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arXiv:1107.5692 · International Journal of Quantum Information

ROBUSTNESS OF DIFFERENT INDICATORS OF QUANTUMNESS IN THE PRESENCE OF DISSIPATION

Gian Luca Giorgi, Fernando Galve, Roberta Zambrini

Published Oct 1, 2011• 4 citations
arXivHTMLPDF

Abstract

The dynamics of a pair of coupled harmonic oscillators in separate or common thermal environments is studied, focusing on different indicators of quantumness, such as entanglement, twin oscillators correlations, and quantum discord. We compare their decay under the effect of dissipation and show, through a phase diagram, that entanglement is more likely to survive asymptotically than twin oscillators correlations.

DOI
10.1142/s0219749911008180

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We investigate the dynamical evolution of quantum discord, entanglement and purity in an open quantum system of two coupled asymmetric harmonic oscillators interacting with a thermal environment. Using the Kossakowski-Lindblad master equation we analyze the time evolution starting with a squeezed vacuum state. In contrast to our previous study on entanglement evolution in asymmetric oscillators, the present work introduces XY-type position-position coupling together with a systematic joint analysis of quantum discord and purity alongside entanglement. We examine the combined effects of the squeezing parameter, asymmetry parameter, coupling constant, dissipation rate and temperature. We find that quantum discord and entanglement exhibit, in general, a non-monotonic decrease over time. Increasing temperature consistently accelerates the degradation of both quantum correlations and purity, whereas increasing dissipation accelerates the degradation of quantum correlations but leads to higher steady-state purity. Increasing the squeezing parameter provides a protective effect by enhancing initial correlations and prolonging entanglement survival time, while increasing the coupling constant leads to higher quantum correlations. The asymmetry parameter exhibits only a weak influence on the correlation evolution. Our analysis reveals that quantum discord demonstrates stronger resilience than entanglement, which can present more complex behaviour including entanglement sudden death and possible temporary revivals and re-suppressions. These findings provide valuable insights for developing robust quantum information protocols and strategies for preserving quantum correlations in realistic open quantum systems, with potential extensions to non-Markovian regimes and multi-mode architectures.
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We study the entanglement dynamics of two entangled spins coupled with a common environment consisting of a large number of harmonic oscillators. Specifically, we study the impacts of both interaction and temperature of the environment on the dynamic quantum correlation, namely, entanglement and quantum discord of two spins via concurrence and global quantum discord criteria. In the present system, we show that the interaction between the spin sub-systems and the common environment causes environmental states to approach a composition of even and odd coherent states, which have different phases, and which are entangled with the spin states. Moreover, using the thermofield approach, we demonstrate quantum correlation stabilization as a result of increasing environmental interaction as well as increasing temperature.