Photon Assisted Tunneling in Quantum Dots

We review experiments on single-electron transport through single quantum dots in the presence of a microwave signal. In the case of a small dot with well-resolved discrete energy states, the applied high-frequency signal allows for inelastic tunnel events that involve the exchange of photons with the microwave field. These photon assisted tunneling (PAT) processes give rise to sideband resonances in addition to the main resonance. Photon absorption can also lead to tunneling via excited states instead of tunneling via the ground state of the quantum dot. The manipulation of quantum dots by a microwave field is an important ingredient for the possible application of quantum dots as solid state quantum bits, which forms a motivation for this review.