Research On Multi-party Quantum Key Distribution Based On Multi-particle Entangled States Technology

Quantum communication has the advantage of unconditional security over the classical communication, and the quantum secret communication based on quantum key distribution is the most practical technology among the quantum information. Now quantum key distribution trends gradually into the stage of practical application with more than 30 years development. The safety and efficient protocol which is easier to implement became an important research field.In this paper,we studied on the multi-party quantum key distribution based on multi-particle entangled state.The main contens are as follows:Firstly,some basic concepts and theory of quantum mechanics are introduced. We describe the basic theory of security of quantum key distribution: Heisenberg's uncertainty principle and quantum cloning theorem, details the concept and related knowledge about quantum bit and quantum entanglement, and illustrates the three kinds of quantum key distribution protocol which is in common use: BB84,B92 and E91.Secondly, we described GHZ states and its particle distribution, present a three party quantum key distribution protocol based on GHZ state.The security of this scheme is decide by the quality of the quantum channel.Through purifing noisy GHZ states,we can get a perfect quantum channel,and then analyse its security.We focus on the measuring device independent(MDI) QKD based on GHZ states.Through analysing the simulation results under certain conditions,we can obtain that the secure key rate using two decoy states is nearly same as the one using infinite decoy states,the secure transmission distance between Alice and the middle node of MDI-QKD is about 190 km.Thirdly, compared to GHZ states, we introduce the advantages of the quantum communication based on W states and the Bell inequality of W states. We present an improved three party quantum key distribution protocol based on three-particle W states. Then we calculate the efficiency of the key, and analyze the security under the interception-and-resend attack and the entangle-and-measure attack. Meanwhile, we propose a four-user quantum key distribution protocol based on four-particles W states. We calculate the efficiency of the key and analyze the security of protocol in the same way. Compared to the QKD based on GHZ states, the QKD based on W states have a greater flexibility in networking.Finally,we summarized the thesis, and prospected the further. Next step, we will need to get the GHZ states entanglement purification gain parameters and calculate the key rate of the QKD based on GHZ states in the actual system. Since four particles W states only select a set of measurement results is used to generate the key, so improving the key efficiency and analysing the security under attack in entanglement- measurement of the QKD based on four particles W states is the work of next step.