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Author Stevens, Martin J.; Baek, Burm; Dauler, Eric A.; Kerman, Andrew J.; Molnar, Richard J.; Hamilton, Scott A.; Berggren, Karl K.; Mirin, Richard P.; Nam, Sae Woo
Title High-order temporal coherences of
chaotic and laser light Type Journal Article
Year 2010 Publication Optics Express Abbreviated Journal Opt. Express
Volume 18 Issue 2 Pages 1430-1437
Keywords (down) SNSPD
Abstract We demonstrate a new approach to measuring high-order temporal coherences that uses a four-element superconducting nanowire single-photon detector. The four independent, interleaved single-photon-sensitive elements parse a single spatial mode of an optical beam over dimensions smaller than the minimum diffraction-limited spot size. Integrating this device with four-channel time-tagging electronics to generate multi-start, multi-stop histograms enables measurement of temporal coherences up to fourth order for a continuous range of all associated time delays. We observe high-order photon bunching from a chaotic, pseudo-thermal light source, measuring maximum third- and fourth-order coherence values of 5.87 ± 0.17 and 23.1 ± 1.8, respectively, in agreement with the theoretically predicted values of 3! = 6 and 4! = 24. Laser light, by contrast, is confirmed to have coherence values of approximately 1 for second, third and fourth orders at all time delays.
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Notes SSPD Approved no
Call Number RPLAB @ gujma @ Serial 685
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Author Gupta, D.; Kadin, A. M.
Title Single-photon-counting hotspot detector with integrated RSFQ readout electronics Type Journal Article
Year 1999 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume 9 Issue 2 Pages 4487-4490
Keywords (down) RSFQ, SSPD, SNSPD
Abstract Absorption of an infrared photon in an ultrathin film (such as 10-nm NbN) creates a localized nonequilibrium hotspot on the submicron length scale and sub-ns time scale. If a strip /spl sim/1 /spl mu/m wide is biased in the middle of the superconducting transition, this hotspot will lead to a resistance pulse with amplitude proportional to the energy of the incident photon. This resistance pulse, in turn, can be converted to a current pulse and inductively coupled to a SQUID amplifier with a digitized output, operating at 4 K or above. A preliminary design analysis indicates that this data can be processed on-chip, using ultrafast RSFQ digital circuits, to obtain a sensitive infrared detector for wavelengths up to 10 /spl mu/m and beyond, with bandwidth of 1 GHz, that counts individual photons and measures their energy with 25 meV resolution. This proposed device combines the speed of a hot-electron bolometer with the single-photon-counting ability of a transition-edge microcalorimeter, to obtain an infrared detector with sensitivity, speed, and spectral selectivity that are unmatched by any alternative technology.
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Call Number Serial 1080
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Author Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim
Title Thermal blinding of gated detectors in quantum cryptography Type Journal Article
Year 2010 Publication Optics Express Abbreviated Journal Opt. Express
Volume 18 Issue 26 Pages 27938-27954
Keywords (down) quantum cryptography; QKD; hacking; SPD; APD
Abstract It has previously been shown that the gated detectors of two commercially available quantum key distribution (QKD) systems are blindable and controllable by an eavesdropper using continuous-wave illumination and short bright trigger pulses, manipulating voltages in the circuit [L. Lydersen et al., Nat. Photonics DOI:10.1038/nphoton.2010.214]. This allows for an attack eavesdropping the full raw and secret key without increasing the quantum bit error rate (QBER). Here we show how thermal effects in detectors under bright illumination can lead to the same outcome. We demonstrate that the detectors in a commercial QKD system Clavis2 can be blinded by heating the avalanche photo diodes (APDs) using bright illumination, so-called thermal blinding. Further, the detectors can be triggered using short bright pulses once they are blind. For systems with pauses between packet transmission such as the plug-and-play systems, thermal inertia enables Eve to apply the bright blinding illumination before eavesdropping, making her more difficult to catch.
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Call Number RPLAB @ gujma @ Serial 729
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Author Wiechers, C.; Lydersen, L.; Wittmann, C.; Elser, D.; Skaar, J.; Marquardt, Ch; Makarov, V.; Leuchs, G.
Title After-gate attack on a quantum cryptosystem Type Journal Article
Year 2011 Publication New J. Phys. Abbreviated Journal
Volume 13 Issue 1 Pages 14
Keywords (down) quantum cryptography; hacking; interception; attack; SPD; APD; QKD
Abstract We present a method to control the detection events in quantum key distribution systems that use gated single-photon detectors. We employ bright pulses as faked states, timed to arrive at the avalanche photodiodes outside the activation time. The attack can remain unnoticed, since the faked states do not increase the error rate per se. This allows for an intercept-resend attack, where an eavesdropper transfers her detection events to the legitimate receiver without causing any errors. As a side effect, afterpulses, originating from accumulated charge carriers in the detectors, increase the error rate. We have experimentally tested detectors of the system id3110 (Clavis2) from ID Quantique. We identify the parameter regime in which the attack is feasible despite the side effect. Furthermore, we outline how simple modifications in the implementation can make the device immune to this attack.
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Call Number RPLAB @ gujma @ Serial 730
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Author Takesue, Hiroki; Nam, Sae Woo; Zhang, Qiang; Hadfield, Robert H.; Honjo, Toshimori; Tamaki, Kiyoshi; Yamamoto, Yoshihisa
Title Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors Type Journal Article
Year 2007 Publication Nature Photonics Abbreviated Journal Nat. Photon.
Volume 1 Issue Pages 343-348
Keywords (down) quantum cryptography, SSPD, QKD, DSP
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Call Number RPLAB @ akorneev @ Serial 609
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