Sensitive multichannel zero-to ultralow-field NMR with atomic magnetometer arrays

Despite its versatility and high chemical specificity, conventional nuclear magnetic resonance (NMR) spectroscopy is limited in measurement throughput due to the need for high-homogeneity magnetic fields, necessitating sequential sample analysis, and expensive devices. Here, we propose a multichannel NMR device that addresses these limitations by leveraging the zero-to ultralow-field (ZULF) regime, where simultaneous detection of multiple samples is carried out via an array of compact optically pumped magnetometers (OPMs). A magnetic field is used only for prepolarization, permitting the use of large-bore, high-field, inhomogeneous magnets that can accommodate multiple samples concurrently. Through systematic improvements, we demonstrate sensitive, high-resolution ZULF NMR spectroscopy with sensitivity comparable to benchtop ¹³C NMR systems. The spectroscopy remains robust without the need for field shimming for periods on the order of weeks. We show the detection of ZULF NMR signals from organic molecules without isotopic enrichment, and demonstrate the parallelized detection of three distinct samples simultaneously as a proof-of-concept, with the ability to scale further to over 100 channels at a cost comparable to traditional liquid state NMR systems. This work sets the stage for using multichannel "NMR camera" devices for inline reaction monitoring, robotic chemistry, quality control, and high-throughput assays.