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Chinese scientists have created the coldest man-made substance ever recorded, cooling a cloud of rubidium atoms to 9.7 picokelvin (pK) aboard China's Tiangong space station. The achievement, announced on November 6, 2026, breaks the previous record of 38 pK set by a German team in 2021 and was published in the journal Science.

🧊 The Record: 9.7 Picokelvin

A picokelvin is one trillionth of a kelvin. At 9.7 pK, the rubidium atom cloud is about one hundred trillion times colder than room temperature and sits just a tiny fraction above absolute zero (−273.15°C), the theoretical lower limit of temperature.

The team was able to stably observe the ultracold cloud for 7 seconds, a dramatic improvement over the roughly 0.05 seconds possible in ground-based experiments.

🛰️ Why Space Was Essential

The key advantage of the space station is its microgravity environment. On Earth, gravity pulls the atom cloud downward, forcing researchers to apply stronger confinement to hold it in place—which introduces excess energy and limits how cold the atoms can become. In orbit, the atoms float freely, requiring only extremely weak confinement to achieve deep cooling.

The experiment was conducted using the Supercold Atom Physics Experiment Cabinet in the Mengtian module of the space station. The team employed a homegrown all-optical trap cooling technique, a more challenging approach than the internationally common magnetic atom-chip trap method. The optical trap is immune to magnetic interference and is better suited for a wider range of quantum simulation experiments.

🔬 Engineering Feat: From Room-Sized to Fridge-Sized

The experimental system was shrunk from 20 cubic meters and 10 tons on the ground to just 0.7 cubic meters and 500 kilograms—compressing a room-sized apparatus into the volume of a refrigerator. The project involved collaboration across atomic physics, laser technology, precision optics, ultra-high vacuum, and aerospace engineering, with the team needing to precisely align more than twenty laser beams onto an atom cloud just tens of micrometers wide, with an error margin of no more than 5 micrometers.

The project was led by the Technology and Engineering Center for Space Utilization under the Chinese Academy of Sciences, in collaboration with Peking University and the Shanghai Institute of Optics and Fine Mechanics.

💡 Scientific and Practical Significance

At such extreme temperatures, atoms slow to a near standstill and exhibit remarkable quantum phenomena, including Bose-Einstein condensates, where disordered atoms behave like a highly ordered "quantum honor guard." This allows scientists to study quantum phase transitions, non-equilibrium dynamics, and quantum many-body correlations with unprecedented clarity.

The breakthrough is expected to advance research in early-universe simulations and ultralight dark matter detection. On the applied side, ultracold atoms can be used to build higher-precision atomic interferometers, quantum sensors, and space-based atomic clocks, serving fields such as Earth's gravity-field measurement, inertial navigation, and tests of fundamental physical constants.

🌍 International Recognition

The Science reviewers described the work as "a milestone in precision manipulation of ultracold atoms" and "the current highest level in the field of ultracold expansion." Nobel laureate Wolfgang Ketterle of MIT called it "a major achievement in the field of ultracold atoms" and "a good starting point to advance atomic thermometry and precision measurement".

The result marks a significant step toward absolute zero and underscores China's growing capability in space-based quantum science.