Research On Practical Quantum Key Distribution With Advantage Distillation

“No secret,no success.” Information security has been vital throughout the ages,and the development of encryption technology is closely related to individuals,families and even countries.In the classical cryptosystems,the crucial problem of distributing key remains unresolved.Until the second half of the 20 th century,with the rapid development of quantum mechanics,quantum key distribution(QKD)came into being,which is based on the properties of single quantum states,and thus a breakthrough has been made on this problem.By combining with “one-time-pad” encryption,QKD provides an intelligent solution to realize unconditionally secure communication.Subsequently,various theoretical works and experimental demonstrations have been reported,which improves the performance of practical QKD systems greatly.For example,the decoy-state method can defeat the photon-number splitting attack caused by multi-photon states in weak coherent states.In addition,the measurement-device-independent QKD(MDI-QKD)protocol was proposed,which can defend all detector side-channel attacks caused by the imperfect devices at the measurement side.Currently,QKD is at the stage of application,but its maturity and practicality leave a lot to be desired.Researchers are trying to further enhance the performance and practicality.Fortunately,by identifying and separating highly correlated bit pairs from weakly correlated information,the advantage distillation(AD)technology provides an efficient scheme to drastically improve the the secret key rate and transmission distance of QKD.However,it is unknown whether the performance of practical QKD systems when considering statistical fluctuations can also be improved with the AD method.This dissertation summarizes my work on the performance improvement of practical QKD systems when considering statistical fluctuations,which mainly includes the following two aspects:(1)To promote the performance of practical BB84 QKD systems,the AD technology is extended into BB84 QKD when considering statistical fluctuations.Simulation results show that the AD method which can increase the correlation of the sifted key has great superiority in improving the performance of practical BB84 QKD systems.When the background error rate is 0.5%,1.5%and 3%,the AD step increases the transmission distance by about 19 km,22 km and 28 km respectively for three-intensity decoy-state BB84 QKD with statistical fluctuations.Moreover,the AD procedure does not change the hardware of practical QKD systems,which can be directly applied to current systems.(2)To make the MDI-QKD protocol more practical,the performance of MDI-QKD with AD is investigated when considering statistical fluctuations.Simulation results show that the AD method can significantly improve the performance of practical MDI-QKD when considering statistical fluctuations.When the background error rate is 0.5%,1.5% and 3%,the AD step increases the transmission distance by about 20 km,26 km,46 km respectively for three-intensity decoy-state MDI-QKD with statistical fluctuations,and about 26 km,35 km,55 km respectively for four-intensity decoy-state MDI-QKD with statistical fluctuations.Moreover,the AD method can make the system more tolerant of background error rate,which is very promising in MDI-QKD protocol when considering statistical fluctuations.