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Dynamics of quantum correlations in two-qubit systems within non-Markovian environments (1205.6419v2)

Published 29 May 2012 in quant-ph

Abstract: Knowledge of the dynamical behavior of correlations with no classical counterpart, like entanglement, nonlocal correlations and quantum discord, in open quantum systems is of primary interest because of the possibility to exploit these correlations for quantum information tasks. Here we review some of the most recent results on the dynamics of correlations in bipartite systems embedded in non-Markovian environments that, with their memory effects, influence in a relevant way the system dynamics and appear to be more fundamental than the Markovian ones for practical purposes. Firstly, we review the phenomenon of entanglement revivals in a two-qubit system for both independent environments and a common environment. We then consider the dynamics of quantum discord in non-Markovian dephasing channel and briefly discuss the occurrence of revivals of quantum correlations in classical environments.

Citations (198)

Summary

Dynamics of Quantum Correlations in Two-Qubit Systems within Non-Markovian Environments

The paper "Dynamics of Quantum Correlations in Two-Qubit Systems within Non-Markovian Environments" by Rosario Lo Franco and colleagues presents a comprehensive paper on the evolution of quantum correlations in bipartite qubit systems subject to non-Markovian environments. This research is pivotal for quantum information processes as it investigates entanglement, nonlocal correlations, and quantum discord, which are essential resources for quantum communication and computing.

Summary of Results

The authors focus on characterizing the dynamics of quantum correlations, particularly entanglement and quantum discord, in two-qubit systems that interact with non-Markovian environments. Non-Markovian environments are characterized by their memory effects, differentiating them from Markovian environments where such memory effects are absent. This distinction is crucial as memory effects can lead to phenomena such as the revival and trapping of correlations.

  • Entanglement Revivals: The paper reviews scenarios where entanglement that has vanished can resurrect over time due to interactions with non-Markovian environments. This revival is observed in systems with independent environments and those with shared environments. The authors demonstrate that non-Markovian environments can counter premature loss of entanglement, also known as entanglement sudden death (ESD), prevalent in Markovian settings.
  • Entanglement Trapping: Trapping refers to the persistence of entanglement over long periods. The authors observed such phenomena in systems embedded within structured environments like photonic crystals. These materials can significantly inhibit spontaneous emission, thereby preserving entanglement.
  • Quantum Discord and other Correlations: The dynamics of quantum discord—an indicator of quantum correlations that remains even when entanglement disappears—is explored under non-Markovian noise. A surprising result is the existence of "frozen" discord, where quantum discord remains constant for certain time intervals in non-Markovian dephasing channels.
  • Dynamics in Classical Environments: The exploration extends to environments where quantum noise is replaced by classical noise, such as random external fields. Even in these cases, there were observable revivals of quantum correlations, suggesting that the environment's classical nature doesn't entirely preclude the recovery of quantum features.

Theoretical and Practical Implications

The implications of these findings are profound, both theoretically and practically. Theoretically, the paper enhances the understanding of how quantum correlations are influenced by environmental characteristics, particularly how non-Markovian dynamics differ from Markovian cases. Practically, these insights could inform the development of quantum technologies where maintaining quantum coherence and correlation over time is crucial.

Future Directions

As quantum technologies evolve, further exploration into more complex and realistic models of non-Markovian environments could shed light on additional mechanisms or configurations that could be leveraged to protect and utilize quantum correlations. Additionally, experimental validation and real-world testing of these theoretical predictions would be indispensable in translating research into practical quantum computing and communication devices.

In summary, this paper enriches the field of quantum information science by systematically analyzing the interplay between quantum systems and non-Markovian environments, revealing potential pathways to extend the effective use of quantum correlations in practical applications.