Theory of real-time feedback on oscillating qubits using weak measurement

ORAL

Abstract

We review our recent work on state estimation and feedback control of single quantum systems based on weak measurement. We discuss two classes of feedback protocols used to control qubit oscillations. The first relies on standard proportional-integral-differential control while the second comprises unitary operations aimed at reversing the phase kicks due to measurement back-action. Analytical expressions for the convergence of state estimation fidelity are also obtained in the continuous measurement limit, by evaluating the fidelity change in an incremental step of the estimation protocol.

*This work was supported in part by a grant from the South African National Research Foundation (Grant 93602), as well as an award by the United States Airforce Office of Scientific Research (Award FA9550-14-1-0151)

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Authors

  • Hermann Uys

    • CSIR and Stellenbosch University, South Africa

  • Pieter du Toit

    • National Metrology Institute of South Africa, South Africa

  • Shaun Burd

    • University of Colorado, and National Insitute of Standards and Technology, USA

  • Humairah Bassa

    • University of KwaZulu-Natal, South Africa

  • Thomas Konrad

    • University of KwaZulu-Natal, South Africa