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Author |
Gabay, Marc; Triscone, Jean-Marc |
Title |
Superconductors: Terahertz superconducting switch |
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Journal Article |
Year |
2011 |
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Nature Photonics |
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Nat. Photon. |
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5 |
Issue |
8 |
Pages |
447-449 |
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fromIPMRAS |
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The use of terahertz pulses to 'gate' interlayer charge transport in a superconductor could lead to a variety of new and interesting applications. |
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RPLAB @ gujma @ |
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777 |
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Author |
Vishveshwara, Smitha |
Title |
Topological qubits: A bit of both |
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Journal Article |
Year |
2011 |
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Nature Physics |
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Nat. Phys. |
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7 |
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450–451 |
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fromIPMRAS |
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'Standard' qubits have been implemented in diverse physical systems. Now, so-called topological qubits are coming into the limelight, and could potentially be used for decoherence-free quantum computing. Coupling these two types of qubit might enable devices that exploit the virtues of both. |
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RPLAB @ gujma @ |
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825 |
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Manova, N. N.; Korneeva, Yu. P.; Korneev, A. A.; Slysz, W.; Voronov, B. M.; Gol'tsman, G. N. |
Title |
Superconducting NbN single-photon detector integrated with quarter-wave resonator |
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Journal Article |
Year |
2011 |
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Tech. Phys. Lett. |
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Tech. Phys. Lett. |
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37 |
Issue |
5 |
Pages |
469-471 |
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SSPD, SNSPD |
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The spectral dependence of the quantum efficiency of superconducting NbN single-photon detectors integrated with quarter-wave resonators based on Si3N4, SiO2, and SiO layers has been studied. |
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RPLAB @ gujma @ |
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664 |
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Lee, B. G.; Assefa, S.; Green, W. M. J.; Min Yang; Schow, C. L.; Jahnes, C. V.; Sheng Zhang; Singer, J.; Kopp, V. I.; Kash, J. A.; Vlasov, Y. A. |
Title |
Multichannel high-bandwidth coupling of ultradense silicon photonic waveguide array to standard-pitch fiber array |
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Journal Article |
Year |
2011 |
Publication |
J. Lightwave Technol. |
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29 |
Issue |
4 |
Pages |
475-482 |
Keywords |
optical waveguides, from chiralphotonics |
Abstract |
A multichannel tapered coupler interfacing standard 250-μm-pitch low-numerical-aperture (NA) polarization-maintaining fiber arrays with ultradense 20- μm-pitch high-NA silicon waveguides is designed and fabricated. The coupler is based on an array of 12 dual-core glass waveguides on 250-μ m pitch that are tapered to a 20- μm pitch, simultaneously providing both pitch and spot-size conversion. At the wide end, the inner core matches the NA and mode profile of standard single-mode fiber. When drawn and tapered, the inner core “vanishes†and the outer core, surrounded by the clad, matches the NA and mode profile of the on-chip photonic waveguide. Ultradense high-efficiency coupling to an array of Si photonic waveguides is demonstrated using a 12-channel polarization-maintaining-fiber pigtailed tapered coupler. Coupling to Si waveguides is facilitated using SiON spot-size converters integrated into the Si photonic IC to provide 2-3-μm mode field diameters compatible with the tapered coupler. The tapered coupler achieves <; 1 dB coupling losses to photonic waveguides. Furthermore, eight-channel coupling is shown with less than -35 dB crosstalk between channels. Finally, a 640-Gb/s wavelength-division-multiplexing signal is coupled into four waveguides occupying 80 μm of chip edge, providing 160-Gb/s per-channel bandwidths. |
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849 |
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Author |
Biercuk, Michael J. |
Title |
A quantum spectrum analyser |
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Journal Article |
Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
Volume |
7 |
Issue |
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Pages |
525–526 |
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fromIPMRAS |
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Noise filters based on so-called dynamical decoupling pulse sequences can suppress decoherence in quantum systems. Turning this idea on its head now provides a new technique for studying the noise itself. |
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RPLAB @ gujma @ |
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826 |
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Bylander, Jonas; Gustavsson, Simon; Yan, Fei; Yoshihara, Fumiki; Harrabi, Khalil; Fitch, George; Cory, David G.; Nakamura, Yasunobu; Tsai, Jaw-Shen; Oliver, William D. |
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Noise spectroscopy through dynamical decoupling with a superconducting flux qubit |
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Journal Article |
Year |
2011 |
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Nature Physics |
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Nat. Phys. |
Volume |
7 |
Issue |
7 |
Pages |
565-570 |
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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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RPLAB @ gujma @ |
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829 |
