Single-photon scattering with counter rotating wave interaction
  Recent experiments have pushed the studies on atom-photon interactions to the ultrastrong regime, which motivates the exploration of physics beyond the rotation wave approximation. Here we study the single-photon scattering on a system composed by a coupling cavity array with a two-level atom in the center cavity, which, by varying two outside coupling parameters, corresponds to a model from a supercavity QED to a waveguide QED with counter-rotating wave (CRW) interaction. By applying a time-independent scattering theory based on the bound states in the scattering region, we find that the CRW interaction obviously changes the transmission valley even in the weak atom-cavity coupling regime; In particular, the CRW interaction leads to an inelastic scattering process and a Fano-type resonance, which is directly observed in the crossover from the supercavity QED case to the waveguide QED case. Predictably, our findings provide the potential of manipulating the CRW effects in realistic systems. 
Qi-Kai He, Wei Zhu, Z. H. Wang and D. L. Zhou
quant-ph