In a groundbreaking development, Princeton University researchers have unveiled a diamond-based quantum sensor capable of revealing intricate magnetic phenomena at scales smaller than a wavelength of light. This innovative technique, detailed in a recent Nature publication, provides unprecedented insights into materials such as graphene and superconductors, which are pivotal to advanced technologies like lossless powerlines and levitating trains.
The announcement comes as scientists have long sought to directly observe electric currents and magnetic fields that behave in seemingly counterintuitive ways at atomic scales. The new sensor, which boasts a sensitivity approximately 40 times greater than previous methods, represents a significant leap in quantum sensing capabilities.
Revolutionizing Magnetic Field Observation
Developed over five years, the diamond-based sensing method utilizes engineered defects within lab-grown diamonds. These defects, which involve a single missing atom in a lattice of billions, interact strongly with magnetic fields, making them ideal for sensing at minute scales. The latest advancement involves implanting two defects in close proximity, allowing them to engage in quantum-mechanical interactions that enhance the sensor’s capabilities.
Nathalie de Leon, associate professor of electrical and computer engineering at Princeton and the study’s senior author, emphasized the revolutionary nature of this technique. “You have this totally new kind of playground,” de Leon remarked. “You just can’t see these things with traditional techniques.”
Exploring Real Quantum Materials
The technique’s ability to probe real materials directly, rather than relying on carefully constructed atomic arrays, marks a significant departure from previous methods. Philip Kim, an experimental physicist at Harvard, noted the importance of this capability. “That’s where the importance comes in,” he said, highlighting the potential to study superconductors and graphene directly.
Kim, who is collaborating with de Leon on complementary techniques, studies superconductors that can be cooled by liquid nitrogen and graphene, a material with promising yet challenging applications. The new sensor’s ability to explore these materials at the quantum level could unlock new technological advancements.
Quantum Entanglement: A New Frontier
The sensor’s development involved firing nitrogen molecules at high speeds into the diamond, creating defects that are just 10 nanometers apart. This proximity allows the defects to become quantum entangled, a phenomenon once described by Albert Einstein as “spooky action at a distance.” Entangled electrons in the nitrogen atoms act in unison, enabling the sensor to detect magnetic fluctuations with remarkable precision.
De Leon explained the significance of this scale, stating, “At this size range, between the atomic scale and the wavelength of visible light, scientists want to measure previously invisible quantities.” These measurements include electron travel distances and the evolution of magnetic vortices in superconductors.
From Pandemic Setbacks to Quantum Advances
The breakthrough originated during the COVID-19 pandemic when Jared Rovny, a Princeton Quantum Initiative postdoctoral fellow, began exploring the theory of magnetic noise. Despite limited lab access, Rovny and de Leon pursued the project out of curiosity, eventually realizing its potential to revolutionize quantum sensing.
Rovny’s background in nuclear magnetic resonance (NMR) played a crucial role in the project’s development. “That NMR side of me was really always thinking about interactions,” Rovny noted. His insights led to the realization that entangled nitrogen vacancy centers could effectively detect correlations in magnetic noise.
“What I realized is that if you entangled them, the presence or absence of a correlation sort of puts its fingerprint onto the system,” Rovny explained.
This discovery allowed the researchers to bypass complex problems and achieve the advantages of two sensors at the cost of one, simplifying the measurement process significantly.
Future Implications and Next Steps
The implications of this research extend beyond immediate scientific applications. By enabling direct observation of quantum materials, the sensor could pave the way for breakthroughs in energy-efficient technologies and advanced computing systems.
Looking ahead, the team plans to further refine the sensor’s capabilities and explore its potential applications in various fields. The paper, “Multi-qubit nanoscale sensing with entanglement as a resource,” was published in Nature on November 26, 2025, and was funded by the Gordon and Betty Moore Foundation, the National Science Foundation, and Oak Ridge Institute for Science and Education.
As the scientific community continues to explore the possibilities of quantum sensing, this breakthrough represents a significant step toward unlocking the mysteries of the quantum world and harnessing its potential for technological innovation.
