2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90417We propose a very simple scheme to test the quantum enatanglement swapping in a priori. In the scheme, we only assume the photon detector can distinguish the vacuum and non-vacuum Fock state rather than the exact Fock number states.To appear in Phys. Rev. A. We shall NOT do the proposed experiment. We hope any experimental group to do itQuantum Physicstext