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    A critique of the two level approximation
    (Springer New York, 2006) Hakioǧlu, Tuǧrul; Savran, Kerim; Meşe, Emine
    The conditions in favor and necessity of a realistic multileveled description of a decohering quantum system is examined. Under these conditions approximate techniques to simplify a multileveled system by its first two levels is unreliable and a realistic multilevel description in the formulation of decoherence is unavoidable. In this regard, the first crucial observation is that, the validity of the two level approximation of a multileveled system is not controlled purely by sufficiently low temperatures. That the type of system-environment coupling and the environmental spectrum have a dominant role over the temperature is demonstrated. Particularly, zero temperature quantum fluctuations induced by the Caldeira-Leggett type linear coordinate coupling can be influential in a wide energy range in the systems allowed transitions. The second crucial observation is that the decoherence times being among the system's short time scales are found to be dominated not by the resonant but non-resonant processes.
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    Öğe
    Non-Markovian decoherence: A critique of the two-level approximation
    (Elsevier Science Bv, 2006) Hakioglu, T.; Savran, Kerim; Sevincli, Haldun; Mese, Emine
    The environmental decoherence in multilevelled systems in the context of two-level approximation is examined. It is found that the environmental temperature plays a minor role in the magnitudes of the decoherence rates whereas, the system-environment coupling and the environmental energy spectrum are dominant. Particularly, the latter is important in zero temperature quantum fluctuations and/or the nonequilibrium noise sources due to the large range of energies present in the environmental modes. Decoherence is found to be dominated by the short time nonresonant processes and this observation severely questions the use of the two-levelled models on decoherence. (C) 2005 Elsevier B.V. All rights reserved.