Photon-assisted tunneling in quantum dots

The manipulation and quantification of the effects produced by an rf field in a mesoscopic structure are fundamental issues in view of developing single-spin-based qubits. Here, we review the experiments on electron transport in quantum dots under microwave irradiation. The electromagnetic vector potential provides excitation of electrons in the leads and in the quantum dot, and an electromotive potential at the leads. The combinations of the two effects go under the name of photon-assisted tunneling. In the present review, the theory of photon-assisted tunneling, based on the Tien-Gordon model applied to the Coulomb-blockade regime of a quantum dot is outlined. An expression for the dc current flowing through the dot in response to a microwave signal is calculated. Then, a classification of different experiments, organized following the different processes adopted to create the dot is presented. Measurements of GaAs split-gate-defined single and double quantum dots as well as lithographically defined SET based on Si/SiGe technology are considered. Finally, recent experiments on a Si/SiO2 commercial flash memory microwave irradiated up to 40 GHz are illustrated, without and with a static magnetic field up to 12 T.