Engineering Spin Coherence in Core-Shell Diamond Nanocrystals

Diamond nanocrystals can harbor spin qubit sensors capable of probing the physical properties of biological systems with nanoscale spatial resolution. These diamond nanosensors can readily be delivered into intact cells and even living organisms. However, applications beyond current proof-of-principle experiments require a substantial increase in sensitivity, which is generally limited by surface-noise-induced spin dephasing and relaxation. In this talk, I will discuss a novel strategy to significantly reduce the surface noise by engineering core-shell structures, which on average result in a 3.5-fold increase in spin coherence and spin-lattice relaxation time. Probing qubit dynamics at a single particle level, furthermore, reveals that the noise characteristics change from a model consistent with a two dimensional dipole fluctuator model to a more dilute three dimensional bath. Our results shed light on the underlying mechanisms governing spin dephasing in diamond nanocrystals and offer an effective noise mitigation strategy based on engineered core-shell structures.