2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/92769We define extension maps as maps that extend a system (through adding ancillary systems) without changing the state in the original system. We show, using extension maps, why a completely positive operation on an initially entangled system results in a non positive mapping of a subsystem. We also show that any trace preserving map, either positive or negative, can be decomposed in terms of an extension map and a completely positive map.6 pagesQuantum Physicstext