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University of Nebraska - Lincoln

2007

Entanglement in spin models

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Thermal Entanglement Of Two Interacting Qubits In A Static Magnetic Field, G. Lagmago Kamta, Andrei Y. Istomin, Anthony F. Starace Jun 2007

Thermal Entanglement Of Two Interacting Qubits In A Static Magnetic Field, G. Lagmago Kamta, Andrei Y. Istomin, Anthony F. Starace

Anthony F. Starace Publications

We study systematically the entanglement of a two-qubit Heisenberg XY model in thermal equilibrium in the presence of an external arbitrarily-directed static magnetic field, thereby generalizing our prior work [G. Lagmago Kamta, A.F. Starace, Phys. Rev. Lett. 88, 107901 (2002)]. We show that a magnetic field having a component in the xy-plane containing the spin-spin interaction components produces different entanglement for ferromagnetic (FM) and antiferromagnetic (AFM) couplings. In particular, quantum phase transitions induced by the magnetic field-driven level crossings always occur for the AFM-coupled qubits, but only occur in FM-coupled qubits when the coupling is of Ising type or ...