Resonance fluorescence of two asymmetrically pumped and coupled two-level systems

TL;DR

This paper investigates the resonance fluorescence of two coupled two-level systems with complex interactions, revealing novel spectral features like Mollow quintuplets and population trapping depending on the coupling nature.

Contribution

It introduces a comprehensive analysis of diverse complex couplings in a driven-dissipative two-atom system, uncovering new spectral phenomena and population dynamics.

Findings

Mollow quintuplet spectra observed under certain couplings

Population trapping phenomena identified

Spectral features depend on coherent and incoherent coupling balance

Abstract

We study a driven-dissipative duo of two-level systems in an open quantum systems approach, modelling a pair of atoms or (more generally) meta-atoms. Allowing for complex-valued couplings in the setup, which are of both a coherent and incoherent character, gives rise to a diverse coupling landscape. We consider several points on this landscape, for example where the coupling between the two coupled two-level systems is dominated by coherent, incoherent, unsymmetrical and even unidirectional interactions. Traversing the coupling terrain leads to remarkable features in the populations of the pair, correlations and optical spectra. Most notably, the famous Mollow triplet spectrum for a single atom may be superseded for a pair by a Mollow quintuplet (or even by a spectral singlet) and the setup allows for population trapping to arise, all depending upon the precise nature of the coupling between the two-level systems.