Observing weakly broken conservation laws in a dipolar Rydberg quantum spin chain

TL;DR

This paper demonstrates that weakly broken conservation laws in a Rydberg quantum spin chain can be detected through non-local observable dynamics, providing insights into fragile integrability in quantum many-body systems.

Contribution

The study experimentally observes and characterizes the effects of weak integrability breaking on non-local observables in a Rydberg atom chain, highlighting their sensitivity to fragile conservation laws.

Findings

Magnetization fluctuations are highly sensitive to integrability breaking.

Anomalous growth observed in non-local observables.

Numerical simulations support experimental results.

Abstract

Integrable quantum many-body systems host families of extensive conservation laws, some of which are fragile: even infinitesimal perturbations can qualitatively alter their dynamical constraints. Here we show that this fragility leaves a clear experimental fingerprint in a one-dimensional quantum spin chain of as few as 14 Rydberg atoms. Weak integrability breaking from interatomic dipolar couplings is directly detectable within experimentally accessible times in the dynamics of non-local observables. In particular, magnetization fluctuations are highly sensitive to the breaking of fragile conservation laws and exhibit anomalous growth, which we observe experimentally; similar signatures appear in a semilocal string observable. Numerical simulations on substantially longer chains and a simplified classical stochastic model reproduce those features. We establish non-local observables as a sensitive probe of fragile conservation laws in quantum spin chains and Rydberg-atom arrays as a platform to test perturbative descriptions of quantum many-body dynamics with weak integrability breaking.