Three-coupled-quantum-well nanostructures as a source of far-infrared entangled light X.Y. Lü, L.L. Zheng, C.L. Ding and X. Yang Eur. Phys. J. D, 63 3 (2011) 489-494 Published online: 28 June 2011 DOI: 10.1140/epjd/e2011-10687-1