Implementation of continuous-variable quantum key distribution with discrete modulation
Takuya Hirano, Tsubasa Ichikawa, Takuto Matsubara, Motoharu Ono, Yusuke Oguri, Ryo Namiki, Kenta Kasai, Ryutaroh Matsumoto, Toyohiro Tsurumaru · Quantum Science and Technology · 2017
We have developed a continuous-variable quantum key distribution (CV-QKD) system that employs discrete quadrature-amplitude modulation and homodyne detection of coherent states of light. We experimentally demonstrated automated secure key generation with a rate of 50 kbps when a quantum channel is a 10 km optical fibre. The CV-QKD system utilises a four-state and post-selection protocol and generates a secure key against the entangling cloner attack. We used a pulsed light source of 1550 nm wavelength with a repetition rate of 10 MHz. A commercially available balanced receiver is used to realise shot-noise-limited pulsed homodyne detection. We used a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification. A graphical processing unit card is used to accelerate the software-based post-processing.