Characterizing measurement and feedback processes in superconducting qubit systems

ORAL

Abstract

New strategies for quantum control have been enabled by integrating nearly quantum-limited amplifiers with long-lived superconducting qubits. We now record high fidelity~single shot measurements that are also QND. We rely on these properties of our measurement to apply an active feedback on a quantum system. Understanding the degree to which they are QND is desirable. For example, if measurements are perfectly QND yet have finite fidelity, repeated measurements can improve the overall fidelity. In this talk, we present a formalism to quantify a number of important independent measurement parameters including fidelity and the QND degree. We then apply this formalism to characterize and optimize a feedback experiment.

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Authors

  • N. Ofek

    Departments of Applied Physics and Physics, Yale University

  • Y. Liu

    Department of Applied Physics, Yale University, Departments of Applied Physics and Physics, Yale University

  • Michael Hatridge

    Departments of Applied Physics and Physics, Yale University, Applied Physics Department, Yale University, Yale Univ. Depts. of Applied Physics and Physics

  • S. Shankar

    Department of Applied Physics, Yale University, Departments of Applied Physics and Physics, Yale University

  • Michel Devoret

    Department of Applied Physics, Yale University, Departments of Applied Physics and Physics, Yale University, Yale Univ. Depts. of Applied Physics and Physics

  • Robert Schoelkopf

    Departments of Applied Physics and Physics, Yale University, Department of Applied Physics, Yale University, Yale University Departments of Applied Physics and Physics