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Author Ma, Xiao-Song; Dakic, Borivoje; Naylor, William; Zeilinger, Anton; Walther, Philip openurl 
  Title Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.  
  Volume 7 Issue 5 Pages 399-405  
  Keywords fromIPMRAS  
  Abstract Quantum simulators are controllable quantum systems that can reproduce the dynamics of the system of interest in situations that are not amenable to classical computers. Recent developments in quantum technology enable the precise control of individual quantum particles as required for studying complex quantum systems. In particular, quantum simulators capable of simulating frustrated Heisenberg spin systems provide platforms for understanding exotic matter such as high-temperature superconductors. Here we report the analogue quantum simulation of the ground-state wavefunction to probe arbitrary Heisenberg-type interactions among four spin-1/2 particles. Depending on the interaction strength, frustration within the system emerges such that the ground state evolves from a localized to a resonating-valence-bond state. This spin-1/2 tetramer is created using the polarization states of four photons. The single-particle addressability and tunable measurement-induced interactions provide us with insights into entanglement dynamics among individual particles. We directly extract ground-state energies and pairwise quantum correlations to observe the monogamy of entanglement.  
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  Call Number (down) RPLAB @ gujma @ Serial 842  
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Author Чулкова, Г. М.; Семенов, А. В.; Корнеев, А. А.; Кардакова, А. И.; Аверьев, Н. В.; Ан, П. П.; Казаков, А. Ю.; Трифонов, А. В. openurl 
  Title Спектральная чувствительность сверхпроводникового однофотонного детектора Type Journal Article
  Year 2011 Publication Журнал радиоэлектроники Abbreviated Journal Ж. радиоэлектрон.  
  Volume 11 Issue Pages 5  
  Keywords SSPD; quantum efficiency; spectral sensitivity  
  Abstract We consider quantum efficiency dependence on photons' energy from hot spot model. Direction of quasiparticles diffusion drive across superconductive film. The maximal quantum efficiency is proportional to a probability of photon absorption. The spectral sensitivity of superconductive single photon detector does not have clearly expressed red limit. Changing regimes of work depends on a wavelength we can get high values of quantum efficiency in visible and infrared range which will be specified by the quality of fabrication of detectors and their consistency with the radiation.

Key words: superconducting single-photon detector, SSPD, quantum efficiency, spectral sensitivity.

В статье представлена зависимость квантовой эффективности от энергии фотона в рамках модели горячего пятна. Диффузия квазичастиц происходит в основном перпендикулярно направлению тока в областях с максимальной плотностью тока. Максимальная квантовая эффективность детектора пропорциональна вероятности поглощения фотона. Несмотря на квантовый характер работы сверхпроводникового однофотонного детектора, он не имеет четко выраженной красной границы. Изменяя режим работы в зависимости от длины волны можно в видимом и инфракрасном диапазонах получать высокие значения квантовой эффективности, которые будут определяться лишь качеством изготовления детекторов и степенью их согласования с излучением.
 
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  Call Number (down) RPLAB @ gujma @ Serial 844  
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Author Belitsky, V.; Desmaris, V.; Dochev, D.; Meledin, D.; Pavolotsky, A. openurl 
  Title Towards Multi-Pixel Heterodyne Terahertz Receivers Type Conference Article
  Year 2011 Publication Proc. 22th Int. Symp. Space Terahertz Technol. Abbreviated Journal  
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  Abstract Terahertz multi-pixel heterodyne receivers introduce multiple challenges for their implementation, mostly due to the extremely small dimensions of all components and even smaller tolerances in terms of alignment, linear dimensions and waveguide component surface quality. In this manuscript, we present a concept of terahertz multi-pixel heterodyne receiver employing optical layout using polarization split between the LO and RF. The frontend isbased on a waveguide balanced HEB mixer for the frequency band 1.6 – 2.0 THz. The balanced HEB mixer followsthe layout of earlier demonstrated APEX T2 mixer. However for the mixer presented here, we implemented split-block layout offering inimized lengths of all waveguides and thus reducing the associated RF loss. The micromachining methods employed for producing the mixer housing and the HEB mixer chip are very suitable for producing multiple structures and hence are in-line with requirements of multi-pixel receiver technology. The demonstrated relatively simple mounting of the mixer chip with self-aligning should greatly facilitate the integration of such multi-channel receiver. Index Terms—Instrumentation, Multi-pixel, Terahertz, Waveguide Balanced Mixer.  
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  Call Number (down) RPLAB @ atomics90 @ Serial 975  
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Author Pentin, I. V.; Smirnov, A. V.; Ryabchun, S. A.; Gol’tsman, G. N.; Vaks, V. L.; Pripolzin, S. I.; Paveliev, D. G. url  doi
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  Title Heterodyne source of THz range based on semiconductor superlattice multiplier Type Conference Article
  Year 2011 Publication IRMMW-THz Abbreviated Journal IRMMW-THz  
  Volume Issue Pages 1-2  
  Keywords NbN HEB mixer, superlattice  
  Abstract We present the results of our studies of the possibility of developing a heterodyne receiver incorporating a hot-electron bolometer mixer as the detector and a semiconductor superlattice multiplier driven by a reference synthesizer as the local oscillator. We observe that such a local oscillator offers enough power in the terahertz range to pump the HEB into the operating state.  
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  Notes Approved no  
  Call Number (down) 6105209 Serial 1384  
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Author Kumar, Sushil; Chan, Chun Wang I.; Hu, Qing; Reno, John L. openurl 
  Title A 1.8-THz quantum cascade laser operating significantly above the temperature of hw/k Type Journal Article
  Year 2011 Publication Nature Physics Abbreviated Journal  
  Volume 7 Issue Pages 166-171  
  Keywords QCL, 2 mW at 155 K and 1.8 THz  
  Abstract Several competing technologies continue to advance the field of terahertz science; of particular importance has been the development of a terahertz semiconductor quantum cascade laser (QCL), which is arguably the only solid-state terahertz source with average optical power levels of much greater than a milliwatt. Terahertz QCLs are required to be cryogenically cooled and improvement of their temperature performance is the single most important research goal in the field. Thus far, their maximum operating temperature has been empirically limited to ~planckω/kB, a largely inexplicable trend that has bred speculation that a room-temperature terahertz QCL may not be possible in materials used at present. Here, we argue that this behaviour is an indirect consequence of the resonant-tunnelling injection mechanism employed in all previously reported terahertz QCLs. We demonstrate a new scattering-assisted injection scheme to surpass this limit for a 1.8-THz QCL that operates up to ~1.9planckω/kB (163 K). Peak optical power in excess of 2 mW was detected from the laser at 155 K. This development should make QCL technology attractive for applications below 2 THz, and initiate new design strategies for realizing a room-temperature terahertz semiconductor laser.  
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  Notes Approved no  
  Call Number (down) Serial 631  
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