  We demonstrate the initialisation, read-out and high-speed manipulation of a
qubit stored in a single 87 Rb atom trapped in a submicron-size optical
tweezer. Single qubit rotations are performed on a sub-100 ns time scale using
two-photon Raman transitions. Using the ``spin-echo'' technique, we measure an
irreversible dephasing time of 34 ms. The read-out of the single atom qubit is
at the quantum projection noise limit when averaging up to 1000 individual
events.
