  Several recently proposed implementations of scalable quantum computation
rely on the ability to manipulate the spin polarization of individual electrons
in semiconductors. The most rapid single-spin-manipulation technique to date
relies on the generation of an effective magnetic field via a spin-sensitive
optical Stark effect. This approach has been used to split spin states in
colloidal CdSe quantum dots and to manipulate ensembles of spins in ZnMnSe
quantum wells with femtosecond optical pulses. Here we report that the process
will produce a coherent rotation of spin in quantum dots containing a single
electron. The calculated magnitude of the effective magnetic field depends on
the dot bandgap and the strain. We predict that in InAs/InP dots, for
reasonable experimental parameters, the magnitude of the rotation is sufficient
and the intrinsic error is low enough for them to serve as elements of a
quantum dot based quantum computer.
