Scientists achieve record-breaking low temperature on China's space station, paving the way for new physics experiments

Record‑Low Temperatures in Space

Scientists aboard China’s Tiangong space station have achieved an unprecedented equivalent temperature of 9.7 picokelvin for a cloud of rubidium atoms. This temperature is roughly four times lower than the previous space‑based record and was measured after a 7‑second free‑expansion period—significantly longer than earlier experiments. The breakthrough, reported in Science, demonstrates the power of optical dipole traps (ODTs) combined with microgravity to push the limits of ultracold physics.

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Why Going Colder Matters

At temperatures near absolute zero, atoms lose their individual identities and form a Bose–Einstein condensate (BEC), a quantum state that behaves as a single, coherent wave. The colder the atoms, the slower they move, which improves the precision of measurements and extends the coherence time of quantum phenomena. In terrestrial labs, gravity pulls atoms out of traps, limiting how low temperatures can be reached and how long experiments can run. Microgravity eliminates this sag, allowing researchers to fine‑tune trapping potentials and explore regimes inaccessible on Earth.

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The Experimental Approach

The Tiangong team used a multi‑stage cooling sequence:

1. Laser cooling to bring roughly 20,000 rubidium atoms into the microkelvin range.
2. Evaporative cooling within an ODT, selectively removing higher‑energy atoms and deepening the condensate.
3. A magnetic‑field gradient to assist the initial cooling stage while keeping the atoms insensitive to magnetic noise.
4. Transfer to a wider optical trap with reduced confinement, which minimized the expansion energy of the cloud.

By tracking the three‑dimensional expansion of the cloud for 7 seconds, the team derived an equivalent temperature of 9.7 pK, with an uncertainty range of 7.0–12.9 pK.

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What This Enables

The new temperature record and extended observation window create several research opportunities:

• Quantum simulation of exotic phases such as Tomonaga‑Luttinger liquids, Bose‑glass, and fractal Mott states, which require ultra‑low energy scales to manifest.
• Space‑based atom interferometry, where longer free‑fall times improve sensitivity for tests of fundamental physics, including the equivalence principle.
• Adjustable‑volume traps that could increase atom numbers, enhancing signal‑to‑noise ratios for precision measurements.

These capabilities position Tiangong as a versatile platform for next‑generation quantum experiments, complementing Earth‑based facilities and other space labs like the International Space Station’s Cold Atom Laboratory.

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Looking Ahead

Future work will likely focus on scaling up atom numbers, refining trap geometries, and integrating additional control fields to sculpt the quantum gas. Such advances could pave the way for space‑borne quantum sensors, ultra‑precise clocks, and perhaps even novel quantum technologies that exploit the unique microgravity environment.

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The achievement underscores how space platforms can overcome terrestrial constraints, offering a new frontier for fundamental physics and precision measurement.