2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/88823We consider the apparatus in a quantum measurement process to be in a mixed state. We propose a simple upper bound on the probability of correctly distinguishing any number of mixed states. We use this to derive fundamental bounds on the efficiency of a measurement in terms of the temperature of the apparatus.3 pages, 2 figuresQuantum Physicstext