Browsing by Author "Brandes, Tobias"

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    Entanglement and parametric resonance in driven quantum systems
    (2010-01) Bastidas, Víctor Manuel; Reina Estupiñán, John Henry; Emary, C.; Brandes, Tobias
    We study the relationship between entanglement and parametric resonance in a system of two coupled time-dependent oscillators. As a measure of bipartite entanglement, we calculate the linear entropy for the reduced density operator, from which we study the entanglement dynamics. In particular, we find that the bipartite entanglement increases in time up to a maximal mixing scenario, when the set of auxiliary dynamical parameters are under parametric resonance. Moreover, we obtain a closed relationship between the correlations in the ground state, the localisation of the Wigner function in phase space, and the localisation of the wave function of the total system.
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    Non-equilibrium entanglement in a driven many-body spin-boson model
    (2009) Bastidas, Víctor Manuel; Reina Estupiñán, John Henry; Brandes, Tobias
    We study the entanglement dynamics in the externally-driven single-mode Dicke model in the thermodynamic limit, when the field is in resonance with the atoms. We compute the correlations in the atoms-field ground state by means of the density operator that represents the pure state of the universe and the reduced density operator for the atoms, which results from taking the partial trace over the field coordinates. As a measure of bipartite entanglement, we calculate the linear entropy, from which we analyze the entanglement dynamics. In particular, we found a strong relation between the stability of the dynamical parameters and the reported entanglement.