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14 February 2007 Free-space quantum key distribution at GHz repetition rates
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Quantum key distribution (QKD) can produce secure cryptographic key for use in symmetric cryptosystems. By adopting clock-recovery techniques from modern telecommunications practice we have demonstrated a free-space quantum key distribution system operating at a transmission rate of 625 MHz at 850 nm. The transmission rate of this system is ultimately limited by the timing resolution of the single-photon avalanche photodiodes (SPADs), and we present a solution to take advantage of SPADs with higher timing resolution that can enable repetition rates up to 2.5 GHz. We also show that with high-repetition-rate sub-clock gating these higher-resolution SPADs can reduce the system's exposure to solar background photons, thus reducing the quantum-bit error rate (QBER) and improving system performance.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. C. Bienfang, Daniel Rogers, Alessandro Restelli, Charles W. Clark, Carl J. Williams, Alan Mink, Barry Hershman, Tassos Nakassis, X. Tang, and D. Su "Free-space quantum key distribution at GHz repetition rates", Proc. SPIE 6476, Optoelectronic Integrated Circuits IX, 64760H (14 February 2007);

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