Possible Schemes for a Single Photon Switch

I consider the effectiveness of a single control photon to route a target photon using two processes: the first one uses the transient excitation of a two-level system and the second one which uses the permanent population transfer in a three-level Λ-system to route the target photon. In the absence of a single control photon and when the system has additional decay channels, I find ways to optimize the success probability of routing with an increasing number of photons in the control field