Observation of non-Hermitian many-body phase transition in a Rydberg-atom array

TL;DR

This paper reports the experimental observation of a non-Hermitian many-body phase transition in a Rydberg-atom array, revealing how interactions influence PT-symmetry breaking and non-Hermitian dynamics.

Contribution

It demonstrates the realization of a non-Hermitian XY model in a Rydberg-atom array and uncovers interaction-driven effects on PT-symmetry breaking at the many-body level.

Findings

Observation of PT-symmetry-breaking phase transition via Loschmidt Echo

Dipole interactions determine the transition point and induce a many-body blockade effect

Non-monotonic system size dependence of Loschmidt Echo decay

Abstract

Non-Hermitian quantum mechanics with parity-time (PT) symmetry offers a powerful framework for exploring the complex interplay of dissipation and coherent interactions in open quantum systems. While PT-symmetry breaking has been studied in various physical systems, its observation on a quantum many-body level remains elusive. Here, we experimentally realize a non-Hermitian XY model in a strongly-interacting Rydberg-atom array. By measuring the Loschmidt Echo of a fully polarized state, we observe distinct dynamical signatures of a PT-symmetry-breaking phase transition. Dipole interactions are found to play a crucial role, not only determining the transition point but also triggering a non-Hermitian many-body blockade effect that protects the Loschmidt Echo from decay with a non-monotonic dependence on the system size. Our results reveal intricate interaction-induced effects on PT-symmetry breaking and open the door for exploring non-Hermitian many-body dynamics beyond single-particle and mean-field paradigms.