2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89609Classification of different forms of quantum entanglement is an active area of research, central to development of effective quantum computers, and similar to classification of error-correction codes, where code duality is broadened to equivalence under all 'local' unitary transforms. We explore links between entanglement, coding theory, and sequence design, by examining multi-spectra of quantum states under local unitary action, and show that optimal error-correcting codes and sequences represent states with high multiparticle entanglement.34 pages. Presented in part at SETA01, Bergen, Norway, May 13-17, 2001. v2: Minor (but annoying) equation typos fixedQuantum Physicstext