Single molecule becomes quantum sensor for imaging proteins at nanoscale
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A new quantum sensing technique could enable measurements of single protein structures and other important molecules, with potential applications in drug discovery and structural biology. A research team from the Institute for Quantum Computing (IQC) at the University of Waterloo developed a new method that uses a single molecule as a quantum sensor. Quantum sensors use unique properties of quantum mechanics to make ultra-precise measurements that traditional sensors cannot achieve.
This technique has never been demonstrated before and uses a class of molecules for this purpose for the first time. Precise imaging of single molecules helps researchers understand how single proteins and other biomolecules behave. It can reveal more information about how diseases develop and the ways drugs interact, potentially helping design more effective treatments. The work is published in the journal Physical Review X.
Reading spins at close range
The sensors probe the spin, or local magnetic environment, of atoms. Because each atom has a unique resonance frequency, if two are close together, they magnetically affect each other.
"Our experiment establishes a new paradigm in nanoscale quantum sensing," said Dr. Raffi Budakian, a professor in the Department of Physics and Astronomy and a faculty member at IQC. "There are other milestones to reach before we have a sensor sensitive to single molecules, but we know how to get there, and this is a huge demonstration. We're not too far away now because of this advancement."
A molecular alternative to diamond
A well-established quantum-sensing technique uses synthetic diamonds designed with atomic-scale defects and involves light to read out signals. Budakian's group used a class of molecules called trityl-OX063 as the quantum sensor. The spin of the sensor is isolated and protected, preserving its quantum properties. Compared with the diamond sensing technique, the sensor can be placed closer to its target to achieve higher sensitivity.
Their method uses the electron spin of the OX063 molecule. The magnetic fields from nearby nuclear spins change the evolution of that electron spin. The resulting signal is detected mechanically using nanowire probes that are 100 nanometers in diameter, about the size of a virus, and 20 microns long, about the diameter of a human hair.
"One key challenge was keeping the OX063 spins coherent long enough to make them useful as sensors," said Sahand Tabatabaei, a Ph.D. candidate at IQC and first author on the paper. "The new control sequence we developed extended the coherence time to 400 microseconds, so it maintained its quantum state roughly 60 times longer than what is achieved with standard spin-echo techniques in the same system."
Closing in on single spins
Budakian said the sensor can already detect the magnetic state of about 10 spins. They know how to get to single spins, which is a key step toward mapping the structure of single molecules.
Current molecular-imaging techniques, while powerful, don't reveal unique molecular structures because they require larger samples.
"Using force detection in quantum sensing is new and opens up a whole new avenue of approaches we can take to get us closer to mapping single protein structures," Budakian said.
Publication details
Long-lived mechanically-detected molecular spins for quantum sensing, Physical Review X (2026). DOI: 10.1103/c994-bzx7
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Citation: Single molecule becomes quantum sensor for imaging proteins at nanoscale (2026, July 28) retrieved 28 July 2026 from https://phys.org/news/2026-07-molecule-quantum-sensor-imaging-proteins.html
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