New funding for quantum science will support researchers exploring dark energy and dark matter, quantum states of sound, and the Universe’s constants.

Imperial physicists have been awarded five of 17 new grants for quantum technology projects funded by UKRI’s Quantum Technologies for Fundamental Physics programme, from a total pot of £6m.

The programme receives joint funding from the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC).

The success of my colleagues is a testament to the remarkable capability Imperial has in quantum science and technology. Professor Ian Walmsley Provost

The grants encourage high-risk discovery and aim to demonstrate how quantum tech can solve long-standing questions in fundamental physics.

Imperial’s Provost, Professor Ian Walmsley, said: "The success of my colleagues in the Quantum Technologies for Fundamental Physics programme is a testament to the remarkable capability Imperial has in quantum science and technology.

“The programme itself illustrates the important symbiosis of science and application: new discovery leads to new technologies, and new technologies enable new discovery. The rapid realisation of this in the quantum domain aligns with Imperial’s ambitions and strengths. 

Quantum states of sound

Dr Michael Vanner and his team will synthesise ‘quantum states of sound’ to help tackle fundamental questions about the universe, such as why we don’t see quantum behaviour in the everyday world, why quantum states are so fragile, and whether gravity plays any role in the boundary between the ‘classical’ world we experience and the strange ‘fuzzy’ world of quantum physics that typically dominates at the microscale.

The team will use technologies originally developed to control the quantum nature of light to create quantum states of high-frequency sound waves in a tiny crystal cooled to near absolute zero in temperature.

More than a quadrillion atoms will participate in these sound waves. This is a mass-scale that is truly gigantic from the perspective of the quantum realm, but still microscopic from the perspective of our everyday world.

Dr Vanner said: "Very excitingly, this grant gives us the support to utilize the tools and techniques we've developed for quantum technologies to tackle a fascinating question about fundamental physics."

Testing theories of dark energy

Professor Ed Hinds and his team will use atom interferometry to shed light on one of the biggest mysteries in cosmology: dark energy. Measurements show that not only is the universe expanding but that the rate of expansion is accelerating. It is postulated that this acceleration is driven by 'dark energy', the nature of which is almost completely obscure. 

The team will probe a particular type of dark energy candidate called the Chameleon field. The field gets its name from its ability to hide in the presence of matter. It can drive the accelerated expansion of the universe yet would be undetectable by previous experiments. By using atom interferometry, it may be possible to find the Chameleon field. 

Atom interferometry uses a quantum superposition of atoms to make an exquisitely sensitive force detector. Because it uses the cold atoms in a vacuum, where there is no other matter, the Chameleon field is not suppressed and so can be seen by the atoms. The new grant provides the group with the resources they need to complete their new measurement of this form of dark energy.

Inconstant constants?

Professor Michael Tarbutt and his team aim to test whether the fundamental constants of nature are really constant. Theories of physics that try to unify gravity with the other fundamental forces, as well as some theories of dark matter and dark energy, tend to predict that the constants are actually changing in time, or that they change according to the local environment.

The team are studying a particularly important fundamental constant – the ratio of the electron mass to the proton mass. To find out whether this constant might be varying, they are building a new type of clock that will be based on vibrational transitions in molecules.

To reach the highest clock precision, the molecules will be cooled to a microkelvin and trapped in a standing wave of light. Any change in the fundamental constants will change the frequency of the clock; the team hope to detect this change.

The award will be used to build an extremely precise laser system that will measure the clock frequency and see how it changes over time.

A quantum jump sensor for dark matter detection

Dr Jack Devlin and his collaborators will use a single electron, held in place in a vacuum by electric and magnetic fields, as a quantum sensor to search for the effects or presence of dark matter. This unknown substance or substances makes up 84% of the matter in the universe, but its nature is a longstanding mystery.  

The team will look for changes in the motion of the trapped electron caused by any nearby dark matter particles. Some types of dark matter with tiny electrical charge (millicharged particles) can collide with the electron, changing its motion.

Other types of dark matter can decay into microwave energy under the right conditions, and this energy can also lead to a change in how the electron moves. The electron’s motion is ‘quantised’ – it can only have certain energies – so in both cases the new energy leads to a detectable ‘jump’ in the electron’s quantum state.  

The researchers plan to use techniques developed previously to make exceptionally precise measurements of intrinsic magnetic fields of the electron, positron, proton, and antiproton, adapting these to unravelling the puzzle of dark matter.

Atom interferometry for dark matter detection

Professor Oliver Buchmueller is the main PI of the AION (Atom Interferometry Observatory and Network) Consortium.

AION will enable a ground-breaking search for ultra-light candidates for dark matter. It will also pave the way for the exploration of gravitational waves – ripples in spacetime created by huge astronomical events – in a previously inaccessible range, opening a new window on the mergers of massive black holes and novel physics in the early Universe.

This is the second award that the AION project has received in the context of the Quantum Technology for Fundamental Physics programme. The additional funding will improve the sensitivity of the next generation of long-baseline quantum detectors, which will use cold atoms in a 10m atom interferometer.

AION is led by Imperial College London and includes the University of Birmingham, the University of Cambridge, Kings College London, the University of Liverpool, the University of Oxford, and the STFC Rutherford Appleton Laboratory.

In addition, the project is in partnership with UK National Quantum Technology Hub in Sensors and Timing, Birmingham, UK, the MAGIS Collaboration, US, and the Fermi National Accelerator Laboratory, US.