2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91855We present an extension of the first proof for the unconditional security of the BB84 quantum key distribution protocol which was given by Mayers. We remove the constraint that a perfect BB84 quantum source is required and the proof given here covers a range of practical quantum sources. Nothing is assumed about the detector except that the efficiency with which signals are detected is basis independent.36 pagesQuantum Physicstext