Quantum gas microscopy of Kardar-Parisi-Zhang superdiffusion

TL;DR

This study experimentally verifies that spin transport in a one-dimensional quantum Heisenberg model exhibits KPZ superdiffusion, using cold-atom quantum simulation and single-spin detection to observe characteristic scaling and non-linearity.

Contribution

It provides the first experimental evidence linking KPZ universality to quantum spin transport in a Heisenberg chain, highlighting the roles of integrability and SU(2) symmetry.

Findings

Domain-wall relaxation follows KPZ dynamical exponent z=3/2

KPZ scaling requires integrability and SU(2) symmetry

Single-spin detection reveals KPZ non-linearity signature

Abstract

The Kardar-Parisi-Zhang (KPZ) universality class describes the coarse-grained behavior of a wealth of classical stochastic models. Surprisingly, it was recently conjectured to also describe spin transport in the one-dimensional quantum Heisenberg model. We test this conjecture by experimentally probing transport in a cold-atom quantum simulator via the relaxation of domain walls in spin chains of up to 50 spins. We find that domain-wall relaxation is indeed governed by the KPZ dynamical exponent $z = 3/2$, and that the occurrence of KPZ scaling requires both integrability and a non-abelian SU(2) symmetry. Finally, we leverage the single-spin-sensitive detection enabled by the quantum-gas microscope to measure a novel observable based on spin-transport statistics, which yields a clear signature of the non-linearity that is a hallmark of KPZ universality.