Scalable nanoscale positioning of highly coherent color centers in prefabricated diamond nanostructures

Nanophotonic devices in color center-containing hosts provide efficient readout, control, and entanglement of the embedded emitters. Yet control over color center formation - in number, position, and coherence - in nanophotonic devices remains a challenge to scalability. Here, we report a controlled creation of highly coherent diamond nitrogen-vacancy (NV) centers with nanoscale three-dimensional localization in prefabricated nanostructures with high yield. Combining nitrogen δ-doping during chemical vapor deposition diamond growth and localized electron irradiation, we form shallow NVs registered to the center of diamond nanopillars with wide tunability over NV number. We report a positioning precision of  ~ 4 nm in depth and 46(1) nm laterally in 280 nm-diameter pillars (102(2) nm in bulk diamond). We reliably form single NV centers with long spin coherence times (average $T_2^{Hahn}=98\mu s$ ) and higher average photoluminescence compared to NV centers randomly positioned in pillars. Our method can improve the performance of various NV-based devices. In the realm of magnetic sensing, we achieve a 3 × improved yield of NV centers with single electron-spin sensitivity over conventional implantation-based methods. Our high-yield defect creation method will enable scalable production of solid-state defect sensors and processors.