Nitrogen-Vacancy Colour Centres in Nanodiamonds as Standard Candle References

Quantitative and reproducible optical characterization of single quantum emitters is crucial for quantum photonic materials research, yet controlling for experimental conditions remains challenging due to a lack of an established reference standard. We propose nanodiamonds containing single nitrogen vacancy (NV$^{-}$) color centers as reliable, stable and robust sources of single-photon emission. We select 4 potential reference emitter candidates from a study of thousands of NV$^{-}$ centers. Candidates were remeasured at a second laboratory, correlating optical pump power and NV$^{-}$ center emission intensity at saturation in addition to corresponding $g^{(2)}(0)$ values. A reference nanodiamond is demonstrated to control for experimental conditions, with reproducible and reliable single-photon emission, as a model for a new single-photon emitter reference standard.