Article abstract
Nature Photonics 1, 343 - 348 (2007)
Published online: 1 June 2007 | doi:10.1038/nphoton.2007.75
Subject Categories: Fibre optics and optical communications | Fundamental optical physics
Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors
Hiroki Takesue1, Sae Woo Nam2, Qiang Zhang3, Robert H. Hadfield2,5, Toshimori Honjo1, Kiyoshi Tamaki1 & Yoshihisa Yamamoto3,4
Abstract
We report the first quantum key distribution (QKD) experiment to enable the creation of secure keys over 42 dB channel loss and 200 km of optical fibre. We used the differential phase shift QKD (DPS-QKD) protocol, implemented with a 10-GHz clock frequency and superconducting single-photon detectors (SSPD) based on NbN nanowires. The SSPD offers a very low dark count rate (a few Hz) and small timing jitter (60 ps, full width at half maximum, FWHM). These characteristics allowed us to achieve a 12.1 bit s–1 secure key rate over 200 km of fibre, which is the longest terrestrial QKD over a fibre link yet demonstrated. Moreover, this is the first 10-GHz clock QKD system to enable secure key generation. The keys generated in our experiment are secure against both general collective attacks on individual photons and a specific collective attack on multiphotons, known as a sequential unambiguous state discrimination (USD) attack.
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
- National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA
- E. L. Ginzton Laboratory, Stanford University, 450 Via Palou, Stanford, California 94305-4088, USA
- National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan
- Present address: Department of Physics, Heriot-Watt University, Edinburgh, EH14 4AS, United Kingdom
Correspondence to: Hiroki Takesue1 e-mail: htakesue@will.brl.ntt.co.jp
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