A single spin in hexagonal boron nitride for vectorial quantum magnetometry.

Quantum sensing based on solid-state spin defects provides a uniquely versatile platform for nanoscale magnetometry under diverse environmental conditions. Operation of most sensors used to-date is based on projective measurement along a single axis combined with computational extrapolation. Here, we show that an individually addressable carbon-related spin defect in hexagonal boron nitride is a multi-axis nanoscale sensor with large dynamic range. For this spin-1 system, we demonstrate how its spin-dependent photodynamics give rise to three optically detected spin resonances that show up to 90% contrast and are not quenched under off-axis magnetic field exceeding 100 mT, enabling sensitivity. Finally, we show how this system can be used to unambiguously determine the three components of a target magnetic field via the use of two bias fields. Alongside these features, the room-temperature operation and the nanometer-scale proximity enabled by the van der Waals host material further consolidate this system as a promising quantum sensing platform.