The Matrix Representation Of Quantum Communication Theory

With the development of the quantum theory, Quantum information theory, which is the study of the achievable limits of information processing within quantum mechanics, become a new research field of theoretical physics. This dissertation contains results on quantum communication. It consists of six chapters. Chapter 1 concentrates on some foundations of quantum informatics; chapter 2 and chapter 3 mainly introduce quantum entanglement and quantum operation; chapter 4 has a look on classical cryptography and quantum cryptography. In chapter 5, a new notation has been introduced into quantum information theory. By this notation, some complex calculations become simple, such as n-dimension entanglement swapping, n-dimension teleportation and so on. In particular, a criterion of general teleportation has been given by the notation, by which Bob know how to construct his local operator. In the same chapter, probabilistic teleportation has been generalized to n-dimensional case. In chapter 6, two new quantum key distribution protocols have been proposed. The efficiency can approach 4 bits secret communication per 2 entangled pairs in these protocols (in BB84 protocol, it is only 1 bit per pair particle).