  We recently demonstrated that strings of trapped atoms inside a standing wave
optical dipole trap can be rearranged using optical tweezers [Y. Miroshnychenko
et al., Nature, in press (2006)]. This technique allows us to actively set the
interatomic separations on the scale of the individual trapping potential
wells. Here, we use such a distance-control operation to insert two atoms into
the same potential well. The detected success rate of this manipulation is
16(+4/-3) %, in agreement with the predictions of a theoretical model based on
our independently determined experimental parameters.
