We now have the world's most sensitive search for dark-matter axions.
The experiment threads a large static magnetic field through a
high-Q microwave cavity, thereby stimulating nearby Milky Way
halo axions to convert into microwave photons.  Any feeble
microwave signal is detected by an exquisitely low noise
radio receiver.  This allows for the first time a search for
axions having plausible couplings to normal matter and radiation.
Our collaboration has recently developed even lower-noise
SQUID-based microwave receivers.  This new receiver technology
is the basis of an improved experiement that will allow detection
of even the most feebly-coupled dark matter axions and would
be able definitely to either detect of exclude axions as the
dominant component of the halo dark matter.