Single atom in free space as a quantum aperture
S. J. van Enk, Harry J. Kimble · Physical Review A · 2000
We calculate exact three-dimensional solutions of Maxwell equations corresponding to strongly focused light beams, and study their interaction with a single atom in free space. We show how the naive picture of the atom as an absorber with a size given by its radiative cross section $\ensuremath{\sigma}=3{\ensuremath{\lambda}}^{2}/2\ensuremath{\pi}$ must be modified. The implications of these results for quantum-information-processing capabilities of trapped atoms are discussed.