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Author |
Billangeon, P.-M.; Nakamura, Y. |
Title |
Superconducting devices: Quantum cups and balls |
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Journal Article |
Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
Volume |
7 |
Issue |
8 |
Pages |
594-595 |
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fromIPMRAS |
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A single microwave photon in a superposition of two states of different frequency is now demonstrated using a superconducting quantum interference device to mediate the coupling between two harmonics of a resonator. Such quantum circuits bring closer the possibility of controlling photon-photon interactions at the single-photon level. |
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RPLAB @ gujma @ |
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820 |
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Zakka-Bajjani, Eva; Nguyen, François; Lee, Minhyea; Vale, Leila R.; Simmonds, Raymond W.; Aumentado, José |
Title |
Quantum superposition of a single microwave photon in two different 'colour' states |
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Journal Article |
Year |
2011 |
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Nature Physics |
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Nat. Phys. |
Volume |
7 |
Issue |
8 |
Pages |
599-603 |
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fromIPMRAS |
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Fully controlled coherent coupling of arbitrary harmonic oscillators is an important tool for processing quantum information. Coupling between quantum harmonic oscillators has previously been demonstrated in several physical systems using a two-level system as a mediating element. Direct interaction at the quantum level has only recently been realized by means of resonant coupling between trapped ions. Here we implement a tunable direct coupling between the microwave harmonics of a superconducting resonator by means of parametric frequency conversion. We accomplish this by coupling the mode currents of two harmonics through a superconducting quantum interference device (SQUID) and modulating its flux at the difference (~7GHz) of the harmonic frequencies. We deterministically prepare a single-photon Fock state and coherently manipulate it between multiple modes, effectively controlling it in a superposition of two different 'colours'. This parametric interaction can be described as a beamsplitter-like operation that couples different frequency modes. As such, it could be used to implement linear optical quantum computing protocols on-chip. |
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RPLAB @ gujma @ |
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822 |
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Tretyakov, Ivan; Ryabchun, Sergey; Finkel, Matvey; Maslennikov, Sergey; Maslennikova, Anna; Kaurova, Natalia; Lobastova, Anastasia; Voronov, Boris; Gol'tsman, Gregory |
Title |
Ultrawide noise bandwidth of NbN hot-electron bolometer mixers with in situ gold contacts |
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Journal Article |
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2011 |
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IEEE Trans. Appl. Supercond. |
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21 |
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3 |
Pages |
620-623 |
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NbN HEB mixer bandwidth |
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We report a noise bandwidth of 7 GHz in the new generation of NbN hot-electron bolometer (HEB) mixers that are being developed for the space observatory Millimetron. The HEB receiver driven by a 2.5-THz local oscillator offered a noise temperature of 600 K in a 50-MHz final detection bandwidth. As the filter center frequency was swept this value remained nearly constant up to the cutoff frequency of the cryogenic amplifier at 7 GHz. We believe that such a low value of the noise temperature is due to reduced radio frequency (RF) loss at the interface between the superconducting film and the gold contacts. We have also performed gain bandwidth measurements at the superconducting transition on HEB mixers with various lengths and found them to be in excellent agreement with the results of the analytical and numerical models developed for the HEB mixer with both diffusion and phonon cooling of hot electrons. |
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RPLAB @ gujma @ |
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716 |
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Lobanov, Y.; Tong, E.; Blundell, R.; Hedden, A.; Voronov, B.; Gol'tsman, G. |
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Large-signal frequency response of an HEB mixer: from 300 MHz to terahertz |
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2011 |
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IEEE Trans. Appl. Supercond. |
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21 |
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3 |
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628-631 |
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waveguide NbN HEB mixers |
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We present a study of the large signal frequency response of an HEB mixer over a wide frequency range. In our experiments, we have subjected the HEB mixer to incident electromagnetic radiation from 0.3 GHz to 1 THz. The mixer element is an NbN film deposited on crystalline quartz. The mixer chip is mounted in a waveguide cavity, coupled to free space with a diagonal horn. At microwave frequencies, electromagnetic radiation is applied through the coaxial bias port of the mixer block. At higher frequencies the input signal passes via the diagonal horn feed. At each frequency, the incident power is varied and a family of I-V curves is recorded. From the curves we identify 3 distinct regimes of operation of the mixer separated by the phonon relaxation frequency and the superconducting energy gap frequency observed at about 3 GHz and 660 GHz respectively. In this paper, we will present observed curves and discuss the results of our experiment. |
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RPLAB @ gujma @ |
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719 |
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