Out-of-time-order correlation functions provide a proxy for diagnosing chaos in quantum systems. We propose and analyze an interferometric scheme for their measurement, using only local quantum control and no reverse time evolution. Our approach utilizes a combination of Ramsey interferometry and the recently demonstrated ability to directly measure Renyi entropies. To implement our scheme, we present a pair of cold-atom-based experimental blueprints; moreover, we demonstrate that within these systems, one can naturally realize the transverse-field Sherrington-Kirkpatrick (TFSK) model, which exhibits certain similarities with fast scrambling black holes. We perform a detailed numerical study of scrambling in the TFSK model, observing an interesting interplay between the fast scrambling bound and the onset of spin-glass order.
@article{arxiv.1607.01801,
title = {Interferometric Approach to Probing Fast Scrambling},
author = {Norman Y. Yao and Fabian Grusdt and Brian Swingle and Mikhail D. Lukin and Dan M. Stamper-Kurn and Joel E. Moore and Eugene A. Demler},
journal= {arXiv preprint arXiv:1607.01801},
year = {2016}
}