Arresting Quantum Chaos Dynamically in Transmon Arrays

TL;DR

This paper demonstrates that in a driven transmon array, specific drive parameters induce emergent conservation laws and approximate integrability, significantly suppressing chaos and preventing thermalization.

Contribution

It reveals how particular Floquet drive conditions can induce emergent conservation laws and arrest quantum chaos in a many-body bosonic system.

Findings

Identification of special drive ratios leading to emergent conservation laws.

Observation of suppressed Lyapunov exponents indicating reduced chaos.

Analytical Floquet-Magnus expansion capturing slow decay dynamics.

Abstract

Ergodic quantum many-body systems evolving under unitary time dynamics typically lose memory of their initial state via information scrambling. Here we consider a paradigmatic translationally invariant many-body Hamiltonian of interacting bosons -- a Josephson junction array in the transmon regime -- in the presence of a strong Floquet drive. Generically, such a time-dependent drive is expected to heat the system to an effectively infinite temperature, featureless state in the late-time limit. However, using numerical exact-diagonalization we find evidence of special ratios of the drive amplitude and frequency where the system develops {\it emergent} conservation laws, and {\it approximate} integrability. Remarkably, at these same set of points, the Lyapunov exponent associated with the semi-classical dynamics for the coupled many-body equations of motion drops by orders of magnitude, arresting the growth of chaos. We supplement our numerical results with an analytical Floquet-Magnus expansion that includes higher-order corrections, and capture the slow dynamics that controls decay away from exact freezing.