The Application Of Quantum Entanglement Swapping Quantum Direct Communication

In the 1980's, a new subject- quantum information, which is the combination of quantum mechanics and information science, came out. The main content it studies is quantum computation and quantum communication. Quantum information science is study how to apply quantum states to encode, i.e., the information can be successfully produced,transmitted,processed and controlled through operating the quantum states and the evolution of quantum states, so compared with classical information, quantum information has shown some distinguished advantages. The quantum mechanics basic principle such as no-cloning theorem ensure quantum information has made a surprise progress both in theoretical and experimental fields in the past two decades, it has created many miracles, such as absolute secure quantum key, quantum dense coding, quantum teleportation, especially directly secure quantum communication which is proposed recently. With the research of related theories and the development of hardware technology, communication technology has been made a great progress. People attach their security and secrecy during the information transmitting. It is one of the key communication technologies on the aspects how to connect accurately the either sides or multi-sides in the communication and assure the information transmission to be secure and secret. The safety of quantum cryptography key primarily structured on the basis of the two major principles of quantum no-cloning theorem and the Heisenberg uncertainty principle which constitute the physical basis of quantum cryptography.Different with quantum key distribution, quantum secure direct communication permits confidential messages to be communicated directly without establishing secret key firstly. Therefore, the transmission security requirements will more higher. As we all know, the classic information can be completely copied so it is impossible to secure direct communicate through the classical channel. However, when we use quantum mechanics to engage in direct communication, it will enable direct communications successfully. The second chapter describes the two quantum direct secure Communication: the ping-pong protocol and quantum dialogue.In 1935, since the concept of quantum entanglement was proposed by Schr6dinger people have paid more and more attention to entanglement. With the recent development of quantum information, many physicists have done much work on quantum entanglement. The third chapter we must first prepare a large number of non-maximal entangled states, then with the help of quantum distillation to transmit qubits by using quantum entanglement swapping in quantum channel. In this scheme we need not transmit the state quibits which carry the secret message in the public channel, and the two users can exchange their messages simultaneously by transmitting the message only one time, so it can be more safely.In the last chapter we revised the scheme described in chapter three, the two users just need to use the non-maximal entangled states as quantum channel, not like last scheme we need to purify the non-maximal entangled states to maximal entangled states, we employ the generally Bell basis to measure the quibits. We can conclude that those we use the non-maximal entangled states but the probability of communication successfully retain unit.