Efficient interaction of light with matter is fundamental to development of modern quantum technologies. In this talk I will discuss the basics of such interactions in a waveguide, and show, how they can be harnessed to generate propagating correlated photon which bears signature of non-equilibrium quantum dynamics. Furthermore, as an application of such interactions, I will introduce a quantum transducer that can be used to implement a quantum internet node with superconducting qubits and optical photons.