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No-Switching Quantum Key Distribution using Broadband Modulated Coherent Light

Andrew M. Lance·Thomas Symul·Vikram Sharma·Christian Weedbrook·Timothy C. Ralph·Ping Koy Lam
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Abstract

We realize an end-to-end no-switching quantum key distribution protocol using continuous-wave coherent light. We encode weak broadband Gaussian modulations onto the amplitude and phase quadratures of light beams at the Shannon's information limit. Our no-switching protocol achieves high secret key rate via a post-selection protocol that utilizes both quadrature information simultaneously. We establish a secret key rate of 25 Mbits/s for a lossless channel and 1 kbit/s, per 17 MHz of detected bandwidth, for 90% channel loss. Since our scheme is truly broadband, it can potentially deliver orders of magnitude higher key rates by extending the encoding bandwidth with higher-end telecommunication technology.

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Andrew M. Lance, Thomas Symul, Vikram Sharma, Christian Weedbrook, Timothy C. Ralph, Ping Koy Lam. 2005-10-28. No-Switching Quantum Key Distribution using Broadband Modulated Coherent Light. https://doi.org/10.1103/physrevlett.95.180503

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