Direct observation of quantum criticality in Ising spin chains

TL;DR

This study employs NMR quantum simulators to directly observe quantum critical points in Ising spin chains through Loschmidt echo measurements, confirming theoretical predictions and demonstrating the system's sensitivity near phase transitions.

Contribution

It introduces a method to detect quantum criticality in spin chains using Loschmidt echo measurements with NMR simulators, providing direct experimental evidence.

Findings

Critical points identified via Loschmidt echo

Experimental results agree with theoretical models

Effective detection in both even and odd spin chains

Abstract

We use NMR quantum simulators to study antiferromagnetic Ising spin chains undergoing quantum phase transitions. Taking advantage of the sensitivity of the systems near criticality, we detect the critical points of the transitions using a direct measurement of the Loschmidt echo. We test our simulators for spin chains of even and odd numbers of spins, and compare the experimental results to theoretical predictions.