On May 3, 6:21 pm, "George Dishman" wrote:

I don't know what the lowest frequency of individual
detected photons is.

Superconducting detectors based on the breaking of quasiparticle
Cooper pairs by absorbed photons go down to the submillimeter
wave range.
http://www.yale.edu/proberlab/Papers..._eucas2003.pdf

There was a Scientific American article on these devices last
year, but darned if I can find my copy...I think it was the one
with autism as the featured cover story.

Jerry