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

Nature Communications

In-orbit operation of an atomic clock based on laser-cooled 87Rb atoms

Liang Liu, Desheng Lü, Weibiao Chen, Tang Li, Qiuzhi Qu, Bin Wang, Lin Li, Wei Ren, Zuoren Dong, Jian-Bo Zhao, Wenbing Xia, Xin Zhao, Jing-Wei Ji, Meifeng Ye, Yanguang Sun, Yuanyuan Yao, Dan Song, Zhaogang Liang, Shanjiang Hu, Dunhe Yu, Xia Hou, Wei Shi, Huaguo Zang, Jingfeng Xiang, Xiangkai Peng, Yuzhu Wang

Published Jul 11, 2018• 189 citations
Publisher

Abstract

Abstract Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10 −13 τ −1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

DOI
10.1038/s41467-018-05219-z

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

Cold atom microwave clock based on intracavity cooling in China space station

Siminda Deng, Wei Ren, Jingfeng Xiang +9 more

Abstract Atomic clocks with higher frequency stability and accuracy than traditional space-borne atomic clocks are the cornerstone of long-term autonomous operation of space-time-frequency systems. We proposed a space cold atoms clock based on an intracavity cooling scheme, which captures cold atoms at the center of a microwave cavity and then executes in situ interactions between the cold atoms and microwaves. As a result of the microgravity environment in space, the cold atoms can interact with the microwaves for a longer time, which aids in realizing a high-precision atomic clock in space. This paper presents the overall design, operational characteristics, and reliability test results of the space atomic clock based on the intracavity cooling scheme designed for the operation onboard the China space station. In addition, the engineering prototype performance of the space cold atoms microwave clock is also presented. The ground test results for the clock show a fractional frequency stability of 1.1 × 10−12 τ−1/2 reaching 2.5 × 10−15 at 200,000 s, providing solid technical and data support for its future operation in orbit.

npj Microgravity•Jun 6, 2024•9 citations

Physics package based on intracavity laser cooling 87Rb atoms for space cold atom microwave clock

Siminda 思敏达 Deng 邓, Wei 伟 Ren 任, Jingfeng Xiang +9 more

Abstract This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation, microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of 1.2 × 10−12 τ −1/2 with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.

Chinese Physics B•May 15, 2024•4 citations

Satellite-borne atomic clock based on diffuse laser-cooled atoms

Yan-Ling Meng, Xiaojun Jiang, Jing Wu +4 more

The technique of laser cooling of atoms gives an opportunity to improve the performance of atomic clocks by using laser-cooled atoms. The most successful cold atom clock, called the atomic fountain, is now widely used as the primary frequency standard in many labs. The cold atom clock for satellite applications, however, has not been reported so far due to special requirements of space applications. Here, we report the development of an engineering model of a satellite-borne cold atom clock, which satisfied all requirements of in-orbit operation. The core of the clock’s principle is the laser cooling of atoms by diffuse laser lights inside the microwave cavity. The structure of the physics package is presented, and its main parameters are also given. The principle and design of the optical bench are described. The initial test results are presented, and the possible improvements are also discussed.

Frontiers in Physics•Sep 16, 2022•4 citations

Initial Tests of a Rubidium Space Cold Atom Clock

Lin Li, Qiuzhi Qu, Bin Wang +9 more

We report the initial test results of a rubidium ( 87 Rb) space cold atom clock (SCAC). The space-qualified 87 Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the control electronics. After the system is integrated, about 10 8 87 Rb cold atoms are captured by magneto-optical trap. The linewidth of the Ramsey fringe is about 10 Hz for the free evolution time of 50 ms on the ground, and the signal-to-noise ratio is measured to be larger than 300. We demonstrate a good medium-term fractional frequency stability of 1.5 × 10 −14 @1000 s in the closed-loop operation on the ground. The main effects of the noise on the stability are also presented, and the optimized operating parameter is analyzed for the operation of SCAC in the microgravity environment.

Chinese Physics Letters•Jun 1, 2016•9 citations

Compact, Continuous-Beam, Cold-Atom Clock for Satellite Applications

H. Wang, Walter F. Buell

Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. The requirements for an atomic clock vary significantly depending on the application, and for many space systems, compactness and robust design are at a premium, and stability dominates over absolute accuracy. We report on progress with our design for a compact laser-cooled Cs- beam atomic clock suitable for satellite applications such as GPS. The basic design features a continuous, cold atomic beam extracted from a magneto-optic trap (MOT). This cold atomic beam is then to be used in a laser-pumped Ramsey clock, with the clock signal derived from either a microwave C-field or, alternatively, by Raman resonance between the Ramsey fields. In order to reduce light shifts from the MOT light and improve signal-to-noise, the atomic beam will be optically deflected and transversely cooled upon extraction from the MOT. We estimate that the shot-noise-limited stability achievable with this physics package can be 2 to 3 orders of magnitude better than current Cs-beam clocks used in satellite applications. We present our experimental progress towards a working frequency standard, including characterization of our six-beam magneto-optic cold atom trap and production and characterization of a cold atomic beam.

