Time-resolved observation of thermalization in an isolated quantum system

TL;DR

This study uses trapped atomic ions to observe how an isolated quantum system thermalizes over time, demonstrating the approach of observables to equilibrium values with controlled experimental parameters.

Contribution

It introduces a highly controllable platform for studying thermalization in quantum systems by manipulating ion interactions and system size.

Findings

Time averages approach microcanonical averages

Fluctuations decay as system thermalizes

Thermalization dynamics are precisely controllable

Abstract

We use trapped atomic ions forming a hybrid Coulomb crystal, and exploit its phonons to study an isolated quantum system composed of a single spin coupled to an engineered bosonic environment. We increase the complexity of the system by adding ions and controlling coherent couplings and, thereby, we observe the emergence of thermalization: Time averages of spin observables approach microcanonical averages while related fluctuations decay. Our platform features precise control of system size, coupling strength, and isolation from the external world to explore the dynamics of equilibration and thermalization.