomical observation runs.
 
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  Notes Approved no  
  Call Number (up) Serial 907  
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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  
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  Area Expedition Conference  
  Notes Recommended by Klapwijk Approved no  
  Call Number (up) Serial 930  
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