Ultimate quantum limit for amplification: a single atom in front of a mirror

We investigate three types of amplification processes for light fields coupling to an atom near the end a one-dimensional semi-infinite waveguide. consider two setups where drive creates population inversion in bare or dressed basis three-level and one setup is due higher-order driven two-level atom. In all cases, waveguide acts as mirror light. find that this enhances ways compared same open Firstly, forces output from travel direction instead being split up into channels. Secondly, interference enables tuning ratio relaxation rates different transitions increase inversion. quantify enhancement these factors show it can be demonstrated standard parameters experiments with superconducting quantum circuits.