1 September 2006 Free-space quantum cryptography in the H-alpha Fraunhofer window
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Free-space Quantum key distribution (QKD) has shown the potential for the practical production of cryptographic key for ultra-secure communications. The performance of any QKD system is ultimately limited by the signal to noise ratio on the single-photon channel, and over most useful communications links the resulting key rates are impractical for performing continuous one-time-pad encryption of today's broadband communications. We have adapted clock and data recovery techniques from modern telecommunications practice, combined with a synchronous classical free-space optical communications link operating in parallel, to increase the repetition rate of a free-space QKD system by roughly 2 orders of magnitude over previous demonstrations. We have also designed the system to operate in the H-alpha Fraunhofer window at 656.28 nm, where the solar background is reduced by roughly 7 dB. This system takes advantage of high efficiency silicon single-photon avalanche photodiodes with <50ps timing resolution that are expected to enable operation at a repetition rate of 2.5 GHz. We have identified scalable solutions for delivering sustained one-time-pad encryption at 10 Mbps, thus making it possible to integrate quantum cryptography into first-generation Ethernet protocols.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
D. J. Rogers, D. J. Rogers, J. C. Bienfang, J. C. Bienfang, A. Mink, A. Mink, B. J. Hershman, B. J. Hershman, A. Nakassis, A. Nakassis, X. Tang, X. Tang, L. Ma, L. Ma, D. H. Su, D. H. Su, Carl J. Williams, Carl J. Williams, Charles W. Clark, Charles W. Clark, } "Free-space quantum cryptography in the H-alpha Fraunhofer window", Proc. SPIE 6304, Free-Space Laser Communications VI, 630417 (1 September 2006); doi: 10.1117/12.680899; https://doi.org/10.1117/12.680899

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