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Author Bylander, Jonas; Gustavsson, Simon; Yan, Fei; Yoshihara, Fumiki; Harrabi, Khalil; Fitch, George; Cory, David G.; Nakamura, Yasunobu; Tsai, Jaw-Shen; Oliver, William D.
Title Noise spectroscopy through dynamical decoupling with a superconducting flux qubit Type (up) Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue 7 Pages 565-570
Keywords fromIPMRAS
Abstract Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy environment. In any particular implementation, however, the efficacy of these methods is sensitive to the specific frequency distribution of the noise, suggesting that these same pulse sequences could also be used to probe the noise spectrum directly. Here we demonstrate noise spectroscopy by means of dynamical decoupling using a superconducting qubit with energy-relaxation time T1=12μs. We first demonstrate that dynamical decoupling improves the coherence time T2 in this system up to the T2=2T1 limit (pure dephasing times exceeding 100μs), and then leverage its filtering properties to probe the environmental noise over a frequency (f) range 0.2-20MHz, observing a 1/fα distribution with α<1. The characterization of environmental noise has broad utility for spin-resonance applications, enabling the design of optimized coherent-control methods, promoting device and materials engineering, and generally improving coherence.
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Call Number RPLAB @ gujma @ Serial 829
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Author Ma, Xiao-Song; Dakic, Borivoje; Naylor, William; Zeilinger, Anton; Walther, Philip
Title Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems Type (up) 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 RPLAB @ gujma @ Serial 842
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Author Tang, Liang; Kocabas, Sukru Ekin; Latif, Salman; Okyay, Ali K.; Ly-Gagnon, Dany-Sebastien; Saraswat, Krishna C.; Miller, David A. B.
Title Nanometre-scale germanium photodetector enhanced by a near-infrared dipole antenna Type (up) Journal Article
Year 2008 Publication Nature Photonics Abbreviated Journal
Volume 2 Issue Pages 226-229
Keywords optical antennas
Abstract A critical challenge for the convergence of optics and electronics is that the micrometre scale of optics is significantly larger than the nanometre scale of modern electronic devices. In the conversion from photons to electrons by photodetectors, this size incompatibility often leads to substantial penalties in power dissipation, area, latency and noise. A photodetector can be made smaller by using a subwavelength active region; however, this can result in very low responsivity because of the diffraction limit of the light. Here we exploit the idea of a half-wave Hertz dipole antenna (length approx 380 nm) from radio waves, but at near-infrared wavelengths (length approx 1.3 microm), to concentrate radiation into a nanometre-scale germanium photodetector. This gives a polarization contrast of a factor of 20 in the resulting photocurrent in the subwavelength germanium element, which has an active volume of 0.00072 microm3, a size that is two orders of magnitude smaller than previously demonstrated detectors at such wavelengths.
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Call Number Serial 858
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Author Julia Toussaint, Roman Grüner, Marco Schubert, Torsten May, Hans-Georg Meyer, Benjamin Dietzek, Jürgen Popp, Matthias Hofherr, Matthias Arndt, Dagmar Henrich, Konstantin Il'in, and Michael Siegel
Title Superconducting single-photon counting system for optical experiments requiring time-resolution in the picosecond range Type (up) Journal Article
Year 2012 Publication Abbreviated Journal AIP REVIEW OF SCIENTIFIC INSTRUMENTS
Volume 83 Issue Pages
Keywords SSPD, picosecond, time-resolution
Abstract We have developed a cryogenic measurement system for single-photon counting, which can be used

in optical experiments requiring high time resolution in the picosecond range. The system utilizes

niobium nitride superconducting nanowire single-photon detectors which are integrated in a timecorrelated

single-photon counting (TCSPC) setup. In this work, we describe details of the mechanical

design, the electrical setup, and the cryogenic optical components. The performance of the complete

system in TCSPC mode is tentatively benchmarked using 140 fs long laser pulses at a repetition

frequency of 75MHz. Due to the high temporal stability of these pulses, the measured time resolution

of 35 ps (FWHM) is limited by the timing jitter of the measurement system. The result was crosschecked

in a Coherent Anti-stokes Raman Scattering (CARS) setup, where scattered pulses from a

