Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

National Science Review

Characterization of laser cooling in microgravity via long-term operations in TianGong-2 space lab

Desheng Lü, Wei Ren, Yuan Sun, Tang Li, Qiuzhi Qu, Bin Wang, Lin Li, Jianbo Zhao, Xin Zhao, Jing-Wei Ji, Meifeng Ye, Jingfeng Xiang, Weibiao Chen, Yuzhu Wang, Liang Liu

Published Aug 29, 2022• 14 citations
Publisher

Abstract

The invention of laser cooling has fundamentally influenced the research frontier of atomic physics and quantum physics, and recently an intense focus has been on the studies of cold atom physics in microgravity environments. Herein, we report the results of our laser cooling experiment in TianGong-2 space lab, which operated for 34 consecutive months in orbit. Over such an extended operation time, the quality of laser cooling did not experience any significant decline, while the properties of laser cooling in orbital microgravity were systematically studied. In particular, we demonstrate magneto-optical trapping and polarization-gradient cooling in orbit and carefully examine their performances. A comparison of the in-orbit and on-ground results indicates that a higher cooling efficiency exists in microgravity, including a smaller loss rate during the trapping and cooling process and lower ultimate temperature of laser-cooled atoms. Our progress has laid the technical foundations for future applications of cold atoms in space missions with operation times of the order of years.

DOI
10.1093/nsr/nwac180

Related papers

Tests of Cold Atom Clock in Orbit

Liang Liu, Desheng Lü, Weibiao Chen +23 more

Since the atomic clock was invented, its performance has been improved for one digit every decade until 90s of last century when the traditional atomic clock almost reached its limit. With laser cooled atoms, the performance can be further improved, and nowadays the cold atom based clocks are widely used as primary frequency standards. Such a kind of cold atom clocks has great applications in space. This paper presents the design and tests of a cold atom clock (CAC) operating in space. In microgravity, the atoms are cooled, trapped, launched and finally detected after being interrogated by microwave field with Ramsey method. The results of laser cooling of atoms in microgravity in orbit are presented and compared with that on ground for the first time. That the full width at half maximum (FWHM) of obtained central Ramsey fringes varies linearly with launching velocity of cold atoms shows the effects of microgravity. With appropriate parameters, a closed-loop locking of the CAC is realized in orbit and the estimated short term frequency stability of $3.0\times 10 ^{-13}/\sqrt{τ}$ has been reached.

arXiv:1709.03256•Sep 11, 2017•4 citations

Laser Cooling Alkaline-earth Atoms for Optical Clock in Chinese Space Station

Guodong Zhao, Jian Guo Xia, Yun Liu +19 more

Abstract This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium (Sr) atomic space optical clock. The system’s core components, physical unit, optical unit, and electrical unit, have a total volume of 306 L and a total mass of 163.8 kg. These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch. The laser sources of the optical unit are composed of diode lasers, and the injection locking of slave lasers is automatically performed by a program. In the experiment, a blue magneto-optical trap of cold atoms was achieved, with the atom numbers estimated to be approximately (1.50 ± 0.13) × 10 6 for 87 Sr and (8.00 ± 0.56) × 10 6 for 88 Sr. This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.

Chinese Physics Letters•Apr 22, 2025•12 citations

Ultracold atoms in a dipole trap in microgravity

Julien Le Mener, Cyrille Métayer, Vincent Jarlaud +2 more

Most cold atoms experiments in microgravity platforms or in Space are achieved using atom chips, leading to limitations in terms of optical access and inhomogeneous magnetic fields. Optical dipole traps do not have these drawbacks but have difficulties producing atomic samples with a large number of atoms at ultra low temperature in the absence of gravity. Here, we report on an efficient evaporative cooling in two-crossed laser beams during parabolic flights. Time-averaged potentials combine the advantages of large capture volume and trap compression, increasing the initial phase space density and collision rate to favor the evaporative process. With this technique we demonstrate the production of an ultra cold gas of $2.5\times 10^4$ rubidium atoms at a temperature below 100 nK in less than 4 seconds. Our experiment paves the way for the development of quantum sensors applied to fundamental physics and geodesy as well as the study of ultracold atomic physics in Space.

arXiv:2602.16645•Feb 18, 2026•1 citation

Precise measurements of quantum magnetism of cold atoms in ground and microgravity environment

