Feedback control of quantum systems using continuous state estimation
Andrew C. DohertyDepartment of Physics, University of Auckland, Private Bag 92019, Auckland, New ZealandKurt JacobsDepartment of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
1999en
ABI
Abstract
We present a formulation of feedback in quantum systems in which the best estimates of the dynamical variables are obtained continuously from the measurement record, and fed back to control the system. We apply this method to the problem of cooling and confining a single quantum degree of freedom, and compare it to current schemes in which the measurement signal is fed back directly in the manner usually considered in existing treatments of quantum feedback. Direct feedback may be combined with feedback by estimation, and the resulting combination, performed on a linear system, is closely analogous to classical linear-quadratic-Gaussian control theory with residual feedback.
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