We demonstrate the all-optical ultrafast manipulation and read-out of optical
transitions in a single negatively charged self-assembled InAs quantum dot, an
important step towards ultrafast control of the resident spin. Experiments
performed at zero magnetic field show the excitation and decay of the trion
(negatively charged exciton) as well as Rabi oscillations between the electron
and trion states. Application of a DC magnetic field perpendicular to the
growth axis of the dot enables observation of a complex quantum beat structure
produced by independent precession of the ground state electron and the excited
state heavy hole spins
