  We propose and demonstrate the sequential initialization, optical control,
and read-out of a single spin trapped in a semiconductor quantum dot. Hole spin
preparation is achieved through ionization of a resonantly excited
electron-hole pair. Optical control is observed as a coherent Rabi rotation
between the hole and charged exciton states, which is conditional on the
initial hole spin state. The spin-selective creation of the charged exciton
provides a photocurrent read-out of the hole spin state.
