  An ensemble of Rubidum atoms can be excited with lasers such that it evolves
into an entangled state with just one collective excitation within the Rydberg
blockade radius. The decay of this state leads to the emission of a single,
antibunched photon. For a hot vapor of Rubidium atoms in a micro cell we
numerically study the feasibility of such a single-photon source under
different experimental conditions like the atomic density distribution and the
choice of electronic states addressed by the lasers. For the excitation process
with three rectangular lasers pulses, we simulate the coherent dynamics of the
system in a truncated Hilbert space. We investigate the radiative behavior of
the moving Rubidum atoms and optimize the laser pulse sequence accordingly. We
find that the collective decay of the single-excitation leads to a fast and
directed photon emission and further, that a pulse sequence similar to a spin
echo increases the directionality of the photon. Finally, we analyze the
residual double-excitations and find that they do not exhibit these collective
decay properties and play only a minor deleterious role.
