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Abstract
We study and compare the time evolutions of concurrence and quantum discord in a driven system of two interacting qubits prepared in a generic Werner state. The corresponding quantum dynamics is exactly treated and manifests the appearance and disappearance of entanglement. Our analytical treatment transparently unveils the physical reasons for the occurrence of such a phenomenon, relating it to the dynamical invariance of the X structure of the initial state. The quantum correlations which asymptotically emerge in the system are investigated in detail in terms of the time evolution of the fidelity of the initial Werner state.
Highlights
Entanglement sudden death is a phenomenon that was widely investigated during recent years in the case of open quantum systems [1] and represents the decrease of the entanglement to zero in a finite time
Our main goal is to verify the occurrence of sudden death and rebirth manifestations in the time evolution of the quantum correlations arising between the two qubits in such a controlled, time-dependent, physical scenario
We exactly evaluate in which way the quantum discord goes with time, since it captures all kinds of nonclassical correlations and can be different from zero even when there is no entanglement
Summary
Entanglement sudden death is a phenomenon that was widely investigated during recent years in the case of open quantum systems [1] and represents the decrease of the entanglement to zero in a finite time. Werner states are X states exhibiting intriguing nonlocal correlations [38] and, play an important role in the quantum information processing All these features make of special interest investigating their dynamics when the physical scenario evolves under controlled time-dependent fields. A detailed analysis of the dynamics of the concurrence and quantum discord, including a comparison between their behaviors, is presented in Section 4 by considering that at the initial time the density operator of the two qubits is a Werner state. This interpretation is based on the time evolution of the fidelity between the initial Werner state and the evolved Werner state. The analytical expression of the fidelity between the Werner state and the generalized Werner state is obtained in Appendix D
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