15 79 , 013828 (2009). [20] P. Horak, S. M. Barnett, and H. Ritsch, Phys. Rev. A 61 , 033609 (2000). [21] P. Horak and H. Ritsch, Phys. Rev. A 63 , 023603 (2001). [22] D. Nagy, G. Szirmai, and P. Domokos, Eur. Phys. J. D 48 , 127 (2008). [23] J. M. Zhang, W. M. Liu, and D. L. Zhou, Phys. Rev. A 77 , 033620 (2008). [24] J. M. Zhang, W. M. Liu, and D. L. Zhou, Phys. Rev. A 78 , 043618 (2008). [25] J. M. Zhang, F. C. Cui, D. L. Zhou, and W. M. Liu, Phys. Rev. A 79 , 033401 (2009). [26] S. Gopalakrishnan, B. L. Lev, and P. M. Goldbart, Na- ture Physics 5 , 845 (2009). [27] M. G. Moore, O. Zobay, and P. Meystre, Phys. Rev. A 60 , 1491 (1999). [28] L. Fallani, C. Fort, N. Piovella, M. Cola, F. S. Cataliotti, M. Inguscio, and R. Bonifacio, Phys. Rev. A 71 , 033612 (2005). [35] J. Larson, S. Fernandez-Vidal, G. Morigi, and M. Lewen- stein, New Journal of Physics 10 , 045002 (2008). [36] J. Larson, B. Damski, G. Morigi, and M. Lewenstein, Phys. Rev. Lett. 100 , 050401 (2008). [37] H. Zoubi and H. Ritsch, Phys. Rev. A 80 , 053608 (2009). [38] D. S. Goldbaum, K. Zhang, and P. Meystre (2009), arXiv: 0911.3234. [39] P. Horak and H. Ritsch, Phys. Rev. A 64 , 033422 (2001). [40] S. A. Gardiner, K. M. Gheri, and P. Zoller, Phys. Rev. A 63 , 051603 (2001). [41] P. Horak, G. Hechenblaikner, K. M. Gheri, H. Stecher, and H. Ritsch, Phys. Rev. Lett. 79 , 4974 (1997). [42] P. Maunz, T. Puppe, I. Schuster, N. Syassen, P. W. H. Pinkse, and G. Rempe, Nature 428 , 50 (2004). [43] S. Nussmann, K. Murr, M. Hijlkema, B. Weber, A. Kuhn, and G. Rempe, Nature Physics 1 , 122 (2005). [44] A. Vukics, J. Janszky, and P. Domokos, Journal of Physics B: At. Mol. Opt. Phys. 38 , 1453 (2005). [45] A. Vukics and P. Domokos, Phys. Rev. A 72 , 031401(R) (2005). [46] U. Leonhardt, T. Kiss, and P. Piwnicki, Eur. Phys. J. D 7 , 413 (1999). [47] D. A. R. Dalvit, J. Dziarmaga, and R. Onofrio, Phys. Rev. A 65 , 053604 (2002). [48] F. Papoff, G. D’Alessandro, and G. L. Oppo, PRL 100 , 123905 (2008). [49] G. D’Alessandro and F. Papoff, Phys. Rev. A 80 , 023804 (2009). [29] W. H. Louisell, Quantum statistical properties of radia- tion (John Wiley & Sons, New York, 1973). [30] F. Marquardt, J. G. E. Harris, and S. M. Girvin, Physical Review Letters 96 , 103901 (2006). [31] Y. Castin, in Coherent atomic matter waves, Lec- ture Notes of Les Houches Summer School , edited by R. Kaiser, C. Westbrook, and F. David (EDP Sciences and Springer-Verlag, 2001), pp. 1–136. [32] C. Maschler, I. B. Mekhov, and H. Ritsch, Eur. Phys. J. D 46 , 545 (2008). [33] A. Vukics, C. Maschler, and H. Ritsch, New J. of Phys. 9 , 255 (2007). [34] A. Vukics, W. Niedenzu, and H. Ritsch, Phys. Rev. A