Wei Wang, Hao Zhu, Li Wang +3 more

Cold atom states are prepared by laser cooling, evaporation cooling and other cooling methods to cool down the atoms close to almost absolute zero in temperature. As a popular research frontier of quantum physics, cold atom physics has been developed to explore, study and measure the spin degrees of freedom in atoms. The precise measurement of the rich quantum magnetism presented by the hyperfine structure of the internal spin freedom is undoubtedly of great significance to basic physics and the innovation of new technologies. With the advantages of microgravity environment and the creation of new extreme conditions, cold atom experimentalists can achieve long-time precision measurement and ultra-low temperature of pK level which is not viable on the ground. The manipulation and precision measurement of quantum magnetism can break through the gravitational limit and reach new parameter regions. In this paper, we review the principles, devices and schemes of cold atom experiments in ground and microgravity environment, the transfer between Zeeman states with different magnetic quantum numbers, magnetic phase transition, time-of-flight imaging and phase contrast imaging. As for the precise measurement, two aspects are emphasized: the deep cooling of atoms under microgravity and the use of non-destructive phase contrast imaging.

Zhongguo kexue. Wulixue Lixue Tianwenxue•May 27, 2021•3 citations

Characterization of isotropic laser cooling for application in quantum sensing

Xin Wang, Yuan Sun, Liang Liu

Quantum sensing with cold atoms is attracting more and more attention in the research frontier of quantum technologies. Isotropic laser cooling serves as a promising platform for this area and its many advantages include compactness, robustness, and not requiring fine-tuning of the optical alignment or magnetic field, which are particularly suitable for field and space applications. We have designed and demonstrated a special form of isotropic laser cooling system that is specifically tailored for the purpose of quantum sensing. In particular, the diffused cooling optical field is generated by hollow laser beam injection and the quality of detection process is improved. Moreover, the effective strength of diffused cooling laser is quantitatively deduced. We have carefully characterized the properties of our system, including the laser cooling performances with respect to different parameter settings, the influences of cooling laser polarization and repumping laser power, and radial atom density distribution. We anticipate that our progress will contribute to the future development of isotropic laser cooling for quantum sensing and quantum precision measurements.

Optics Express•Nov 26, 2021•7 citations

Dynamic equation for evaporative cooling of trapped atoms in microgravity

Xiaolong Yuan, Jiachen Yu, H. Li +4 more

In this paper, to investigate how atoms evaporate and cool in microgravity environments of the space station, we have developed the dynamic equation for evaporative cooling of trapped atoms and obtained the analytical expression of atomic temperature with respect to trapping laser parameters and gravitational acceleration. In our model, the evaporation of atoms is equivalent to applying a damping force to the trapped atoms, and the evaporative cooling process of trapped atoms is comprehended as the damped oscillation of trapped atoms in the optical dipole traps. By introducing the gravity in our model, we obtained the analytical model of temperature variation with gravity after cooling, and the theoretical results agree well with the evaporation experiment of rubidium-87 atoms on the ground. Our theoretical results show that, compared with the atomic evaporative cooling experiment on the ground, the microgravity environment of the space station can achieve cooler atomic gases when the losses of atoms, such as the one-body loss caused by background-gas collisions and the three-body recombination loss caused by interatomic inelastic collisions, can be ignored.

