  The experimental observation of quantum phenomena in strongly correlated many
particle systems is difficult because of the short length- and timescales
involved. Obtaining at the same time detailed control of individual
constituents appears even more challenging and thus to date inhibits employing
such systems as quantum computing devices. Substantial progress to overcome
these problems has been achieved with cold atoms in optical lattices, where a
detailed control of collective properties is feasible but it is very difficult
to address and hence control or measure individual sites. Here we show, that
polaritons, combined atom and photon excitations, in an array of cavities such
as a photonic crystal or coupled toroidal micro-cavities, can form a strongly
interacting many body system, where individual particles can be controlled and
measured. All individual building blocks of the proposed setting have already
been experimentally realised, thus demonstrating the potential of this device
as a quantum simulator. With the possibility to create attractive on-site
potentials the scheme allows for the creation of highly entangled states and a
phase with particles much more delocalised than in superfluids.
