Research On Plug-play Twin Field Quantum Key Distribution Protocol

As an important branch of quantum informatics,Quantum secure communication is based on the Quantum Key Distribution(QKD)technology,which is based on the basic principles of quantum mechanics that can realize the unconditional and secure transmission of keys.Although quantites of results have been achieved in the field of QKD,it still unable to break through the limits of bit rate and transmission distance without quantum repeaters.Fortunately,Twin-field quantum key distribution(TF-QKD)protocol were proposed in 2018,which break through the limits of bit rate and transmission distance without quantum repeaters.In addition,this protocol can be regarded as the conversion of the MDI-QKD protocol from two-photon interference to single-photon interference,so it retains the advantages of the MDI-QKD protocol and resists attacks on the detector side.The TF-QKD protocol has a higher key rate and a longer transmission distance than other QKD protocols.However,this protocol requires consistent preparation of dual light sources and phase coordination at long distances.Therefore it has greater difficulty in technical implementation.The Reference-frame-independent(RFI)QKD protocol combined with Plug-play structure,which can not only realizes automatic compensation of the phase and polarization of the QKD system,but also realize the secure transmission of the secret key of the two communication users under a single light source when the reference phase is not aligned.Focusing on the practical TF-QKD protocol,this paper proposes a TF-QKD protocol based on the Plug-play structure.Further more,we applies the RFI protocol idea to this protocol.The main research contents are as follows:Firstly,plenty of basic knowledge related to quantum information has been learnd,including the basic assumptions of density operators and quantum mechanics,Shannon entropy,von Neumann entropy,and two typical QKD protocols of BB84 and B92.Then the safety defect caused by a single untrusted light source in the two-way QKD system is analyzed,and the solution of adopting the idea of light source monitoring is given.Finally,the basic content and security analysis of RFI-QKD protocol,MDI-QKD protocol and TF-QKD protocol are briefly introduced.Secondly,The MDI-TF-QKD protocol based on the Plug-play structure is proposed.Using a single light source,combining with the Plug-play structure and decoy state modulation technology.The system avoids safety defects caused by inconsistent preparation of dual light sources,and realizes automatic compensation of polarization and phase shift without additional polarization and phase compensation modules.Meanwhile,we compared the performance of the protocol under untrusted sources by using the Matlab simulation,trusted sources and statistical fluctuations of limited code length.The result of the simulation shows that the key generation rate and transmission distance of the protocol are almost the same.And even under statistical fluctuations in the limited code length,the protocol can still break through the limits of the bit rate and transmission distance.The safety distance exceeds400 km,which further verifies the feasibility of the program.Thirdly,following the research content of Chapter 3,we applies the RFI protocol scheme to the MDI-TF-QKD protocol,and proposes a novel scheme RFI-TF-QKD protocol,which solves the problem of the misalignment of the reference systems of the two communication parties.By using random phase segments to form a data set to collect more information to estimate the amount of information of Eavesdropper,which reduces the requirements of phase in system.Combining the advantages of the RFI protocol with the advantages of the MDI-TF-QKD protocol,the protocol further improves the robustness and controllability of the system.Finally,the performance of this protocol under non-RFI and RFI protocols is compared through numerical simulation.The results show that the RFI-TF-QKD protocol has better error resistance performance.What's more,even under untrusted sourcesthe transmission distance of this protocol can still be greater than 500 km.