Studies On Quantum Correlation Dynamics Of Three Aubits In Dissipative Environments

An actual quantum system is not closed and therefore will unavoidably be affected by its surrounding environment. Due to the interaction with its environment, the quantum system is very fragile and is easy to lose its coherence, which is the main obstacle for the implementation of quantum information processing. Therefore, it is of great significance to investigate the decoherence dynamics in open quantum systems and search possible approaches to protect the coherence of system from the influence of its environments. This thesis mainly concentrates on several quantum correlations dynamics of three qubits within different reservoirs.In this thesis, we investigate the dynamics of pairwise quantum discord (QD) for a mixed three-qubit W-type state in three independent non-Markovian reservoirs at zero temperature, each of which is modeled by a leaky cavity with Lorentzian spectral density. The influence of the environment’s amount of non-Markovianity, the detuning between the qubit frequency and the cavity centre frequency, and the purity of the initial state on the QD dynamics are analyzed in detail. It is found that in the non-Markovian regime the system-reservoir interactions induce QD revivals and oscillations no matter whether the detuning is zero or not. Moreover, QD can be preserved for a long time if the non-Markovian condition and the detuning condition are satisfied simultaneously.We also study the decoherence dynamics of single qubit interacting with different dissipative vacuum reservoir (sub ohmic、super ohmic、and ohmic), and then analyze three kinds of quantum correlation dynamics of three qubits within dissipative vacuum environment. Our study show that negativity、pairwise QD and measurement-induced disturbance can result in correlation revival phenomenon under the non-Markovian regime. Moreover, the existence of a bound state between the qubit and its reservoir as well as the non-Markovian effect are two essential ingredients for the quantum correlation preservation in a long time limit. Futhermore, if the bound state is absent within the strong non-Markovian regime, there exist the phenomenon of oscillation and revival for quantum correlation. Besides, we explicitly analyze the formation condition of bound state and the preservation mechanism of quantum correlation.