Axion Detection in the Micromaser
  We report on a scheme for highly efficient detection of single microwave photons, with application to detecting certain exotic particles such as the axion. This scheme utilises an experiment known as the micromaser and the phenomenon of trapping states to amplify the signal and produce a cascade of detector counts in a field ionization detector. The cascade provides a time-resolved signal marking the presence of a single photon. For experimentally achievable parameters, the detection efficiency exceeds 90 percent. 
M. L. Jones, G. J. Wilkes and B. T. H. Varcoe