Study Of Quantum Correlations In Open Weak-coupled Quantum Systems

The establishment of quantum mechanics provides effective research tools for the in-depth development of physics, as well as other subjects, such as chemistry, biology and information science, and other numerous science and technology research topics. Quantum information theory is such a frontier field which combines quantum mechanics and information science.As a kind of quantum nonlocal phenomenon, quantum entanglement is not only one of the most significant features that distinguish quantum mechanics from classical mechanics, but also an important physical resource used in quantum information theory, and as a crucial role in achieving quantum teleportation, quantum cryptography and quantum computation, it has been the focus of scientific research for many years. In realistic applications, quantum systems are always unavoidable influenced by external environments, which will weaken or destroy the entanglement of quantum system, however, in some special cases, environments can help the generation of the systems’entanglement. Based on the extensive research work in present, this thesis mainly focus on quantum entanglement evolutions in weakly coupled bipartite systems under the influence of spin-star environments, and the effect of interaction between the environments on the quantum correlation. This thesis is arranged as follows:In Chapter1, the influence of the decoherence in open quantum systems on energy trans-fer in the dimer system is introduced, and the exact analytical expression for the transition probability in the dimer system for different situations is also given, i.e., zero temperature and thermal equilibrium state environment, independent and correlated environments.In Chapter2, entanglement evolutions in weakly coupled bipartite systems with large energy level difference under the influence of spin-star environments are discussed, with the simply case of pure initial environment state, and the case of thermal equilibrium environment state.In Chapter3, the influence of the Ising-type interaction between spin-star environments on the quantum correlation of the bipartite system is considered, both in the case of pure initial state and the thermal equilibrium state.Finally, the conclusions and discussion are given.