2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/127724We show theoretically that arbitrary coherent rotations can be performed quickly (with a gating time ~1 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 η~ 10^{-3} in GaAs quantum dots, within reach of several known error-correction protocols4+ pages, 3 figures; v2: Streamlined presentation, final version published in PRB (Rapid Comm.)Mesoscale and Nanoscale Physicstext