Direct equivalence between quantum phase transition phenomena in radiation-matter and magnetic systems: Scaling of entanglementJ. Reslen1, L. Quiroga1 and N. F. Johnson2
1 Departamento de Física, Universidad de Los Andes A.A. 4976, Bogotá D.C., Colombia
2 Centre for Quantum Computation and Department of Physics, University of Oxford Clarendon Laboratory - Parks Road, OX1 3PU, UK
received 2 September 2004; accepted in final form 2 November 2004
published online 8 December 2004
We show that the quantum phase transition arising in a standard radiation-matter model (Dicke model) belongs to the same universality class as the infinitely coordinated, transverse-field XY model. The effective qubit-qubit exchange interaction is shown to be proportional to the square of the qubit-radiation coupling. A universal finite-size scaling is derived for the corresponding two-qubit entanglement (concurrence) and a size-consistent effective Hamiltonian is proposed for the qubit subsystem.
03.65.Ud - Entanglement and quantum nonlocality (e.g. EPR paradox, Bell's inequalities, GHZ states, etc.).
73.43.Nq - Quantum phase transitions.
75.10.-b - General theory and models of magnetic ordering.
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