As the superposition principle is basic to quantum mechanics, the interference effects occur very widely in quantum systems. Interferences are especially important in quantum optics and one of the most remarkable developments has been the possibility of interference of independent, but indistinguishable particles. These interferences, besides being very fundamental, have important applications in the context of quantum entanglement and superradiance. An important component of superradiance is the initial preparation of the system in Dicke states which can be shown to be multiparticle entangled states. Thus the production of Dicke states with higher number of excitations remains a challenge and a new option is the repeated measurements of photons starting from a fully excited system of quantum emitters. These ideas are quite generic and applicable to a wide variety of quantum sources. Our studies suggest new kind of enhancement in the efficiency of nonlinear optical processes in systems prepared in entangled states.