We have performed experiments to probe directly the thermal
conductance of suspended nanostructures with lateral dimensions
~100nm. It has been recently predicted that at low temperatures,
thermal conductance in such a structure approaches a universal
value of
for each massless, ballistic 1D channel, independent of
material characteristics. We have developed ultra-sensitive, low
dissipation dc-SQUID-based noise thermometry, and extreme
isolation from the electronic environment in order to perform
this measurement at temperatures <100mK. We will
report our very recent successful measurements of this universal
quantum of thermal conductance and the implications for single
photon and possibly single phonon calorimetry.
Physics