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Author Tol, J. van; Brunel, L.-C.; Wylde, R. J.
Title A quasioptical transient electron spin resonance spectrometer operating at 120 and 240 GHz Type Journal Article
Year 2005 Publication Rev. Sci. Instrum. Abbreviated Journal Rev. Sci. Instrum.
Volume 76 Issue (up) 7 Pages 074101 (1 to 8)
Keywords Schottky, noise temperature
Abstract A new multifrequency quasioptical electron paramagnetic resonance (EPR) spectrometer is described. The superheterodyne design with Schottky diode mixer/detectors enables fast detection with subnanosecond time resolution. Optical access makes it suitable for transient EPR (TR-EPR) at 120 and 240 GHz. These high frequencies allow for an accurate determination of small g-tensor anisotropies as are encountered in excited triplet states of organic molecules like porphyrins and fullerenes. The measured concentration sensitivity for continuous-wave (cw) EPR at 240 GHz and at room temperature without cavity is 1013 spins/cm3 (15 nM) for a 1 mT linewidth and a 1 Hz bandwidth. With a Fabry-Perot cavity and a sample volume of 30 nl, the sensitivity at 240 GHz corresponds to [approximate]3×109 spins for a 1 mT linewidth. The spectrometer's performance is illustrated with applications of transient EPR of excited triplet states of organic molecules, as well as cw EPR of nitroxide reference systems and a thin film of a colossal magnetoresistance material.
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Notes Actually, noise spectral density is given (3e-19 W/Hz) Approved no
Call Number Serial 588
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Author Ursin, R.; Tiefenbacher, F.; Schmitt-Manderbach, T.; Weier, H.; Scheidl, T.; Lindenthal, M.; Blauensteiner, B.; Jennewein, T.; Perdigues, J.; Trojek, P.; Ömer, B.; Fürst, M.; Meyenburg, M.; Rarity, J.; Sodnik, Z.; Barbieri, C.; Weinfurter, H.; Zeilinger, A.
Title Entanglement-based quantum communication over 144km Type Journal Article
Year 2007 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 3 Issue (up) 7 Pages 481-486
Keywords fromIPMRAS
Abstract Quantum entanglement is the main resource to endow the field of quantum information processing with powers that exceed those of classical communication and computation. In view of applications such as quantum cryptography or quantum teleportation, extension of quantum-entanglement-based protocols to global distances is of considerable practical interest. Here we experimentally demonstrate entanglement-based quantum key distribution over 144km. One photon is measured locally at the Canary Island of La Palma, whereas the other is sent over an optical free-space link to Tenerife, where the Optical Ground Station of the European Space Agency acts as the receiver. This exceeds previous free-space experiments by more than an order of magnitude in distance, and is an essential step towards future satellite-based quantum communication and experimental tests on quantum physics in space.
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Call Number RPLAB @ gujma @ Serial 797
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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 Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 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 Jiang, Ling; Miao, Wei; Zhang, Wen; Li, Ning; Lin, Zhen Hui; Yao, Qi Jun; Shi, Sheng-Cai; Svechnikov, S. I.; Vakhtomin, Y. B.; Antipov, S. V.; Voronov, B. M.; Kaurova, N. S.; Gol'tsman, G. N.
Title Characterization of a quasi-optical NbN superconducting HEB mixer Type Journal Article
Year 2006 Publication IEEE Trans. Microwave Theory Techn. Abbreviated Journal IEEE Trans. Microwave Theory Techn.
Volume 54 Issue (up) 7 Pages 2944-2948
Keywords NbN HEB mixers
Abstract In this paper, the performance of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer, cryogenically cooled by a close-cycled 4-K refrigerator, is thoroughly investigated at 300, 500, and 850 GHz. The lowest receiver noise temperatures measured at the respective three frequencies are 1400, 900, and 1350 K, which can go down to 659, 413, and 529 K, respectively, after correcting the loss and associated noise contribution of the quasi-optical system before the measured superconducting HEB mixer. The stability of the quasi-optical superconducting HEB mixer is also investigated here. The Allan variance time measured with a local oscillator pumping at 500 GHz and an IF bandwidth of 110 MHz is 1.5 s at the dc-bias voltage exhibiting the lowest noise temperature and increases to 2.5 s at a dc bias twice that voltage.
