| Records |
| Author |
Slysz, W.; Wegrzecki, M.; Bar, J.; Grabiec, P.; Górska, M.; Latta, C.; Zwiller, V.; Pearlman, A.; Cross, A.; Korneev, A.; Kouminov, P.; Smirnov, K.; Voronov, B.; Gol’tsman, G.; Verevkin, A.; Currie, M.; Sobolewski, R. |
| Title |
Fiber-coupled quantum-communications receiver based on two NbN superconducting single-photon detectors |
Type |
Conference Article |
| Year |
2005 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
5957 |
Issue  |
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Pages |
59571K (1 to 10) |
| Keywords |
SSPD, SNSPD, single-photon detectors, quantum communication, quantum cryptography, superconductors, infrared optical detectors |
| Abstract |
We present the design and performance of a novel, two-channel single-photon receiver, based on two fiber-coupled NbN superconducting single-photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders covering an area of 100 μm2 and are known for ultrafast and efficient counting of single, visible-to-infrared photons. Their operation has been explained within a phenomenological hot-electron photoresponse model. Our receiver is intended for fiber-based quantum cryptography and communication systems, operational at near-infrared (NIR) telecommunication wavelengths, λ = 1.3 μm and λ = 1.55 μm. Coupling between the NbN detector and a single-mode optical fiber was achieved using a specially designed, micromechanical photoresist ring, positioned directly over the SSPD active area. The positioning accuracy of the ring was below 1 μm. The receiver with SSPDs was placed (immersed) in a standard liquid-helium transport Dewar and kept without interruption for over two months at 4.2 K. At the same time, the optical fiber inputs and electrical outputs were kept at room temperature. Our best system reached a system quantum efficiency of up to 0.3 % in the NIR radiation range, with the detector coupling efficiency of about 30 %. The response time was measured to be about 250 ps and was limited by our read-out electronics. The measured jitter was close to 35 ps. The presented performance parameters show that our NIR single photon detectors are suitable for practical quantum cryptography and for applications in quantum-correlation experiments. |
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SPIE |
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Editor |
Rogalski, A.; Dereniak, E.L.; Sizov, F.F. |
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Infrared Photoelectronics |
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1459 |
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| Author |
Verevkin, A. A.; Pearlman, A.; Slysz, W.; Zhang, J.; Sobolewski, R.; Chulkova, G.; Okunev, O.; Kouminov, P.; Drakinskij, V.; Smirnov, K.; Kaurova, N.; Voronov, B.; Gol’tsman, G.; Currie, M. |
| Title |
Ultrafast superconducting single-photon detectors for infrared wavelength quantum communications |
Type |
Conference Article |
| Year |
2003 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
5105 |
Issue |
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Pages |
160-170 |
| Keywords |
NbN SSPD, SNSPD, applications, single-photon detector, quantum cryptography, quantum communications, superconducting devices |
| Abstract |
We have developed a new class of superconducting single-photon detectors (SSPDs) for ultrafast counting of infrared (IR) photons for secure quantum communications. The devices are operated on the quantum detection mechanism, based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The detectors are fabricated from 3.5-nm-thick NbN films and they operate at 4.2 K inside a closed-cycle refrigerator or liquid helium cryostat. Various continuous and pulsed laser sources have been used in our experiments, enabling us to determine the detector experimental quantum efficiency (QE) in the photon-counting mode, response time, time jitter, and dark counts. Our 3.5-nm-thick SSPDs reached QE above 15% for visible light photons and 5% at 1.3 – 1.5 μm infrared range. The measured real-time counting rate was above 2 GHz and was limited by the read-out electronics (intrinsic response time is <30 ps). The measured jitter was <18 ps, and the dark counting rate was <0.01 per second. The measured noise equivalent power (NEP) is 2 x 10-18 W/Hz1/2 at λ = 1.3 μm. In near-infrared range, in terms of the counting rate, jitter, dark counts, and overall sensitivity, the NbN SSPDs significantly outperform their semiconductor counterparts. An ultrafast quantum cryptography communication technology based on SSPDs is proposed and discussed. |
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SPIE |
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Donkor, E.; Pirich, A.R.; Brandt, H.E. |
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Quantum Information and Computation |
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no |
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Serial |
1514 |
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Verevkin, A. A.; Zhang, J.; Slysz, W.; Sobolewski, R.; Lipatov, A. P.; Okunev, O.; Chulkova, G.; Korneev, A.; Gol’tsman, G. N. |
| Title |
Superconducting single-photon detectors for GHz-rate free-space quantum communications |
Type |
Conference Article |
| Year |
2002 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
4821 |
Issue |
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Pages |
447-454 |
| Keywords |
NbN SSPD, SNSPD, single-photon detector, thin-film superconductivity, quantum cryptography, ultrafast communications |
| Abstract |
We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from 5% at wavelength λ = 1550 nm up to 10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm – 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography. |
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SPIE |
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Ricklin, J.C.; Voelz, D.G. |
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Free-Space Laser Communication and Laser Imaging II |
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no |
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Serial |
1523 |
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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 |
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| Volume |
13 |
Issue |
1 |
Pages |
14 |
| Keywords |
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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RPLAB @ gujma @ |
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730 |
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Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim |
| Title |
Hacking commercial quantum cryptography systems by tailored bright illumination |
Type |
Journal Article |
| Year |
2010 |
Publication |
Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
| Volume |
4 |
Issue |
10 |
Pages |
686 - 689 |
| Keywords |
quantum cryptography, hacking, QKD, APD |
| Abstract |
The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built of off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies. |
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RPLAB @ gujma @ |
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657 |
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