Coherent optical control in quantum dots

Recent years have witnessed considerable progress in optical experiments on single quantum dots. It is now possible to control the quantum states of the confined carriers (electrons, excitons or biexcitons) with a high degree of coherence. The experimental achievements include Rabi oscillations of the fundamental interband (excitonic) transition, two-photon Rabi oscillations between the ground and biexciton state or quantum-logical CNOT gate exploiting the conditional dynamics of the biexciton system. Further schemes have been proposed theoretically, like optical spin control using Raman adiabatic passage or a controlled decoherence experiment in a time-domain interference setup. The lecture will be focused on the theoretical description of these optical control experiments. First, a brief discussion of the spectral properties and selection rules for optical transitions in quantum dots will be given. Then, the quantum dynamics of the two-level (exciton) and four-level (biexciton) system will be analyzed, leading to an idealized description of the experiments. Finally, the essential features of the carrier-phonon coupling and the resulting decoherence in a real system will be discussed. (author)