2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90624We show that a quantum control procedure on a two-level system including dissipation gives rise to a semi-group corresponding to the Lie algebra semi-direct sum gl(3,R)+R^3. The physical evolution may be modelled by the action of this semi-group on a 3-vector as it moves inside the Bloch sphere, in the Bloch ball.4 pages. Proceedings of Group 24, Paris, July, 2002Quantum Physicstext