A novel error correction protocol for continuous variable quantum key distribution

Kadir Gümüş; Tobias A Eriksson; Masahiro Takeoka; Mikio Fujiwara; Masahide Sasaki; Laurent Schmalen; Alex Alvarado

doi:10.1038/s41598-021-90055-3

A novel error correction protocol for continuous variable quantum key distribution

Sci Rep. 2021 May 17;11(1):10465. doi: 10.1038/s41598-021-90055-3.

Authors

Kadir Gümüş^{1

2}, Tobias A Eriksson^{3

4}, Masahiro Takeoka³, Mikio Fujiwara³, Masahide Sasaki³, Laurent Schmalen⁵, Alex Alvarado⁶

Affiliations

¹ Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, 5600MB, The Netherlands. kadir.guemues@kit.edu.
² Karlsruhe Institute of Technology, Communications Engineering Lab, 76131, Karlsruhe, Germany. kadir.guemues@kit.edu.
³ National Institute of Information and Communications Technology (NICT), 4-2-1 Nukui-kitamachi, Koganei, Tokyo, 184-8795, Japan.
⁴ Infinera, Fredsborgsgatan 24, 117 43, Stockholm, Sweden.
⁵ Karlsruhe Institute of Technology, Communications Engineering Lab, 76131, Karlsruhe, Germany.
⁶ Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, 5600MB, The Netherlands.

Abstract

Reconciliation is a key element of continuous-variable quantum key distribution (CV-QKD) protocols, affecting both the complexity and performance of the entire system. During the reconciliation protocol, error correction is typically performed using low-density parity-check (LDPC) codes with a single decoding attempt. In this paper, we propose a modification to a conventional reconciliation protocol used in four-state protocol CV-QKD systems called the multiple decoding attempts (MDA) protocol. MDA uses multiple decoding attempts with LDPC codes, each attempt having fewer decoding iteration than the conventional protocol. Between each decoding attempt we propose to reveal information bits, which effectively lowers the code rate. MDA is shown to outperform the conventional protocol in regards to the secret key rate (SKR). A 10% decrease in frame error rate and an 8.5% increase in SKR are reported in this paper. A simple early termination for the LDPC decoder is also proposed and implemented. With early termination, MDA has decoding complexity similar to the conventional protocol while having an improved SKR.