China Focus: Scientists make breakthrough in scouting dark matter with quantum technique

HEFEI -- An international team led by Chinese scientists has employed cutting-edge quantum technology in a direct quest for the universe's most elusive matter, an extraordinary endeavor that has significantly advanced detection capabilities.

In the vast expanse of the universe, visible matter, ranging in size from the tiniest speck of dust to massive celestial bodies like Earth, even whole galaxies, constitutes only about 5 percent of the total mass of the cosmos. The remaining 95 percent is believed to be comprised of dark matter and dark energy.

Identifying dark matter, the exotic component that profoundly influences the structure and evolution of our universe, continues to elude scientists.

Among the possible candidates are weakly-interacting massive particles (WIMPs) and axions. Axions have emerged as a particularly intriguing subject for investigation, while the search for WIMPs has not identified the invisible matter thus far.

Quantum precision measurement technology, which harnesses incredible properties like quantum spin and quantum entanglement, enables an ultra-sensitive detection of minuscule energy levels, offers a revolutionary approach in the search for the dark matter.

The scientists from the University of Science and Technology of China and University of California, Berkeley, have exploited polarized noble gas to establish a super-sensitive axion detector based on quantum spin interactions.

The detector increases interaction sensitivity up to 145-fold compared to conventional methods. Moreover, it has achieved an astronomical reduction for the interference caused by classical magnetic fields, avoiding the spurious signals.

Although the team has not yet discovered definitive proof of axion dark matter, they have placed the most stringent constraints ever known on neutron-neutron coupling that expands into the "axion window," a theoretically favored mass range where the hypothetical particles are likely to be hiding.

The experiment has set a new benchmark in this field by improving previous constraints by a factor of at least 50, according to a study published recently in the journal Physical Review Letters.

The results highlight the vast potential of quantum technology in the realm of dark matter exploration, demonstrating the role of cutting-edge tech in advancing frontier science.

The research is "distinguished by the application of two new developments -- magnetic amplification and signal templates" that allowed the team to improve sensitivity "by about two orders of magnitude beyond the existing state of the art," commented W. Michael Snow, a physicist from Indiana University Bloomington.

Apart from the Earth-based experiment, Peng Xinhua, the team's leader, proposed a plan in 2023 to deploy quantum sensors to China's space station, utilizing the high-speed motion of the space station around the Earth to support the search for axions.

This study also holds significant potential for practical applications, such as improving the accuracy of magnetic resonance imaging for precision medicine and enabling more advanced deep-sea explorations, said Peng.