  We present a scheme for scalable quantum information processing (QIP) with
atomic ensembles and flying photons. Using the Rydberg blockade, we encode the
qubits in the collective atomic states, which could be manipulated fast and
easily due to the enhanced interaction, in comparison to the single-atom case.
We demonstrate that our proposed gating could be applied to generation of
two-dimensional cluster states for measurement-based quantum computation.
Moreover, the atomic ensembles also function as quantum repeaters useful for
long distance quantum state transfer. We show the possibility of our scheme to
work in bad cavity or in weak coupling regime, which could much relax the
experimental requirement. The efficient coherent operations on the ensemble
qubits enable our scheme to be switchable between quantum computation and
quantum communication using atomic ensembles.
