Dependency model for high-performance quantum-key-distribution systems

A precise estimation of the detection response is essential for a high-performance and secure quantum-key -distribution (QKD) system. Single-photon avalanche diodes (SPADs) are widely applied to estimate the single -photon yields. However, in the presence of the dead time and afterpulse of the SPADs, the estimations of gains in previous models are biased, which will lead to ill-fitting optimized parameters and greatly degrade the system performance. Here, we develop a dependency model for providing more accurate optimization to achieve higher -performance QKD systems. Moreover, to further improve the system performance, our model guides users to choose proper dead time. Our simulation results indicate that our model plays an important role in the practical application and deployment of QKD systems.