Data Processing Algorithm Design Of Continuous Variable Quantum Key Distribution Systems

Quantum Key Distribution(QKD)is an important application of quantum information and quantum cryptography.The basic principles of quantum mechanics ensure its physical unconditional security.Continuous Variable Quantum Key Distribution(CVQKD)technology has been rapidly developed in recent years due to its potential of high bit rate and its good integration with classical optical communications,and has made great theoretical and experimental achievements progress.Generally,the standard CVQKD system includes two stages,namely quantum communication stage and data processing stage.In the CVQKD system,the data processing phase includes bit frame synchronization,phase compensation,secret reconciliation and privacy amplification.The secret reconciliation and the privacy amplification are called data post-processing.At present,the actual CVQKD system has such problems as the bit frame can not be accurately synchronized,the phase shift estimation is inaccurate,the compromise between the efficiency of the secret negotiation and the frame error rate,the rate of the key generation,and the actual security of the system are also existed.Data processing algorithms affect the secure transmission distance,secure key rate and the actual security of the CVQKD systems.Therefore,our analysis and research of data processing algorithms is of great importance to improve the performance and practical security of the actual CVQKD system.This paper focuses on how to improve the performance of the key modules of CVQKD system and the practical security of CVQKD system based on data-processing algorithm.The main contents are as follows:1.Practical security of CVQKD systems under finite-dimensional effect of multidimensional reconciliation is analyzed and studied.The reason for the finite dimensional effect is analyzed: the multidimensional reconciliation scheme establishes a binary virtual channel by d-dimensional rotation,exchanging data on the classical public authentication channel.Due to the finite dimension d in the multidimensional reconciliation scheme,the signal-to-noise ratio(SNR)between the quantum channel and the virtual channel will not be matched.This effect will eventually lead to an overly high key rate assessment,which introduces practical security issues in the CVQKD system.Different from the practical security problem caused by the hardware devices of CVQKD system,the practical security problem induced by the finite-dimensional effect is caused by the post-processing software algorithm.Such solution provide a new approach to improve the practical security of the CVQKD system in the future.2.Design and Implementation of Phase Estimation Algorithm in CVQKD System.The phase estimation problem of CVQKD system is analyzed and a high-precision phase estimation algorithm based on feedback optimization technique is proposed.In addition,the performance of the algorithm is analyzed.It provides algorithm safeguard and new thought to achieve more stable,better performance CVQKD system.3.Privacy amplification algorithm of Toeplitz matrix based on linear feedback shift register is proposed in the CVQKD system.First of all,the principle and technique of privacy amplification are introduced.Secondly,how to construct Toeplitz matrix based on linear feedback shift register is proposed,and privacy amplification algorithm of LFSR-based Toeplitz matrix is proposed.Finally,the security of the algorithm is analyzed.The LFSR-based Toeplitz matrix not only improves the operation speed,but also saves the hardware resources,so as to effectively improve the speed of CVQKD system in the stage of privacy amplification.It has high practicability,while it guarantees high-speed and long-distance CVQKD system.