What is it about?
This research is about using the most sensitive magnetic field sensor in the world to hunt for hints of entirely new forces of nature that we have not seen before. Just like magnets interact with each other, some theories suggest that the spinning cores (spins) of particles like those in atoms could interact with each other in new, exotic ways over surprisingly long distances. These forces could be a sign of new particles or explain the mystery of dark matter. We built a special sensor, an "atomic comagnetometer," that uses a cloud of heated potassium, rubidium, and neon atoms. When these atoms are prepared in a quantum state, they become incredibly sensitive to tiny magnetic signals. We then rotated two heavy lead blocks near this sensor. If the new force exists, the spinning particles inside the moving lead blocks should create a tiny, telltale signal in our atom cloud. To see this incredibly faint signal, we had to build a super-quiet lab, reducing interfering vibrations by over 700 times. After analyzing 108 hours of data, we found no clear sign of this force, which means it must be weaker than we could detect. By not finding it, we've set the most stringent limits on its strength to date, ruling out a large part of the territory where it could have been hiding.
Featured Image
Photo by Gabriel Vasiliu on Unsplash
Why is it important?
This work is important because it pushes the boundaries of how we test the fundamental laws of the universe. The Standard Model of particle physics is incredibly successful but incomplete—it doesn't explain gravity or dark matter. Searching for new, weak forces is a key way to look for physics beyond it. Our experiment is uniquely timely for two reasons. First, our new "hybrid spin-resonance" technique is a major engineering advance. It makes the sensor both extremely sensitive and remarkably stable over long periods, a critical combination that has been very difficult to achieve. Second, we have dramatically improved the search for these specific forces. Our new constraints are up to 1,000 times more sensitive than previous limits for a certain range. This effectively shrinks the map of where new physics could be, guiding future theories and experiments. It demonstrates that tabletop quantum sensors, not just giant particle colliders, can play a crucial role in answering the biggest questions in physics.
Perspectives
As a corresponding author, this project represents the thrilling convergence of precision engineering, quantum control, and fundamental physics exploration. The most rewarding aspect was tackling the immense challenge of vibration isolation—a seemingly mundane problem that became the key to unlocking unprecedented sensitivity. Seeing the team's innovative solution, combining a vibration-isolated foundation with a custom vacuum chamber, achieve a 700-fold suppression of noise was a profound reminder that groundbreaking discoveries often depend on mastering such technical details. I hope this work inspires two groups: physicists, by showing the power of quantum metrology to explore new physics, and engineers, by demonstrating that overcoming tough instrumentation challenges can directly contribute to fundamental science. Personally, I see this not as an end, but as a beginning. The techniques we've developed, from the HSR regime to vibration control, create a powerful new platform. We are now poised to use this platform to search for other exotic interactions and even for dark matter itself, continuing the decades-long pursuit of understanding the universe's deepest symmetries that started with the pioneering work of scientists like C. S. Wu.
Kai Wei
Beihang University
Read the Original
This page is a summary of: Search for a parity-violating long-range spin-dependent interaction, Proceedings of the National Academy of Sciences, October 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2512538122.
You can read the full text:
Resources
Contributors
The following have contributed to this page
