The Dynamic Characteristics Of The Quantum Discord Between Atoms In The Cavities

Quantum information and quantum computation are newly developing subject in recent ten years. It not only improves the algorithms using quantum principle to perform a number of taska that are either impossible to realize or less efficient for classical computer, but also reveals a number of counterintuitive quantum effect. Quantum entanglement is a kind of pure quantum effects. As an important physical resource in quantum information processing, quantum entanglement has been discussed widely. However, with the deeply investigating, it is known that the entanglement is only a part of a quantum correlation. A general resource for quantum information is quantum correlation, so the quantum discord was introduced to describe the quantum correlation. It is very significant and to study the quantum discord and find its potential application in quantum communication and quantum computation. In this thesis, the basic theory and measurement method of quantum entanglement and correlation are introduced firstly. Then, we focus our research on the quantum discord dynamics of two-qubit quantum systems, mainly including two parts as follows:(1) Studied is the discord dynamics of two space-separated atoms, one of them in Jaynes-Cummings cavity and the other isolated completely. We analyze the effect of the number of the cavity photons and the initial entanglement on the quantum discord dynamics in detail, not considering the interactions between two atoms. The results show that there are sudden changes of discord when the number of photons in the cavity is not zero, but quantum discord has no sudden death. In additional, the discord does not depend on the two kinds of the most entangled initial states. (2) We investigate the discord and quantum entanglement dynamics of two atoms in Jaynes-Cummings cavity respectively. The effects of the photon number in the cavity and the initial states on the quantum entanglement and discord dynamics are also discussed. For this model, the discord sudden death and entanglement sudden death appear when the photon number in cavity is not zero, but there are not discord sudden changes. The time of the discord decaying is dependent on the initial state.