One- and two-photon scattering from generalized V-type atoms
  The one- and two-photon scattering matrix S is obtained analytically for a one-dimensional waveguide and a point-like scatterer with N excited levels (generalized V -type atom). We argue that the two-photon scattering matrix contains sufficient information to distinguish between different level structures which are equivalent for single-photon scattering, such as a V -atom with N = 2 excited levels and two two-level systems. In particular, we show that the scattering with the V -type atom exhibits a destructive interference effect leading to two-photon Coupled-Resonator-Induced Transparency, where the nonlinear part of the two-photon scattering matrix vanishes when each incident photon fulfills a single-photon condition for transparency. 
Eduardo S\'anchez-Burillo and Luis Mart\'in-Moreno and David Zueco and   Juan Jos\'e Garc\'ia-Ripoll
quant-ph cond-mat.quant-gas