Detection of quantum critical points by a probe qubit

TL;DR

This paper introduces a method to detect quantum critical points by coupling a probe qubit to a quantum system, leveraging increased sensitivity near phase transitions, demonstrated with an NMR quantum simulator on Ising spin chains.

Contribution

The paper presents a novel technique for identifying quantum phase transitions using a probe qubit, applicable to different types of transitions in spin chains.

Findings

Successful detection of quantum critical points in an Ising spin chain.

Demonstrated increased sensitivity of the system near critical points.

Applicable to multiple types of quantum phase transitions.

Abstract

Quantum phase transitions occur when the ground state of a quantum system undergoes a qualitative change when an external control parameter reaches a critical value. Here, we demonstrate a technique for studying quantum systems undergoing a phase transition by coupling the system to a probe qubit. It uses directly the increased sensibility of the quantum system to perturbations when it is close to a critical point. Using an NMR quantum simulator, we demonstrate this measurement technique for two different types of quantum phase transitions in an Ising spin chain.