Research On The Key Issues Of Optical Fiber Quantum Secure Communication System

The communication of information are essential for people to contact with each other.In the information era,it becomes vital to ensure the security of information transmission.With the rapid development of quantum information technology,quantum secure commu-nication,as a theoretically unconditionally secure communication method,has attracted widespread attention.Unlike the classical cryptosystem based on computational complex-ity,quantum secure communication guaranteed by the principles of quantum mechanics are more defensive to attack and eavesdropping.Since the first quantum secure communication protocol,BB84 protocol,was proposed,quantum secure communication has made signifi-cant progress in theory,experiment and practicality in this decades.Quantum secure com-munication has been gradually applied in government,finance and national defence fields.The deployment and application of "the Beijing-Shanghai quantum backbone","the Micius satellite",and commercial quantum key distribution systems signify that China is at the forefront of the world in the field of quantum secure communication.The first and second chapters of this dissertation introduce the research progress in quantum secure communication and provide an overview of quantum secure communica-tion.Currently,quantum secure communication system is moving forward to be more prac-tical and efficient in different application environment,specifically,to pursue a higher key rate and longer transmission distance with more flexibility and efficiency.The outline of the remainder of this dissertation is as follows:(1)Research on the reference-frame-independent quantum key distribution protocol using the heralded pair-coherent sourceBy analyzing the protocols of quantum key distribution(QKD)and taking the imperfect source preparation into account,the reference-frame-independent QKD(RFI-QKD)proto-col with the heralded pair coherent source(HPCS)is proposed.Compared with the atten-uated weak coherent source(WCS),the HPCS has more single photon state components.Besides,this protocol combines the loss-tolerant protocol and the RFI-QKD protocol that does not require reference frame calibration and can tolerate the influence of source flaws.Simulation results show that the performance of RFI-QKD with HPCS outperforms that of WCS,which provides reference significance for the performance optimization of the quan-tum secure communication system.(2)Quantum communication scheme with freely selectable usersConsidering that the users involved in communication vary with the transmitted infor-mation in a practical quantum communication network,the quantum communication scheme with freely selectable users is proposed.The sender,Alice,can freely select the users who wants to share secret keys,while non-active users will not participate in secret key sharing.This scheme can significantly improve the flexibility and efficiency of the whole quantum secure communication system through the bidirectional QKD protocol and the circular quan-tum secret sharing protocol.(3)A fully symmetrical quantum key distribution system capable of preparing and mea-suring quantum statesBased on the encoding schemes of the existing QKD system,the fully symmetrical QKD system that enables quantum states to be prepared and measured simultaneously with-out compromising system performance is proposed.In this system,both parties have iden-tical and symmetrical implementations,which not only facilitates system integration and reduces the complexity of system construction,but also greatly improves the flexibility and practicability of the QKD system.Besides,the system is a one-way communication system.This equipment is beneficial for both parties to enhance the secure key rates by increas-ing the repetition frequency without considering the coding problems caused by the timing sequence,which further promotes the practicality of QKD system.(4)Study on the performance of reference-frame-independent quantum key distribution protocol based on wavelength division multiplexingCombined with the existing QKD networks,the specific performance of the RFI-QKD protocol based on wavelength division multiplexing(WDM)under different channel pa-rameters is analyzed theoretically.Furthermore,the affects of channel crosstalk noise and Raman scattering noise on the secure key generation rates and transmission distance of the RFI-QKD system in co-fiber-transmission of quantum and classical signals are studied.The combination of WDM technology with high communication capacity and RFI-QKD proto-col resistant to environmental disturbance are of great significance for the practical applica-tion of QKD network.