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Dark matter is an elusive type of matter that does not emit, absorb or reflect light, interacting very weakly with ordinary matter. These characteristics make it impossible to detect using conventional technologies used by physicists to study matter particles.
As it has never been observed before, the exact composition of dark matter remains unknown. One proposed theory is that this elusive type of matter is comprised of light particles with very small masses, below 1 eV (electronvolt), which behave more like waves than particles.
Researchers at the University of Tokyo and Chuo University recently explored the possibility of searching for sub-GeV dark matter using quantum sensors, advanced systems that rely on quantum mechanical effects to detect extremely weak signals.
Their paper, published in Physical Review Letters, highlights the potential of these highly sensitive sensing systems for tracking the velocity and direction of light dark matter.
"I was checking recent papers in the quantum physics category on arXiv and found that distributed quantum sensing has become a fairly hot topic," Hajime Fukuda, first author of the paper, told Phys.org.
"We were then wondering if we can use this technology in our field (i.e., high-energy physics) and came up with the idea to use it for dark matter detection."
Measuring the velocity and direction of dark matter
The recent study by Fukuda and his colleagues was aimed at combining recent quantum engineering advances with particle physics, specifically to improve ongoing searches for dark matter. To search for hypothetical heavy dark matter particles, physicists have so far primarily tried to pick up small vibrations or signals that would emerge if these particles collided with specific materials, atoms or nuclei inside dark matter detectors.
"When employing these approaches, it is straightforward to measure the velocity of dark matter, although experimentally this is of course difficult," said Fukuda.
"For light dark matter, however, we typically use excitation of some discrete mode, so that it is not possible to see the velocity. We found that we can measure the velocity of light dark matter not by measuring spatially extended signals (recoil tracks) but by measuring by spatially extended detectors."
In their paper, the researchers thus introduced an entirely new strategy that could be used to measure the velocity of dark matter and the direction it is coming from. This strategy entails the use of several dark matter detectors and a quantum measurement protocol.
The data collected by these detectors would be treated as quantum sensor data, from which researchers could extract information about the velocity and direction of dark matter. Fukuda and their colleagues performed a series of analyses to assess the potential of their approach and found that it would significantly improve the sensitivity of detectors.
"Earlier works introduced other methods to search for light dark matter, which for instance relied on an elongated detector or a classical array of detectors," explained Fukuda. "However, these methods depend on the detailed type of the interaction, while our method relies on a quantum sensor array and is far more general. Also, the sensitivity attained by our method is better."
A new route for future dark matter searches
The new approach to search for light dark matter introduced by this research team could soon be refined further and applied in real experiments. This recent study could also inspire other particle and high-energy physicists to explore the potential of quantum sensing systems for both dark matter searches and the precise study of other particles.
"We showed that quantum methods could play an important role in high-energy physics," added Fukuda.
"I think that there could be other applications for quantum sensors in our field and am excited to continue exploring this possibility. In our next studies, we could also improve our method and try to measure not only the velocity but also the dark matter distribution by the sensor array."
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