Researchers at the University of Chicago and Argonne National Laboratory have pinpointed the microscopic origins of surface noise that limits the performance of diamond-based quantum sensors, a breakthrough published February 5, 2026, in Physical Review Materials. These sensors, utilizing defects in diamond called nitrogen-vacancy (NV) centers, hold immense promise for detecting incredibly weak signals from the molecular to the biological scale. However, proximity to diamond surfaces introduces disruptive noise—until now, a poorly understood phenomenon. “One long-standing challenge has been understanding why shallow NV centers lose coherence so quickly,” said Giulia Galli, professor at UChicago Pritzker School of Molecular Engineering and senior scientist at Argonne. This study reveals that the key isn’t what spins exist on the surface, but how they move, paving the way for engineering quieter, more powerful quantum sensors.
Nitrogen-Vacancy Centers’ Coherence Limited by Surface Noise
Researchers published their findings in Physical Review Materials on February 5, 2026, with the paper designated an Editors’ Suggestion. The team utilized first-principles surface models combined with quantum dynamics simulations to unravel the mechanisms at play. The study demonstrates that surface defects created during fabrication, such as dangling bonds, host unpaired electrons that fluctuate and generate magnetic noise, disrupting the NV center’s quantum state. “During the fabrication process of diamond surfaces for sensing applications, undesired surface defects may be created, including what we call dangling bonds,” explained UChicago PME PhD candidate Jonah Nagura, lead author of the study.
Crucially, the research shows oxygen- and nitrogen-terminated surfaces preserve coherence better than hydrogen- and fluorine-terminated ones, though surface-electron relaxation and hopping are the dominant factors. “The electron spins present at the surface interact with the same laser pulses that are used to manipulate and read out the NV center,” Nagura said, detailing how laser-driven electron hopping generates additional noise.
First-Principles Modeling Reveals Dynamical Decoherence Mechanisms
A new theoretical framework is illuminating the sources of quantum decoherence that plague diamond-based sensors, offering a path toward significantly improved performance. The team’s simulations, combining density functional theory with quantum decoherence modeling, reveal that fluctuating paramagnetic defects and charge noise aren’t static problems. Jonah Nagura, a PhD candidate at UChicago PME and lead author, explained that “dangling bonds” created during fabrication can host unpaired electrons, generating magnetic noise.
Critically, the study demonstrates that surface-electron relaxation and hopping—driven by laser pulses used to read the NV center—are dominant factors in coherence loss. “However, while termination chemistry and facet orientation do matter, we found that it is surface-electron relaxation and hopping that dominate the coherence of shallow NVs,” Nagura said. Oxygen- and nitrogen-terminated surfaces showed promise in preserving coherence, while hydrogen- and fluorine-terminated surfaces introduced stronger noise.
“One long-standing challenge has been understanding why shallow NV centers lose coherence so quickly,”
Oxygen/Nitrogen Termination Preserves Near-Bulk NV Coherence
Researchers discovered that the type of chemical termination on the diamond surface dictates the level of quantum noise experienced by the NV centers, with oxygen- and nitrogen-terminated surfaces proving particularly effective at preserving coherence—even for centers just a few nanometers below the surface. The team’s simulations pinpointed that surface-electron relaxation and hopping are primary drivers of decoherence, exceeding the impact of the specific spins present on the surface. Hydrogen- and fluorine-terminated surfaces, in contrast, introduced significantly more magnetic noise, drastically reducing coherence times.
