The Haloscope at Yale Sensitive To Axion CDM (HAYSTAC) is a tunable microwave cavity experiment searching for axion dark matter in the galactic halo.  HAYSTAC is a high-frequency offshoot of the earlier ADMX experiment, formerly known as ADMX-HF, and has been able to probe mass ranges above 23 micro-eV in the cosmologically sensitive region of the axion parameter space. 

HAYSTAC uses dilution refrigeration and cutting-edge parametric amplification techniques to maximize the signal-to-noise ratio and dramatically reduce scan times, advancing the search for axion dark matter to new regions of the parameter space.  HAYSTAC also acts as a testbed for new technologies.  The squeezed-state receiver that will be used in Phase II of the HAYSTAC experiment is the first such receiver to be implemented in dark matter detector.