Theoretical And Experimental Research On High Performance Quantum Secure Communication

Encryption and decryption of information has been hostile in all ages,and information security is also a key issue for people.Moreover,with the development of the related quantum algorithms and quantum computers in recent years,current communication networks are facing a greater threat.The unconditional security of quantum key distribution(QKD)is guaranteed by quantum mechanics and it provides a new solution to the current communication security problem.As the first QKD protocol,the BB84 protocol was proposed by Bennet and Brassard in 1984.It is through nearly 40 years of development that QKD has gradually moved from theoretical researches to practical applications.In this process,many QKD protocols and methods are proposed to improve the system security.For example,we use the decoy-state method to ensure the security of the source part,and the measurement-device-independent QKD protocol(MDI-QKD)is used to overcome the loopholes of the detectors.In this paper,the relevant theoretical and experimental researches on quantum secure communication are carried out.Moreover,we pay more attention to the improvement of system efficiency,and specifics are shown below:1.Experimental verification of the high-performance MDI-QKD protocol.MDI-QKD has high system security,but its key rate is at a low level,especially considering the statistical fluctuations.Fortunately,the 4-intensity and double scanning MDI-QKD with joint estimation and collective constrians can greatly improve the performance of the system.Then,we build a set of MDI-QKD experimental system using the time-bin and phase encoding scheme,and a proof-of-principle experiment of double-scanning method is performed for the first time.Here,we applied polarization and phase calibration techniques,and the two-photon interference visibility of the system is 48%.Due to the latest optimization algorithm,the influence of finite-data-size is significantly reduced.Our system has 50 MHz repetition rate,and a complete 150 km QKD experiment can be finished in only 5minutes.Compared with other similar MDI-QKD schemes,double-scanning method is more suitable for the practical scenarios.In other words,our work lays the foundation for the practical application of quantum secure communication systems in the future.2.An efficient method for selecting optimal QKD protocol.Before the actual secure quantum communication,it is necessary for the server to select the best QKD protocol according to the legal user equipments.Currently,the local search algorithm(LSA)is commonly used,consuming a lot of computing resources.Thus,we proposed a selection method based on machine learning.Here,we use the random forest classifier to choose the best protocol by learning a large amount of data,and the accuracy of the classifier is 98.2%.Compared with the LSA,the efficiency is improved by more than 1000 times.In conclusion,our work provides new ideas for the large-scale application of quantum secure communication networks in the future.