| Quantum information theory, which provides new principles and methods for information science, is a combination of information theory and quantum mechanics. The remote transmission of quantum information is not only a main subject in the field of quantum information, but also an essential process in quantum remote communication and quantum computation. It is significant for both basic theory and practical application.There are two important questions in quantum information transmitting . One is how to prepare entangled quantum states since quantum entanglement is an absolutely necessary resource in quantum communication. The other is how to reduce the consumption of both quantum and classical resources in quantum communication. Taking the problems stated above into account, the schemes for preparation of entangled states, quantum teleportation and remote state preparation are mainly discussed in this dissertation. The main results are as follows:(1) A scheme is proposed for preparation of the symmetrical W state and two kinds of unsymmetrical W-class states via cavity QED system. Although the two kinds of W-class states are different from each other, they have the same character. It is this character that can result in a controlled teleportation which is deterministic and unilateral.(2) Several schemes are proposed for remote transmission of unknown quantum information -Quantum Teleportation via cavity QED. To begin with, in the scheme for direct Bell-state-measurement (BSM)- free controlled teleportation of unknown atomic states, the Von Neumann measurement on single atom can take the place of direct BSM, which is still a bottle-neck problem for quantum information, with the help of cavity QED. The binary quantum state is rewritten in decimal form and a simple expression is given for complicated multipartite problem. Next, in the scheme for teleportation of an arbitrary multipartite GHZ-class state by one EPR pair, only one EPR pair and 3 classical bits are needed, which greatly lessens the oppressiveness of both quantum and classical channels. Then, in the scheme for deterministic, unilateral and controlled teleportation via cavity QED, Alice can determinately send her state to anyone of her agents, whereas the agents can not, with the channel being noiseless. What the agents can do is just to control the teleporting process, which enhance the security of the communication.Besides,based on the schemes discussed above,it is easy to see the character of an entangled state which can accomplish deterministic teleportation via cavity QED. What's more,the theoretical scheme is proposed for deterministic teleportation of two qubits arbitrary state via a super-operator.(3) Two kinds of schemes are given for remote transmission of known quantum information -Remote State Preparation(RSP). The one is the scheme for controlled RSP of n-qubit equatorial state. In the process, only one GHZ state and (n-1) EPR pairs are needed with (n+1) cbits consumed and there is one supervisor to control the quantum communication process. The other is the scheme for RSP of an arbitrary state of one-qubit via cavity QED with only 1cbit consumed. This scheme can be fulfilled in two different ways. The difference between them is that the entangled states in quantum channels are different, that is. to say, the number of entangled bits(ebit) needed in the process are not equal. In addition, this scheme can be generalized to RSP of an arbitrary multi-atom state.
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