High-throughput GPU layered decoder of quasi-cyclic multi-edge type low density parity check codes in continuous-variable quantum key distribution systems

Yang Li,Wei Huang,Yong Li,Jie Yang,Xiaofang Zhang,Bingjie Xu,Li Ma

doi:10.1038/s41598-020-71534-5

Abstract

The decoding throughput during post-processing is one of the major bottlenecks that occur in a continuous-variable quantum key distribution (CV-QKD) system. In this paper, we propose a layered decoder to decode quasi-cyclic multi-edge type LDPC (QC-MET-LDPC) codes using a graphics processing unit (GPU) in continuous-variable quantum key distribution (CV-QKD) systems. As described herein, we optimize the storage methods related to the parity check matrix, merge the sub-matrices which are unrelated, and decode multiple codewords in parallel on the GPU. Simulation results demonstrate that the average decoding speed of LDPC codes with three typical code rates, i.e., 0.1, 0.05 and 0.02, is up to 64.11 Mbits/s, 48.65 Mbits/s and 39.51 Mbits/s, respectively, when decoding 128 codewords of length {10}^{{6}} simultaneously without early termination.

Highlights

The decoding throughput during post-processing is one of the major bottlenecks that occur in a continuous-variable quantum key distribution (CV-Quantum key distribution (QKD)) system
One category is the discrete variable QKD (DV-QKD), where the key information is encoded on discrete Hilbert space, and the other is the continuous variable QKD (CV-QKD), where the key information is encoded on continuous Hilbert space, such as the quadratures of coherent states
Given that the messages can be updated at variable/check nodes and can be performed in parallel, the layered belief propagation (BP) decoding algorithm is deployed on graphics processing unit (GPU)

Summary

Introduction

The decoding throughput during post-processing is one of the major bottlenecks that occur in a continuous-variable quantum key distribution (CV-QKD) system. We propose a layered decoder to decode quasi-cyclic multi-edge type LDPC (QC-MET-LDPC) codes using a graphics processing unit (GPU) in continuous-variable quantum key distribution (CV-QKD) systems. The two participants in a CV-QKD system desire to establish a secret key for one another over a long distance with a very low signal-to-noise ratio. It naturally brings a problem on how to design codes with excellent error-correction capability, under such a stringent channel condition. In this case, only low-rate codes with very long block lengths can be exploited to achieve high efficiency key reconciliation

Methods

Results

Conclusion