Critical Quantum metrology with a finite-component quantum phase transition

TL;DR

This paper demonstrates that finite-component quantum systems near a phase transition can achieve enhanced measurement sensitivity through quantum Fisher information, despite the challenges of critical slowing down.

Contribution

It introduces metrological protocols leveraging the superradiant phase transition in the quantum Rabi model, showing improved sensitivity scaling.

Findings

Quantum Fisher information scales favorably near the transition.

Critical slowing down does not prevent sensitivity enhancement.

Finite-component systems can outperform traditional quantum metrology methods.

Abstract

Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily-high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by the closing of the energy gap, which implies a critical slowing down and an inevitable growth of the protocol duration. Here, we design different metrological protocols that make use of the superradiant phase transition of the quantum Rabi model, a finite-component system composed of a single two-level atom interacting with a single bosonic mode. We show that, in spite of the critical slowing down, critical quantum optical systems can lead to a quantum-enhanced time-scaling of the quantum Fisher information, and so of the measurement sensitivity.