Application Of Discrete-Phase-Randomized Source In Twin-Field Quantum Key Distribution

With the rapid development of information technology,the security of information transmission has become more and more important.At present,asymmetric encryption algorithms are widely used to encrypt information in the communication process,whos security depend on the computational complexity of the encryption algorithm.But with the rapid development of computer technology,especially the development of quantum computer,these encryption methods will be threatened.However,based on the basic theory of quantum mechanics,quantum key distribution(QKD)can combine with one-time-pad encryption to achieve point-to-point unconditional secure communication.Since the first QKD protocol(BB84)was proposed,many researchers have proposed a series of protocols to promote the development of QKD.Before the birth of the twin-field quantum key distribution(TF-QKD)protocol,the performance of QKD protocols were limited by the "rate-loss" bound.However,due to the ability to break the "rate-loss" bound,TF-QKD and its variants have attracted widespread attention.Moreover,in order to ensure the security of the protocol,weak coherent states with continuous randomized phases are always assumed in the test mode,but this assumption is difficult to meet in practice.To solve this problem,some researchers have applied discrete-phase-randomized source in the variant protocols of TF-QKD to enhance the practical security.At the same time,the phase post-selection process is required in many variant protocols of TF-QKD,which will reduce the key rate in the low channel loss range.Therefore,in order to improve the security and performance of practical QKD systems,this thesis proposes two improved discretephase-randomization(DPR)TF-QKD protocols.The main research includes the following two aspects:1.We propose a DPR-TF-QKD protocol without phase post-selection in the code mode.In order to solve the problem of difficulty in implementing continuous-phase-randomized sources,we use discrete-phase-randomized source to replace the continuous-phase-randomized source in the TFQKD protocols.Meanwhile,phase post-selection process means that more information needs to be announced during the classical post processing stage,which may reduce the transmission efficiency of QKD systems.To solve these problems,we removed the phase post-selection process from the code mode,and conducted security analysis and numerical simulation for the protocol.The simulation results show that,with only a small number of discrete phases,our improved protocol can break the "rate-loss" bound and improve the key rate in the low channel loss range.2.We propose a DPR-TF-QKD protocol without phase post-selection both in the code mode and the test mode.In order to further simplify the process of the practical QKD protocol,we removed the phase post-selection process in the test mode,and conducted security analysis and numerical simulation for the protocol.The simulation results show that,with only a small number of discrete phases,our improved protocol can break the "rate-loss" bound,simplify the implementation process of the DPR-TF-QKD protocol,and improve the practicality of the TF-QKD protocol.