Analytical determination of multi-time correlation functions in quantum chaotic systems

TL;DR

This paper analytically derives the time evolution of multi-point correlation functions, including the out-of-time-ordered correlator, in quantum chaotic systems using a random matrix approach, and compares predictions with numerical experiments.

Contribution

It introduces an analytical method to compute multi-time correlation functions in quantum chaos, extending understanding of their dynamics and relation to chaos bounds.

Findings

Dynamical correlations relate to Fourier transforms of wave-functions.

Predicted correlation dynamics match numerical simulations in spin chains.

Results suggest implications for quantum Markovianity and chaos bounds.

Abstract

The time-dependence of multi-point observable correlation functions are essential quantities in analysis and simulation of quantum dynamics. Open quantum systems approaches utilize two-point correlations to describe the influence of an environment on a system of interest, and in studies of chaotic quantum system, the out-of-time-ordered correlator (OTOC) is used to probe chaoticity of dynamics. In this work we analytically derive the time dependence of multi-point observable correlation functions in quantum systems from a random matrix theoretic approach, with the highest order function of interest being the OTOC. We find in each case that dynamical contributions are related to a simple function, related to the Fourier transform of coarse-grained wave-functions. We compare the predicted dynamics to exact numerical experiments in a spin chain for various physical observables. We comment on implications towards the emergence of Markovianity and quantum regression in closed quantum systems, as well as relate our results to known bounds on chaotic dynamics.