Nonclassical Effects Of Quantum Systems In Non-Markovian Environments

Non-classical effects of quantum system are peculiar quantum effects different from the classical physics, which are caused by interactions between quantum sys-tems. Generally, interactions with outside environments will destroy non-classical effects of open quantum systems. It has become a hot issue in the quantum optics field how to maintain or enhance non-classical effects of open quantum systems by quantum controlling technology. In recent years, it has been noted that the mem-ory effects of non-Markovian environments can make the dynamical behaviors of quantum systems recovered. Whether can the non-classical effects be maintained or enhanced by quantum controlling technology in non-Markovian environments? The aim of this paper is to investigate the non-classical effects of two independent two-level atoms in non-Markovian environments. The main contents are as follows:1.Several typical non-classical effects of quantum system and the basic theory of open quantum system are introducted briefly.2.The quantum entropic uncertainty and entanglement witness in two-atom system coupling with non-Markovian environments is studied by the time-convolutionless master-equation approach. The influence of non-Markovian effect and detuning on the quantum entropic uncertainty relation and entanglement witness in the presence of quantum memory is discussed in detail. The result shows that, only when two non-Markovian reservoirs are identical, the increasing detuning and non-Markovian effect can cut down the entropic uncertainty of measurement outcomes, reduce the lower bound of the entropic uncertainty relation, increase the time re-gion during which the entanglement can be witnessed, and effectively protect the entanglement region witnessed by the lower bound of the entropic uncertainty rela-tion. The results can be applied in quantum measurement, quantum cryptography task and quantum information processing.3.The squeezing dynamics of two atoms is researched, based on the model of Chapter2. The results show that, in the non-Markovian regime, the bigger the detuning and the stronger the non-Markovian effect are, the better the squeezing is preserved. And the squeezing of two atoms can be effectively protected for a long time when both non-Markovian effect and detuning are present simultane-ously. The results would be useful in high-precision measurement and quantum communication.4.Analytical solution and entanglement swapping of two atom-cavity system, where each cavity is coupled to a Lorentzian reservoir, has been investigated by the non-Markovian master equation method. We first gain the analytical solution of two atom-cavity system in non-Markovian environments and discuss in detail the influence of the atom-cavity coupling, the non-Markovian effect and the initial state purity on the entanglement dynamics and the entanglement swapping. The results show that, the entanglement can be swapped between any two qubits by the interaction, such as between two atoms, between two cavities and between a atom and its cavity. In a short time, several pairs of entanglement alternate and decrease oscillate damply, but after a long time, four pairs of entanglement will decrease monotonically. We obtain two steady entanglement states in Marko-vian and non-Markovian regimes, respectively, and put forward an entanglement swapping scheme utilizing interaction atom with cavity in two atom-cavity dissi-pative system, and provide a new way copying entanglement that several pairs of entanglement can be simultaneously prepared by a pair of entanglement in non-Markov environments. The results will play a crucial role in quantum information, quantum communication and quantum computing.5.The quantum discord of two atoms, which are in two Ohmic reservoirs or in two Ohmic reservoirs with a Lorentz-Drude cutoff function, respectively, is considered. We find that, the quantum discord can be effectively protected not only in Lorentzian reservoirs but also in Ohmic reservoirs with a Lorentz-Drude cutoff function, and the bigger the detuning and the stronger the non-Markovian effect are, the better the robustness of the quantum discord is.6.The population dynamics of two atoms is discussed by means of the idea of Chapter5. The results show that the two atoms can be effectively trapped in the excited states not only in Lorentzian reservoirs but also in Ohmic reservoirs with a Lorentz-Drude cutoff function.7.A summary and outlook is presented.