The Freezing And Sudden Change Phenomenon Of Quantum Discord Under Local Noise Environment

As a burgeoning inter-discipline of quantum mechanics and information theory, quantuminformation science has accomplished grand achievements in recent years. Quantumentanglement is one of the most important physical resources, which can give rise to theexponential speedup capacity for quantum computation. However, quantum entanglement isjust a special kind of quantum correlation, which cannot account for all the quantumcorrelations. Moreover, recent studies indicate that there exists a kind of quantum states whichis separable but has nonzero quantum correlation, and can be used to quantum accelerationcomputation. Therefore, it is a crucial problem to investigate the property of quantumcorrelations, especially the different property from that of quantum entanglement.This thesis is focused on the freezing and sudden change phenomenon of quantumdiscord under local noise environment. In Chapter1, we introduce the concept andoperational meaning of quantum discord, which is a basic formula for quantum correlations.In addition, we review the previous studies and results on the quantum correlation dynamics.In Chapter2, we analyze the dynamical evolution of quantum discord of a class of Belldiagonal states under local bit-flip channels, and derive the necessary and sufficientconditions for the freezing quantum discord. In chapter3, we study the sudden changeproperty of geometric quantum discord in multipartite cavity-reservoir systems. We find thatthe dynamical property of quantum correlations have the intrinsic connection between thecavity and reservoir systems. Moreover, we investigate the difference of sudden changebetween the fidelity of RSP and the geometric quantum discord. Finally, we give a briefsummary and outlook on the work of this thesis.