Theoretical Study Of Quantum Direct Communication Achieved By Quantum Repeater

The classical communication can not meet the increasing needs of information transmissions with the rapidly develop of technology. It is always an open topic about how to improve the efficiency and security of information transmission. Quantum Communication provides a new direction to the improvement of information technology. In recent years, fast development of quantum communication on experiment achieves many researchers' attention. Quantum Security Direct Communication (QSDC) becomes one of the most important parts of quantum communication because of its own advantages.This thesis has been divided into four chapters. In the first three chapters, we introduce the current research of quantum communication, some foundations of quantum informatics and some quantum communication protocols based on quantum entanglement. In chapter 4, basing on the quantum entanglement, we give several schemes of QSDC, and a proposal to realize long distances QSDC by quantum repeater. Furthermore, the code-decode formula is also laid out. Then, a safe bidirectional quantum message consignation and communication scheme is proposed. In this scheme, both the two parties of communication can store the secret information into the third party, and the most critical part is that the third party can not get any useful information from the storage information. The two authority parties can take the secret information at any time when they need.