Effective evolution of quantum systems using coarse graining maps

摘要

Very often in an experiment the access to a measuring apparatus is verylimited. We investigate a possible effective description of a quantum system, when anexperimenter has access to an experimental apparatus described by a POVM, and hasno information about the quantum system under study. A coarse graining CPTP map isintroduced, that maps the state of the quantum system into a compressed effective state,from which one obtains the same measurement statistics.