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Advances in Mathematical Physics
Volume 2012 (2012), Article ID 375182, 15 pages
http://dx.doi.org/10.1155/2012/375182
Research Article

Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems

1Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John’s, NL, Canada A1C 5S7
2Theoretical Division, Los Alamos National Laboratory, MS B213, Los Alamos, NM 87545, USA
3Dipartimento di Matematica e Fisica, and Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica, Via Musei 41, 25121 Brescia, Italy
4Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Via Bassi 6, 27100 Pavia, Italy
5Department of Applied Physics, Polytechnic Institute of NYU, 6 MetroTech Center, Brooklyn, NY 11201, USA

Received 6 March 2012; Accepted 17 May 2012

Academic Editor: P. G. Kevrekidis

Copyright © 2012 M. Merkli et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We consider an open quantum system of not directly interacting spins (qubits) in contact with both local and collective thermal environments. The qubit-environment interactions are energy conserving. We trace out the variables of the thermal environments and qubits to obtain the time-dependent reduced density matrix for two arbitrary qubits. We numerically simulate the reduced dynamics and the creation of entanglement (concurrence) as a function of the parameters of the thermal environments and the number of qubits, . Our results demonstrate that the two-qubit entanglement generally decreases as increases. We show analytically that, in the limit , no entanglement can be created. This indicates that collective thermal environments cannot create two-qubit entanglement when many qubits are located within a region of the size of the environment coherence length. We discuss possible relevance of our consideration to recent quantum information devices and biosystems.