Quantum Sensing of Nuclear Magnetism

Nuclear spins are remarkable quantum sensors in their own right: weakly coupled to their environment, exquisitely well characterized, and exploitable across an enormous range of energy scales. The same properties that make nuclear magnetic resonance (NMR) the workhorse of analytical chemistry and medical imaging also make nuclear spin ensembles powerful probes of fundamental physics, from searches for ultralight dark matter with the Cosmic Axion Spin Precession Experiment (CASPEr) to tests of fundamental symmetries enabled by zero- to ultralow-field (ZULF) NMR. In this talk, I will give a broad overview of how nuclear magnetism connects precision measurement to chemical and biological sensing, and then focus on our recent work using nitrogen-vacancy (NV) centers in diamond as microscopic optical magnetometers for NMR at low magnetic field. By detecting electron-mediated spin-spin (J) couplings — chemically specific, magnetic-field-independent observables — we are working toward a quantum diamond microscope capable of spatially resolved, chemically selective magnetic resonance microscopy of hyperpolarized metabolites, bridging the gap between fundamental-physics-style spin sensing and practical biochemical analysis.