Here we report the size reduction and effects on nitrogen-vacancy centres in nanodiamonds by air oxidation using a combined atomic force and confocal microscope. The average height reduction of individual crystals as measured by atomic force microsco
py was 10.6 nm/h at 600 {deg}C air oxidation at atmospheric pressure. The oxidation process modified the surface including removal of non-diamond carbon and organic material which also led to a decrease in background fluorescence. During the course of the nanodiamond size reduction, we observed the annihilation of nitrogen-vacancy centres which provided important insight into the formation of colour centres in small crystals. In these unirradiated samples, the smallest nanodiamond still hosting a stable nitrogen-vacancy centre observed was 8 nm.
Photon interference among distant quantum emitters is a promising method to generate large scale quantum networks. Interference is best achieved when photons show long coherence times. For the nitrogen-vacancy defect center in diamond we measure the
coherence times of photons via optically induced Rabi oscillations. Experiments reveal a close to Fourier transform (i.e. lifetime) limited width of photons emitted even when averaged over minutes. The projected contrast of two-photon interference (0.8) is high enough to envisage the applications in quantum information processing. We report 12 and 7.8 ns excited state lifetime depending on the spin state of the defect.
