Engineering interacting spin systems in diamond for quantum technologies

Solid-state spins with controlled dipolar interactions constitute a powerful platform for quantum technologies. Ensembles of coherent spins with tunable density and controlled dimensionality provide a starting point for investigating strongly interacting spin systems in which novel, many-body states can arise and enable advancements in quantum sensing and simulation such as interaction-driven localization or dipolar-driven spin squeezing. Defects spins in diamond, such as nitrogen-vacancy (NV) centers, represent a promising platform to explore due to their rich recent history of investigation. However, outstanding challenges include the creation of dense, two-dimensional NV ensembles, engineering their nonzero dipolar interactions, and controlling surface proximity for metrological utility. We demonstrate that delta doping during plasma-enhanced chemical vapor deposition diamond growth provides a key route to achieving control over dimensionality and dipolar interactions. We pioneer the creation of 2D, strongly interacting dipolar ensembles in (111)-oriented diamond, which though minimally explored to date, provide unique advantages for leveraging dipolar-driven entanglement schemes and exploring new interacting spin physics. We demonstrate an increased density of grown, preferentially aligned NV centers, resulting in the creation of NV ensembles with a high magnetic sensitivity, and we engineer NV centers with close proximity to the diamond surface for high spatial resolution sensing. The capabilities we have developed are leveraged by NV applications across diverse fields from 2D magnetism to optomechanics, ultimately enabling the pursuit of new frontiers in quantum sensing and simulation in the solid state.