[1] Feng Z B and Yan R Y 2010 Chin. Phys. Lett. 27 010301
[2] Zhan Y B, Zhang Q Y, Wang Y W and Ma P C 2010 Chin. Phys. Lett. 27 010307
[3] Dong P, Zhang G and Cao Z L 2010 Chin. Phys. Lett. 27 030301
[4] Li J B, Cheng M T, Yang Z J and Hao Z H 2009 Chin. Phys. Lett. 26 113202
[5] Dugic M and Jeknic-Dugic J 2009 Chin. Phys. Lett. 26 090306
[6] Pirandola S, Mancini S, Vitali D and Tombesi P 2003 Phys. Rev. A 68 062317
[7] Fermani R, Mancini S and Tombesi P 2004 Phys. Rev. A 70 045801
[8] Adesso G, Ericsson M and Illuminati F 2007 Phys. Rev. A 76 022315
[9] Barnett S M and Radmore P M 1997 Methods in Theoretical Quantum Optics (Oxford: Clarendon)
[10] Adesso G and Illuminati F 2007 J. Phys. A 40 7821
[11] Duan L M, Giedke G, Cirac J I and Zoller P 2000 Phys. Rev. Lett. 84 2722