Cancelling laser noise in atomic quantum sensors 

Results from a UK collaboration overcome major obstacle towards building large-scale atom interferometers.   

A prototype quantum sensor developed by the Atom Interferometer Observatory and Network (AION) consortium has demonstrated, for the first time, that a key principle behind next-generation quantum detectors can work under realistic conditions.   

The study shows how comparing two spatially separated atom interferometers, instruments that use lasers to precisely manipulate and measure the behaviour of atoms, will allow laser noise, one of the fundamental limitations in atom interferometry, to be effectively cancelled.  

This enables signals to be recovered even when individual measurements are dominated by laser noise and opens the door to searches for gravitational waves from the early universe and signatures of exotic forms of dark matter.  

The work forms part of the AION collaboration that brings together researchers from Cambridge’s Cavendish Laboratory and other institutions across the UK to develop next-generation quantum sensing technologies.  

This research was published in Nature. 

Cancelling noise in quantum measurements 

Understanding what the Universe is made of and identifying new sources of gravitational waves remain major challenges in modern physics.  

Both problems require measuring extremely small signals that can easily be lost in background noise. Finding reliable ways to detect them is essential for exploring parts of the Universe that current experiments cannot access.  

Long-baseline atom interferometers are emerging as one of the most promising tools for this. They work by using lasers to split clouds of atoms and then bring them back together, allowing tiny changes in their motion to be measured with extreme precision.  

AION uses ultracold strontium, which is also the basis of some of the most precise atomic clocks ever built, and is harnessing the power of the ultranarrow clock transition in strontium. 

However, even at this transition the technique faces a major challenge. The laser used to control the experiment produces phase noise that is far greater than the signals researchers are trying to measure. Left uncorrected, this noise completely obscures the interesting physics.  

To overcome this, scientists have proposed a differential approach, comparing two interferometers so that shared noise cancels out. These experiments hence rely on comparing the behaviour of two clouds of atoms held at different locations and interrogated by the same laser. Any difference between the two could point to previously hidden signals, for example the presence of a dark matter field.  

This method underpins plans for next-generation detectors, and has now for the first time been demonstrated in fermionic strontium 87 atoms, the isotope at the basis of the proposed detectors. The results provide the first experimental validation of a key principle underlying long-baseline atom interferometers, helping to resolve a central challenge in their design.  

Within the AION programme, researchers are developing the technologies needed to scale up these systems to experiments capable of probing new regions of the Universe.

The Cambridge team around Prof Tiffany Harte, Dr Jeremiah Mitchell, and Prof Ulrich Schneider is leading experimental work on atom cooling and further cold-atom techniques essential for maximising the sensitivity of future large-baseline detectors, coordinating instrument design, and developing simulation tools and theoretic models of systematic effects for noise mitigation. The researchers based at the Cavendish Laboratory co-designed the prototype instrument and informed the characterisation of noise and data analysis techniques that would be used for fundamental physics signal extraction exemplified in the paper. 

AION also forms part of a wider international programme helping to advance large-scale atom interferometers for fundamental physics. 

This includes close partnerships with the MAGIS-100 effort at Fermilab and associated US institutions and proposals such as the Atom Interferometry CERN Experiment (AICE), which would apply similar techniques over much longer distances. 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. 

The AION collaboration includes researchers from Imperial College London, Kings College London, the Universities of Birmingham, Cambridge, Liverpool, and Oxford, and the STFC Rutherford Appleton Laboratory. 

The programme has been initially supported by the Quantum Technologies for Fundamental Physics (QTFP) programme, a joint STFC–EPSRC initiative. 

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Reference: 

Baynham, C.F.A., Hobson, R., Buchmüller, O. et al. ‘A prototype differential atom interferometer for fundamental physics.’ Nature (2026). DOI: 10.1038/s41586-026-10617-1 

Image:

Polarisation of blue laser light being adjusted before cooling atoms to near absolute zero. Credit: Dr Thomas Walker © Imperial College London.

 

Adapted from an Imperial College London press release.