Research On The Dynamic Routing In Quantum Cryptography Communication Network And Entangled Bell State Measurement

Due to the excellent performance of the Quantum communication’s unconditional security and entanglement, more and more people pay their attention to it. On the one hand, there are many natural advantages in the quantum communication, which classical communication cannot match and do not have; on the other hand, the need for network and information security is also increasing. Quantum entanglement is the most peculiar phenomenon in quantum mechanics. What’s more, the non-destructive measurements and analysis of the unknown entangled pairs is very important to secure use the quantum entanglement properties in the future. Quantum key distribution is not only the earliest development in quantum communication, but also one of the most mature schemes. Quantum Crypotography communication based on quantum key distribution scheme has been proved to be absolute security. The quantum key distribution network based on trusted relay has gradually become the preferred quantum secure communication network solutions for its scalability and more mature technology. So how to ensure the security of quantum communication network hasbecome an important issue to be resolved.Based on this, this paper focuses on two aspects: research on the non-destructive measurement method of Bell state; dynamic route selection algorithm based on the Game Theory and the remaining amount of the keys in links.Firstly, this paper introduces the basic concepts and principles of quantum communication, as well as the current domestic and abroad development status. Secondly, we present the basic physical principles of the quantum mechanics which the quantum communication relying on, and make a elaboration of two important and widely used quantum key distribution protocol: BB84 protocol and the B92 protocol.Thirdly, on the base of traditional Bell state measurement methods, aiming at the drawback that the traditional methods may produce irreversible damage to the entangled photons-pairs’ initial quantum state, we propose a new non-destructive measurement method of Bell states. With the help of two auxiliary modes and two measurement modules Q and Q+, this scheme makes use of some quantum logic devices and optical devices, such as the CNOT and the polarization splitting prism. Based on two single-photon detectors’ detect result, we can classfiy the four Bell states into two kinds while the initial states remain unchanged.Finally, based on the study about Game Theory and the remaining amount of the keys in links, we propose the dynamic routing algorithm in quantum communication network. In quantum crypotography communication network, the security and the balance use of the key are dispensable. When the message is transmitted over the network, we treat the sender and the receiver as a party of a game, the attacker as the other, and also regard the security of the message and the remaining amount of the keys in links as the income. Both sides use different strategies to game, gain their values of the corresponding income. By solving the corresponding linear programming equation, the optimal policy choice probability is obtained, which can balance the security and the efficiency of the network. When the remaining amount of the keys in links or the topology of the network changes, the probability of the routing may update, which will eventually drive the network to achieve optimal steady state.There are still some deficiencies in this paper. Bell-state non-destructive measurement method proposed in this paper cannot identify all the four Bell states, and the calculation of the proposed dynamic routing method in quantum communication network is too complicated in practice. These problems require further research and exploration.