Observation of eight-wave mixing via electromagnetically induced transparency Zhenkun Wu, Chenzhi Yuan, Zhaoyang Zhang, Huaibin Zheng, Shuli Huo, Ruyi Zhang, Ruimin Wang and Yanpeng Zhang EPL, 94 6 (2011) 64005 Published online: 08 June 2011 DOI: 10.1209/0295-5075/94/64005