2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90795We propose and analyze a quantum version of Szilard's ``one-molecule engine.'' In particular, we recover, in the quantum context, Szilard's conclusion concerning the free energy ``cost'' of measurements: $ΔF \geq k_B T\ln2$ per bit of information.9 pages, 1 figureQuantum Physicstext