Reconciliation for CV-QKD using globally-coupled LDPC codes**Project supported by the National Natural Science Foundation of China (Grant Nos. 61801522, 61972418, and 61872390), the Natural Science Foundation of Hunan Province, China (Grant Nos. 2019JJ40352 and 2017JJ3415), and the Special Foundation for Distinguished Young Scientists of Changsha City, China (Grant No. kq1905058).

Abstract

Reconciliation is a necessary step in postprocessing of continuous-variable quantum key distribution (CV-QKD) system. We use globally coupled low-density parity-check (GC-LDPC) codes in reconciliation to extract a precise secret key from the raw keys over the authenticated classical public channel between two users. GC-LDPC codes have excellent performance over both the additive Gaussian white noise and binary-erasure channels. The reconciliation based on GC-LDPC codes can improve the reconciliation efficiency to 95.42% and reduce the frame error rate to 3.25 × 10–3. Using distillation, the decoding speed can achieve 23.8 Mbits/s and decrease the cost of memory. Given decoding speed and low memory usage, this makes the proposed reconciliation method viable approach for high-speed CV-QKD system.