Observing single quantum trajectories of a superconducting qubit: ensemble properties and driven dynamics

ORAL

Abstract

We use weak measurements to track individual quantum trajectories of a superconducting qubit embedded in a microwave cavity. Using a near-quantum-limited parametric amplifier, we selectively measure either the phase or amplitude of the cavity field, and thereby confine trajectories to either the equator or a meridian of the Bloch sphere. We analyze ensembles of trajectories to determine statistical properties such as the most likely path and most likely time connecting pre and post-selected quantum states. We compare our results with theoretical predictions derived from an action principle for continuous quantum measurement. Furthermore, by introducing a qubit drive, we investigate the interplay between unitary state evolution and non-unitary measurement dynamics.

*This work was supported by the IARPA CSQ program and the ONR.

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Authors

  • Steven Weber

    • QNL, University of California, Berkeley

  • K.W. Murch

    • Department of Physics, Washington University

  • A. Chantasri

    • Department of Physics and Astronomy and Rochester Theory Center, University of Rochester

  • J. Dressel

    • Department of Electrical Engineering, University of California, Riverside

  • A.N. Jordan

    • Department of Physics and Astronomy and Rochester Theory Center, University of Rochester ; Institute of Quantum Studies, Chapman University

  • I. Siddiqi

    • QNL, University of California, Berkeley