Chinese Physicists Set New Cold-Temperature Record Aboard Tiangong Space Station

Physicists working aboard China's Tiangong space station have cooled a cloud of rubidium atoms to the lowest temperature ever recorded in an orbiting laboratory, a result that pushes the country's cold-atom program past a longstanding benchmark in low-temperature physics. The team, led by Wei Xiong, described the result in a paper published this week in Science, reporting an effective temperature of 9.7 picokelvin, with an uncertainty range of 7.0 to 12.9 picokelvin above absolute zero.

That is roughly four times colder than the previous record of 38 picokelvin, which was set in a ground-based drop-tower facility rather than in orbit, Phys.org reported. Around 20,000 rubidium atoms were trapped and chilled using a combination of laser cooling, evaporative cooling and a magnetic-field gradient, then held in an optical dipole trap formed by crossed laser beams — a sequence that, on the ground, would take only a fraction of a second before gravity pulled the cloud out of the trap entirely. Researchers released the resulting atom cloud into a wider trap and tracked its expansion in three dimensions for seven seconds, far longer than the two-second window available in the earlier drop-tower test.

A longer look than NASA's own experiment

The milestone invites comparison with the Cold Atom Laboratory, the NASA instrument that has operated aboard the International Space Station since 2018 and produced the first Bose-Einstein condensates ever created in Earth orbit. Both devices pursue the same basic goal: using microgravity to study matter at temperatures impossible to sustain for long on the ground, where gravity pulls ultracold atom clouds out of their traps within fractions of a second. The Tiangong team's longer observation window, as Interesting Engineering noted, gave researchers an unusually extended look at how a quantum gas behaves once external forces are almost entirely removed.

At picokelvin temperatures, atoms slow down enough to settle into a single collective quantum state called a Bose-Einstein condensate, a form of matter that behaves less like a cloud of separate particles and more like one coherent wave. The paper's authors describe such condensates as versatile platforms for quantum simulation, useful for probing exotic quantum phases of matter that are difficult or impossible to study at room temperature on Earth.

What's next

The experiment, carried out inside a dedicated cold-atom rack on Tiangong, is part of a broader push by China's crewed space program, overseen by the China Manned Space Engineering Office, to use the station as a platform for fundamental physics rather than purely engineering or life-sciences research. Since reaching its current three-module configuration, the station has steadily added experiment racks covering fields from combustion science to fluid physics, and the cold-atom facility is among the most technically demanding of them. The paper's authors propose eventually building a space-based atom interferometer, a device that could test fundamental principles such as the equivalence principle — the idea underpinning general relativity that all objects fall at the same rate regardless of mass or composition — with far greater precision than is possible on Earth. No date has been given for the next phase of the research.