Enhancing the performance of entanglement-based WDM-QKD.

Entanglement-based quantum key distribution (EB-QKD) is considered an important implementation method for fully connected quantum networks. Due to practical considerations for conserving fiber resources, the demand for integrating EB-QKD into existing optical networks through wavelength-division multiplexing (WDM) in the same fiber (referred to as EB-WDM-QKD) is increasingly urgent. However, the noise generated from the classical system is an inherent limitation that restricts the performance of EB-WDM-QKD. In this work, we proposed an improved scheme that employs optical amplifiers to enhance the performance of EB-WDM-QKD. Under the fixed classical received power scenario, the transmission distance can be increased by more than 70 km compared to the original EB-WDM-QKD scheme without amplifiers. Moreover, for the scenario where the launch power of data lasers and amplifiers in the classical channel is non-adjustable, we applied the advantage distillation (AD) method to further enhance the performance of EB-WDM-QKD, and the transmission distance can be enhanced by more than 50 km. Our work can significantly enhance the performance of the EB-WDM-QKD system by optimizing the configuration of the classical subsystem and the post-processing of the quantum subsystem. The methods have the potential to be extended to various WDM-QKD systems, providing new perspectives for the advancement of WDM-QKD.