Scientists have cooled atoms to the coldest temperature ever recorded, using a laser trap aboard China's Tiangong space station, Live Science reported.
The experiment brought a cloud of atoms down to 10 picokelvins — barely above absolute zero, the theoretical lower limit of temperature, which is minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius) and the threshold at which particles are believed to stop moving. The team reported the result Nov. 5 in the journal Science, in a paper titled "Quantum gases below 10 picokelvin in space."
The researchers used "optical tweezers," more formally an optical-dipole trap, which hold atoms in a laser beam. They placed 20,000 rubidium atoms in the trap to restrict their motion. That reduced movement, together with the weightlessness of the station's low-gravity environment, allowed the cloud to reach temperatures much lower than are possible on Earth, Live Science said. "This record-low temperature could stimulate a new generation of ODT-based experiments in quantum simulation and precision measurements in space," the researchers wrote.
How it compares, and why absolute zero stays out of reach
The Tiangong result follows similar experiments that, Live Science said, citing Science News, reached 52 picokelvins on the International Space Station and 38 picokelvins in a weightless drop from a tall tower. The Chinese team also created a Bose-Einstein condensate, a quantum state in which very cold atoms clump and behave akin to a single atom, sometimes called a fifth state of matter.
Getting all the way to absolute zero is another matter. One interpretation of the third law of thermodynamics is that it would take an infinite number of steps, "which means you will never get there," Saibal Mitra, a physics professor at Missouri State University, told Live Science in a 2024 interview cited in the new report. He also said a heat sink at absolute zero would let someone build a machine that was 100% efficient, violating the second law. Space helps researchers get close because microgravity lets atoms "float" and cool more efficiently.
The Science paper's author list, as given by Live Science, begins with W. Xiong, T. Li, S. Jin and Q. Huang and includes many additional colleagues, with X. Chen listed last. The result is a laboratory milestone, not a consumer technology, and the researchers framed it as a foundation for future space-based quantum work rather than a claim that the temperature floor of the universe has been reached.