Maximally entangled state of two weak magnetic fields in single-molecule magnets via four-wave mixing Chunling Ding, Zhiming Zhan, Xin-You Lü and Ji-Bing Liu Eur. Phys. J. D, 67 10 (2013) 206 Published online: 18 October 2013 DOI: 10.1140/epjd/e2013-40117-3