A spin-embedded diamond optomechanical resonator with mechanical quality factor exceeding one million

TL;DR

This paper reports the development of diamond optomechanical resonators with high mechanical quality factors exceeding one million and long spin coherence times, enabling strong photon-phonon interactions for quantum technologies.

Contribution

It introduces a robust fabrication method for high-Q diamond optomechanical devices with embedded spins, achieving both high mechanical quality and preserved spin coherence.

Findings

Mechanical Q factor > 10^6 at cryogenic temperatures

Spin coherence times up to 270 μs for NV centers

High optomechanical cooperativity at low power

Abstract

Diamond optomechanical crystal (OMC) devices with embedded color center spins are promising platforms for a broad range of applications in quantum sensing, networking, and computing applications, offering an interface between a GHz-frequency mechanical mode and both optical photons and coherent spins. A crucial but elusive step towards realizing this platform is to engineer a device with a high-quality factor mechanical mode while preserving the bulk-like coherence of embedded spins. Here we demonstrate sideband-resolved diamond OMCs with mechanical quality factors in excess of $10^6$ at cryogenic temperatures, and find coherence times up to $T_2$ = 270 $\mu$s for embedded nitrogen vacancy (NV) centers. Furthermore, we measure these devices across five orders of magnitude in intracavity optical power, demonstrating robust power handling and a high optomechanical cooperativity ($C\gg1$) at cryogenic temperatures that is essential for a broad range of quantum protocols requiring strong, coherent interactions between photons and phonons. These results are enabled by a robust, high-throughput method for forming single-crystal diamond membranes in combination with chemical vapor deposition (CVD) diamond overgrowth with nitrogen $\delta$-doping. We discuss the prospects of this platform for hybrid spin-mechanical devices in the quantum regime.