Research On The Entanglement-based Quantum Secure Communication Protocols

Based on the basic laws of quantum mechanics,quantum communication protects information security with unconditional security.It has attracted widespread attention in recent years and is developing gradually to the practical application.Quantum communication mainly consists of quantum key distribution,quantum secure direct communication(QSDC),quantum secret sharing,quantum teleportation and quantum dense coding.The former three are known as quantum secure communication or quantum cryptography.As one of the features of quantum mechanics,quantum entanglement has extensive studies and applications in the area of quantum secure communication.The main content of this dissertation is the research on the entanglement-based quantum secure communication protocols and related issues.Firstly,we propose a QSDC protocol with entanglement source and single-photon measurement,and its security analysis and performance simulation are studied.The proposed protocol using both an spontaneous parametric down-conversion entanglement source and a quasi-ideal entanglement source is thoroughly studied,and the theory and simulation difference between the two types of entanglement sources is compared.Secrecy capacity is derived from Wyner's wiretap channel theory and its lower bound is estimated with Gottesman-Lo-Lütkenhaus-Preskill theory and the decoy state method.The simulation performance shows that due to the heralding function,the secrecy capacity increases effectively.With the decoy state method,the performance of the protocol using the spontaneous parametric down-conversion entanglement source is almost equal to that with the ideal entanglement source.The advantages of the protocol include:(1)the use of entanglement source and single-photon measurement combines the advantages of heralding function of entanglement and the relative ease of single-photon measurement;(2)using the heralding function of the entanglement source,the secrecy capacity increases effectively.Secondly,we present a protocol for quantum secure communication using quantum teleportation,and its security analysis in a noisy channel is studied.We study the protocol in details,and the simplified single-particle operations and Bell-basis measurement together with specific steps are all given.The non-ideal entanglement distribution is studied with entanglement distillation and the wiretap channel theory,respectively.Quantum bit improvable rate is derived thus the influence of noise in the channel is quantified.Finally,we study the teleportation of particles in an environment of a multi-body quantum system,and under this circumstance it is called quantum tele-transformation(QTT).QTT can change a many-body system into an arbitrary shape in space.Combined with the above quantum communication protocol using teleportation,secure communication among arbitrary number of users can be realized with QTT.QTT simplifies the conceptual understanding of the non-local processes in quantum information and has widespread applications,for example,the teleportation of an isolated particle and entanglement swapping of a two-particle system.In multi-particle systems,QTT can be used to distribute tasks in distributed quantum computing and perform non-local gate operations.