Quantum key distribution (QKD) establishes secure links between remote communication partners. As a key problem for various QKD protocols, security analysis gives the number of secret keys regardless of the eavesdropper’s computational power, which can be done both analytically and numerically. Compared to analytical methods, numerical ones are more general since they can be directly applied to almost all QKD protocols without additional techniques. However, current numerical methods are based on some assumptions such as working in asymptotic limit and collective attacks from eavesdroppers. In this work, we remove these assumptions and develop an unconditional numerical security analysis for general QKD protocols. We also give an example of applying the method to the recent Phase-Matching QKD. Our result shows that the key rate can surpass the linear key rate bound in finite-size cases even with simpler protocol designs.
Dr. Hongyi Zhou received his Bachelor's degree in theoretical physics from Peking University in 2014. He received his Ph.D. degree from Tsinghua University in 2019. Hongyi Zhou is now a research assistant at the Institute of Computing Technology, Chinese Academy of Sciences. His current research is focused on quantum cryptography and quantum optics.