Non-Markovian homodyne-mediated feedback on a two-level atom: a quantum trajectory treatment

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Title Non-Markovian homodyne-mediated feedback on a two-level atom: a quantum trajectory treatment
Author Wang, Jin; Wiseman, Howard Mark; Milburn, Gerard
Journal Name Chemical Physics
Year Published 2001
Place of publication Netherlands
Publisher North-Holland
Abstract Quantum feedback can stabilize a two-level atom against decoherence (spontaneous emission), putting it into an arbitrary (specified) pure state. This requires perfect homodyne detection of the atomic emission, and instantaneous feedback. Inefficient detection was considered previously by two of us. Here we allow for a non-zero delay time τ in the feedback circuit. Because a two-level atom is a non-linear optical system, an analytical solution is not possible. However, quantum trajectories allow a simple numerical simulation of the resulting non-Markovian process. We find the effect of the time delay to be qualitatively similar to that of inefficient detection. The solution of the non-Markovian quantum trajectory will not remain fixed, so that the time-averaged state will be mixed, not pure. In the case where one tries to stabilize the atom in the excited state, an approximate analytical solution to the quantum trajectory is possible. The result, that the purity (P=2Tr[ρ2]−1) of the average state is given by P=1−4γτ (where γ is the spontaneous emission rate) is found to agree very well with the numerical results.
Peer Reviewed Yes
Published Yes
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Copyright Statement Copyright 2001 Elsevier. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal's website for access to the definitive, published version.
Volume 268
Issue Number -
Edition -
Page from 221
Page to 235
ISSN 0301-0104
Date Accessioned 2002-04-16
Language en_AU
Research Centre Centre for Quantum Dynamics
Subject PRE2009-Theoretical Physics
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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