Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors

Takesue, Hiroki; Nam, Sae Woo; Zhang, Qiang; Hadfield, Robert H.; Honjo, Toshimori; Tamaki, Kiyoshi; Yamamoto, Yoshihisa

doi:10.1038/nphoton.2007.75

Cited by 710 publications

(494 citation statements)

References 39 publications

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“…SSPDs feature a relatively high quantum efficiency at infrared wavelengths, combined with low time jitter, low dark counts, and high counting rates [2]. This makes these detectors promising for quantum optical studies and long-distance quantum cryptography applications [3].…”

Section: Introductionmentioning

confidence: 99%

Impedance model for the polarization-dependent optical absorption of superconducting single-photon detectors

Driessen

Braakman

Reiger

et al. 2009

Eur. Phys. J. Appl. Phys.

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Abstract.We measured the single-photon detection efficiency of NbN superconducting single-photon detectors as a function of the polarization state of the incident light for different wavelengths in the range from 488 nm to 1550 nm. The polarization contrast varies from ∼5% at 488 nm to ∼30% at 1550 nm, in good agreement with numerical calculations. We use an optical-impedance model to describe the absorption for polarization parallel to the wires of the detector. For the extremely lossy NbN material, the absorption can be kept constant by keeping the product of layer thickness and filling factor constant. As a consequence, the maximum possible absorption is independent of filling factor. By illuminating the detector through the substrate, an absorption efficiency of ∼ 70% can be reached for a detector on Si or GaAs, without the need for an optical cavity.PACS. 85.25.-j Superconducting devices -13.88.+e Polarization in interactions and scattering

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Section: Introductionmentioning

confidence: 99%

Impedance model for the polarization-dependent optical absorption of superconducting single-photon detectors

Driessen

Braakman

Reiger

et al. 2009

Eur. Phys. J. Appl. Phys.

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“…1, 2 An SNSPD consists of a thin wire of superconducting material biased close to its critical current, which becomes resistive after the absorption of a single photon, leading to a detection through an amplified voltage pulse. Their low dark count rate, fast response time, small jitter, and high efficiency favour their use in various demanding quantum optics applications such as quantum key distribution, 3 quantum networking, 4 device-independent quantum information processing 5 and deep-space optical communication. 6 Notably, SNSPDs can be integrated into photonic circuits, 7,8 and their applications extend beyond quantum optics, including light detection and ranging, 9 integrated circuit testing, 10 and fiber optic sensing.…”

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confidence: 99%

Optically probing the detection mechanism in a molybdenum silicide superconducting nanowire single-photon detector

Caloz

Korzh

Timoney

et al. 2017

Applied Physics Letters

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We experimentally investigate the detection mechanism in a meandered molybdenum silicide (MoSi) superconducting nanowire single-photon detector by characterising the detection probability as a function of bias current in the wavelength range of 750 to 2050 nm. Contrary to some previous observations on niobium nitride (NbN) or tungsten silicide (WSi) detectors, we find that the energycurrent relation is nonlinear in this range. Furthermore, thanks to the presence of a saturated detection efficiency over the whole range of wavelengths, we precisely quantify the shape of the curves. This allows a detailed study of their features, which are indicative of both Fano fluctuations and position-dependent effects.

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“…9 In QKD, the quantum bit error rate (QBER) increases as the length of the fiber increases. A secure key cannot be obtained from the sifted key when QBER exceeds a certain level, which limits the QKD distance.…”

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confidence: 99%

Superconducting Nanowire Single-Photon Detector with Ultralow Dark Count Rate Using Cold Optical Filters

Shibata

Shimizu

Takesue

et al. 2013

Appl. Phys. Express

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We report the fabrication of a superconducting nanowire single-photon detector (SSPD or SNSPD) with an ultralow dark count rate. By introducing optical band-pass filters at the input of the SSPD and cooling the filters at 3 K, the dark count rate is reduced to less than 1/100 at low bias. An SSPD with 0.1 cps dark count rate and 5.6% system detection efficiency at 1550 nm wavelength is obtained. We show that a quantum key distribution (QKD) over 300 km of fiber is possible based on a numerical calculation assuming a differential phase shift QKD protocol implemented with our SSPDs.Superconducting single-photon detectors (SSPDs or SNSPDs) based on ultrathin superconducting nanowires are now widely used as high-performance single-photon detectors in many fields such as quantum information and quantum optics. 1-3 SSPDs offer a wide detection wavelength range from ultraviolet to infrared, a high detection efficiency (η) of more than 10%, a low dark count rate (DCR) of 10 to 1000 cps, and a small timing jitter (Δt) of less than 100 ps. There have been many efforts to further improve their performance. In particular, many studies have been attempted to increase system η, and recently, a very high system η of 93% has been reported using amorphous WSi. [4][5][6] Besides η, the DCR is also an important factor determining the performance of single-photon detectors. The figure of merit of a single-photon detector is usually represented as η/(DCRΔt). 7,8 In the figure of merit, decreasing DCR has the same weight as that of increasing η.The importance of low DCR is also evident in long-distance quantum key distribution (QKD) experiments. 9 In QKD, the quantum bit error rate (QBER) increases as the length of the fiber increases. A secure key cannot be obtained from the sifted key when QBER exceeds a certain level, which limits the QKD distance.Since the QBER is usually governed by the DCR of the detector, a single-photon detector with low DCR is essential for long-distance QKD. Actually, to achieve the QKD distance of 260 km, the longest reported so far, SSPDs were operated in a very low-bias region to strongly reduce DCR (DCR = 1 cps, η = 3%). 10 To further increase the distance of QKD, an SSPD with lower DCR is necessary.In this letter, we describe the fabrication of an SSPD with a dark count rate below 1 cps.The fabrication process of the device is as follows. 11,12 NbN thin films of 3.5 nm thickness were synthesized at 350°C on a MgO (100) substrate by reactive DC magnetron sputtering. The meander pattern of NbN was fabricated by the standard e-beam process using a negative resist and C 2 F 5 dry etching. The size of the meander is 10 × 10 μm2 with a line and space width of 80 nm. Then, the cavity structure was formed on the meander using the standard photolithography process to enhance the detection efficiency. The cavity was

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Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors

Cited by 710 publications

References 39 publications

Impedance model for the polarization-dependent optical absorption of superconducting single-photon detectors

Impedance model for the polarization-dependent optical absorption of superconducting single-photon detectors

Optically probing the detection mechanism in a molybdenum silicide superconducting nanowire single-photon detector

Superconducting Nanowire Single-Photon Detector with Ultralow Dark Count Rate Using Cold Optical Filters

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