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Journal of Physics A Mathematical and General

Entanglement of a two-qubit system with anisotropic couplings in nonuniform magnetic fields

Zhan-Ning Hu, S. H. Youn, Kicheon Kang, Chongil Kim

Published Aug 2, 2006• 20 citations
Publisher

Abstract

We investigate the quantum entanglement of the ground state and the mixed states at finite temperatures for a two-qubit system within the framework of an anisotropic Heisenberg XYZ model in the presence of a nonuniform magnetic field. As a measure of the entanglement, the concurrence of the two-qubit states is calculated and is analysed in detail as a function of the coupling constants, magnetic field and temperature. Consequently, we show that the combined influence of the anisotropic interaction and the nonuniformity of the magnetic fields predicts much pronounced entanglement properties.

DOI
10.1088/0305-4470/39/33/019

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We investigate the thermal entanglement of a two-qubit anisotropic Heisenberg XYZ model with both uniform and nonuniform magnetic fields in the x-z plane at thermal equilibrium. For the uniform magnetic field case, it is shown that the value of the critical magnetic field B(subscript c) may be broadened by changing the direction of the magnetic field and that the revival of entanglement is due to the combined influence of the magnetic field and the Heisenberg model's partial anisotropy in the plane which is perpendicular to the magnetic field. Moreover, the direction of the magnetic field will have an effect on the critical temperature T(subscript c) only when the field strength is large enough. For the nonuniform magnetic field case it is found that, for any direction of the magnetic field, the introduction of inhomogeneity in the magnetic field always broadens the critical magnetic field B(subscript c), but diminishes the maximum entanglement.