Researchers in China have achieved a record-breaking low temperature aboard the Tiangong space station, reaching an equivalent temperature of 9.7 picokelvin. The study, published in Science by Wei Xiong and colleagues, breaks the previous record of 52 picokelvin set at the International Space Station's Cold Atom Laboratory.
The team cooled roughly 20,000 rubidium atoms using laser cooling and evaporative cooling to create a Bose-Einstein condensate (BEC) in an optical dipole trap. BECs form near absolute zero, where atoms behave as a shared quantum wave. The optical dipole trap uses focused laser beams to hold neutral atoms in place.
The measured temperature carries an uncertainty range from 7.0 to 12.9 picokelvin. The free expansion time for measurements lasted 7 seconds, longer than the 2-second window in drop-tower experiments or the 1-second window at the International Space Station.
Optical dipole traps had not directly produced a condensate under microgravity conditions before this study. Previous attempts faced challenges from gravity pulling atoms downward in traps. Space-based experiments offer advantages over short-duration drop towers by providing extended microgravity environments for measurements.
The researchers note the new system enables quantum simulation to explore low-temperature physics. Potential applications include studies of exotic quantum phases and construction of a space-based atom interferometer for precision tests of fundamental physics principles.