A definitive number of atoms on demand: controlling the number of atoms   in a-few-atom magneto-optical trap
  A few 85Rb atoms were trapped in a micron-size magneto-optical trap with a high quadrupole magnetic-field gradient and the number of atoms was precisely controlled by suppressing stochastic loading and loss events via real-time feedback on the magnetic field gradient. The measured occupation probability of single atom was as high as 99%. Atoms up to five were also trapped with high occupation probabilities. The present technique could be used to make a deterministic atom source. 
Seokchan Yoon, Youngwoon Choi, Sangbum Park, Jaisoon Kim, Jai-Hyung   Lee, and Kyungwon An