2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93077Students Alice and Bob take an examination in their quantum mechanics class, and thereby illustrate some aspects of energy decoherence.10 pages, LaTeX, no figures. v2: Added paragraph re Bartlett, Rudolph and Spekkens (quant-ph/0507214)Quantum Physicstext