β-barium borate crystal have been detected with the same time resolution.
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Call Number RPLAB @ seleznev @ Serial 885
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Author Sahu, Mitrabhanu; Bae, Myung-Ho; Rogachev, Andrey; Pekker, David; Wei, Tzu-Chieh; Shah, Nayana; Goldbart, Paul M.; Bezryadin, Alexey
Title Individual topological tunnelling events of a quantum field probed through their macroscopic consequences Type (up) Journal Article
Year 2009 Publication Nature Phys. Abbreviated Journal Nature Phys.
Volume 5 Issue Pages 503-508
Keywords phase slips, superconducting nanowires
Abstract Phase slips are topological fluctuations that carry the superconducting order-parameter field between distinct current-carrying states. Owing to these phase slips, superconducting nanowires acquire electrical resistance. In such wires, it is well known that at higher temperatures phase slips occur through the process of thermal barrier-crossing by the order-parameter field. At low temperatures, the general expectation is that phase slips should proceed through quantum tunnelling events, which are known as quantum phase slips. However, resistive measurements have produced evidence both for and against the occurrence of quantum phase slips. Here, we report evidence for the observation of individual quantum phase-slip events in homogeneous ultranarrow wires at high bias currents. We accomplish this through measurements of the distribution of switching currents for which the width exhibits a rather counter-intuitive, monotonic increase with decreasing temperature. Importantly, measurements show that in nanowires with larger critical currents, quantum fluctuations dominate thermal fluctuations up to higher temperatures.
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Notes Recommended by Klapwijk Approved no
Call Number Serial 928
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Author Kerr, A. R.; Feldman, M. J.; Pan, S.-K.
Title Receiver noise temperature, the quantum noise limit, and the role of the zero-point fluctuations Type (up) Journal Article
Year 1996 Publication Electronics division internal report NO. 304 Abbreviated Journal
Volume Issue Pages 1-10
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Call Number RPLAB @ atomics90 @ Serial 947
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Author Shurakov, A.; Tong, Cheuk-yu E.; Grimes, P.; Blundell, R.; Golt'sman, G.
Title A microwave reflection readout scheme for hot electron bolometric direct detector Type (up) Journal Article
Year 2015 Publication IEEE Trans. THz Sci. Technol. Abbreviated Journal IEEE Trans. THz Sci. Technol.
Volume 5 Issue Pages 81-84
Keywords HEB detectors
Abstract In this paper, we propose and present data from a fast THz detector based on the repurpose of hot electron bolometer mixers (HEB) fabricated from superconducting NbN thinfilm. This detector is essentially a traditional NbN bolometer element that operates under the influence of a microwave pump. The in-jected microwave power serves the dual purpose of enhancing the detector sensitivity and reading out the impedance changes of the device in response to incidentTHz radiation. We have measured an optical Noise Equivalent Power of 4 pW/ Hz for our detector at a bath temperature of 4.2 K. The measurement frequency was 0.83 THz and the modulation frequency was 1.48 kHz. The readout

scheme is versatile and facilitates both high-speed operation as well as multi-pixel applications.
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Call Number RPLAB @ atomics90 @ Serial 950
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Author Trifonov, A.; Tong, C.-Y. E.; Blundell, R.; Ryabchun, S.; Gol'tsman, G.
Title Probing the stability of HEB mixers with microwave injection Type (up) Journal Article
Year 2015 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 25 Issue 3 Pages 2300404 (1 to 4)
Keywords NbN HEB mixer, stability, Allan-variance
Abstract Using a microwave probe as a tool, we have performed experiments aimed at understanding the origin of the output-power fluctuations in hot-electron-bolometer (HEB) mixers. We use a probe frequency of 1.5 GHz. The microwave probe picks up impedance changes of the HEB, which are examined upon demodulation of the reflected wave outside the cryostat. This study shows that the HEB mixer operates in two different regimes under a terahertz pump. At a low pumping level, strong pulse modulation is observed, as the device switches between the superconducting state and the normal state at a rate of a few megahertz. When pumped much harder, to approximate the low-noise mixer operating point, residual modulation can still be observed, showing that the HEB mixer is intrinsically unstable even in the resistive state. Based on these observations, we introduced a low-frequency termination to the HEB mixer. By terminating the device in a 50-Ω resistor in the megahertz frequency range, we have been able to improve the output-power Allan time of our HEB receiver by a factor of four to about 10 s for a detection bandwidth of 15 MHz, with a corresponding gain fluctuation of about 0.035%.
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ISSN 1051-8223 ISBN Medium
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Call Number Serial 1355
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Author Meledin D.; Desmaris V.; Ferm S.-E.; Fredrixon M.; Henke D.; Lapkin I.; Nyström O.; Pantaleev M.; Pavolotsky A.; Strandberg M.; Sundin E.; Belitsky V.
Title APEX Band T2: A 1.25 – 1.39 THz Waveguide Balanced HEB Receiver Type (up) Journal Article
Year 2008 Publication Abbreviated Journal
Volume Issue Pages 181-185
Keywords
Abstract A waveguide 1.25–1.39 THz Hot Electron Bolometer (HEB) balanced receiver was successfully developed, characterized and installed at the Atacama Pathfinder EXperiment (APEX) telescope. The receiver employs a quadrature balanced scheme using a waveguide 90-degree 3 dB RF hybrid, HEB mixers and a 180-degree IF hybrid. The HEB mixers are based on ultrathin NbN film deposited on crystalline quartz with a MgO buffer layer. Integrated into the multi-channel APEX facility receiver (SHeFI), the results presented here demonstrate exceptional performance; a receiver noise temperature of 1000 K measured at the telescope at the center of the receiver IF band 2-4 GHz, and at an LO frequency of 1294 GHz. Stability of the receiver is fully in line with the SIS mixer bands of the SHeFI, and gives a spectroscopic Allan time of more than 200 s with a noise bandwidth of 1 MHz.
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Call Number RPLAB @ atomics90 @ Serial 974
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Author Gershenzon, E. M.; Il'in, V. A.; Litvak-Gorskaya, L. B.; Filonovich, S. R.
Title Character of submillimeter photoconductivity in n-lnSb Type (up) Journal Article
Year 1979 Publication Sov. Phys. JETP Abbreviated Journal Sov. Phys. JETP
Volume 49 Issue 1 Pages 121-128
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Abstract A comprehensive investigation was made of the submillimeter photoconductivity of n -1nSb in the range of wavelengths L = 0.6-8 mm, magnetic fields H = 0-30 kOe, electric fields E = 0.01-0.5 V/cm, and temperatures T = 1.3-30 K. The kinetics of the photoconductivity processes as a function of T, E; and H is investigated. It is shown that impurity photoconductivity does exist for any degree of compensation of extremely purified n-InSb. Particular attention is paid to the hopping photoconductivity realized in strongly compensated n-1nSb (K > 0.8).
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Call Number RPLAB @ phisix @ Serial 985
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