Gaoqiang Wang

Qubit-based synchronization offers a novel approach for quantum key distribution (QKD), simplifying system architecture and reducing implementation costs by leveraging the exchanged qubits. However, the performance of such schemes hinges on accumulating sufficient qubit events, rendering them vulnerable to local clock drift—particularly in high-channel-loss scenarios. This study investigates the impact of frequency instability in non-ideal oscillators, emphasizing clock drift-induced deterioration on QKD performance in these challenging, lossy conditions. We develop a computational model to quantify the secure key rate of QKD systems as a function of clock frequency stability. Through simulations and experimental validation with two distinct clock configurations, we demonstrate that oscillator stability becomes a key bottleneck in high-loss scenarios. By integrating target frequency scanning and clock offset recovery method, we verify our model via Monte Carlo simulations. Experimental validation confirms these findings, demonstrating a secure key rate of 0.37 bps at 67 dB channel loss—empirically validating the trade-off relationship among clock frequency stability, channel loss and acquisition time.