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Author |
Gustafsson, Martin V.; Santos, Paulo V.; Johansson, Göran; Delsing, Per |
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Title |
Local probing of propagating acoustic waves in a gigahertz echo chamber |
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Journal Article |
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2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
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4 |
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338-343 |
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In the same way that micro-mechanical resonators resemble guitar strings and drums, surface acoustic waves resemble the sound these instruments produce, but moving over a solid surface rather than through air. In contrast with oscillations in suspended resonators, such propagating mechanical waves have not before been studied near the quantum mechanical limits. Here, we demonstrate local probing of surface acoustic waves with a displacement sensitivity of 30amRMSHz-1/2 and detection sensitivity on the single-phonon level after averaging, at a frequency of 932MHz. Our probe is a piezoelectrically coupled single-electron transistor, which is sufficiently fast, non-destructive and localized to enable us to track pulses echoing back and forth in a long acoustic cavity, self-interfering and ringing the cavity up and down. We project that strong coupling to quantum circuits will enable new experiments, and hybrids using the unique features of surface acoustic waves. Prospects include quantum investigations of phonon-phonon interactions, and acoustic coupling to superconducting qubits for which we present favourable estimates. |
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RPLAB @ gujma @ |
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813 |
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Korotkov, Alexander N. |
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Title |
Entanglement preservation: The Sleeping Beauty approach |
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Journal Article |
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2012 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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8 |
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2 |
Pages |
107-108 |
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Two-qubit entanglement can be preserved by partially measuring the qubits to leave them in a 'lethargic' state. The original state is restored using quantum measurement reversal after the qubits have travelled through a decoherence channel. |
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RPLAB @ gujma @ |
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814 |
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Author |
Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho |
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Title |
Protecting entanglement from decoherence using weak measurement and quantum measurement reversal |
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Journal Article |
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2012 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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8 |
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2 |
Pages |
117-120 |
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fromIPMRAS |
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Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death. |
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RPLAB @ gujma @ |
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815 |
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Bason, Mark G.; Viteau, Matthieu; Malossi, Nicola; Huillery, Paul; Arimondo, Ennio; Ciampini, Donatella; Fazio, Rosario; Giovannetti, Vittorio; Mannella, Riccardo; Morsch, Oliver |
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Title |
High-fidelity quantum driving |
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Journal Article |
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2012 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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8 |
Issue |
2 |
Pages |
147-152 |
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fromIPMRAS |
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Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experimental constraints. Here we experimentally implement two optimal high-fidelity control protocols using a two-level quantum system comprising Bose-Einstein condensates in optical lattices. The first is a short-cut protocol that reaches the maximum quantum-transformation speed compatible with the Heisenberg uncertainty principle. In the opposite limit, we realize the recently proposed transitionless superadiabatic protocols in which the system follows the instantaneous adiabatic ground state nearly perfectly. We demonstrate that superadiabatic protocols are extremely robust against control parameter variations, making them useful for practical applications. |
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RPLAB @ gujma @ |
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816 |
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Shurakov, Alexander; Tong, Edward; Blundell, Raymond; Gol'tsman, Gregory |
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Title |
Microwave stabilization of HEB mixer by a microchip controller |
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Conference Article |
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2012 |
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IEEE MTT-S international microwave symposium digest |
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1-3 |
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HEB mixer stability, microwave injection, Allan variance, Allan time |
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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. |
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Montreal, QC, Canada |
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857 |
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Henrich, D.; Dorner,S.; Hofherr, M.; Il'in, K.; Semenov, A.; Heintze, E.; Scheffler, M.; Dressel, M.; Siegel, M. |
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Title |
Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content |
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Journal Article |
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Year |
2012 |
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J. Appl. Phys. |
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112 |
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SSPD, SNSPD, magnetron sputtering, spectrum, NbN film, nitrogen concentration |
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The spectral detection efficiency and the dark count rate of superconducting nanowire
single-photon detectors (SNSPD) have been studied systematically on detectors made from thin
NbN films with different chemical compositions. Reduction of the nitrogen content in the 4 nm
thick NbN films results in a decrease of the dark count rates more than two orders of magnitude
and in a red shift of the cut-off wavelength of the hot-spot SNSPD response. The observed
phenomena are explained by an improvement of uniformity of NbN films that has been confirmed
by a decrease of resistivity and an increase of the ratio of the measured critical current to the
depairing current. The latter factor is considered as the most crucial for both the cut-off
wavelength and the dark count rates of SNSPD. Based on our results we propose a set of criteria
for material properties to optimize SNSPD in the infrared spectral region. VC 2012 American
Institute of Physics. [http://dx.doi.org/10.1063/1.4757625] |
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D. Henrich, S. Dorner, M. Hofherr, K. Il'in, A. Semenov, E. Heintze, M. Scheffler, M. Dressel, M. Siegel |
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Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content |
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RPLAB @ seleznev @ |
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877 |
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Author |
Inderbitzin, K.; Engel, A.; Schilling, A.; Il'in, K.; Siegel, M. |
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An ultra-fast superconducting Nb nanowire single-photon detector for soft x-rays |
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Journal Article |
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2012 |
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Appl. Phys. Lett. |
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101 |
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SSPD, SNSPD, x-ray, Nb |
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Although superconducting nanowire single-photon detectors (SNSPDs) are well studied regarding the
detection of infrared/optical photons and keV-molecules, no studies on continuous x-ray photon
counting by thick-film detectors have been reported so far. We fabricated a 100 nm thick niobium
x-ray SNSPD (an X-SNSPD) and studied its detection capability of photons with keV-energies in
continuous mode. The detector is capable to detect photons even at reduced bias currents of 0.4%,
which is in sharp contrast to optical thin-film SNSPDs. No dark counts were recorded in extended
measurement periods. Strikingly, the signal amplitude distribution depends significantly on the photon
energy spectrum.VC |
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RPLAB @ seleznev @ |
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878 |
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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 |
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Superconducting single-photon counting system for optical experiments requiring time-resolution in the picosecond range |
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Journal Article |
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2012 |
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AIP REVIEW OF SCIENTIFIC INSTRUMENTS |
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83 |
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SSPD, picosecond, time-resolution |
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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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RPLAB @ seleznev @ |
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885 |
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Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. |
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Title |
Evanescent states and nonequilibrium in driven superconducting nanowires |
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Journal Article |
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2012 |
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Phys. Rev. B |
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Phys. Rev. B |
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85 |
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224503(1-10) |
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Al HEB, Al superconducting nanowire, global state, bimodal state, quasiclassical kinetic equations, Usadel equation |
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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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898 |
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Pütz, P.; Honingh, C. E.; Jacobs, K.; Justen, M.; Schultz, M.; Stutzki, J. |
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Title |
Terahertz hot electron bolometer waveguide mixers for GREAT |
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Journal Article |
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2012 |
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Astron. Astrophys. |
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A&A |
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542 |
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L2 |
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HEB mixer, applications |
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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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