Time-resolved charge detection and back-action in quantum circuits

This paper reviews investigations of back-action phenomena occurring in systems, where quantum dots are capacitively coupled to quantum point contact charge detectors. Two back-action mechanisms are discussed: first, back-action caused by shot-noise in the quantum point contact, and second, indirect back-action via ohmic heating of the crystal lattice. Experiments focusing on the first aspect consist of the measurement of shot noise at finite frequencies in the range between 0.01 and 0.7 THz. Experiments of the second kind result in the observation of finite current through a double quantum dot system at zero applied source–drain bias voltage. Such a current is possible in the presence of a phonon-system which is not in thermodynamic equilibrium with the electronic system. The double quantum dot acts as a thermoelectric engine extracting electric power from the temperature difference between the two thermal reservoirs.