Physical Review A•Apr 16, 2024•2 citations
The invention of laser cooling has fundamentally influenced the research frontier of atomic physics and quantum physics, and recently an intense focus has been on the studies of cold atom physics in microgravity environments. Herein, we report the results of our laser cooling experiment in TianGong-2 space lab, which operated for 34 consecutive months in orbit. Over such an extended operation time, the quality of laser cooling did not experience any significant decline, while the properties of laser cooling in orbital microgravity were systematically studied. In particular, we demonstrate magneto-optical trapping and polarization-gradient cooling in orbit and carefully examine their performances. A comparison of the in-orbit and on-ground results indicates that a higher cooling efficiency exists in microgravity, including a smaller loss rate during the trapping and cooling process and lower ultimate temperature of laser-cooled atoms. Our progress has laid the technical foundations for future applications of cold atoms in space missions with operation times of the order of years.
Since the atomic clock was invented, its performance has been improved for one digit every decade until 90s of last century when the traditional atomic clock almost reached its limit. With laser cooled atoms, the performance can be further improved, and nowadays the cold atom based clocks are widely used as primary frequency standards. Such a kind of cold atom clocks has great applications in space. This paper presents the design and tests of a cold atom clock (CAC) operating in space. In microgravity, the atoms are cooled, trapped, launched and finally detected after being interrogated by microwave field with Ramsey method. The results of laser cooling of atoms in microgravity in orbit are presented and compared with that on ground for the first time. That the full width at half maximum (FWHM) of obtained central Ramsey fringes varies linearly with launching velocity of cold atoms shows the effects of microgravity. With appropriate parameters, a closed-loop locking of the CAC is realized in orbit and the estimated short term frequency stability of 3.0×10−13/τ3.0\times 10 ^{-13}/\sqrt{τ}3.0×10−13/τ​ has been reached.
Abstract This study presents an achievement of laser cooling of alkaline-earth atoms in the Chinese Space Station’s strontium (Sr) atomic space optical clock. The system’s core components, physical unit, optical unit, and electrical unit, have a total volume of 306 L and a total mass of 163.8 kg. These compact and robust units can overcome mechanical vibrations and temperature fluctuations during space launch. The laser sources of the optical unit are composed of diode lasers, and the injection locking of slave lasers is automatically performed by a program. In the experiment, a blue magneto-optical trap of cold atoms was achieved, with the atom numbers estimated to be approximately (1.50 ± 0.13) × 10 6 for 87 Sr and (8.00 ± 0.56) × 10 6 for 88 Sr. This work establishes a foundation for atomic confinement and high-precision interrogation in space-based optical clocks and expands the frontiers of cold atom physics in microgravity.
Most cold atoms experiments in microgravity platforms or in Space are achieved using atom chips, leading to limitations in terms of optical access and inhomogeneous magnetic fields. Optical dipole traps do not have these drawbacks but have difficulties producing atomic samples with a large number of atoms at ultra low temperature in the absence of gravity. Here, we report on an efficient evaporative cooling in two-crossed laser beams during parabolic flights. Time-averaged potentials combine the advantages of large capture volume and trap compression, increasing the initial phase space density and collision rate to favor the evaporative process. With this technique we demonstrate the production of an ultra cold gas of 2.5×1042.5\times 10^42.5×104 rubidium atoms at a temperature below 100 nK in less than 4 seconds. Our experiment paves the way for the development of quantum sensors applied to fundamental physics and geodesy as well as the study of ultracold atomic physics in Space.
Cold atom states are prepared by laser cooling, evaporation cooling and other cooling methods to cool down the atoms close to almost absolute zero in temperature. As a popular research frontier of quantum physics, cold atom physics has been developed to explore, study and measure the spin degrees of freedom in atoms. The precise measurement of the rich quantum magnetism presented by the hyperfine structure of the internal spin freedom is undoubtedly of great significance to basic physics and the innovation of new technologies. With the advantages of microgravity environment and the creation of new extreme conditions, cold atom experimentalists can achieve long-time precision measurement and ultra-low temperature of pK level which is not viable on the ground. The manipulation and precision measurement of quantum magnetism can break through the gravitational limit and reach new parameter regions. In this paper, we review the principles, devices and schemes of cold atom experiments in ground and microgravity environment, the transfer between Zeeman states with different magnetic quantum numbers, magnetic phase transition, time-of-flight imaging and phase contrast imaging. As for the precise measurement, two aspects are emphasized: the deep cooling of atoms under microgravity and the use of non-destructive phase contrast imaging.
Quantum sensing with cold atoms is attracting more and more attention in the research frontier of quantum technologies. Isotropic laser cooling serves as a promising platform for this area and its many advantages include compactness, robustness, and not requiring fine-tuning of the optical alignment or magnetic field, which are particularly suitable for field and space applications. We have designed and demonstrated a special form of isotropic laser cooling system that is specifically tailored for the purpose of quantum sensing. In particular, the diffused cooling optical field is generated by hollow laser beam injection and the quality of detection process is improved. Moreover, the effective strength of diffused cooling laser is quantitatively deduced. We have carefully characterized the properties of our system, including the laser cooling performances with respect to different parameter settings, the influences of cooling laser polarization and repumping laser power, and radial atom density distribution. We anticipate that our progress will contribute to the future development of isotropic laser cooling for quantum sensing and quantum precision measurements.
In this paper, to investigate how atoms evaporate and cool in microgravity environments of the space station, we have developed the dynamic equation for evaporative cooling of trapped atoms and obtained the analytical expression of atomic temperature with respect to trapping laser parameters and gravitational acceleration. In our model, the evaporation of atoms is equivalent to applying a damping force to the trapped atoms, and the evaporative cooling process of trapped atoms is comprehended as the damped oscillation of trapped atoms in the optical dipole traps. By introducing the gravity in our model, we obtained the analytical model of temperature variation with gravity after cooling, and the theoretical results agree well with the evaporation experiment of rubidium-87 atoms on the ground. Our theoretical results show that, compared with the atomic evaporative cooling experiment on the ground, the microgravity environment of the space station can achieve cooler atomic gases when the losses of atoms, such as the one-body loss caused by background-gas collisions and the three-body recombination loss caused by interatomic inelastic collisions, can be ignored.