Optimized phase switching using a single atom nonlinearity
  We show that a nonlinear phase shift of pi can be obtained by using a single two level atom in a one sided cavity with negligible losses. This result implies that the use of a one sided cavity can significantly improve the pi/18 phase shift previously observed by Turchette et al. [Phys. Rev. Lett. 75, 4710 (1995)]. 
Holger F. Hofmann, Kunihiro Kojima, Shigeki Takeuchi, and Keiji Sasaki