The rise of cavity-QED has made it possible to fully exploit the light-matter interaction, at the most fundamental level: single atoms and single photons. Our team in C2N has developed quantum-dot-based interfaces which can be used as efficient emitters of single photons, leading to the creation of the company Quandela. A strong challenge remains: developing quantum nodes that implement logic operations on incoming photons, using the interaction with a single stationary qubit. During the last decade, we have also built a practical theoretical toolbox, allowing to simulate the cavity-QED effects in light-matter interfaces. By doing so, we made a theoretical breakthrough: it becomes possible to exactly describe many complex cavity-QED phenomena, with the much simpler and practical framework of waveguide-QED. This allows implementing numerical and analytical strategies which were previously out of reach. During this internship we want to explore the potential of this breakthrough, extending it to the study of spin-photon interfaces and to the strong-coupling regime of cavity-QED.