A team at the University of Waterloo’s Institute for Quantum Computing has developed a quantum sensing method that uses a single molecule as the sensing element, an approach the researchers say could eventually make it possible to measure the structure of individual proteins and other biologically important molecules, with potential applications in drug discovery and understanding how diseases develop. “Our experiment establishes a new paradigm in nanoscale quantum sensing,” said Dr. Raffi Budakian, the physics professor who led the work, published in Physical Review X.
The method relies on a class of molecules called trityl-OX063 and detects the electron spin of the molecule, which shifts slightly in response to nearby nuclear spins. Rather than reading that signal optically, as is common with diamond-based quantum sensors, the team reads it mechanically through nanowire probes roughly 100 nanometers wide and 20 microns long — the first demonstration of this approach. “Using force detection in quantum sensing is new and opens up a whole new avenue of approaches,” Budakian said, since the sensor can be placed closer to its target than diamond-based alternatives, improving sensitivity.
A central challenge was keeping the molecule’s spin coherent, meaning stable and measurable, for long enough to be useful. “The new control sequence we developed extended the coherence time to 400 microseconds,” said Sahand Tabatabaei, a PhD candidate at IQC and the paper’s first author — roughly 60 times longer than standard spin-echo techniques achieve in the same system. The sensor can currently detect signals from about 10 spins, and the researchers say they already know how to push the technique down to single spins, a milestone that would open the door to mapping individual molecules atom by atom. The work was supported in part by the Canada First Research Excellence Fund.
Endnotes
- Sahand Tabatabaei, Raffi Budakian, et al., “Long-Lived Mechanically Detected Molecular Spins for Quantum Sensing,” Physical Review X, July 27, 2026, DOI: 10.1103/c994-bzx7.
- University of Waterloo, “Using a molecule as a quantum sensor,” news release via EurekAlert!, July 28, 2026.
Featured image credit: Cristián Peña, Fermilab