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Author Takesue, Hiroki; Dyer, Shellee D.; Stevens, Martin J.; Verma, Varun; Mirin, Richard P.; Nam, Sae Woo
Title (down) Quantum teleportation over 100 km of fiber using highly efficient superconducting nanowire single-photon detectors Type Journal Article
Year 2015 Publication Abbreviated Journal Optica
Volume 2 Issue Pages
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Abstract Quantum teleportation is an essential quantum operation by which we can transfer an unknown quantum state to a remote location with the help of quantum entanglement and classical communication. Since the first experimental demonstrations using photonic qubits and continuous variables, the distance of photonic quantum teleportation over free-space channels has continued to increase and has reached >100 km. On the other hand, quantum teleportation over optical fiber has been challenging, mainly because the multifold photon detection that inevitably accompanies quantum teleportation experi- ments has been very inefficient due to the relatively low de- tection efficiencies of typical telecom-band single-photon detectors. Here, we report on quantum teleportation over optical fiber using four high-detection-efficiency supercon- ducting nanowire single-photon detectors (SNSPDs). These SNSPDs make it possible to perform highly efficient multi- fold photon measurements, allowing us to confirm that the quantum states of input photons were successfully tele- ported over 100 km of fiber with an average fidelity of 83.7  2.0%.
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Call Number RPLAB @ alex_kazakov @ Serial 1004
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Author Takemoto, K.; Nambu, Y.; Miyazawa, T.; Sakuma, Y.; Yamamoto, T.; Yorozu, S.; Arakawa, Y.
Title (down) Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors Type Journal Article
Year 2015 Publication Sci. Rep. Abbreviated Journal
Volume 5 Issue Pages 14383
Keywords SSPD, SNSPD applications, quantum key distribution, QKD
Abstract Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD). At the distance of 100 km, we obtained the maximal secure key rate of 27.6 bps without using decoy states, which is at least threefold larger than the rate obtained in the previously reported 50-km-long QKD experiment. We also succeeded in transmitting secure keys at the rate of 0.307 bps over 120 km. This is the longest QKD distance yet reported by using known true SPSs. The ultralow multiphoton emissions of our SPS and ultralow dark count of the SNSPD contributed to this result. The experimental results demonstrate the potential applicability of QD SPSs to practical telecom QKD networks.
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Notes Approved no
Call Number Serial 1104
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Author Trifonov, A.; Tong, C.-Y. E.; Blundell, R.; Ryabchun, S.; Gol'tsman, G.
Title (down) Probing the stability of HEB mixers with microwave injection Type 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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Notes Approved no
Call Number Serial 1355
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Author Beck, M.; Klammer, M.; Rousseau, I.; Gol’tsman, G. N.; Diamant, I.; Dagan, Y.; Demsar, J.
Title (down) Probing superconducting gap dynamics with THz pulses Type Conference Article
Year 2015 Publication CLEO Abbreviated Journal CLEO
Volume Issue Pages SM3H.3 (1 to 2)
Keywords superconducting gap; electric fields; femtosecond pulses; near infrared radiation; picosecond pulses; superconductors; thin films
Abstract We studied superconducting gap dynamics in a BCS superconductor NbN and electron doped cuprate superconductor PCCO following excitation with near-infrared (NIR) and narrow band THz pulses. Systematic studies on PCCO imply very selective electron-phonon coupling.
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Publisher Optical Society of America Place of Publication Editor
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Notes Approved no
Call Number Serial 1345
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Author Anosov, A. A.; Nemchenko, O. Yu.; Less, Yu. A.; Kazanskii, A. S.; Mansfel'd, A. D.
Title (down) Possibilities of acoustic thermometry for controlling targeted drug delivery Type Journal Article
Year 2015 Publication Acoust. Phys. Abbreviated Journal
Volume 61 Issue 4 Pages 488-493
Keywords acoustic thermometry, liposome suspension, thermography
Abstract Model acoustic thermometry experiments were conducted during heating of an aqueous liposome suspension. Heating was done to achieve the liposome phase transition temperature. At the moment of the phase transition, the thermal acoustic signal achieved a maximum and decreased, despite continued heating. During subsequent cooling of the suspension, when lipids again passed through the phase transition point, the thermal acoustic signal again increased, despite a reduction in temperature. This effect is related to an increase in ultrasound absorption by the liposome suspension at the moment of the lipid phase transition. The result shows that acoustic thermography can be used to control targeted delivery of drugs mixed in thermally sensitive liposomes, the integrity of which is violated during heating to the phase transition temperature.
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Notes Approved no
Call Number Serial 1130
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