High-Q Diamond Optomechanical Crystals with Preserved Spin Coherence

Diamond optomechanical crystal (OMC) devices with embedded color center spins are promising platforms for quantum sensing, networking, and computing applications, offering versatile couplings between gigahertz-frequency mechanical modes, optical photons, and spin qubits. However, a key challenge lies in fabricating thin, uniform, single-crystal diamond membranes suitable for high-quality nanophotonic and nanomechanical device integration. Here, we demonstrate diamond OMCs exhibiting excellent optical, mechanical, and spin properties, enabled by the development of a diamond smart-cut technique combined with chemical vapor deposition (CVD) overgrowth. The device achieves high optical quality factors of 43,000 at telecom wavelengths and record-high mechanical quality factors of 1.9 million at cryogenic temperatures. Furthermore, we show that spin coherence is preserved in the nanofabricated structures, with nitrogen-vacancy (NV) centers exhibiting long spin coherence times of T₂ = 270 μs at room temperature. These results establish a scalable platform that combines high-performance optomechanics with coherent spin control, providing a promising interface between distinct quantum systems.