Optimizing Multidimensional Reconciliation Algorithm For Continuous-Variable Quantum Key Distribution

In the information era,people are enjoying faster communication and more and more concerned about the security of communication.Quantum Cryptography was born to meet the growing severe requirements for communication security.With the peculiar properties of microscopic particles,Quantum cryptography not only prove its unconditional security,but also detect the presence of eavesdroppers.Rely onth those properties,quantum cryptography provides better security guarantees for information transmission and information processing.Quantum Key Distribution?QKD?is an indispensable branch of quantum cryptography.In recent years,continuous variable Quantum Key Distribution?CVQKD?research has developed rapidly.One of the main difficulties of the CVQKD protocol is that the secure communication distance does not meet the requirements of people.So how does the CVQKD protocol enable remote? We have found the performance of reconciliation was the main reason for restricting the remote of CVQKD protocol.The paper will discuss the reconciliation algorithm of CVQKD.First,we introduce an efficient multidimensional reconciliation.An interesting property of the Gaussian distribution When the random variable obeys the standard Gaussian distributionN?0,1_n? on R^d whose covariance matrix is the identity is that it has a spherical symmetry in R^d.In this paper,the random vector x follows nonuniform Gaussian distribution,then the normalized random vector has a uniform distribution on the unit sphere S^d-1.Finally we can reconciliate the quantum key.This reconciliation can reduces the computational complexity,improves the reconciliation efficiency and extend the transmission distance of CVQKD system.On the basis of multidimensional reconciliation,we utilize the continuous density evolution to find the channel parameters threshold ?*.then design the optimal irregular LDPC code corresponding to the threshold ?* by the differential evolution method.To a certain extent,extended security key transmission distance of CVQKD system.Thank to the previous effort,the signal to noise ratio threshold dropped to about 0.2.Based on low SNR,We propose the repetition codes mentioned: It show that starting from a code of rate R achieving an efficiency ? for a SNR s on the BIAWGNC,one can use the repetition scheme of length k to build a new code of rate R'=R/ k,achieving an efficiency ?' for a SNR s'=s/ k.This algorithm effectively reduces the convergence signal-to-noise-ratio threshold and extends the secure range of communication distance.The simulation results indicate that the convergence signal-to-noise-ratio can be less than-7.798 d B,the data reconciliation can achieve an efficiency of 90.27% with the block length of 2×10⁶.The amount of secure secret key extracted under optimal attack is about 0.22kb/s,and the secure range of communication distance is extended up to 80 km.