Interferometric Approach to Probing Fast Scrambling

TL;DR

This paper introduces an interferometric method to measure out-of-time-order correlators in quantum systems, enabling chaos diagnosis without reversing time evolution, and applies it to a model related to black hole physics.

Contribution

It proposes a novel interferometric scheme for measuring quantum chaos indicators using local control and demonstrates its implementation in cold-atom systems.

Findings

The scheme allows measurement of out-of-time-order correlators without reversing time.

Numerical analysis shows the TFSK model exhibits fast scrambling behavior.

The study reveals an interplay between scrambling bounds and spin-glass order onset.

Abstract

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.