Improving the security of quantum key distribution with multi-step advantage distillation

How to improve the key rate is an important question to analyze the security of quantum key distribution (QKD). Based on the one-step advantage distillation (OSAD), the key rate and transmission distance can be improved. In this work, we propose the multi-step advantage distillation (MSAD), which can further improve the key rate compared with OSAD. By applying MSAD, the single-photon QKD protocol and decoy-state QKD protocol are, respectively, analyzed. The analysis results demonstrate that MSAD can sharply improve the key rate under the condition of high error rate or long transmission distance.