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arXiv · 2511.19831

Nanophotonic magnetometry in a spin-dense diamond cavity

Nicholas J. Sorensen·Elham Zohari·Joshua S. Wildeman·Sigurd Flågan·Vinaya K. Kavatamane·Paul E. Barclay
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Abstract

Quantum sensors based on the nitrogen-vacancy (NV) center in diamond are leading platforms for high-sensitivity magnetometry with nanometer-scale resolution. State-of-the-art implementations, however, typically rely on bulky free-space optics or sacrifice spatial resolution to achieve high sensitivities. Here, we realize an integrated platform that overcomes this trade-off by fabricating monolithic whispering-gallery-mode cavities from a diamond chip containing a high density of NV centers and by evanescently coupling excitation to and photoluminescence from the cavity using a tapered optical fiber. Employing a lock-in-amplified Ramsey magnetometry scheme, we achieve a photon-shot-noise-limited DC sensitivity of $58\,\text{nT}/\sqrt{\text{Hz}}$ -- the best sensitivity reported to date for a nanofabricated cavity-based magnetometer. The microscopic cavity size enables sub-micrometer-scale spatial resolution and low-power operation, while fiber-coupling provides a path to scalable on-chip integration. Arrays of such sensors could enable NV-NMR spectroscopy of sub-nanoliter samples, new magnetic-gradient imaging architectures, and compact biosensing platforms.

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Nicholas J. Sorensen, Elham Zohari, Joshua S. Wildeman, Sigurd Flågan, Vinaya K. Kavatamane, Paul E. Barclay. 2025-11-25. Nanophotonic magnetometry in a spin-dense diamond cavity. https://arxiv.org/abs/2511.19831

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