In search of dark matter with the world’s coolest quantum detectors

One of science’s greatest mysteries may be one step closer to a solution. Approximately 80% of the matter in the universe is dark, meaning it cannot be seen. In fact, dark matter is passing through us constantly—perhaps at a rate of trillions of particles per second.

We know it exists because we can see the effects of its gravity, but experiments so far have failed to detect it.

Taking advantage of the most advanced quantum technologies, scientists from Lancaster University, University of Oxford and Royal Holloway, University of London are building the most sensitive dark matter detectors to date.

Their public exhibition entitled “A quantum view of the invisible universe” is on display at this year’s flagship Royal Society Summer Science Exhibition from 2 to 7 July 2024. Related research is also published in Journal of Low Temperature Physics.

Researchers include Drs. Michael Thompson, Professor Edward Laird, Dr. Dmitry Zmeev and Dr. Samuli Autti from Lancaster, Professor Jocelyn Monroe from Oxford and Professor Andrew Casey from RHUL.

EPSRC Fellow Dr. Autti said: “We are using quantum technology at ultra-low temperatures to build the most sensitive detectors to date. The aim is to observe this mysterious matter directly in the laboratory and solve one of the biggest puzzles in science.”

There is indirect observational evidence of the typical density of dark matter in galaxies, but the mass of the constituent particles and their possible interactions with ordinary atoms are unknown.

The theory of particle physics suggests two possible dark matter candidates: new particles with interactions so weak that we have not yet observed them, and very light, wave-like particles called axons. The team is building two experiments, one to look for each.

Of the two candidates, the new particles with ultra-weak interactions can be detected through their collisions with ordinary matter. However, whether these collisions can be identified in an experiment depends on the mass of dark matter being searched for. Most searches to date would be able to detect dark matter particles weighing between five and 1,000 times more than a hydrogen atom, but it is possible that much lighter dark matter candidates may have been missed. .

The Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology (QUEST-DMC) team aims to achieve the world’s leading sensitivity to collisions with dark matter candidates with masses from 0.01 to a few hydrogen atoms. To achieve this, the detector is made of superfluid helium-3, cooled to a macroscopic quantum state and instrumented with superconducting quantum amplifiers. The combination of these two quantum technologies creates the sensitivity to measure the extremely faint signatures of dark matter collisions.

By contrast, if dark matter is made of stocks, they will be extremely light – more than a billion times lighter than a hydrogen atom – but correspondingly more abundant. Scientists wouldn’t be able to detect collisions with stocks, but they could look instead for another signature — an electrical signal that results when stocks break in a magnetic field.

This effect can only be measured using an extremely sensitive amplifier that works with the highest precision allowed by quantum mechanics. Therefore, the Quantum Sensors for the Hidden Sector (QSHS) team is developing a new class of quantum amplifier that is suitable for searching for an action signal.

The stand at this year’s exhibition will enable visitors to observe the unseen with imaginative hands-on exhibits for all ages.

Demonstrating how we infer dark matter from observing galaxies, there will be a gyroscope-in-a-box that moves in surprising ways due to invisible angular momentum. There will also be glass marbles that are transparent in liquid, showing how invisible masses can be observed using clever experiments.

A light-dilution refrigerator will demonstrate how the team achieves ultra-low temperatures, and a model of the dark matter particle collision detector will show how our universe would behave if dark matter behaved like normal matter.

Visitors can then search for dark matter with a model action detector by scanning the frequency of a radio receiver, and they can also create their own parametric amplifier using a pendulum.

Cosmologist Carlos Frenk, Fellow of the Royal Society and Chair of the Public Engagement Committee, said: “Science is vital in helping us understand the world we live in—past, present and future. I urge visitors to of all ages to come together with an open mind, curiosity and enthusiasm and celebrate the extraordinary scientific achievements that are benefiting us all.”