Two quantum sensing technologies, optically pumped magnetometers (OPMs) and nitrogen-vacancy (NV) centers in diamond, are transforming how chemists and materials scientists measure the otherwise invisible, according to a comprehensive new review posted on arXiv by researchers at Harvard University and Jagiellonian University in Krakow.
The review, led by Piotr Put (Harvard/Jagiellonian), Arjun Pillai, Xuan Hoang Le, Mikhail D. Lukin, and Hongkun Park, systematically compares the two platforms across a range of chemical and materials applications. Both exploit the quantum properties of atomic-scale sensors to detect magnetic fields with extraordinary sensitivity, but they operate in fundamentally different regimes.
Two approaches, complementary strengths
OPMs use macroscopic vapor cells containing 10^11 to 10^14 alkali atoms (typically cesium or rubidium). Laser light polarizes the atoms’ spins, and magnetic fields cause the polarization to precess, which is read out optically. The result is extreme bulk sensitivity, down to sub-femtotesla per square-root hertz, but with millimeter-to-centimeter spatial resolution. OPMs can detect fields through metal walls, making them uniquely suited for monitoring chemical reactions inside sealed reactors.
NV centers, by contrast, are point defects in the diamond crystal lattice, a nitrogen atom adjacent to a missing carbon atom. Each NV center is a single atomic-scale magnetometer that can be addressed optically. They offer nanoscale spatial resolution (down to roughly 10 nanometers), multimodal sensing (magnetic fields, temperature, electric fields, and strain), and can operate across a broad temperature range from cryogenic to 600 K. Their sensitivity per root hertz is lower than OPMs, typically in the picotesla range, but their spatial resolution opens entirely different applications.
The review’s key comparison table quantifies the trade-offs: OPMs achieve DC sensitivity of 0.16-100 fT/Hz^(1/2) and AC sensitivity of 0.2-100 fT/Hz^(1/2) at kilohertz frequencies, while NV centers achieve 5 pT/Hz^(1/2) to 1 microT/Hz^(1/2) for DC and 200 fT/Hz^(1/2) to 1 microT/Hz^(1/2) for AC. OPMs are roughly 10-1,000 times more sensitive per root bandwidth, but NV centers offer roughly 10^5 times better spatial resolution.
Chemical analysis
In zero-to ultralow-field (ZULF) NMR, OPMs are the primary platform, detecting J-coupling spectra, the through-bond magnetic interactions between nuclei, without the need for strong superconducting magnets. This allows chemical identification in environments where traditional high-field NMR is impractical. The paper notes that hyperpolarization techniques such as PHIP and SABRE can boost signal-to-noise ratios by several orders of magnitude, making ZULF NMR practical for real samples.
NV centers extend NMR to the nanoscale. Using the CASR (continuous adiabatic swept rotation) protocol, they achieve chemical-shift resolution in picoliter volumes, with detection limits as low as 50 femtomoles of tert-butanol via Overhauser DNP hyperpolarization. For paramagnetic species, NV dynamic quantum sensing achieves a limit of detection of 10 attomoles for gadobutrol, a contrast agent.
Real-time monitoring
OPMs can monitor chemical reactions inside sealed metal reactors, hydrogenations, enzymatic reactions, because low-frequency magnetic signals penetrate metal casings. This allows time-resolved tracking of reaction progress without the need for sampling or optical access.
NV centers, meanwhile, can track surface chemistry at the single-molecule level, monitoring self-assembled monolayers, detecting free radicals via relaxometry, and sensing pH through the charge-state switching between NV^- and NV^0.
Materials applications
In operando battery diagnostics, OPMs detect charge storage inhomogeneities and weak transient internal currents in lithium-ion cells, information that is invisible to conventional electrical measurements. NV centers complement this with nanoscale detection of current distributions and ion dynamics at electrode-electrolyte interfaces.
For high-throughput chemical assays, the review discusses multiplexed OPM arrays for parallel screening and nanodiamond-based assays for multi-well plate formats. The combination of bulk sensitivity (OPMs) and nanoscale resolution (NV centers) means that quantum sensing can now span virtually the entire range of length scales relevant to chemistry and materials science.
Status
The review was posted to arXiv on July 8, 2026, and has not yet been submitted to a peer-reviewed journal. Given its scope, 22 pages covering principles, applications, and outlook, it is likely targeting a major review journal such as Chemical Reviews, Nature Reviews Chemistry, or Nature Reviews Physics.
Disclosure: Based on an arXiv preprint that has not undergone peer review.
Sources
[1] Put, P., Pillai, A., Le, X.H., Lukin, M.D., & Park, H. “Quantum Sensors for Chemistry and Materials Science.” arXiv:2607.07848 (2026). https://arxiv.org/abs/2607.07848