title: Superluminal light propagation assisted by Zeeman coherence.
abstract: We have observed a dispersionlike absorption (or gain) spectrum at the D1 transition in a Rb vapor cell filled with a buffer gas, due to Zeeman coherence of the ground states in a double Lambda configuration. Meanwhile, we have also observed superluminal pulse propagation. It is experimentally demonstrated that the front speed of a light pulse still equals the light speed c in vacuum, although the group velocity of the light pulse is(-2.2+/-0.6) x 10(4) m/s.
authors.affiliation: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: He
authors.forename: Zhengfeng
authors.initials: Z
authors.lastname: Hu
authors.forename: Yuzhu
authors.initials: Y
authors.lastname: Wang
authors.forename: Ligang
authors.initials: L
authors.lastname: Wang
authors.forename: Shiyao
authors.initials: S
authors.lastname: Zhu