A scalable GaP-on-diamond spin-photon interface

Silicon-vacancy (SiV) center in diamond is a promising platform for realizing quantum networks due to its exceptional optical properties. To enhance the spin-photon interaction, integration of SiV centers with nanophotonic cavities is ideal due to their strong confinement potential for scalability. The current leading approach is to integrate SiV centers into suspended photonic crystal cavities carved out of the diamond itself. However, this approach is difficult to scale due to the weak nonlinear properties of diamond and the challenges of fabrication. In this work, we demonstrate the scalable high-yield fabrication of planar gallium-phosphide (GaP)-on-diamond photonic crystal (PhC) cavities coupled to SiV centers with high cooperativity (C>1). We observe strong modulation of the cavity transmission by the spin-resolved transitions of coupled SiV centers, demonstrating the potential for GaP-on-diamond as a platform for scalable quantum networking.