Research Papers in Physics and Astronomy


Date of this Version

March 2002


Published by American Physical Society. Phys. Rev. Lett. 88, 107901 (2002). Copyright © 2002 American Physical Society. Permission to use.


We investigate the entanglement of a two-qubit anisotropic Heisenberg XY chain in thermal equilibrium at temperature T in the presence of an external magnetic field B along the z axis. By means of the combined influences of anisotropic interactions and a magnetic field B, one is able to produce entanglement for any finite T, by adjusting the magnetic field strength. This contrasts with the isotropic interaction or the B = 0 cases, for which there is no entanglement above a critical temperature Tc that is independent of the external B field.

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