2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/123366Problem of classification of all the set of entangled states is considered. Invariance of entangled states relative to transformations from a group of symmetry of qubit space leads to classification of all states of the system through irreducible representations from that group. Excess of entropy of a subsystem over entropy of the whole system indicates the presence of entaglement in the system.Presented at the NATO ARW "Quantum Communication and Security", 10-13 September 2006, Gdansk, PolandQuantum Physicstext