Research Of Entanglement Concentration And Directly Measurement Concurrence Based On Electro-Optical System

Quantum theory is one of the two footstones of modern physics. It provides the new methods of the description on the nature and the ways of thinking to people. On one hand, the classical physics cannot meet with the requirement of the person for the more secure communications and the faster computing speed. On the other hand, with the development of science and technology, the quantum information process and quantum computing have unlimited potential. Whether in the quantum information process or quantum computation, the maximally entangled states plays a significance role. However, when the maximally entangled states which are prepared for the practical applications have the interaction influence with environment, the quality of the entanglement will be inevitably degraded which will make the maximally entangled states into the mixed state or the partially entangled state. In general, to ensure the quantum information process or quantum computing protocols can been executed successfully a quantum entanglement concentration procedure should been performed at the beginning of the whole protocols.This thesis firstly analyzes the conventional ECPs and discuss the advantages and disadvantages. Base on the study of classical entanglement concentration protocols, he proposes two ECPs which are especially useful in different situations. The first article is: electronic cluster state entanglement concentration based on charge detection. In this article, he proposes a protocol for electronic cluster states with a high success probability which may be useful in current solid quantum computation. The second article is: entanglement concentration for W-type entangled coherent states. This protocol not only can obtain the maximally entangled ECS with some success probability, but also can increase the amplitude of the coherent state. Therefore, it is especially useful in long-distance quantum communication, if the photon loss is considered.This thesis also focus on the search field of direct measurement concurrence. With the studying of existing protocols, the third article is: direct measurement of the concurrence for two-qubit electron spin entangled pure state base on charge detection.