Pairwise Entanglement in finite spin chains at finite temperature

J.M. MATERA; N. CANOSA; R. ROSSIGNOLI

Departemento de Física, FCEyN, UBA

Workshop; THE QUANTUM MECHANICS OF THE XXI CENTURY: MANIPULATION OF COHERENT ATOMIC MATTER : Eleventh J. J. Giambiagi Winter School.; 2009

Departamento de Física, FCEyN, UBA, CONICET

We examine the thermal pairwise entanglement in  a symmetric system of n spins fully connected through  anisotropic $XYZ$ - type couplings embedded in a  transverse magnetic field. We consider both the exact evaluation together with that obtained with the static path+ random phase approximation RPA and the ensuing mean field + RPA. The latter is shown to provide an accurate analytic description of the thermal concurrence in large systems. We also analyze the limit temperature for pairwise entanglement, which is shown to increase for large fields. Special finite size effects are also discussed.