on silicon*

Trivalent erbium ions (Er³⁺) are promising spin defects for developing quantum memories in quantum communication networks due to their unique spin-photon interface at telecommunication band. To this end, controlling the local host environment to enable long-lived Er³⁺ electron spins in a technology compatible platform is key. Here, we report on a new qubit system Er³⁺: CeO₂ (cerium dioxide) epitaxially grown on silicon with near-zero nuclear spin environment critical for supporting long-lived spins¹ and in a silicon compatible platform² for device integration.  We study the optical and spin coherence properties of Er³⁺ in this system and demonstrate narrow homogeneous linewidth of 440 kHz with an optical coherence time of 0.72 μs at 3.6 K³. The slow spin-lattice relaxation enables direct observation of spin dynamics at 3.6 K. The Er³⁺ electron spins have a reasonable long spin relaxation of 2.5 ms and a spin coherence of 0.66 μs (in the isolated ion limit)³. These findings indicate the potential of Er³⁺:CeO₂ qubit systems as a scalable platform for quantum networks and communication applications.

(1) S. Kanai, et al. PNAS. 119, e2121808119 (2022).

(2) G. Grant, et al. arXiv:2309.16644 (2023).

(3)  J. Zhang, et al. arXiv:2309.16785 (2023).