A Study Of Design In Quantum Dialogue By Using Entangled States

Quantum information science combined with quantum mechanics and information science,which has been developed more than twenty years, becoming one of the newest cross-linkedsubjects. The security of quantum communication is based on the fundamental laws ofmechanics, such as non-cloning theorem and uncertainty principle. Due to the unconditionalsecurity, quantum has drawn attention of many researchers. The rapid development of quantumcommunication has injected new vitality into the traditional field. And it brings a series ofunique function, such as improving the operation speeds, increasing the capacity and so on.Entanglement is one of the basic properties of quantum system. Entangled state as animportant carrier of quantum communication, which plays a very important role. No matterhow far apart between the interconnected subsystems, any changes of one sub system will affectthe behavior of another sub system. Secure quantum communication without informationdisclosure can be ensured by using the proper encoding. The unique properties of entangledstates made it widely used in quantum fields, such as quantum cryptography, quantumcomputation and so on.In this paper, we have analyzed the basic knowledge of quantum communication, such asvector space, basic theory. The main content of this paper is dense-coding and step transmissionfor quantum protocol, which provide a solid theoretical basis for quantum dialogue. The mainpoints and innovation we obtained in the dissertation are as follows:(1) By analyzing the principles in quantum states, we present two efficiently methods torealize quantum dialogue, which two users can complete encoding by using one-waytransmission. We carry out unitary operations and step transmission on the fixed coefficientquantum states, which improve the security of communication. During the process ofcommunication, almost all the emitted particle can be used to carry2-bit secret messagesbesides the decoy photons, the intrinsic efficiency for qubits approaches the value of100%. Itthe end, we analysis the protocols in detail.(2) We put forward a variable coefficient quantum dialogue scheme by using the uniquestructure of quantum states. By this way, each W state can carry three bits of secret informationand the measurement result is encrypted without information leakage. Furthermore, we utilizethe entangle properties of W state and decoy photo checking technique to realize three-timechannel detection, which can improve the efficiency and security of the scheme.