2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/20773Linear response theory describes quantum measurement with an arbitrary detector weakly coupled to a measured system. This description produces generic quantitative relation characterizing the detector that is analogous to the fluctuation-dissipation theorem for equilibrium systems. The detector characteristic obtained in this way shows how efficient the trade-off is between the back-action dephasing and information acquisition by the detector.12 pages, 1 figureMesoscale and Nanoscale PhysicsQuantum Physicstext