  Large-scale entanglement of nitrogen-vacancy (NV) centers in diamond will
require integration of NV centers with optical networks. Toward this goal, we
present the fabrication of single-crystalline gallium phosphide (GaP)
resonator-waveguide coupled structures on diamond. We demonstrate coupling
between 1 {\mu}m diameter GaP disk resonators and waveguides with a loaded Q
factor of 3,800, and evaluate their potential for efficient photon collection
if integrated with single photon emitters. This work opens a path toward
scalable NV entanglement in the hybrid GaP/diamond platform, with the potential
to integrate on-chip photon collection, switching, and detection for
applications in quantum information processing.
