Classical and quantum correlations under decoherence / Correlações clássicas e quânticas sob decoerência

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

26/08/2009

RESUMO

Recently, in the context of discrete variables, the existence of quantum correlations that are more general than entanglement was identified. We may conjecture that these correlations are a very important resource in quantum information science and in some areas of physics. However, this fragile resource is quickly destroyed by the decoherence process. In this dissertation, we present results concerning the dynamics of general quantum correlations and its classical counterpart. To begin with, we introduce the research area and review topics and concepts that are used throughout the dissertation: decoherence, dynamics of open quantum systems, Bells inequalities, entanglement theory, sudden death and sudden birth of entanglement, concepts of classical information theory, the quantum discord, and a model of quantum computation without entanglement. Later, we study the dynamics of the general quantum correlations and their classical counterpart under decoherence. Specifically, we consider a two qubit system, initially in a state with maximal mixed marginals, interacting independently with some kinds of environment (phase flip, bit flip, bit-phase flip, and phase damping). We identify, for the first time, three different kinds of dynamical behaviour of the general quantum correlation and its classical counterpart. One of these dynamical behaviours presents a sudden change in the decaying rate of both classical and quantum correlations. We also show a necessary condition for the classical correlation to remain constant under decoherence. It gives us the possibility to define an analytically computable measure of classical and quantum correlations. This operational measure of correlations may facilitate its experimental measurement. The extension of this operational measure of classical and quantum correlations for more general states will be important to study the role of these correlations in quantum phase transitions, non equilibrium thermodynamics, etc. Finally, we extend our results investigating also the system-environment and environment-environment correlations. For the system considered here, we show that the decoherence process exists without any bipartite entanglement between system and environment. On the other hand, bipartite classical correlation and bipartite quantum correlation of separable states are created in this process. We also note that the bipartite quantum correlation is completely destroyed at the end of the decoherence process. We believe that these results can support a better understanding of decoherence.

ASSUNTO(S)

teoria quântica dinâmica de sistemas quânticos abertos teoria quântica - decoêrencia teoria quântica - correlações informação quântica fisica geral desigualdade de bell

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