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arXiv · 1311.5472

Reversing quantum trajectories with analog feedback

G. de Lange·D. Ristè·M. J. Tiggelman·C. Eichler·L. Tornberg·G. Johansson·A. Wallraff·R. N. Schouten·L. DiCarlo
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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 $\tildeη \approx 0.5$, 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.

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G. de Lange, D. Ristè, M. J. Tiggelman, C. Eichler, L. Tornberg, G. Johansson, A. Wallraff, R. N. Schouten, L. DiCarlo. 2013-11-21. Reversing quantum trajectories with analog feedback. https://doi.org/10.1103/physrevlett.112.080501

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