2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90932We deduce from a microscopic point of view the equation that describes how the state of a particle crossing a medium decoheres. We apply our results to the example of a particle crossing a gas, computing explicitly the Lindblad operators in terms of the interaction potential between the particle and a target of the medium. We interpret the imaginary part of the refraction index as a loss of quantum coherence, that is reflected in the disappearance of interference patterns in a Young experiment.24 pages, 2 figuresQuantum PhysicsCondensed Mattertext