  The desire to understand the interaction between light and matter has
stimulated centuries of research, leading to technological achievements that
have shaped our world. One contemporary frontier of research into light-matter
interaction considers regimes where quantum effects dominate. By understanding
and manipulating these quantum effects, a vast array of new quantum-enhanced
technologies become accessible. In this thesis, I explore and analyze
fundamental components and processes for quantum optical devices with a focus
on solid-state quantum systems. This includes indistinguishable single-photon
sources, deterministic sources of entangled photonic states, photon-heralded
entanglement generation between remote quantum systems, and deterministic
optically-mediated entangling gates between local quantum systems. For this
analysis, I make heavy use of an analytic quantum trajectories approach applied
to a general Markovian master equation of an optically-active quantum system,
which I introduce as a photon-number decomposition. This approach allows for
many realistic system imperfections, such as emitter pure dephasing, spin
decoherence, and measurement imperfections, to be taken into account in a
straightforward and comprehensive way.
