Verified Universal Breakdown of Kibble-Zurek Scaling in Fast Quenches

TL;DR

This study experimentally confirms that in fast quantum quenches, the defect density no longer follows the traditional Kibble-Zurek scaling but instead becomes universally dependent on the quench range, revealing a breakdown of the expected universality.

Contribution

The paper provides the first experimental verification of the predicted breakdown of Kibble-Zurek scaling in fast quenches using a trapped-ion quantum simulator.

Findings

Identification of a critical quench rate separating two dynamical regimes.

Observation of KZM scaling at slow quenches and universal scaling at fast quenches.

Experimental evidence of the breakdown of KZM universality in quantum systems.

Abstract

The Kibble-Zurek mechanism (KZM) predicts that when a system is driven through a continuous phase transition, the density of topological defects scales universally with the quench rate. Recent theoretical work [H.-B. Zeng \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{130}, 060402 (2023)] has challenged this picture, showing that under sufficiently fast quenches, both the defect density and freezing time become independent of the quench rate and instead scale universally with the quench range. Here, we experimentally test this prediction using a single trapped-ion qubit to simulate fast quantum quenches in the Landau-Zener and 1D Rice-Mele models. We identify a critical quench rate \( v_c \) that scales with the quench range \( \delta_{\max} \), separating two distinct dynamical regimes. In the Rice-Mele model, for \( v < v_c \), the defect density follows the KZM scaling \( \sim v^{1/2} \); for \( v > v_c \), it exhibits a universal scaling \( \sim \delta_{\max} \), independent of the quench rate. Our results provide direct experimental evidence of the predicted breakdown of KZM universality under fast quenches.