Quantum Correlation Dynamics In Different Environments

The principle of state superposition is one of the most intriguing features of the microscopic world. When the principle of state superposition is applied to the composite system, it leads to the appearance of the fantastic phenomenon, which is termed as the quantum entanglement. With the rapid development of quantum information, quantum entanglement becomes an important resource for quantum communication and quantum computation. However, quantum information can still achieve without any entanglement because quantum correlation plays a key role in this task. Hence, quantum correlation(including quantum entanglement, quantum discord and additionally some other measures) becomes the important research of quantum information.This thesis mainly focuses on the evolution behavior of tripartite quantum correlations within different environments, and includes the following three aspects:1. We investigate the tripartite entanglement dynamics of three two-level atoms in a multi-mode vacuum field. By considering the influences of the interatomic distance and the initial condition on the lower bound of concurrence and the tripartite negativity, we show that an optimal interatomic distance can be found to minimize the collective damping. Interestingly, at the same optimal distance, the tripartite entanglement would be maximized in the open dynamics process. In the case of shorter interatomic distance, the tripartite entanglement can display the oscillatory behavior in the initial short-time limit and be trapped in a stationary value in the long-time limit. In addition, the tripartite entanglement for the general situation with different interatomic distances is also discussed.2. We investigate the dynamics and improvement of tripartite quantum correlations in three atoms interacting with the independent cavities, in terms of genuinely multipartite concurrence, lower bound of concurrence and tripartite geometric quantum discord. By choosing the GHZ and W states as atomic initial states and the vacuum state as the initial state of the cavities, we study the relationship between the initial state and entanglement transfer, and the robustness of different correlation measures. The results show that the different initial states can control entanglement transfer between the subsystems, and the tripartite geometric quantum discord is more robust than tripartite entanglement in the evolution process. Then, we propose the optimal scheme to improve tripartite entanglement in certain conditions via the weak measurement and quantum measurement reversal. In addition, we find that our study also works for the N-qubit GHZ state by using genuinely multipartite concurrence.3. Entanglement dynamical evolution of three two-level atoms coupled to a common environment is investigated. We utilize the tripartite negativity to quantify entanglement and analyze the effect of the initial state, pairwise dipole-dipole interactions on the entanglement dynamical properties of the system by means of numerical calculations. Results show that a novel quantum interference can be controlled by the relative phase of initially entangled states of the atoms. And the excited-state population can be trapped in the long time limit. Besides, the tripartite entanglement can be enhanced by choosing the appropriate conditions.