UC Santa Barbara

Nitrogen-vacancy(NV) centers in diamonds are a prominent example of solid-state spin qubits for applications in quantum information. However, the assembly of solid-state spins, including NVs or auxiliary spins near the diamond surface, with a controlled nanoscale spatial precision remains an outstanding challenge. Consequently, the pathway towards scaling up both quantum simulation and entanglement-enhanced sensing using NVs remains unclear. Furthermore, near-surface NVs tend to exhibit degraded properties, including spin coherence and charge state stability. Firstly, we will discuss the charge state instabilities of shallow NVs. We discover that the charge state stability depends on the local discrete environment, and our observation is consistent with a model of a single electron trap near the NV center. We also discuss protocols that can be used to alleviate the charge state effect on NV measurement. Secondly, we will discuss the utilization of entanglement with auxiliary reporter spins to improve the sensitivity of T1 relaxometry. Thirdly, we will discuss two methods to engineer two-dimensional NV ensembles and the decoherence dynamics due to the many-body noise in such strongly interacting dipolar spin systems. Lastly, we will present our recent progress, where we combine a DNA-based patterning technique with nitrogen-vacancy (NV) quantum sensors in diamond to sense two-dimensional arrays of molecular spins programmably patterned via a monolayer of DNA origami on a diamond surface. We control the spacing of chelated Gd3+ spins down to 6 nm precision and verify this control by observing a linear relationship between proximal NVs’ T1 relaxation rate and the designated number of Gd3+ spins per origami unit. We confirm the preservation of the charge state and spin coherence of the proximal, shallow NV centers and discuss ongoing work towards probing ordered, strongly interacting two-dimensional spin networks on the diamond surface.