All-optical determination of one or two emitters using polarization-enhanced photon correlations of nitrogen-vacancy centers in diamond

Qubit technologies using nitrogen-vacancy color centers in diamond require precise knowledge of the centers, including the number of emitters within a diffraction-limited region and their orientations. However, it is challenging to determine the number of emitters when there is a finite background, which affects the precision of resulting quantum protocols. Here we show the photoluminescence (PL) intensity and quantum correlation (Hanbury Brown and Twiss) measurements as a function of polarization for one- and two-emitter systems. The sample was produced by implanting low concentrations of adenine $\left(C_5{H}_5{N}_5\right)$ into a low nitrogen chemical vapor deposition diamond. This approach yielded well-spaced regions with few nitrogen-vacancy centers. We were able to differentiate between two emitter systems and single emitters with background by mapping the PL intensity and quantum correlation as a function of polarization. This method allows us to quantify the background signal at implanted sites, which may vary from off-site background levels. This approach also provides a valuable all-optical mechanism for the determination of one or two emitter systems useful for quantum sensing, communication, and computation tasks.