A Miniaturized Metalens‐Based Spin Defect Quantum Sensor

Nanoscale quantum sensing with solid‐state spins enables high‐spatial‐resolution detection of microscopic physical phenomena, benefiting from their surface proximity, atomic‐scale dimensions and optical addressability. The miniaturization of such sensing platforms is critical for broadening the applications. High‐resolution optical imaging of solid‐state spins typically requires bulky multi‐lens objectives. Here, we report a single dielectric ultraflat metalens capable of both exciting and collecting fluorescence from spin defects. The high spatial resolution, comparable with traditional objective, is demonstrated through the optical imaging of spin defects in diamond. The nanoscale electromagnetic field sensing with spin defects in constrained space is subsequently realized, due to the high numerical aperture and small size of the metalens. Our work provides a platform for developing integrated nanoscale quantum sensing devices. The results will promote the compatibility of solid‐state spin quantum sensor in various practical environment.