paper

Reversing quantum trajectories with analog feedback

arXiv:1311.5472 · doi:10.1103/PhysRevLett.112.080501

Abstract

We demonstrate the active suppression of transmon qubit dephasing induced by dispersive measurement, using parametric amplification and analog feedback. By real-time processing of the homodyne record, the feedback controller reverts the stochastic quantum phase kick imparted by the measurement on the qubit. The feedback operation matches a model of quantum trajectories with measurement efficiency , consistent with the result obtained by postselection. We overcome the bandwidth limitations of the amplification chain by numerically optimizing the signal processing in the feedback loop and provide a theoretical model explaining the optimization result.

5 pages, 4 figures, and Supplementary Information (7 figures)

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