If you ask where is the coldest point in the universe? Scientists point to the Chinese space station.
The coldest spot in the universe "settled" on the Chinese Space Station
The Space Application Engineering and Technology Center of the Chinese Academy of Sciences held a press conference on the results of the China Space Station and announced that a team of Chinese scientists had "sharpened their swords for fifteen years" and broke the low-temperature record of mankind so far in the ultra-cold atomic physics experimental cabinet of the National Space Laboratory, known as the "super refrigerator". They prepared the coldest man-made substance currently known and achieved the "settlement" of the coldest point in the known universe on the Chinese Space Station.
On the eve of the release of the results, a special press conference was held in Beijing. Photo by China News Service reporter Sun Zifa
Specifically, based on the National Space Laboratory's "super refrigerator", Chinese scientists took the lead in using all-optical trap cooling technology to successfully reduce the equivalent temperature of the rubidium atomic cloud to 9.7 picokelvin (pK), which is 14 orders of magnitude lower than room temperature, and can observe continuously for 7 seconds.
This major breakthrough work, which marks a major step forward for Chinese scientists to reach absolute zero (0K, equivalent to minus 273.15 degrees Celsius), was led by the Center for Space Application Engineering and Technology of the Chinese Academy of Sciences and jointly completed by Peking University and the Shanghai Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences. In the early morning of November 6, Beijing time, the related paper "Quantum Gases Below 10 Pikelvin in Space" was published online in the international academic journal "Science".
According to reports, with the support of the China Manned Space Engineering Office, the Chinese Academy of Sciences, etc., the China Space Station ultra-cold atomic physics experimental cabinet project began to be demonstrated in 2011. It was successfully developed in 2022 and launched with the "Mengtian" module. It has now broken the human low-temperature record. The project scientific team and engineering team have pooled their wisdom and research for 15 years.
Scientific poster of the results of this project. Photo courtesy of the Space Application Center of the Chinese Academy of Sciences
Using the ultra-cold atomic physics experimental cabinet of the China Space Station, Chinese scientists took the lead in using all-optical traps to "trap" atomic clouds, reduce the light intensity for evaporative cooling to reduce the temperature of the atomic clouds, and then use non-adiabatic diffusion for deep cooling, ultimately achieving a record low temperature breakthrough.
Compared with the international "magnetic trap" solution, the ultra-cooled Chinese solution is more difficult, but has more obvious advantages. All-optical traps are easier to achieve precise control of multiple beams in a space environment, are insensitive to magnetic field interference, are compatible with a variety of quantum simulation experiments, and have greater advantages in engineering reliability and scientific scalability.
After the Chinese plan was determined, the project team successively completed key technical research on ultra-high vacuum physics systems, high-power fiber lasers, long-term continuous laser frequency stabilization, and high-precision integrated physical optical machines. It integrated a 20-cubic-meter, 10-ton experimental system on the ground into a 0.7-cubic-meter, 0.5-ton ultra-cold atomic physics experimental cabinet.
In the microgravity environment of the space station, only very weak restraints are needed to complete the cooling process. The cooling efficiency is greatly improved, the temperature can be dropped to a lower level, and the continuous observation time can be longer.
A major achievement in the field of ultracold atoms
Moving toward absolute zero has been a century-long challenge for the physics community. The experimental results published this time surpass those of international counterparts, indicating that China has now reached the first-class level of international experimental technology related to cold atom physics, and proves the innovation and superiority of the cold atom physics experimental platform of the China Space Station.
Wolfgang Ketterle, Nobel Prize winner in physics and professor of the Department of Physics at MIT, commented that this is a major achievement in the field of ultracold atoms; this achievement is now a good starting point to advance atomic temperature measurement and precision measurement.
Scientific poster of the results of this project. Photo courtesy of the Space Application Center of the Chinese Academy of Sciences
Reviewers of "Science" believe that the results of this work are an important milestone in the precise control of ultra-cold atoms and are of great value to basic physics research and applications such as space navigation and earth observation. They have set a new record for ultra-low temperature expansion.
At the press conference, Chinese scientists explained that this low-temperature record-setting result will, in a scientific sense, help solve basic physical problems such as phase transitions of quantum gases at extremely low temperatures, non-equilibrium dynamics, and quantum many-body correlations, and promote research on cutting-edge topics such as simulation of the early universe and detection of ultra-light dark matter.
In terms of application, it can not only provide a pure and flexible experimental platform for quantum simulation, but also provide key support for emerging quantum technologies such as high-precision atomic clocks, atomic interference inertial measurement, and quantum computing. At the same time, ultra-low temperature atoms can be used in higher-precision atomic interferometers, quantum sensors and space time-frequency benchmarks to serve the earth's gravity field measurement, inertial navigation and basic physical constant testing. In the future, they will help enhance China's international competitiveness in the field of space quantum technology. (over)
