China Space Station Cools Rubidium Atoms to Record 9.7 Picokelvin
Chinese scientists have successfully cooled a cloud of rubidium atoms to 9.7 trillionths of a degree above absolute zero aboard the China Space Station, setting a new world record for the coldest man-made matter ever recorded, the Global Times reported. The Department of Space Science and Applications at the Chinese Academy of Sciences announced the milestone on Thursday. Researchers observed the ultracold atomic cloud for seven seconds inside the Mengtian laboratory module.
The experiment brought the equivalent temperature of the rubidium atomic cloud down to 9.7 picokelvin, which is about 14 orders of magnitude lower than room temperature. DongA Science noted that the joint research team included Peking University in Beijing and the Shanghai Institute of Optics and Fine Mechanics. The findings are scheduled for publication in the international journal Science on November 6 in a paper titled “Quantum gases below 10 picokelvin in space.”
Microgravity Environment Overcomes Earth-Bound Gravity Limits
Absolute zero, minus 273.15 degrees Celsius, is the theoretical lower limit of temperature. Scientists use magnetic or optical traps to confine and slow down atoms, but Earth’s gravity restricts how far researchers can weaken those traps without losing the particles. The microgravity environment of Tiangong allowed the team to weaken the traps much further, using an optical trap with precisely controlled laser beams; previous ultracold gases in space had been realized using atom-chip-based magnetic traps.
In the microgravity environment, scientists could weaken the traps much further without losing the atoms. The resulting atomic cloud expanded at a speed of just a few micrometers per second, giving researchers an observation window of seven seconds, compared with around 0.05 seconds in earlier ground-based experiments and about two seconds aboard the International Space Station.
Earlier Temperature Records Set in Germany and Aboard the International Space Station
Prior to the new milestone, the University of Bremen in Germany held the record using a microgravity drop tower in 2021, where researchers achieved an equivalent temperature of 38 picokelvin. That drop-tower setup allowed for observation periods of about two seconds.
In 2022, NASA’s Cold Atom Laboratory aboard the International Space Station reached an equivalent temperature of 52 picokelvin. The newly announced Chinese space station experiment improved upon those figures, recording 9.7 picokelvin with an uncertainty of plus 3.2 and minus 2.7 picokelvin, according to DongA Science.
Engineering Challenges Behind the Mengtian Laboratory Module Facility
The Cold Atom Physics Research facility operating inside the Mengtian module represents a significant miniaturization effort. Developed under the leadership of the Shanghai Institute of Optics and Fine Mechanics, engineers compressed laboratory equipment that originally occupied 20 cubic meters and weighed 10 tons into a compact cabinet measuring 0.7 cubic meters and weighing around 500 kilograms.
Wang Qiang, commander-in-chief of the space application system of China’s manned space program, stated that the project began its initial planning in 2011. It required 15 years of collaboration among scientific and engineering teams before achieving the breakthrough.
Scientists Invite Global Researchers to Use Ultracold Quantum Facility
At ultracold temperatures, atoms can share a single quantum state and behave collectively, a phenomenon known as Bose–Einstein condensation. Researchers expect the achievement to be used to explore new physical phenomena or to study exotic quantum states that emerge at ultralow temperatures.
Lü Congmin, chief designer of the space application system, extended an invitation to scientists worldwide to conduct research using the facility, pledging to share the experimental platform and scientific data.
Questions About Picokelvin Physics Aboard Tiangong
What specific atom was used to reach 9.7 picokelvin in the Tiangong experiment?
Researchers used rubidium-87 atoms to create the ultracold atomic gas inside the Mengtian module.
When was the Mengtian laboratory module launched to the Chinese space station?
The Mengtian experiment module was launched into orbit in October 2022, following the launch of the Tianhe core module in April 2021.