Recent progress in solid-state cavity-QED with semiconductor quantum dots enables efficient photonic quantum gates. Apart from studies of fundamentally new cavity QED effects, those systems allow the generation of high-brightness quantum light in Fock space at a strongly reduced experimental complexity. This opens up, for instance, a new kind of “quantum-light spectroscopy” that was not possible before, with applications and in order to address open questions in bio-molecular spectroscopy and microscopy. At the same time, the quantum dot cavity-QED systems can be used to create large entangled states involving potentially several tens of photons in a deterministic way, avoiding post-selection and therefore much more efficient exploration of those highly entangled systems, cluster and graph states, first steps in this direction will be shown.