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Published February 1, 2019 | Supplemental Material + Published + Submitted
Journal Article Open

Out-of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling

Abstract

Out-of-time-ordered correlators (OTOCs) have received considerable recent attention as qualitative witnesses of information scrambling in many-body quantum systems. Theoretical discussions of OTOCs typically focus on closed systems, raising the question of their suitability as scrambling witnesses in realistic open systems. We demonstrate empirically that the nonclassical negativity of the quasiprobability distribution (QPD) behind the OTOC is a more sensitive witness for scrambling than the OTOC itself. Nonclassical features of the QPD evolve with timescales that are robust with respect to decoherence and are immune to false positives caused by decoherence. To reach this conclusion, we numerically simulate spin-chain dynamics and three measurement protocols (the interferometric, quantum-clock, and weak-measurement schemes) for measuring OTOCs. We target experiments based on quantum-computing hardware such as superconducting qubits and trapped ions.

Additional Information

© 2019 American Physical Society. (Received 23 June 2018; published 1 February 2019) J. R. G. A. was supported by a fellowship from the Grand Challenges Initiative at Chapman University. N. Y. H. is grateful for funding from the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center (NSF Grant No. PHY-1125565) with support from the Gordon and Betty Moore Foundation (GBMF-2644); a Graduate Fellowship from the Kavli Institute for Theoretical Physics, supported by the NSF under Grant No. NSF PHY-1125915; the Walter Burke Institute for Theoretical Physics at Caltech; and a Barbara Groce Graduate Fellowship. J. D. was partially supported by the Army Research Office (ARO) Grants No. W911NF-15-1-0496 and No. W911NF-1-81-0178. The authors wish to thank Paul Dieterle, Poul Jessen, Andrew Keller, Oskar Painter, and Mordecai Waegell for helpful discussions.

Attached Files

Published - PhysRevLett.122.040404.pdf

Submitted - 1806.09637.pdf

Supplemental Material - suppl_mat.pdf

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