Two-photon emission in detuned resonance fluorescence

TL;DR

This paper explores two-photon correlations in detuned resonance fluorescence, combining theories to better understand and control multiphoton emission, and proposes experimental evidence for quantum coherence from photoluminescence.

Contribution

It introduces a combined theoretical framework for frequency-resolved photon correlations and homodyning in detuned resonance fluorescence, advancing understanding of multiphoton emission regimes.

Findings

Identification of side peak two-photon correlations

Proposal to observe quantum coherence via photoluminescence symmetry collapse

Connection of theory with recent experimental results

Abstract

We discuss two-photon correlations from the side peaks that are formed when a two-level system emitter is driven coherently, with a detuning between the driving source and the emitter (quasi-resonance fluorescence). We do so in the context of the theories of frequency-resolved photon correlations and homodyning, showing that their combination leads to a neat picture compatible with perturbative two-photon scattering that was popular in the early days of quantum electrodynamics. This should help to control, enhance and open new regimes of multiphoton emission. We also propose a way to evidence the quantum coherent nature of the process from photoluminescence only, through the observation of a collapse of the symmetry of the lineshape accompanied by a surge of its intensity of emission. We discuss several of our results in the light of recent experimental works.