A team led by Imperial College London has demonstrated a key technique for future quantum sensors that could detect gravitational waves and dark matter.
By comparing two long-baseline atom interferometers, shared laser noise can be cancelled, allowing weak signals to be recovered even when individual measurements are dominated by noise. The experiment, conducted at Imperial's Ultracold Strontium Laboratory, used ultracold strontium-87 atoms and an ultrastable clock laser.
Key Details of the Experiment
- The study was conducted using a tabletop prototype at Imperial's Ultracold Strontium Laboratory.
- Two spatially separated clouds of ultracold strontium-87 were interrogated by a single ultrastable clock laser.
- Large additional phase noise was intentionally introduced to simulate the conditions of long-baseline detectors.
- Individual interferometers showed no usable signal, but comparing the two allowed a clear correlation and signal recovery.
- The combined measurement operates at the fundamental quantum limit.
- An oscillating signal mimicking a gravitational wave or dark matter field was also detected under those conditions.
"We've known for a long time that quantum sensors can help us understand the universe... I can't wait for the day when signals from an atom are telling us about a black hole that merged millions of years ago."
— Dr Charles Baynham, co-lead of the Ultracold Strontium Laboratory
The work is part of the Atom Interferometer Observatory and Network (AION) collaboration, which includes researchers from the Universities of Birmingham, Cambridge, Liverpool, King's College London, and Oxford, along with STFC Rutherford Appleton Laboratory. The programme was supported by the Quantum Technologies for Fundamental Physics (QTFP) STFC–EPSRC initiative.
Significance for Future Detectors
The results support the differential interferometry approach planned for next-generation detectors, such as the MAGIS experiment at Fermilab and the proposed Atom Interferometry CERN Experiment (AICE).
"We have taken some of the most precise instruments ever built—atomic clocks and atom interferometers—and shown that they can be repurposed to open entirely new windows onto the invisible parts of our Universe."
— Dr Richard Hobson, co-lead of the Ultracold Strontium Laboratory
"This work marks an important milestone towards future large-scale quantum sensors for fundamental physics."
— Professor Oliver Buchmueller, Principal Investigator of the AION collaboration
The research was published in Nature.