  We present a new scheme for cluster states generation based on atomic
ensembles and the dipole blockade mechanism. The protocol requires identical
single photon sources, one ensemble per physical qubit, and regular
photodetectors. The general entangling procedure is presented, as well as a
procedure that generates Q-qubit GHZ states with probability p ~ eta^{Q/2},
where eta is the combined detection and source efficiency. This is
significantly more efficient than any known robust probabilistic entangling
operation. The GHZ states form the basic building block for universal cluster
states - a resource for the one-way quantum computer.
