Scientists Achieve Record-Low Temperature Aboard China’s Tiangong Space Station
Physicists reached 9.7 trillionths of a degree above absolute zero in microgravity.
1New Quantum Temperature Record
Physicists aboard China’s Tiangong space station have achieved a record-low temperature of 9.7 trillionths of a degree above absolute zero. This milestone surpasses the previous record of 38 trillionths set in a terrestrial drop tower. The experiment utilized roughly 20,000 rubidium atoms, marking a significant advancement in cooling quantum gases.
2Gravity as a Barrier
On Earth, gravity limits how loose an atomic trap can be, as atoms simply fall out if the trap is too weak. This constraint has historically stalled ground-based laboratories at approximately 350 trillionths of a degree. Space-based experiments allow for longer free-fall times, enabling researchers to push these physical boundaries further.
3Optical Trapping Mechanism
Unlike NASA’s Cold Atom Laboratory, which employs magnetic fields, the Chinese team utilized crossed laser beams to trap atoms. This optical approach allows researchers to hold atoms regardless of their magnetic state. The apparatus has been operational within the station’s Mengtian module since October 2022, facilitating unique quantum gas experiments in orbit.
4Overcoming Microgravity Challenges
Weightlessness initially hindered the evaporation process, as the lack of gravity prevented hot atoms from spilling out of the trap. To compensate, researchers introduced a magnetic field gradient to mimic gravitational tilt. This adjustment successfully increased the condensate fraction to 89%, effectively cooling approximately 23,000 rubidium atoms to near-zero motion.
5Measuring Atomic Motion
The temperature was determined by observing the expansion rate of the atomic cloud after the trap was released. The atoms drifted outward at a speed of 70 to 88 micrometers per second. This extremely slow expansion confirms the record-low thermal state, with an uncertainty margin of roughly three trillionths of a degree.
6Experimental Discrepancies and Jitter
Computer simulations predicted a slightly lower temperature of 7.4 trillionths of a degree. The research team attributed the variance to jitter within the laser beams used for trapping. Despite this minor discrepancy, the ability to observe the cloud for seven seconds in free fall demonstrates the high precision of the orbital setup.
7Future Scientific Applications
The team aims to use this technology to study exotic quantum phases that only emerge at these extreme temperatures. Furthermore, they intend to develop an atom interferometer in orbit. Such a device could provide a rigorous test of the equivalence principle, investigating whether all objects fall at the same rate in space.
8Significance of Orbital Research
This experiment, published in the journal Science, highlights the potential of space-based platforms for fundamental physics research. By overcoming the limitations of terrestrial gravity, scientists can explore quantum mechanics with unprecedented sensitivity. Future iterations will focus on increasing the number of atoms held and extending the duration of free-flight observations.