Optimizing Single-Photon Avalanche Photodiodes for Dynamic Quantum Key Distribution Networks

Quantum key distribution (QKD) networks can provide unconditional secure communications among many remote users. In real QKD networks, with the dynamic access and quit of nodes, qualities of various user links and the link lengths among different users, such as transmission loss, are different and changing. Customized optimization that aims at various channel environments offers a network performance benefit. In this paper, we propose including the detection efficiency, dark-count probability, and afterpulse rate of the single-photon avalanche photodiode (SPAD) into the parameter optimization by controlling its voltage and temperature to optimize the secure key rates in dynamic QKD networks. The result shows that our method improves the network adaptability to the variation and asymmetry of channel and profits the establishment of QKD networks in a complex channel environment. This method is suitable for arbitrary SPAD-based QKD system and network architecture.