Single semiconductor nanocrystals are studied by means of ultrafast laser spectroscopy. In these structures beeing referred to as quantum dots (QDs) carriers occupy the discrete quantum mechanical states in a narrow (typically ~10nm) three-dimensional confinement potential. Exhibiting remakably long electronic dephasing times QDs are considered as promising candidates for the building blocks of a solid state based quantum computer. Novel spectroscopic techniques are applied to examine the carrier dynamics in single QDs accomplishing a time-resolution of few picoseconds. Furthermore the coherent manipulation of the electronic state by optical pulses is demonstrated. Finally the developped techniques are transfered and enhanced to study QD molecules, which are formed by quantum mechanically coupled pairs of QDs.
«