Globalized Nonlinear Critical Quantum Metrology by Two-photon Rabi-Stark model

TL;DR

This paper introduces a modified two-photon quantum Rabi model with Stark coupling, enabling a tunable, global critical point that enhances quantum metrology precision across a wide parameter range.

Contribution

The authors propose combining Stark coupling with the two-photon QRM to create a tunable critical point, broadening the application of nonlinear critical quantum metrology.

Findings

Quantum Fisher information diverges over a wide parameter range.

The protocol achieves high measurement precision globally.

Strong squeezing is maintained as a quantum resource.

Abstract

Squeezing as a quantum resource for quantum metrology is robust against decoherence and dissipation, while the conventional nonlinear two-photon quantum Rabi model (QRM) provides a squeezing resource immune to the divergence problem of preparation time of probe state (PTPS). However the critical point of the two-photon QRM is locally restricted to one single point, which hinders a wider application. In the present work we propose to combine the Stark coupling with the two-photon QRM to realize a tunable critical point so that the nonlinear critical quantum metrology can be globalized. As demonstrated by the diverging quantum Fisher information (QFI) the protocol enables us to acquire a high measurement precision in a wide range of coupling parameter rather than locally at a single critical point. Moreover, We find that the QFI not only manifests criticality but also exhibits universality. As a particular merit of our protocol, a strong squeezing can be globally retained as the leading quantum resource, while at the same time the PTPS remains in a finite order.