Physics

Quantum technology

Mathematics

Quantum phase transition

Statistical physics

Quantum critical point

Open quantum system

Geometry

Quantum mechanics

Quantum phases

Quantum

Quantum sensor

Quantum metrology

Scaling

Physical Review Letters

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 exploit 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 probes can achieve a quantum-enhanced time scaling of the sensitivity in frequency-estimation protocols.

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition