Some kind of invisible material is out there affecting the motions of stars and galaxies, but thus far, no one has been able to directly detect the substance—called dark matter—itself. But some are hoping that we can tap the growing field of quantum science to finally find it.
Scientists at the U.S. Department of Energy’s Fermi National Accelerator Laboratory and the University of Chicago have demonstrated a new technique based on quantum technology that will advance the search for dark matter, which accounts for 85% of all matter in the universe.
“We know that there’s a huge amount of mass all around us that isn’t made of the same stuff you and I are made of,” said Fermilab scientist Aaron Chou, co-author of a paper published in Physical Review Letters on the new technique. “The nature of dark matter is a really compelling mystery that a lot of us are trying to solve.”
In particular, there are two kinds of subatomic particles that scientists have hypothesized as possible ways that dark matter could appear. The collaboration has developed new devices based on quantum computing bits that will be able to detect the weak signals emitted by either of these particles, if they exist: one called an “axion,” and the other called a “hidden photon,” a particle that possibly interacts with the photons— particles of light—of the visible universe.
The technique now demonstrated by the Fermilab-University of Chicago team could enable searches for dark matter to proceed 1,000 times faster than previous methods.
Using light to detect dark particles
Physicists have made little progress in detecting axions since their existence was proposed more than 30 years ago.
“Experiments using conventional techniques were just nowhere near what they needed to be for us to be able to detect higher-mass axion dark matter,” Chou said. “The noise level is way too high.”
But over the past decade, scientists have become increasingly good at harnessing the properties of quantum mechanics, the laws that govern the strange behavior of particles at the smallest levels of the universe, in order to create new technology. One such achievement is a “qubit,” or quantum computing bit. These can be incredibly sensitive to even the smallest perturbations—which is exactly what you want in a detector.
In the team’s new technique, qubits are designed to detect the photons that would be produced when dark matter particles interact with an electromagnetic field. A specially built device called a superconducting cavity provides a way to accumulate and store the signal photon. The qubit, inserted into the cavity, then measures the photon.
The technique will benefit the search for any dark matter candidate because when invisible particles convert into photons, they can be detected.