Progress in the microwave cavity search for dark matter axions

Abstract

Very light axions represent an excellent dark matter candidate, and may be detected by their resonant conversion to photons in a microwave cavity within a strong magnetic field. Current experiments are commencing searches for cosmic axions in the 1-100 μeV range constituting our galactic halo. The sensitivity of these experiments largely results from the development of quantum-limited amplifiers, such as SQUIDs and Josephson Parametric Amplifiers; future experiments may achieve even greater sensitivity by evading the standard quantum limit on noise temperature altogether.