ar X iv : q ua nt - p h / 05 10 16 2 v 1 20 O ct 2 00 5 Entanglement dynamics for two interacting spins

We study the dynamical generation of entanglement for a quantum system consisting in a pair of interacting spins, s1 and s2, in a constant magnetic field. Three different situations are considered: a) s1 = s2 = 1/2, b) s1 → ∞, s2 = 1/2 and c) s1 = s2 → ∞, corresponding respectively to a fully quantum system (two interacting qubits), a quantum degree of freedom coupled to a semiclassical one (a qubit in contact with an environment) and a fully semiclassical system, which displays chaotic behavior. The time evolution of entanglement for initially separable states is measured using the von-Neumann entropy and the linear entropy, and a comparison is made between the two. Compactness of the phase space and chaos in the classical limit are seen to have a strong influence on the recoherences of the system.