New quantum sensing technique for Nuclear Magnetic Resonance

An Experimental schematic. Microwave loop antenna near the diamond sensor chip drives both NV (purple) and TEMPOL electronic spins (blue). Hyperpolarized NMR signals from the sample nuclear spins (orange) are detected by NV ensemble fluorescence readout from the diamond chip. Photo: Dominik B. Bucher.

Nuclear magnetic resonance (NMR) spectroscopy suffers from poor sensitivity compared to other analytical techniques, because it relies on the weak magnetic fields produced by a small thermal nuclear spin polarization. Consequently, a conventional NMR apparatus typically uses large sample volumes of about a milliliter which is large enough to contain around a million biological cells.

Researchers from the University of Maryland’s Quantum Technology Center (QTC) have reported a new quantum sensing technique that allows high-resolution NMR spectroscopy on small molecules in dilute solution in a 10 picoliter sample volume—roughly equivalent to a single cell.

The team has yet developed a system that utilizes nitrogen-vacancy quantum defects in diamonds to detect the NMR signals produced by picoliter-scale samples. The technique has been enhanced by combining quantum diamond NMR with a hyperpolarization method that boosts the sample’s nuclear spin polarization—and hence NMR signal strength—by more than a hundred-fold.

The results reported a NMR with femtomole molecular sensitivity. (

The study has been published in Physical Review X.

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