Chip integration of quantum emitters is a crucial milestone for scalable quantum photonic information processing. Among optically active defect centers for quantum photonics, diamond color centers are promising because of their long spin coherence times and high photon emission rates. However, for a coherent-photon emission, they typically require a cryogenic environment to protect optical coherence from thermal phonons, which makes chip integration challenging. In this paper, we develop a chip-integrated diamond photonic crystal cavity embedding an ensemble of nitrogen-vacancy (NV) centers. We confirm cryogenic operation by observing Purcell enhancement of NV-center emission via an edge-coupled optical fiber. This result demonstrates successful integration of diamond color centers, a photonic crystal cavity, and an optical waveguide-fiber package, representing a key step toward scalable diamond-based quantum communication platforms.
@article{arxiv.2604.06984,
title = {Scalable on-chip integration of diamond color centers for cryogenic quantum photonics},
author = {H. Kurokawa and K. Sato and M. Kamata and S. Ishida and H. Matsukiyo and N. Pholsen and M. Nishioka and S. Ji and H. Otsuki and S. Hachuda and M. Kunii and T. Tamanuki and K. Kimura and K. Takenaka and Y. Sekiguchi and S. Onoda and S. Iwamoto and T. Baba and H. Kosaka},
journal= {arXiv preprint arXiv:2604.06984},
year = {2026}
}