Decoherence of Bell states by local interactions with a suddenly quenched spin environment

Pierre Wendenbaum, Bruno G. Taketani, and Dragi Karevski
Phys. Rev. A 90, 022125 – Published 29 August 2014

Abstract

We study the dynamics of disentanglement of two qubits initially prepared in a Bell state and coupled at different sites to an Ising spin chain in a transverse field (ITF) playing the role of a dynamic spin environment. The initial state of the whole system is prepared in a tensor product state ρBellρchain, where the state of the chain is taken to be given by the ground state |G(λi) of the ITF Hamiltonian HE(λi) with an initial field λi. At time t=0+, the strength of the transverse field is suddenly quenched to a new value, λf, and the whole system (chain + qubits) undergoes a unitary dynamics generated by the total Hamiltonian HTot=HE(λf)+HI, where HI describes a local interaction between the qubits and the spin chain. The resulting dynamics leads to a disentanglement of the qubits, which is described through Wootters' concurrence, due to their interaction with the nonequilibrium environment. The concurrence is related to the Loschmidt echo, which in turn is expressed in terms of the time-dependent covariance matrix associated with the ITF. This permits a precise numerical and analytical analysis of the disentanglement dynamics of the qubits as a function of their distance, bath properties, and quench amplitude. In particular, we emphasize the special role played by a critical initial environment.

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  • Received 26 May 2014

DOI:https://doi.org/10.1103/PhysRevA.90.022125

©2014 American Physical Society

Authors & Affiliations

Pierre Wendenbaum1,2, Bruno G. Taketani2, and Dragi Karevski1,*

  • 1Institut Jean Lamour, dpt P2M, Groupe de Physique Statistique, Université de Lorraine-CNRS, B.P. 70239, F-54506 Vandœuvre-lès-Nancy Cedex, France
  • 2Theoretische Physik, Universität des Saarlandes, D-66123 Saarbrücken, Germany

  • *dragi.karevski@univ-lorraine.fr

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Vol. 90, Iss. 2 — August 2014

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