To catch and reverse a quantum jump mid-flight

Invited

Abstract

Quantum physics differs fundamentally from classical physics in that the measurement of a quantity cannot always give certain results, even in the ideal case where both the preparation and the measurement of the system is perfect. This idea is epitomized in the phenomenon of quantum jumps, first hypothesized by Bohr in his description of the radiation emitted by an excited hydrogen atom, and now routinely observed in the laboratory on a single quantum entity. Quantum jumps are fundamentally random: the time at which they occur cannot be predicted. However, modern measurement theory stipulates that it is possible to obtain an advance warning signalling the imminent occurence of jump, before its full completion. Consequently, it is possible to reverse the jump if it is initiated by a coherent drive. We have successfully caught and reversed jumps by implementing the indirect QND measurement of a superconducting artificial atom that undergoes a transition from its ground state G to a dark state D. This is achieved by monitoring the occupancy of an auxiliary bright level B coupled to G through a Rabi drive. Our experimental results, in agreement with the predictions of quantum trajectory theory with essentially no adjustable parameters, provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as early detection of error syndromes for computation and sensing. More generally, our results provide support to the point of view that a single system under continuous, efficient observation is characterized by a time-dependent wave-function inferred from the record of previous measurement outcomes, and whose meaning is that of an objective, generalized degree of freedom.

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Presenters

  • Zlatko Minev

    Yale Univ, Applied Physics, Yale University, Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA

Authors

  • Zlatko Minev

    Yale Univ, Applied Physics, Yale University, Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA

  • Shantanu O. Mundhada

    Department of Applied Physics, Yale University, Applied Physics, Yale University, Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA

  • Shyam Shankar

    Yale Univ, Applied Physics, Yale University, Department of Applied Physics, Yale University

  • Philip Reinhold

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

  • Ricardo Guttierez

    The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, University of Auckland

  • Robert Schoelkopf

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

  • Mazyar Mirrahimi

    Yale Univ, Quantic Team, INRIA Paris, QUANTIC, INRIA Paris, QUANTIC, INRIA, Paris; YQI, Yale University, INRIA Paris and Yale University

  • Howard J Carmichael

    The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, University of Auckland

  • Michel H. Devoret

    Yale Univ, Applied Physics, Yale University, Department of Applied Physics, Yale University, Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA