24 October 2016 Continuous operation of four-state continuous-variable quantum key distribution system
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Abstract
We report on the development of continuous-variable quantum key distribution (CV-QKD) system that are based on discrete quadrature amplitude modulation (QAM) and homodyne detection of coherent states of light. We use a pulsed light source whose wavelength is 1550 nm and repetition rate is 10 MHz. The CV-QKD system can continuously generate secret key which is secure against entangling cloner attack. Key generation rate is 50 kbps when the quantum channel is a 10 km optical fiber. The CV-QKD system we have developed utilizes the four-state and post-selection protocol [T. Hirano, et al., Phys. Rev. A 68, 042331 (2003).]; Alice randomly sends one of four states {|±α⟩,|±𝑖α⟩}, and Bob randomly performs x- or p- measurement by homodyne detection. A commercially available balanced receiver is used to realize shot-noise-limited pulsed homodyne detection. GPU cards are used to accelerate the software-based post-processing. We use a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification.
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Takuto Matsubara, Takuto Matsubara, Motoharu Ono, Motoharu Ono, Yusuke Oguri, Yusuke Oguri, Tsubasa Ichikawa, Tsubasa Ichikawa, Takuya Hirano, Takuya Hirano, Kenta Kasai, Kenta Kasai, Ryutaroh Matsumoto, Ryutaroh Matsumoto, Toyohiro Tsurumaru, Toyohiro Tsurumaru, } "Continuous operation of four-state continuous-variable quantum key distribution system", Proc. SPIE 9996, Quantum Information Science and Technology II, 99960S (24 October 2016); doi: 10.1117/12.2241766; https://doi.org/10.1117/12.2241766
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