双场量子密钥分发协议的相位离散化分析

双场量子密钥分发协议（TF-QKD）的提出，突破性地将密钥速率改善为与信道透过率的平方根相关，可以在没有量子中继器的情况下克服密钥速率容量界。在传统的TF-QKD协议中，需要相干光源所添加的随机相位是连续的。然而在现实条件中，这样的假设经常无法满足，由此会降低协议的实际安全性。针对此问题提出了一种在测试模式和编码模式下具有随机相位离散化特征的TF-QKD协议，并使用了离散随机相位情况下的诱骗态方法进行分析。仿真结果表明，只需要少量的离散相位，随机相位离散化TF-QKD协议的密钥速率也可以超过密钥速率容量界，从而为TF-QKD协议的实际应用提供参考。

Random phase discretization analysis of twin-field quantum key distribution protocol

With the development of the twin-field quantum key distribution protocol(TF-QKD), now this protocol can improve the key rate to square root of the channel transmissivity. It can overcome the limit of the key rate capacity without quantum repeater. In the traditional TF-QKD protocol, it is necessary that the random phase of coherent light source is continuous. However, in reality, this assumption is often not satisfied. So it will reduce the actual security of the protocol. To solve this problem, this paper proposed a TF-QKD protocol with random phase discretization in test mode and coding mode. This paper used the decoys in discrete random phase to analyze the performance of this protocol. The simulation results show that the transmission characteristics of random phase discretization TF-QKD can exceed the limit of key rate capacity, which provides a reference for the implementation of TF-QKD.