  We propose and analyze a new method to produce single and entangled photons
which does not require cavities. It relies on the collective enhancement of
light emission as a consequence of the presence of entanglement in atomic
ensembles. Light emission is triggered by a laser pulse, and therefore our
scheme is deterministic. Furthermore, it allows one to produce a variety of
photonic entangled states by first preparing certain atomic states using simple
sequences of quantum gates. We analyze the feasibility of our scheme, and
particularize it to: ions in linear traps, atoms in optical lattices, and in
cells at room temperature.
