Estimation of the repeatedly projected reduced density matrix under decoherence

Hiromichi Nakazato, Kazuya Yuasa, B. Militello, A. Messina

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    Decoherence is believed to deteriorate the ability of a purification scheme that is based on the idea of driving a system to a pure state by repeatedly measuring another system in interaction with the former and hinder for a pure state to be extracted asymptotically. Nevertheless, we find a way out of this difficulty by deriving an analytic expression of the reduced density matrix for a two-qubit system immersed in a bath. It is shown that we can still extract a pure state if the environment brings about only dephasing effects. In addition, for a dissipative environment, there is a possibility of obtaining a dominant pure state when we perform a finite number of measurements.

    Original languageEnglish
    Article number042114
    JournalPhysical Review A - Atomic, Molecular, and Optical Physics
    Issue number4
    Publication statusPublished - 2008 Apr 21


    ASJC Scopus subject areas

    • Atomic and Molecular Physics, and Optics
    • Physics and Astronomy(all)

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