Zero- to ultralow-field nuclear magnetic resonance and its applications

As a complementary analysis tool to conventional high-field nuclear magnetic resonance (NMR), zero- to ultralow-field (ZULF) NMR detects nuclear magnetization signals in the sub-microtesla regime. Spin-exchange relaxation-free (SERF) atomic magnetometers provide a new generation of sensitive detectors for ZULF NMR. Owing to features such as low cost, high resolution, and portability, ZULF NMR has recently attracted considerable attention in chemistry, biology, medicine, and tests of fundamental physics. This review describes the basic principles, methodology, and recent experimental and theoretical development of ZULF NMR as well as its applications in spectroscopy, quantum control, imaging, NMR-based quantum devices, and tests of fundamental physics. The future prospects of ZULF NMR are also discussed.