Two-photon resonance fluorescence of two interacting non-identical quantum emitters

TL;DR

This paper analyzes two interacting, non-identical quantum emitters under two-photon resonance, deriving analytical expressions for their fluorescence and demonstrating the potential for high-precision distance estimation and superresolution imaging.

Contribution

It provides the first analytical solutions for the stationary state of non-identical emitters under two-photon resonance, highlighting their use in quantum sensing.

Findings

Two-photon resonance fluorescence spectra are highly sensitive to emitter distance.

Coherent two-photon excitation dominates over first-order processes in certain regimes.

The formalism enables superresolution imaging of quantum emitters.

Abstract

We study a system of two interacting, non-indentical quantum emitters driven by a coherent field. We focus on the particular condition of two-photon resonance and obtain analytical expressions for the stationary density matrix of the system and observables of the fluorescent emission. Importantly, our expressions are valid for the general situation of non-identical emitters with different transition energies. Our results allow us to determine the regime of parameters in which coherent two-photon excitation, enabled by the coherent coupling between emitters, is dominant over competing, first-order processes. Using the formalism of quantum parameter estimation, we show that the features imprinted by the two-photon dynamics into the spectrum of resonance fluorescence are particularly sensitive to changes in the distance between emitters, making two-photon excitation the optimal driving regime for the estimation of inter-emitter distance. This can be exploited for applications such as superresolution imaging of point-like sources.