2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91107An arbitrary polarization state of a single-mode biphoton is considered. The operationalistic criterion is formulated for the orthogonality og these states. It can be used to separate a biphoton with an arbitrary degree of polarization from a set of biphotons orthogonal to it. This is necessary fro the implementation of quantum cryptography protocol based on three-level systems. The experimental test of this criterion amounts to the observation of the anticorrelation effect for a biphoton with an arbitraty polarization state.4 pages, 2 figures, 1 tableQuantum Physicstext