Engineering spin-photon quantum interfaces from erbium-oxygen complexes in silicon*

Optically-interfaced spins in solids can enable quantum technologies, such as quantum networks, quantum transducers, and quantum sensors. The trivalent erbium ion (Er³⁺), coordinated with oxygen, could serve as a quantum light matter interface in the telecom band, as it has narrow optical transitions and long spin coherence in oxide hosts. Here, we are developing a spin-photon interface from erbium-oxygen (Er-O) complexes in silicon nanophotonics. Silicon-on-insulator wafers are implanted with Er⁺ and ¹⁶O⁺ and waveguides and cavities are fabricated using CMOS techniques. Photoluminescence, measured at ~4 Kelvin, reveals several sites between 1530-1540nm, with relaxation lifetimes of T₁~1.3ms. The emission rate is increased by coupling to a cavity with Q ~70,000 and mode volume ~0.042 um³. The measured Purcell enhancement is used to estimate the oscillator strength, spontaneous emission time, branching ratio, and the optical dipole moment of the transition. Hole burning is also used to measure narrow spectral diffusion linewidths. Furthermore, we will use superconducting micro-resonators to determine g-tensors and spin coherence. Scalable fabrication of Er-O doped silicon makes this platform promising for on-chip quantum technologies in the microwave and telecommunications band.