  Manipulation of single spins is essential for spin-based quantum information
processing. Electrical control instead of magnetic control is particularly
appealing for this purpose, since electric fields are easy to generate locally
on-chip. We experimentally realize coherent control of a single electron spin
in a quantum dot using an oscillating electric field generated by a local gate.
The electric field induces coherent transitions (Rabi oscillations) between
spin-up and spin-down with pi/2 rotations as fast as ~55ns. Our analysis
indicates that the electrically-induced spin transitions are mediated by the
spin-orbit interaction. Taken together with the recently demonstrated coherent
exchange of two neighboring spins, our results demonstrate the feasibility of
fully electrical manipulation of spin qubits.
