  We briefly overview our recent results on nonequilibrium interactions between
neighboring electrically isolated nanostructures. One of the nanostructures is
represented by an externally biased quantum point contact (drive-QPC), which is
used to supply energy quanta to the second nanostructure (detector). Absorption
of these nonequilibrium quanta of energy generates a dc-current in the
detector, or changes its differential conductance. We present results for a
double quantum dot, a single quantum dot or a second QPC placed in the detector
circuit. In all three cases a detection of quanta with energies up to ~1 meV is
possible for bias voltages across the drive-QPC in the mV range. The results
are qualitatively consistent with an energy transfer mechanism based on
nonequilibrium acoustic phonons.
