Rate-Compatible LDPC Codes for Continuous-Variable Quantum Key Distribution in Wide Range of SNRs Regime

Area of Science:

• Quantum Information Science
• Coding Theory
• Quantum Cryptography

Background:

• Continuous-variable quantum key distribution (CV-QKD) faces challenges from variable quantum channel noise and low signal-to-noise ratios (SNRs).
• Existing rate-compatible methods for CV-QKD are resource-intensive, consuming significant hardware and secret key resources.

Purpose of the Study:

• To propose a novel design rule for rate-compatible low-density parity-compatible (LDPC) codes applicable to CV-QKD.
• To enable coverage of all potential SNRs using a single check matrix for enhanced efficiency.

Main Methods:

• Design of long block length rate-compatible LDPC codes with a single check matrix.
• Implementation of these codes for information reconciliation in CV-QKD systems.

Main Results:

• Achieved a high reconciliation efficiency of 91.80% in CV-QKD information reconciliation.
• Demonstrated superior hardware processing efficiency and a lower frame error rate compared to existing schemes.
• Attained a high practical secret key rate and extended transmission distance in unstable quantum channels.

Conclusions:

• The proposed LDPC code design offers an efficient solution for CV-QKD under challenging channel conditions.
• This approach significantly enhances the practicality and performance of CV-QKD systems.
• The single check matrix design optimizes resource utilization while maintaining high security and reliability.