Scientists aboard China’s Tiangong space station have achieved the coldest temperature ever recorded, cooling a cloud of 20,000 rubidium atoms to 9.7 trillionths of a degree above absolute zero.
This record-breaking experiment, conducted within the station’s Mengtian module, leverages microgravity to observe quantum matter for an unprecedented seven seconds.
The research, published in the journal Science on Nov. 5, details how a team from the Chinese Academy of Sciences and Peking University utilized an optical-dipole trap (ODT) to manipulate the atoms. By cooling the rubidium to 9.7 picokelvins, the team surpassed the previous record of 38 picokelvins, set in 2021 by researchers at the University of Bremen using a drop tower.
This achievement increases precision, pushing the boundaries of what is physically attainable. Absolute zero, defined as minus 459.67 degrees Fahrenheit, remains a theoretical limit where all atomic motion ceases, yet this space-based experiment brings matter closer to that point than previously possible on Earth.
Engineering Constraints in Orbit
The technical challenge of the experiment lay in miniaturization. Engineers at the Shanghai Institute of Optics and Fine Mechanics were tasked with shrinking laboratory equipment that traditionally spans 706 cubic feet and weighs 22,000 pounds into a compact cabinet of roughly 25 cubic feet, weighing 1,100 pounds, Discover Magazine reported. This system includes the lasers, vacuum hardware, and precision optics required to maintain the optical tweezers necessary for the trap.
Microgravity is the primary enabler for these results. On Earth, gravity accelerates atoms downward, limiting observation windows to fractions of a second. Aboard the Tiangong, the atoms drift in a weightless environment, allowing researchers to track the expansion of the Bose-Einstein condensate for seven seconds. This extended window is critical for studying the wave-like behavior of atoms at extreme temperatures.
“This record-low temperature could stimulate a new generation of ODT-based experiments in quantum simulation and precision measurements in space,” the researchers wrote in the journal Science.
Comparing Global Quantum Platforms
The Tiangong experiment joins a lineage of space-based quantum research, most notably NASA’s Cold Atom Laboratory (CAL) on the International Space Station, which produced a Bose-Einstein condensate in 2018. While NASA’s Cold Atom Laboratory has reached 52 picokelvins, the Chinese team’s ability to hit 9.7 picokelvins sets a new benchmark for thermal efficiency in orbit.
| Experiment Facility | Record Temperature | Year |
|---|---|---|
| Tiangong (China) | 9.7 pK | 2026 |
| University of Bremen (Germany) | 38 pK | 2021 |
| ISS (NASA) | 52 pK | 2022 |
Future Applications in Precision Measurement
Beyond breaking records, the research aims to refine atom interferometry. By manipulating atoms at these extreme scales, scientists can create instruments capable of measuring gravitational fields with exquisite sensitivity. Such technology could eventually test Einstein’s theory of gravity or assist in the detection of gravitational waves.
“Only the interaction energy changes,” coauthor Xuzong Chen of Peking University explained to Science, detailing the process of loosening the laser trap to allow the cloud to expand under controlled conditions. The team reported that 90 percent of the atoms occupied the condensate state during the test.
Despite the success, the third law of thermodynamics dictates that absolute zero remains unreachable. As Saibal Mitra, a professor of physics at Missouri State University, noted in an earlier interview with Live Science, reaching zero would require an infinite number of steps, and any heat sink at that temperature would technically violate the second law of thermodynamics by allowing for 100% efficiency.
The research team has indicated that their all-optical cooling platform is designed for modularity, intending to share the facility with global researchers for future quantum simulation tasks. Whether these techniques can scale to more complex quantum systems or remain limited to specific atomic species like rubidium is a question the researchers have yet to address in their public findings.
