Quantum Entanglement Between Two Atoms In Double Cavity System

Quantum entanglement, which is different from classical theories, is a nonlocal correlation between quantum systems, and as a key physical resource, it plays a crucial role in quantum information processes. In recent years, the research of quantum entanglement is mainly about the preparations, the measurements and the applications of it. Quantum entanglement can be generated in kinds of physical systems, such as cavity quantum electrodynamics (QED), trapped ions and linear optical systems, etc. Recently, the measurement of entanglement between two bodies has been relatively perfect. And although it has been deeply researched, the measurement of entanglement for many bodies is still not clear. Thus, a further in-deepth study of the measurement of entanglement is still needed. In the process of dynamic evolution, quantum entanglement shows some characteristics, such as entanglement sudden death (ESD), revival of entanglement and entanglement sudden birth (ESB). These features are very different from the decoherence behavior. The latter shows a gradual process in infinite time, while the former are sudden changes within finite time. Although the phenomenon has attracted extensive researches, it is still unclear what reason causes it and what is the physics behind. Cavity QED, which mainly concerns the interaction of photons and others, such as atoms, molecules and ions, etc., in high-finesse microcavities, provides a good setting for the research of entanglement. The information exchange between atoms and photons, which means transformation between the stationary qubits and the flying qubits, can be realized by cavity QED system. Based on this, the transformation, storage and operation of quantum information will be realized, and eventually quantum network will be constructed. In order to demonstrate the quantum network, we need expand the single cavity QED system to double-cavity or multi-cavity QED system, which means the spatial separation of atoms. Separated double-cavity system, such as double Jaynes-Cummings model, is a basic model for the realization of spatial separation between atoms. And it can help us understand of entanglement features and factors affecting them to study of the evolution of the entanglement dynamics in it. Quantum systems are inevitably affected by the environment, and these interactions, such as the decay of atoms and cavities, can affect the control and application of it. Therefore fully consideration of the impact of these effects is a research subject we must face with.In this paper, we first introduce the qualitative and quantitative description of entanglement. The former refers to determine whether the state is entangled and the latter refers to the measurement of entanglement. As for the measurement of entanglement, we mainly introduce the partial entropy and the concurrence for the entanglement in two-body system. Then we introduce the three characteristics of entanglement, study the evolution of entanglement between atoms in different cavity field environments and finally analyze the influence of the mean photon number, the detuning and the decay of atom on these characteristics. In squeezed vacuum field, we can weaken the ESD by decreasing the mean photon number, increasing the detuning and decay rate. The dead entanglement can not revive when the mean photon number is large enough; and the detuning can be used to stabilize entanglement. The larger the decay rate is, the faster the entanglement decreases to zero.