The hunt for dark matter is about to cool significantly. Scientists are developing super-cool quantum technology to search for the most elusive and mysterious things in the universe, which currently represent one of science’s greatest mysteries.
Despite the fact that dark matter exceeds the amount of ordinary matter in our universe by about six times, scientists do not know what it is. This is at least partly because no experiment devised by mankind has ever been able to detect it.
To tackle this conundrum, scientists from several universities across the UK teamed up to build two of the most sensitive dark matter detectors ever seen. Each experiment will look for a different hypothetical particle that could contain dark matter. Although they have some of the same qualities, the particles also have some radically different properties and therefore require different detection techniques.
The equipment used in both experiments is so sensitive that the components must be cooled to a thousandth of a degree above absolute zero, the theoretical and unattainable temperature at which all atomic movement would cease. This cooling must occur to prevent interference or “noise” from the world from corrupting the measurement.
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“We are using quantum technology at extremely low temperatures to create the most sensitive detectors yet,” team member Samuli Autti of Lancaster University said in a statement. “The goal is to observe this mysterious matter directly in the laboratory and solve one of the biggest mysteries in science.”
How dark matter left scientists in the dark
Dark matter poses a big problem for scientists because, although it makes up about 80 to 85% of the universe, it remains virtually invisible to us. This is because dark matter does not interact with light or “everyday” matter – and if it does, these interactions are rare or very weak. Or maybe both. We just don’t know.
But because of these properties, scientists know that dark matter cannot be composed of electrons, protons and neutrons – all part of the baryon family of particles that make up everyday matter in things like stars, planets, moons, our bodies, ice cream. and the cat next door. All the “normal” things we can see.
The only reason we think dark matter actually exists at all is because this mysterious substance has mass. So it interacts with gravity. Dark matter can influence the dynamics of ordinary matter and light through this interaction, allowing its presence to be inferred.
Astronomer Vera Rubin discovered the presence of dark matter, previously theorized by scientist Fritz Zwicky, because she saw some galaxies spinning so fast that if their only gravitational influence came from visible baryonic matter, they would fly apart. However, what scientists really want is not a deduction, but rather a positive detection of dark matter particles.
One of the hypothetical particles currently considered a prime suspect for dark matter is the very bright “axion”. Scientists also theorize that dark matter could be composed of more massive (as yet unknown) new particles with interactions so weak that we have not yet observed them.
Both axions and these unknown particles would exhibit ultraweak interactions with matter that could theoretically be detected with sufficiently sensitive equipment. But two prime suspects mean two investigations and two experiments. This is necessary because current dark matter searches typically focus on particles with masses between 5 and 1000 times the mass of a hydrogen atom. This means that if the dark matter particles are brighter, they can be missed.
The Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology (QUEST-DMC) experiment is designed to detect the collision of ordinary matter with dark matter particles in the form of weakly interacting unknown new particles that have masses between 1% and several times the mass. hydrogen atom. QUEST-DMC uses superfluid helium-3, a light and stable isotope of helium with a nucleus of two protons and one neutron, cooled to a macroscopic quantum state to achieve record sensitivity in observing ultraweak interactions.
However, QUEST-DMC would not be able to detect extremely light axions, which are thought to have masses billions of times lighter than a hydrogen atom. This also means that such axions would not be detectable by their interaction with ordinary matter particles.
But what they lack in mass, axions are thought to make up for in number, with these hypothetical particles thought to be extremely abundant. That means it’s better to look for these dark matter suspects using a different signature: the small electrical signal that results from the decay of axions in a magnetic field.
If such a signal exists, its detection would require stretching the detectors to the maximum level of sensitivity allowed by the rules of quantum physics. The team hopes that their quantum sensors for the hidden sector A quantum amplifier (QSHS) would be capable of this.
If you are in the UK, the public can view the QSHS and QUEST-DMC experiments at Lancaster University’s Summer Science Exhibition. Visitors will also be able to see how scientists infer the presence of dark matter in galaxies using a gyroscope in a box that moves strangely due to an invisible angular momentum.
In addition, the exhibit includes a lighted dilution refrigerator that demonstrates the ultra-low temperatures required by quantum technology, while its model dark matter particle collision detector shows how our universe would behave if dark matter interacted with matter and light in the same way as everyday matter.
The team’s papers detailing the QSHS and QUEST-DMC experiments have been published in The European Physical Journal C and on the paper’s arXiv repository page.