2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/215481In this paper, we investigate the optimal nonadditive quantum error-detecting codes with distance two. The the numerical simulation shows that, with n being can be 5, 6, 7, 8, 10 and 12, such the n-qubit quantum error-detecting codes with maximal number of codewords can be found. Therein, except the n=7 case, the n-vertex loop graphs help find the optimal quantum codes.6 pages, 22 figuresQuantum Physicstext