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Berlin 2005 – scientific programme

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Q: Quantenoptik und Photonik

Q 42: Quanteninformation II

Q 42.7: Talk

Tuesday, March 8, 2005, 15:30–15:45, HU Audimax

Bi-partite and global entanglement in a many-particle system with collective spin coupling — •Cristian Ionescu1,2, Razmik Unanyan1,3, and Michael Fleischhauer11Fachbereich Physik, Technische Universität Kaiserslautern — 2Institute for Space Science, Bucharest, Romania — 3Institute for Physical Research of Armenian National Academy of Sciences, Ashtarak, Armenia

Bipartite and global entanglement are analyzed for the ground state of a system of N spin 1/2 particles interacting via a collective spin-spin coupling described by the Lipkin-Meshkov-Glick (LMG) Hamiltonian. Under certain conditions which includes the special case of a supersymmetry, the ground state can be constructed analytically.

In the case of an antiferromagnetic coupling and for an even number of particles this state undergoes a smooth crossover as a function of the continuous anisotropy parameter γ from a separable (γ=∞) to a maximally entangled many-particle state (γ=0). From the analytic expression for the ground state bipartite and global entanglement are calculated. In the thermodynamic limit a discontinuous change of the scaling behavior of the bipartite entanglement is found at the isotropy point γ=0. For finite systems with total spin J=N/2 the scaling behavior changes at γcrit=1/J.

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