Quantum phase transition, spectral signatures and polaritonic properties of coupled cavity arrays The enormous progress in controlling quantum optical and atomic systems has prompted ideas for new experimental realizations of strongly-correlated many body systems operating with light. These systems consist of photons confined in optical cavities, which interact strongly with atoms or atomiclike structures, see Figure. Due to the interaction between the two particle species optical nonlinearities appear, leading to a quantum phase transition from Mott to superfluid phase where photons are present! Exhibiting these intriguing properties light-matter systems might be used as quantum simulators for other strongly-correlated many body systems, such as the Bose-Hubbard model or might find their applications in quantum information processing. |