2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/101541We show that universal quantum logic can be achieved using only linear optics and a quantum shutter device. With these elements, we design a quantum memory for any number of qubits and a CNOT gate which are the basis of a universal quantum computer. An interaction-free model for a quantum shutter is given.21 pages, 12 figures. Section 5 replaces quant-ph/0512020Quantum Physicstext