%0 Journal Article
%A Relaño Pérez, Armando
%A Pérez Fernández, P.
%A Arias, J. M.
%A Dukelsky, J.
%A García Ramos, J. E.
%T Decoherence due to an excited-state quantum phase transition in a two-level boson model
%D 2009
%@ 1050-2947
%U https://hdl.handle.net/20.500.14352/44423
%X The decoherence induced on a single qubit by its interaction with the environment is studied. The environment is modeled as a scalar two-level boson system that can go through either first-order or continuous-excited-state quantum phase transitions, depending on the values of the control parameters. A mean-field method based on the Tamm-Damkoff approximation is worked out in order to understand the observed behavior of the decoherence. Only the continuous-excited-state phase transition produces a noticeable effect in the decoherence of the qubit. This is maximal when the system-environment coupling brings the environment to the critical point for the continuous phase transition. In this situation, the decoherence factor (or the fidelity) goes to zero with a finite-size scaling power law.
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