An Efficient Fiber-Based Microcavity Platform for Tin-Vacancy Centers in Diamond

Realizing long-distance quantum networks requires efficient interfaces between photons and stationary quantum memories. The Tin-Vacancy (SnV) center in diamond emerged as a promising solid-state based spin photon interface, featuring spin-selective optical transitions, long memory times and efficient spin control. Scaling to multi-node networks, however, necessitates efficient coupling between these defect centers and optical cavities.

Here, we demonstrate the integration of single, individually addressable SnV centers in a micrometer-thin diamond membrane into an open, fully tunable cryogenic microcavity to achieve emission enhancement into a single optical mode. The cavity, operated inside a dilution refrigerator at ~1 K, exhibits passive mechanical stability below 10 pm. We observe a pronounced Purcell-induced lifetime reduction, evidencing strong light–matter interaction. Operating in the high-cooperativity regime, coherent coupling is confirmed through emitter-induced extinction in cavity transmission.

Furthermore, our platform enables integration of a superconducting magnet and microwave antenna for spin readout and control, marking a key step toward efficient spin–photon interfaces based on group-IV color centers in diamond.