  Photon emission is the hallmark of light-matter interaction and the
foundation of photonic quantum science, enabling advanced sources for quantum
communication and computing. Although single-emitter radiation can be tailored
by the photonic environment, the introduction of multiple emitters extends this
picture. A fundamental challenge, however, is that the radiative dipole-dipole
coupling rapidly decays with spatial separation, typically within a fraction of
the optical wavelength. We realize distant dipole-dipole radiative coupling
with pairs of solid-state optical quantum emitters embedded in a nanophotonic
waveguide. We dynamically probe the collective response and identify both
super- and subradiant emission as well as means to control the dynamics by
proper excitation techniques. Our work constitutes a foundational step toward
multiemitter applications for scalable quantum-information processing.
