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arXiv · 2605.25152

Dispersive readout of cavity-coupled solid-state sensor with near-unity readout fidelity

Hanfeng Wang·Shuang Wu·Matthew E. Trusheim·Avetik Harutyunyan·Dirk R. Englund
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Abstract

Solid-state quantum sensors based on ensembles of nitrogen-vacancy (NV) centers in diamond have emerged as powerful platforms for high-precision metrology. Coupling the NV ensemble to a microwave cavity mode in a cavity quantum electrodynamics (cQED) configuration enables spin readout that surpasses the limitations of conventional optical detection, achieving sub-picotesla magnetic sensitivities. However, existing continuous-wave cQED approaches remain far from the intrinsic spin-projection-noise limit due to spin saturation and power broadening. Here, we introduce a dispersive cQED readout technique to overcome these fundamental limitations in NV ensemble sensing. We develop a comprehensive theoretical framework describing the dispersive interaction and analyze the time-domain dynamics of a strongly-coupled NV-cavity system. Our results indicate near-unity inverse readout fidelity and femtotesla-level sensitivity using a commercially available diamond NV ensemble. Importantly, the dispersive readout exhibits a distinct sensitivity scaling that improves as 1/N with increasing number of spins N, providing a practical pathway toward approaching the standard quantum limit for solid-state spin-ensemble sensors.

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Hanfeng Wang, Shuang Wu, Matthew E. Trusheim, Avetik Harutyunyan, Dirk R. Englund. 2026-05-24. Dispersive readout of cavity-coupled solid-state sensor with near-unity readout fidelity. https://arxiv.org/abs/2605.25152

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