2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91675An entanglement purification scheme for arbitrary unknown(mixed and pure non-maximally) entangled ionic states is proposed by using linear optical elements. The main advantage of the scheme is that not only two-ion maximally entangled pairs but also four-ion maximally entangled pairs can be extracted from the less entangled pairs. The scheme is within current technology.6 pages, 3 figuresQuantum Physicstext