Enhancing CV-QKD Information Reconciliation via Soft-Value Disclosure

Abstract

In continuous-variable quantum key distribution (CV-QKD) protocols, random bit sequences are encoded into quadrature amplitudes of weak coherent light. The homodyne measurement results of the quantum signals are continuous values that can enhance the error-correction efficiency through soft-decision (SD) decoding. However, implementing SD decoding in typical CV-QKD error-correction processes is challenging because the party receiving the quantum signal is not the same as the party performing the error correction. In this letter, we propose a novel method to overcome this limitation by sharing partial information on homodyne measurement results between two parties via an authenticated public channel, thereby enabling SD decoding. Numerical simulations demonstrated that the quantum bit error rate for error-free QKD transmission increased from approximately 1% using conventional methods to 3.5% using the proposed approach.