  Sources of entangled electromagnetic radiation are a cornerstone in quantum
information processing and offer unique opportunities for the study of quantum
many-body physics in a controlled experimental setting. While multi-mode
entangled states of radiation have been generated in various platforms, all
previous experiments are either probabilistic or restricted to generate
specific types of states with a moderate entanglement length. Here, we
demonstrate the fully deterministic generation of purely photonic entangled
states such as the cluster, GHZ, and W state by sequentially emitting microwave
photons from a controlled auxiliary system into a waveguide. We tomographically
reconstruct the entire quantum many-body state for up to $N=4$ photonic modes
and infer the quantum state for even larger $N$ from process tomography. We
estimate that localizable entanglement persists over a distance of
approximately ten photonic qubits, outperforming any previous deterministic
scheme.
