Single photon emission from lithographically-positioned engineered nanodiamonds for cryogenic applications

Nitrogen-vacancy centres in nanodiamonds (NDs) provide a promising resource for quantum photonic systems. However, developing a technology beyond proof-of-principle physics requires optimally engineering its component parts. In this work, we present a hybrid materials platform by photolithographically positioning ball-milled isotopically-enriched NDs on broadband metal reflectors. The structure enhances the photonic collection efficiency, enabling cryogenic characterisation despite the limited numerical aperture imposed by our cryostat. Our device, with SiO$_2$ above a silver reflector, allows us to perform spectroscopic characterisation at 16 K and measure autocorrelation functions confirming single-photon emission (g$^2$(0)<0.5). Through comparative studies of similar hybrid device configurations, we can move towards optimally engineered techniques for building and analysing quantum emitters in wafer-scale photonic environments.