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Author (up) Maslennikov, S. url  openurl
  Title RF heating efficiency of the terahertz superconducting hot-electron bolometer Type Journal Article
  Year 2014 Publication arXiv Abbreviated Journal arXiv  
  Volume 1404.5276 Issue Pages 1-4  
  Keywords superconducting hot-electron bolometer mixer, HEB, NbN, distributed model, HEB model, HEB mixer model, heat balance equa-tions, conversion gain, RF heating efficiency, noise temperature, simulation, Euler method  
  Abstract We report results of the numerical solution by the Euler method of the system of heat balance equations written in recurrent form for the superconducting hot-electron bolometer (HEB) embedded in an electrical circuit. By taking into account the dependence of the HEB resistance on the transport current we have been able to calculate rigorously the RF heating efficiency, absorbed local oscillator (LO) power and conversion gain of the HEB mixer. We show that the calculated conversion gai nis in excellent agreement with the experimental results, and that the substitution of the calculated RF heating efficiency and absorbed LO power into the expressions for the conversion gain and noise temperature given by the analytical small-signal model of the HEB yields excellent agreement with the corresponding measured values  
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  Notes Approved no  
  Call Number RPLAB @ atomics90 @ Serial 954  
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Author (up) Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A; Vacelet, T url  doi
openurl 
  Title Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges Type Journal Article
  Year 2014 Publication Appl. Phys. Lett. Abbreviated Journal <ef><bf><bc>Appl. Phys. Lett.  
  Volume 104 Issue Pages 052605(1-4)  
  Keywords NbN HEB mixers, local oscillator power, RF nonuniform absorption  
  Abstract We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film.  
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  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 935  
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Author (up) Murphy, A.; Semenov, A.; Korneev, A.; Korneeva, Y.; Gol’tsman, G.; Bezryadin, A. url  openurl
  Title Dark counts initiated by macroscopic quantum tunneling in NbN superconducting photon detectors Type Miscellaneous
  Year 2014 Publication arXiv Abbreviated Journal  
  Volume Issue Pages  
  Keywords NbN SSPD  
  Abstract We perform measurements of the switching current distributions of three w = 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijarvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors.  
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  Notes Approved no  
  Call Number murphy2014dark Serial 1356  
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Author (up) Ozhegov, R. V.; Gorshkov, K. N.; Vachtomin, Y. B.; Smirnov, K. V.; Finkel, M. I.; Goltsman, G. N.; Kiselev, O. S.; Kinev, N. V.; Filippenko, L. V.; Koshelets, V. P. url  doi
openurl 
  Title Terahertz imaging system based on superconducting heterodyne integrated receiver Type Conference Article
  Year 2014 Publication Proc. THz and Security Applications Abbreviated Journal Proc. THz and Security Applications  
  Volume Issue Pages 113-125  
  Keywords SIS mixer, SIR, THz imaging  
  Abstract The development of terahertz imaging instruments for security systems is on the cutting edge of terahertz technology. We are developing a THz imaging system based on a superconducting integrated receiver (SIR). An SIR is a new type of heterodyne receiver based on an SIS mixer integrated with a flux-flow oscillator (FFO) and a harmonic mixer which is used for phase-locking the FFO. Employing an SIR in an imaging system means building an entirely new instrument with many advantages compared to traditional systems.

In this project we propose a prototype THz imaging system using an 1 pixel SIR and 2D scanner. At a local oscillator frequency of 500 GHz the best noise equivalent temperature difference (NETD) of the SIR is 10 mK at an integration time of 1 s and a detection bandwidth of 4 GHz. The scanner consists of two rotating flat mirrors placed in front of the antenna consisting of a spherical primary reflector and an aspherical secondary reflector. The diameter of the primary reflector is 0.3 m. The operating frequency of the imaging system is 600 GHz, the frame rate is 0.1 FPS, the scanning area is 0.5 × 0.5 m2, the image resolution is 50 × 50 pixels, the distance from an object to the scanner was 3 m. We have obtained THz images with a spatial resolution of 8 mm and a NETD of less than 2 K.
 
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  Publisher Springer Netherlands Place of Publication Dordrecht Editor Corsi, C.; Sizov, F.  
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  Series Editor Series Title Abbreviated Series Title  
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  ISSN 978-94-017-8828-1 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number Serial 1368  
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Author (up) Ozhegov, R.; Elezov, M.; Kurochkin, Y.; Kurochkin, V.; Divochiy, A.; Kovalyuk, V.; Vachtomin, Y.; Smirnov, K.; Goltsman, G. doi  openurl
  Title Quantum key distribution over 300 Type Conference Article
  Year 2014 Publication Proc. SPIE Abbreviated Journal Proc. SPIE  
  Volume 9440 Issue Pages 1F (1 to 9)  
  Keywords SSPD, SNSPD applicatins, quantum key distribution, QKD  
  Abstract We discuss the possibility of polarization state reconstruction and measurement over 302 km by Superconducting Single- Photon Detectors (SSPDs). Because of the excellent characteristics and the possibility to be effectively coupled to singlemode optical fiber many applications of the SSPD have already been reported. The most impressive one is the quantum key distribution (QKD) over 250 km distance. This demonstration shows further possibilities for the improvement of the characteristics of quantum-cryptographic systems such as increasing the bit rate and the quantum channel length, and decreasing the quantum bit error rate (QBER). This improvement is possible because SSPDs have the best characteristics in comparison with other single-photon detectors. We have demonstrated the possibility of polarization state reconstruction and measurement over 302.5 km with superconducting single-photon detectors. The advantage of an autocompensating optical scheme, also known as “plugandplay” for quantum key distribution, is high stability in the presence of distortions along the line. To increase the distance of quantum key distribution with this optical scheme we implement the superconducting single photon detectors (SSPD). At the 5 MHz pulse repetition frequency and the average photon number equal to 0.4 we measured a 33 bit/s quantum key generation for a 101.7 km single mode ber quantum channel. The extremely low SSPD dark count rate allowed us to keep QBER at 1.6% level.  
  Address  
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  Publisher SPIE Place of Publication Editor Orlikovsky, A. A.  
  Language Summary Language Original Title  
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  Area Expedition Conference International Conference on Micro- and Nano-Electronics  
  Notes Approved no  
  Call Number RPLAB @ sasha @ ozhegov2014quantum Serial 1048  
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