In this project, we will control photonic nanostructures by external feedback, optical injection and synchronization. This will allow us to study nonlinear dynamics in quantum systems and to externally manipulate and stabilize light-matter interaction in the regime of quantum electrodynamics (cQED). We will experimentally and theoretically address a) optical injection and feedback control of quantum dot (QD)–microlasers, b) quantum control cQED systems via delayed single photon feedback, and c) mutually coupled and synchronized chaotic microcavity systems. In a) we will advance the concepts of time-delayed coupling in standard semiconductor laser diodes to few photon states, where quantum fluctuations contribute to or even dominate over the usual classical dynamics. Feedback-coupling in microlasers will allow us to explore the limits of a classical description of chaotic laser dynamics via the Lang-Kobayashi rate equations and to develop an advanced model taking cQED- and QD-specific effects into account. This subject will be complemented by the study of optical injection of coherent light and non-classical light into microlasers to influence and study mode-locking, chaos and stimulated emission down to the quantum level. Single photon feedback in b) will be applied to stabilize coherent coupling of light and matter and to act against decoherence which constitutes a major bottleneck for application of semiconductor nanostructures in quantum information technology. In c) the mutual coupling of microlasers will be used to study synchronization of chaotic quantum devices at the single photon limit and to explore the underlying physics of isochronal synchronization. Our work will have important impact at an interdisciplinary level on the development of nonlinear dynamical systems towards the quantum limit and the understanding of fundamental light-matter interaction in the presence of time delayed single photon feedback.