Simple phase recovery using multi-pilot tones and Wiener filters for continuous variable quantum key distribution
Jinpeng Liao, Wenjun Fan, J. Y. Huang, Hao Xiao, Dawei Wang · Optics Express · 2025
The performance of local local oscillator-based continuous-variable quantum key distribution (LLO-CVQKD) systems is critically limited by phase recovery accuracy. To address the phase mismatch between independently operated lasers at the transmitter and receiver, this work proposes a multi-pilot scheme integrated with advanced digital filtering for optimized phase estimation. Through systematic comparisons of the rectangular filter, Savitzky-Golay filter, and Wiener filter, experimental results confirm that Wiener filtering has superior noise suppression capabilities based on multiple frequency pilot-tones. Implemented under the Gaussian-modulated coherent state (GMCS) protocol, our findings reveal that dual-pilot, four-pilot, and eight-pilot configurations all enhance phase recovery precision compared to single-pilot approaches, with the dual-pilot scheme achieving optimal balance between system complexity and performance. In a 20 km fiber link with a 1 GHz system repetition rate and a 2.83 SNU modulation variance, the dual-pilot Wiener-filtered configuration achieves an asymptotic secret key rate of almost 80 Mbps, establishing an innovative approach for practical LLO-CVQKD phase recovery.