Research On High Dimensional Measurement-Device-Independent Quantum Key Distribution System

In principle,the unconditional security can be promised by quantum communication,it has been recognized as a feasible countermeasure against hacking in the future.Quantum key distribution(QKD)is one of the main formats to realize quantum communication,it enables two legitimate parties to share secret keys securely even under the quantum eavesdropping.However,there is a big gap between theory and practice of QKD,many security loopholes have been exploited in practical implementations of QKD.Fortunately,Measurement-device-independent QKD(MDI-QKD)not only eliminates all detector side channel attacks,but also utilizes the decoy-state techniques to get rid of source flaws,which make it an easier and safer way to implement practical QKD schemes.Due to the low key generation rate of MDI-QKD,the research on MDI-QKD protocol is of great significance to improve its performance and efficiency,and accelerate the development and applications of practical QKD.This thesis focuses on the analyses and designs of high dimensional MDI-QKD protocols.Firstly,the basic concepts,the current situations and the envisions of quantum communication are presented.Secondly,the physical basics of quantum communication are introduced briefly,including quantum state superposition principle,quantum state non-cloning theorem,Heisenberg uncertainty principle,quantum bit,quantum logic gates,BB84 protocol,B92 protocol and the time-reversed EPR QKD protocol.Thirdly,the theory and physical scheme of quantum state fusion and fission are discussed,according to its properties,the matching mode conversion circuits of the four dimensional photon state are designed.By combining quantum state fusion/fission module with the matching mode conversion circuit,two photon states can be transmitted in the single optical channel every time.Using the quantum sate fusion and fission scheme to encode and decode,and basing on the single photon source and plug-play structure,a high dimensional MDI-QKD scheme is proposed,and its security is guaranteed by the security of the time reversed EPR-based QKD protocol.The numerical simulation results of the proposed scheme and low dimensional MDI-QKD scheme indicates that the key generation is improved by 2~10 times,and the secure distance is extended by 6~60 km under different polarization misalignment errors.Therefore,the proposed high dimensional MDI-QKD protocol based on quantum fusion and fission is feasible to improve the performance of MDI-QKD system,furthermore,it is useful for the practical MDI-QKD scheme and the construction of wide area quantum communication networks.Fourthly,the research on a complete Hyperentangled Bell state analysis(HBSA)for two-photon states entangled in polarization and time-bin degrees of freedom(DOFs)is presented,it can distinguish 16 hyperentangled Bell states,and the encoding scheme of two DOFs of single photon state is designed.By combining HBSA with encoding scheme,the MDI-QKD scheme based on high dimensional Bell state analyzer is proposed.Utilizing this high dimensional Bell state analyzer in the Bell state measurement of MDI-QKD,which not only enables the two legitimate parties to encode in two DOFs of single photon state,but also improves the efficiency of Bell state analysis,hence,the encoding capacity,the bits utilization rate and the transmitting information content are all improved.The security of the proposed protocol is based on the security of the time reversed EPR-based QKD protocol,moreover,the proposed scheme is easy to implement with current technology.The proposal for this MDI-QKD scheme based on high dimensional Bell state analyzer is to find a new way to improve the performance of practical MDI-QKD scheme,i.e.,the multi-DOFs encoding scheme and HBSA is an alternative for MDI-QKD system.Finally,this thesis is concluded with a summary and some advices on the future work.