A prototype quantum sensor developed by researchers at Imperial College London has demonstrated for the first time in real life that a key concept behind future quantum detectors may work beyond ideal laboratory assumptions.
The study showed that experimental noise can be effectively removed by comparing two long-baseline atom interferometers, highly sensitive instruments that use lasers to track the movement of atoms. As a result, scientists can recover meaningful signals even when individual measurements seem completely overwhelmed.
This advance could help pave the way for future searches for gravitational waves from the early universe and possible signatures of exotic forms of dark matter.
The research is part of the Atom Interferometer Observatory and Network (AION), a UK-wide collaboration led by Imperial that is developing the next generation of quantum sensing technology.
The survey results are nature.
Exploring the universe using quantum sensors
One of the biggest unanswered questions in physics is what the universe is made of. Scientists are also looking for new sources of gravitational waves, ripples in space-time produced by some of the most powerful events in the universe.
Both goals rely on detecting very weak signals that can easily disappear beneath background noise. If researchers want to explore regions of space that cannot be reached with current equipment, developing methods that can reliably separate these signals from interference is essential.
One of the most promising tools for this task is the long-baseline atom interferometer. These devices use lasers to split clouds of atoms and later recombine them, allowing researchers to measure minute changes in the movement of atoms with incredible precision.
This technique compares two clouds of atoms located in different locations but controlled by the same laser. Differences in their behavior could indicate the existence of previously unseen phenomena, such as dark matter fields.
However, the laser itself has a major drawback. The phase noise generated during operation is much stronger than the signal scientists are trying to detect. Without a way to remove this noise, you will not be able to see the desired measurements.
Researchers have long proposed solving this problem by comparing two interferometers and canceling out the noise they share. Although this idea forms the basis for future detector designs, it has not previously been demonstrated under realistic experimental conditions.
Dr Charles Baynham, Co-Director of the Ultra-Cold Strontium Laboratory at Imperial College London, commented on the significance of this result:
“We have long known that quantum sensors can help us understand the universe, but only recently have we been able to build quantum sensors at the resolution we need.
“We are extremely proud of our team’s efforts to make these sensors a reality. We can’t wait for the signals from atoms to tell us about the black holes that merged millions of years ago.”
Quantum noise canceling test
To test this concept, the team built a tabletop experimental system at the Imperial Ultra-Cold Strontium Laboratory.
This setup used two widely separated clouds of ultracold strontium-87 atoms measured using a single ultrastable clock laser. This was designed to reproduce conditions expected in future large-scale detectors, where noise control becomes increasingly difficult.
To create a particularly demanding test, the researchers intentionally added large amounts of extra phase noise to the system, far beyond what a clock laser would normally produce. The goal was to mimic the environment expected in a long-baseline atom interferometer.
In this situation, each interferometer became virtually unusable on its own. The interference fringes necessary for measurement were buried in noise.
But when scientists compared the two interferometers, the underlying signal reappeared. Although the individual measurements appeared random, the relationship between the two datasets revealed the actual behavior of the system. The combined results reach fundamental limits imposed by quantum physics and confirm that the noise-canceling approach works as intended.
The team then introduced additional vibrational signals designed to mimic the effects of passing gravitational waves and dark matter fields.
Even in situations where neither interferometer produced useful information on its own, the added signal remained clearly detectable when both systems were analyzed together.
Towards future dark matter and gravitational wave detectors
Our results provide the first experimental confirmation of the central principles behind long-baseline atom interferometry and address one of the most important challenges facing its development.
Through the AION program, researchers are working to extend these technologies to larger instruments that can explore previously inaccessible regions of space.
AION is also involved in broader international efforts, including close collaboration with MAGIS projects at Fermilab and other U.S. institutions. Researchers are working together to develop large-scale atom interferometers designed for fundamental physics research.
One proposed future project is the Atomic Interferometer CERN Experiment (AICE), which would apply similar techniques over much longer distances. Once built, AICE will chart a new direction for CERN by using quantum sensing technology to study fundamental physics on an unprecedented scale. It also has the potential to become one of the largest quantum experiments ever built.
Dr Richard Hobson, co-director of Imperial’s cryogenic strontium laboratory, said:
“We have shown that we can take some of the most precise instruments ever created, atomic clocks and atomic interferometers, and reuse them to open entirely new windows into invisible parts of the universe.
“While our current experiment is just a prototype, extending it to full-scale facilities at laboratories such as CERN and Fermilab will allow us to tackle some of physics’ deepest mysteries, including the nature of dark matter.”
Imperial researchers continue to develop plans for a larger system as part of a global effort to build a new generation of quantum sensors.
In the future, these detectors could explore currently inaccessible gravitational wave frequencies, explore entirely new forms of matter, and provide new ways to study the universe.
Professor Oliver Buchmuller, Principal Investigator of Imperial’s AION Collaboration, added:
“This work is an important milestone toward future large-scale quantum sensors in fundamental physics. It demonstrates under realistic experimental conditions a key technology relevant to next-generation atom interferometer facilities currently under development internationally, such as MAGIS at Fermilab and the proposed AICE facility at CERN.”
The AION collaboration is led by Imperial College London and includes researchers from the University of Birmingham, the University of Cambridge, Liverpool King’s College, the University of Oxford and the STFC Rutherford Appleton Institute.
This project received support from the Quantum Technologies for Fundamental Physics (QTFP) program, a joint initiative of STFC and EPSRC.
