New quantum sensing technology reveals sub-atomic signals

More information:
S. Alex Breitweiser et al, Quadrupolar Resonance Spectroscopy of Individual Nuclei Using a Room-Temperature Quantum Sensor, Nano Letters (2024). DOI: 10.1021/acs.nanolett.4c04112

Journal information:
Nano Letters

“It’s a bit like diagnosing a patient based on symptoms,” he explains. “The data points to something unusual, but there are often multiple possible explanations. It took quite a while to arrive at the correct diagnosis.”

Looking ahead, the researchers see vast potential for their method to address pressing scientific challenges. By characterizing phenomena that were previously hidden, the new method could help scientists better understand the molecular mechanisms that shape our world.

“Traditional NQR produces something like an average—you get a sense of the data as a whole, but know nothing about the individual data points. With this method, it’s as though we’ve uncovered all the data behind the average, isolating the signal from one nucleus and revealing its unique properties.”

The periodic signals looked like an experimental artifact, but persisted after extensive troubleshooting. Returning to textbooks from the 1950s and ’60s on nuclear magnetic resonance, Breitweiser identified a physical mechanism that explained what they were seeing, but that had previously been dismissed as experimentally insignificant.

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Deciphering the signals

Determining the theoretical underpinnings of the unexpected experimental result took significant effort. Ouellet had to carefully test various hypotheses, running simulations and performing calculations to match the data with potential causes.

An unexpected discovery

The discovery stemmed from an unexpected observation during routine experiments. Alex Breitweiser, a recent doctoral graduate in Physics from Penn’s School of Arts & Sciences and the paper’s co-first author, who is now a researcher at IBM, was working with nitrogen-vacancy (NV) centers in diamonds—atomic-scale defects often used in quantum sensing—when he noticed unusual patterns in the data.

“This technique allows us to isolate individual nuclei and reveal tiny differences in what were thought to be identical molecules,” says Lee Bassett, Associate Professor in Electrical and Systems Engineering (ESE), Director of Penn’s Quantum Engineering Laboratory (QEL) and the paper’s senior author.

Described in Nano Letters, the new method is so precise that it can detect the NQR signals from individual atoms—a feat once thought unattainable. This unprecedented sensitivity opens the door to breakthroughs in fields like drug development, where understanding molecular interactions at the atomic level is critical.

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