To catch and reverse a quantum jump mid-flight


In quantum physics, measurements can fundamentally yield discrete and random results. Emblematic of this feature is Bohr’s 1913 proposal of quantum jumps between two discrete energy levels of an atom1. Experimentally, quantum jumps were first observed in an atomic ion driven by a weak deterministic force while under strong continuous energy measurement2,3,4. The times at which the discontinuous jump transitions occur are reputed to be fundamentally unpredictable. Despite the non-deterministic character of quantum physics, is it possible to know if a quantum jump is about to occur? Here we answer this question affirmatively: we experimentally demonstrate that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable ‘flight’, by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of each completed jump is continuous, coherent and deterministic. We exploit these features, using real-time monitoring and feedback, to catch and reverse quantum jumps mid-flight—thus deterministically preventing their completion. Our findings, which agree with theoretical predictions essentially without adjustable parameters, support the modern quantum trajectory theory5,6,7,8,9 and should provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as the early detection of error syndromes in quantum error correction.

Data availability The data that support the findings of this study are available from the corresponding authors on reasonable request.

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Z.K.M. and M.H.D. acknowledge discussion with V. V. Albert, R. Blatt, S. M. Girvin, S. Korotkov, K. Mølmer, N. Ofek, W. D. Phillips, M. P. Silveri and H. M. Wiseman. V. V. Albert addressed one aspect of the Lindblad theoretical modelling regarding the waiting time. Use of facilities was supported by the Yale Institute for Nanoscience and Quantum Engineering (YINQE), the Yale SEAS cleanroom and the US National Science Foundation MRSEC DMR 1119826. This research was supported by Army Research Office under grant number W911NF-14-1-0011. R.G.-J. and H.J.C. acknowledge the support of the Marsden Fund Council from government funding, administered by the Royal Society of New Zealand under contract number UOA1328.

Z.K.M. initiated, designed and performed the experiment, designed the sample, analysed the data and carried out the initial theoretical and numerical modelling of the experiment. Z.K.M. conceived the experiment based on theoretical predictions by H.J.C. H.J.C. and R.G.-J. performed the presented theoretical modelling and numerical simulations. S.O.M. contributed to the experimental set-up and design of the device. S.O.M. and S.S. contributed to the fabrication of the device. P.R. and R.J.S. assisted with the FPGA. M.M. contributed theoretical support. M.H.D. supervised the project. Z.K.M. and M.H.D. wrote the manuscript. H.J.C. contributed the theoretical supplement. All authors provided suggestions for the experiment, discussed the results and contributed to the manuscript.

Competing interests

R.J.S. and M.H.D. are founders, and R.J.S. is an equity shareholder, of Quantum Circuits, Inc.

Correspondence to Z. K. Minev or M. H. Devoret.


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