Nonreciprocal frequency conversion with chiral $Λ$-type atoms

Abstract

In this paper, we begin with a model of a Λ-type atom whose both transitions are chirally coupled to a waveguide and then extend the model to its giant-atom version. We investigate the singlephoton scatterings of the giant-atom model in both the Markovian and non-Markovian regimes. It is shown that the chiral atom-waveguide couplings enable nonreciprocal, reflectionless, and efficient frequency conversion, while the giant-atom structure introduces intriguing interference effects to the scattering behaviors, such as ultra-narrow scattering windows. The chiral giant-atom model exhibits quite different scattering spectra in the two regimes and, in particular, demonstrates non-Markovicity induced nonreciprocity under specific conditions. These phenomena can be understood from the effective detuning and decay rate of the giant-atom model. Our results have potential applications in integrated photonics and quantum network engineering.

Excite atom-photon bound state inside the coupled-resonator waveguide coupled with a giant atom

“…Recently, the atom-waveguide system has been generalized to studies of interactions between the photon in the waveguide and a giant atom, where an artificial atom (quantum emitter) is fabricated to couple multiple points on the waveguide. Due to the fact that multi-path quantum interferences are included in interactions between waveguide photons and giant atoms, a variety of interesting quantum optical phenomena have been explored, including bound states or dressed states [23,[30][31][32][33], decoherence-free interaction [34][35][36][37], electromagnetically-induced transparency [38][39][40][41], and many others [42][43][44][45][46][47][48][49][50][51]. Relevant experiments have also been demonstrated that microwave photons or propagating phonons have been successfully coupled to an artificial gaint atom [35,39,52].…”