  We discuss the basic properties of a recently proposed hybrid light-matter
system of strongly interacting photons in an array of coupled cavities each
doped with a single two level system. Using the non-linearity generated from
the photon blockade effect, we predict strong correlations between the hopping
photons in the array, and show the possibility of observing a phase transition
from a polaritonic insulator to a superfluid of photons. In the Mott phase,
this interaction can be mapped to an array of spins. We show how the remaining
Hamiltonian, in conjunction with individual spin manipulation, can thus be used
for simulating spin chains (useful for state transfer protocols) and cluster
state quantum computation.
