The Remote Preparation Of Quantum State Based On Quantum Entanglements

The theory of quantum information is a result from the comnination of quantum mechanics and information theory, with it, many a impossible tasks within the classic information theory world be able to be realized. By using quantum state as information unit, quantum communication can be taken to effectively convey some information. Moreover, as a very important branch of quantum information science, quantum communication is an early-researched area in quantum information, which includes quantum teleportation, remote state preparation, quantum cloning, etc.In the field of quantum information, quantum entanglement, as the most remarkable difference between quantum mechanics and classical physics, plays a key role in the quanut minformation processing. Quantum entanglement is a very strange and unbelievable phenomenon. When the whole quantum system is composed of several subsystems, one can measure any subsystem and the corresponding measurement result will be independent but closely related to the parameters of the other subsystem’s measurement results. While disposing the quantum information, quantum entanglement, as an information resource, is commonly employed, and plays a most indispensable role. For example, quantum entanglement can be widely used in remote state preparation, quantum dense coding, quantum teleportation, and so on. So far, people have already known clealy the properties of quantum entanglement in the two subsystems case or the two qubits case, and a lot of schemes about preparing quantum entanglement have been proposed, too. However, quantum entanglement, in the multisystem case or the multiparticle case, especially in the multi-level particle case, is still in exploration.In this paper, based on the special properties of quanut mentanglement, we explore a kind of quantum communication, remote state preparation. Considerring different quantum channels and the distrinct forms oh the prepared state, we successfully design some simple and practical schemes of remote state preparation, which can be stated as follows:1. We present a new scheme for probabilistic remote preparation of a general two-qubit state by using twoW-type states as the shared quantum channel and a proper POVM instead of the usual positive measurement. Also we explore the scheme’s applications to five special ensembles of two-qubit states. The success probability and the classical communication cost in different cases are calculated minutely, respectively, which show that the remote two-qubit preparation can be realized with higher probability after consuming some more classical bits provided that the two-qubit state to be prepared is chosen from the special ensembles.2. We propose an efficient scheme for remotely preparing an arbitrary three-qubit state with a four-qubit cluster state and an Einstein-Podolsky-osen state as the shared quantum resource. Using an appropriate set of eight-qubit mutually orthogonal measurement basis, the remote three-qubit preparation is successfully completed with the probability of1/8in general case. Then to achieve our concerns of improving the probability of this protocol, some special ensembles of three-qubit states are minutely investigated. As a result, it is shown that the total probability of the RSP protocol, in these particular cases, can be improved to1/4and1/2, respectively, or even that the RSP protocol can be realized with unit success probability.At last, we make a summary of this thesis, and put forward the prospect for groping work in the future.