Quantum thermometry using the ac Stark shift within the Rabi model

TL;DR

This paper introduces a novel theoretical approach to analyze qubit dynamics in strongly coupled qubit-oscillator systems, leading to a new expression for the ac Stark shift that enables precise quantum thermometry of oscillators.

Contribution

It develops a non-Markovian master equation method beyond the Jaynes Cummings model, providing a new way to perform accurate qubit thermometry in strong coupling regimes.

Findings

Derived a new expression for the ac Stark shift.

Developed a numerical method for qubit dynamics.

Enabled precise quantum thermometry of oscillators.

Abstract

A quantum two level system coupled to a harmonic oscillator represents a ubiquitous physical system. New experiments in circuit QED and nano-electromechanical systems (NEMS) achieve unprecedented coupling strength at large detuning between qubit and oscillator, thus requiring a theoretical treatment beyond the Jaynes Cummings model. Here we present a new method for describing the qubit dynamics in this regime, based on an oscillator correlation function expansion of a non-Markovian master equation in the polaron frame. Our technique yields a new numerical method as well as a succinct approximate expression for the qubit dynamics. We obtain a new expression for the ac Stark shift and show that this enables practical and precise qubit thermometry of an oscillator.