Nonequilibrium interactions between two quantum circuits

We briefly overview our recent results on nonequilibrium interactions between neighbouring 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. (Some figures in this article are in colour only in the electronic version) 1