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ISSN 0018-9480 ISBN Medium
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Notes Approved no
Call Number Serial 1448
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Author Lindgren, M.; Currie, M.; Zeng, W.-S.; Sobolewski, R.; Cherednichenko, S.; Voronov, B.; Gol'tsman, G. N.
Title Picosecond response of a superconducting hot-electron NbN photodetector Type Journal Article
Year 1998 Publication Appl. Supercond. Abbreviated Journal Appl. Supercond.
Volume 6 Issue (up) 7-9 Pages 423-428
Keywords NbN SSPD, SNSPD
Abstract The ps optical response of ultrathin NbN photodetectors has been studied by electro-optic sampling. The detectors were fabricated by patterning ultrathin (3.5 nm thick) NbN films deposited on sapphire by reactive magnetron sputtering into either a 5×10 μm2 microbridge or 25 1 μm wide, 5 μm long strips connected in parallel. Both structures were placed at the center of a 4 mm long coplanar waveguide covered with Ti/Au. The photoresponse was studied at temperatures ranging from 2.15 K to 10 K, with the samples biased in the resistive (switched) state and illuminated with 100 fs wide laser pulses at 395 nm wavelength. At T=2.15 K, we obtained an approximately 100 ps wide transient, which corresponds to a NbN detector response time of 45 ps. The photoresponse can be attributed to the nonequilibrium electron heating effect, where the incident radiation increases the temperature of the electron subsystem, while the phonons act as the heat sink. The high-speed response of NbN devices makes them an excellent choice for an optoelectronic interface for superconducting digital circuits, as well as mixers for the terahertz regime. The multiple-strip detector showed a linear dependence on input optical power and a responsivity =3.9 V/W.
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ISSN 0964-1807 ISBN Medium
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Notes Approved no
Call Number Serial 1584
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Author Li, Mo; Pernice, W. H. P.; Xiong, C.; Baehr-Jones, T.; Hochberg, M.; Tang, H. X.
Title Harnessing optical forces in integrated photonic circuits Type Journal Article
Year 2008 Publication Nature Abbreviated Journal Nature
Volume 456 Issue (up) 7221 Pages 480-484
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ISSN 0028-0836 ISBN Medium
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Notes Approved no
Call Number RPLAB @ s @ Serial 425
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Author Rodriguez-Morales, F.; Zannoni, R.; Nicholson, J.; Fischetti, M.; Yngvesson, K. S.; Appenzeller, J.
Title Direct and heterodyne detection of microwaves in a metallic single wall carbon nanotube Type Journal Article
Year 2006 Publication Applied Physics Letters Abbreviated Journal Appl. Phys. Lett.
Volume 89 Issue (up) 8 Pages 083502
Keywords carbon nanotube, GHz heterodyne detector, direct detector
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ISSN 0003-6951 ISBN Medium
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Notes Approved no
Call Number Serial 565
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Author Gabay, Marc; Triscone, Jean-Marc
Title Superconductors: Terahertz superconducting switch Type Journal Article
Year 2011 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 5 Issue (up) 8 Pages 447-449
Keywords fromIPMRAS
Abstract 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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Notes Approved no
Call Number RPLAB @ gujma @ Serial 777
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Author Billangeon, P.-M.; Nakamura, Y.
Title Superconducting devices: Quantum cups and balls Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 8 Pages 594-595
Keywords fromIPMRAS
Abstract 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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Call Number RPLAB @ gujma @ Serial 820
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Author 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 Type Journal Article
Year 2011 Publication Nature Physics Abbreviated Journal Nat. Phys.
Volume 7 Issue (up) 8 Pages 599-603
Keywords fromIPMRAS
Abstract 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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Notes Approved no
Call Number RPLAB @ gujma @ Serial 822
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