Exchange-controlled single-electron-spin rotations in quantum dots

We show theoretically that arbitrary coherent rotations can be performed quickly (with a gating time $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$) and with high fidelity on the spin of a single confined electron using control of exchange only, without the need for spin-orbit coupling or ac fields. We expect that implementations of this scheme would achieve gate error rates on the order of $\ensuremath{\eta}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}$ in GaAs quantum dots, within reach of several known error-correction protocols.