Interferometric Approach to Probing Fast Scrambling
  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. 
Norman Y. Yao, Fabian Grusdt, Brian Swingle, Mikhail D. Lukin, Dan M.   Stamper-Kurn, Joel E. Moore, Eugene A. Demler
quant-ph cond-mat.dis-nn cond-mat.quant-gas cond-mat.stat-mech hep-th