Early Termination of Low-Density Parity-Check Codes for Continuous-Variable Quantum Key Distribution

2025-07-04

AI Summary

In continuous-variable quantum key distribution (CV-QKD), low throughput and poor real-time performance of low-density parity-check (LDPC) code decoding via the sum-product (belief propagation, BP) algorithm hinder practical deployment. To address this, we propose an optimized BP decoding method incorporating an adaptive early-stopping criterion: posterior probabilities are dynamically monitored during iterations, and convergence-triggered termination eliminates redundant iterations without compromising bit-error-rate (BER) performance. Simulation and experimental results demonstrate that the proposed strategy increases secure key rate throughput by up to 182%, significantly enhancing the real-time processing capability and engineering feasibility of CV-QKD systems. The core innovation lies in the first integration of an adaptive early-stopping mechanism into the BP decoding pipeline for CV-QKD, enabling joint optimization of error-correction performance and decoding speed.

Technology Category

• Computer Vision: Learning & Optimization for CV
• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: LLM based quality controls for crowd work
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics

Abstract

We analyse the impact of log a-posteriori early termination on the decoding throughput of reconciliation for continuous-variable quantum key distribution. Increases in decoded secret key rate throughput of up to 182% are reported in both simulations and experiments.

Problem

• Improving decoding throughput for quantum key distribution
• Analyzing early termination impact on LDPC codes
• Increasing secret key rate by up to 182%

Innovation

• Early termination of LDPC decoding
• Log a-posteriori ratio for throughput
• 182% secret key rate increase