Opportunities for Diamond Quantum Metrology in Biological Systems

Sensors that harness quantum mechanical effects can enable high sensitivity and high spatial resolution probing of their environment. The nitrogen-vacancy defect in diamond, a single, optically accessible electronic spin, is a promising quantum sensor that can operate in soft and living systems and provides nanoscale spatial resolution when hosted inside a diamond nanoparticle. Nanodiamond quantum sensors are nontoxic, amenable to surface functionalization, and can be introduced into a variety of living systems. The optical readout of the spin provides detailed information about the local electromagnetic and thermal environment in a noninvasive way. In this Perspective, we introduce the different modalities that nanodiamond quantum sensors offer, highlight recent progress in quantum sensing of biological systems, and discuss remaining challenges and directions for future efforts.