Meso and Macroscopic Quantum States of Light

We investigate the nature of correlated photons from three dipole-coupled two-level atomic systems and find the clear signatures of the entangled matter states on the nature of the emitted photons. The presence of two phases, as predicted by Dicke a long time back, is evident in the far-field spectrum. The phase transition between these two phases and the behaviour of concurrence, discord and monogamy in both these phases are explicated. The effect of the atomic configuration is pointed out in the optical domain. We then investigate another macroscopic state of condensed photons, where photonic superfluidity and supersolidity are pointed out with exact solutions of the relevant mean field equations: nonlinear Schrodinger equation with a source. The earlier experimental observation of the superfluid phase opens the way for the possible realization of photonic supersolidity. We further highlight the deep connection between entanglement, coherence, and path predictability in the much-studied multi- slit experiments.