Quantum Sensor Heralds Breakthroughs in Physics

Professor John Ellis, Clerk Maxwell Professor of Theoretical Physics and visiting scientist at the European Organisation for Nuclear Research (CERN) and Dr Christopher McCabe, Reader in Physics, provided scientific motivation behind the prototype quantum sensor, which was developed by scientists at Imperial College London.

The sensor was used in a study that demonstrated how comparing two atom interferometers, instruments that use lasers to measure precisely the quantum behaviour of atoms, allows experimental noise to be effectively cancelled.

This enables signals to be recovered even when individual measurements are overwhelmed, and opens the door to searches for signatures of exotic forms of dark matter and gravitational waves from the distant universe.

The work forms part of the Atom Interferometer Observatory and Network (AION) collaboration, which is led by Imperial College, and brings together researchers from institutions across the UK, including King's, to develop next-generation quantum sensing technologies.

This research was recently published in Nature.

Not only will the new quantum sensor have the potential to reveal the origins of black holes weighing billions of times the mass of the sun or detect the presence of dark matter fields, but it could also be applied to problems closer to home.

Professor Ellis explains:

"One example is geodesy, the science of accurately measuring and understanding the Earth's geometric shape and gravitational field. Current technology enables small holes in the earth, such as tunnels and caves, to be located and mapped, but with more precise instruments, you can look for the distribution of matter on a much larger scale.

"There are potential applications in climate monitoring, where a large quantum sensor could more effectively track the factors influencing environmental change, or in creating an un-jammable navigation system, as an alternative to vulnerable global positioning systems."

To better understand the impact of this achievement, the prototype quantum sensor can be compared to the early development of particle colliders. Before the Large Hadron Collider (LHC) enabled landmark discoveries such as the Higgs Boson, smaller prototype colliders first demonstrated that the technology itself was viable.

Professor Ellis says:

"Like the small hadron colliders, this is an enabling experiment. While they didn't make the headline discoveries themselves, they showed the technology worked and paved the way for everything that followed.

"This result is similar. The prototype sensor, with its ability to better recover signals that were previously immeasurable, demonstrates a crucial capability that future experiments will build upon."

Within the AION programme, researchers are now developing the technologies needed to scale up these systems to experiments capable of probing new frontiers in fundamental physics.

Dr McCabe says:

"Atom interferometry brings together quantum technology, cosmology, and particle physics, and it's exciting to be working on a project that spans all three. As the technology develops, I'm particularly excited about what this could reveal about the nature of dark matter, one of the deepest unsolved mysteries in science.

"Working out theoretically what these sensors can measure that wasn't possible before is one of the most rewarding parts of my research. Within AION, this is a two-way conversation where the theory shapes the technology as it develops, and the technology opens up new theoretical questions in return."

AION also forms part of a wider international programme that includes close partnerships with the MAGIS effort at Fermilab and associated US institutions, helping to advance large-scale atom interferometers for fundamental physics.

This includes proposals such as the Atom Interferometry CERN Experiment (AICE), which would apply similar techniques over much longer distances. Professor Ellis and Dr McCabe are contributing the theoretical foundations for AICE, continuing their role in shaping the scientific case for next-generation atom interferometry. If realised, AICE would represent a new direction for CERN, applying quantum sensing to fundamental physics at scale. Such facilities could also rank among the largest quantum experiments of their kind.