•Jun 30, 2002•1 citation
Abstract Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10 −13 τ −1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.
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 Atomic clocks with higher frequency stability and accuracy than traditional space-borne atomic clocks are the cornerstone of long-term autonomous operation of space-time-frequency systems. We proposed a space cold atoms clock based on an intracavity cooling scheme, which captures cold atoms at the center of a microwave cavity and then executes in situ interactions between the cold atoms and microwaves. As a result of the microgravity environment in space, the cold atoms can interact with the microwaves for a longer time, which aids in realizing a high-precision atomic clock in space. This paper presents the overall design, operational characteristics, and reliability test results of the space atomic clock based on the intracavity cooling scheme designed for the operation onboard the China space station. In addition, the engineering prototype performance of the space cold atoms microwave clock is also presented. The ground test results for the clock show a fractional frequency stability of 1.1 × 10−12 τ−1/2 reaching 2.5 × 10−15 at 200,000 s, providing solid technical and data support for its future operation in orbit.
Abstract This article proposes a new physics package to enhance the frequency stability of the space cold atom clock with the advantages of a microgravity environment. Clock working processes, including atom cooling, atomic state preparation, microwave interrogation, and transition probability detection, are integrated into the cylindrical microwave cavity to achieve a high-performance and compact physics package for the space cold atom clock. We present the detailed design and ground-test results of the cold atom clock physics package in this article, which demonstrates a frequency stability of 1.2 × 10−12 τ −1/2 with a Ramsey linewidth of 12.5 Hz, and a better performance is predicted with a 1 Hz or a narrower Ramsey linewidth in microgravity environment. The miniaturized cold atom clock based on intracavity cooling has great potential for achieving space high-precision time-frequency reference in the future.
The technique of laser cooling of atoms gives an opportunity to improve the performance of atomic clocks by using laser-cooled atoms. The most successful cold atom clock, called the atomic fountain, is now widely used as the primary frequency standard in many labs. The cold atom clock for satellite applications, however, has not been reported so far due to special requirements of space applications. Here, we report the development of an engineering model of a satellite-borne cold atom clock, which satisfied all requirements of in-orbit operation. The core of the clock’s principle is the laser cooling of atoms by diffuse laser lights inside the microwave cavity. The structure of the physics package is presented, and its main parameters are also given. The principle and design of the optical bench are described. The initial test results are presented, and the possible improvements are also discussed.
We report the initial test results of a rubidium ( 87 Rb) space cold atom clock (SCAC). The space-qualified 87 Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the control electronics. After the system is integrated, about 10 8 87 Rb cold atoms are captured by magneto-optical trap. The linewidth of the Ramsey fringe is about 10 Hz for the free evolution time of 50 ms on the ground, and the signal-to-noise ratio is measured to be larger than 300. We demonstrate a good medium-term fractional frequency stability of 1.5 × 10 −14 @1000 s in the closed-loop operation on the ground. The main effects of the noise on the stability are also presented, and the optimized operating parameter is analyzed for the operation of SCAC in the microgravity environment.
Highly stable atomic frequency standards are of increasing importance for a variety of space applications, ranging from communication to navigation and time transfer to tests of fundamental science. The requirements for an atomic clock vary significantly depending on the application, and for many space systems, compactness and robust design are at a premium, and stability dominates over absolute accuracy. We report on progress with our design for a compact laser-cooled Cs- beam atomic clock suitable for satellite applications such as GPS. The basic design features a continuous, cold atomic beam extracted from a magneto-optic trap (MOT). This cold atomic beam is then to be used in a laser-pumped Ramsey clock, with the clock signal derived from either a microwave C-field or, alternatively, by Raman resonance between the Ramsey fields. In order to reduce light shifts from the MOT light and improve signal-to-noise, the atomic beam will be optically deflected and transversely cooled upon extraction from the MOT. We estimate that the shot-noise-limited stability achievable with this physics package can be 2 to 3 orders of magnitude better than current Cs-beam clocks used in satellite applications. We present our experimental progress towards a working frequency standard, including characterization of our six-beam magneto-optic cold atom trap and production and characterization of a cold atomic beam.