Proposal for optical U(1) rotations of electron spin trapped in a quantum dot

We present a proposal to optically implement rotations of the electron spin in a quantum dot about the growth direction (z axis). In particular, we make use of the analytic properties of sech pulses in two-level systems to realize spin rotations about the growth direction by an arbitrary angle, for which we give an analytical expression. We propose to use this scheme to experimentally demonstrate this spin rotation. Using realistic system and pulse parameters we find the fidelity of the rotation to be more than 96% for pulses in the picosecond regime, and robust against small errors in pulse parameters. We design a feedback (adaptive) loop to correct for errors originating from unintended dynamics. The rotation is still evident-albeit with a large fidelity loss-in the ensemble case, providing the possibility of demonstration of this optical spin rotation in an ensemble of quantum dots.