Plasmonically engineered nitrogen-vacancy spin readout.

Ultra-precise readout of single nitrogen-vacancy (NV) spins holds promise for major advancements in quantum sensing, computing, and communication technologies. Here we present a rigorous open quantum theory capable of simultaneously capturing the optical, vibronic, and spin interactions of the negatively charged NV center, both in the presence and absence of plasmonic interaction. Our theory is verified against existing experiments in the literature. We predict orders of magnitude brightness and contrast enhancements in optically detected magnetic resonance (ODMR) and NV spin qubit readout arising from plasmonic interaction. Such optimal enhancements occur in carefully engineered parameter regions, necessitating rigorous modelling prior to experimentation. Our theory equips the community with a tool to identify such regions.