2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/137250We demonstrate a scheme for controlling a large quantum system by acting on a small subsystem only. The local control is mediated to the larger system by some fixed coupling Hamiltonian. The scheme allows to transfer arbitrary and unknown quantum states from a memory on the large system (``upload access'') as well as the inverse (``download access''). We study sufficient conditions of the coupling Hamiltonian and give lower bounds on the fidelities for downloading and uploading.4 pages, 2 figuresQuantum Physicstext