News on China's scientific and technological development.

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SanWenYu

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China's Tianqin project is a space-borne gravitational-wave observatory consisting of three satellites orbiting the earth.

Out of the four milestones, the project has finished the second with the Tianqin-1 (天琴一号) satellite, the first of the three planned satellites, operational in orbit. In March, 2022, the satellite acquired gravity field data of the earth (全球重力场数据), making China the third country in the world that has such capability.

The gravity field data is "of strategic value to economic development and national defense." according to Professor Zhong Min who works for the School of Geospatial Engnineering and Science at Sun Yat-Sen University (中山大学测绘学院).

Back in November, 2019, during the first milestone, the project detected and meaured laser beams bounced back from all the five reflectors on the moon. China thus became the third country, after the US and France, that has done so. This laid the foundation for sending the three satillites in orbit with centimeter precision.

近日，记者从中山大学获悉，2022年3月，“天琴一号”卫星再次传来喜讯。它在轨运行期间还获得全球重力场数据。这是我国首次使用国产自主卫星测得的全球重力场数据，“天琴一号”使得我国成为世界上第三个有能力自主探测全球重力场的国家。

中山大学测绘学院教授钟敏告诉记者：“地球重力场数据对国计民生具有重大战略意义，能服务于大地测量、地球物理、油气资源勘探、防灾减灾、国防安全等领域。”
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2019年6月8日，珠海凤凰山顶，刚刚建成三个月的天琴计划激光测距台站传来好消息：成功获得月面发射器回波信号。天琴团队一鼓作气，到11月历史性地测到了月面上全部五个反射镜信号，使我国成为继美国、法国后世界上第三个成功测得全部五个月球反射镜的国家，实现了中国人30年测月的突破。这是天琴计划的第“0”步，旨在解决未来三颗卫星的厘米级精确入轨问题。
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Overbom

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SanWenYu said:
The gravity field data is "of strategic value to economic development and national defense."
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Thats interesting. What are the economic and national defence aspects in gravitational-wave detection? I always though gravitational-wave detection was all about scientific experiment
 
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SanWenYu

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Overbom said:
Thats interesting. What are the economic and national defence aspects in gravitational-wave detection? I always though gravitational-wave detection was all about scientific experiment
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I was wondering about the same, in particular the "national defense" part. Unfortunately, the prof. did not elaborate.

My uneducated guess would be that submarines under water and underground constructions, for example, can change the gravity field.
 
S

SanWenYu

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Overbom said:
Thats interesting. What are the economic and national defence aspects in gravitational-wave detection? I always though gravitational-wave detection was all about scientific experiment
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Ah, I misread your question. Professor Zheng was talking about possible benefits of having the gravity field data of the earth, not gravitational-wave detection.
 
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SanWenYu

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Liquid-Nitrogen-Cooled Ca+ Optical Clock with Systematic Uncertainty of 3×10−18​

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We present a liquid-nitrogen-cooled Ca+ optical clock with an overall systematic uncertainty of 3.0×10−18. In contrast to the room-temperature Ca+ optical clock that we have reported previously, the cryogenic black-body radiation (BBR) shield in vacuum is cooled to 82±5 K using liquid nitrogen. We also implement an ion trap with a reduced heating rate and improved laser cooling. This allows the ion temperature to fall to the Doppler-cooling limit during the clock operation and the systematic uncertainty associated with the secular (thermal) motion of the ion is reduced to <1×10−18. The uncertainty arising from the probe laser light shift and the servo error is also reduced to <1×10−19 and 4×10−19 with the hyper-Ramsey method and the higher-order servo algorithm, respectively. By comparing the output frequency of the cryogenic clock to that of a room-temperature clock, the differential BBR shift between the two is determined with a fractional statistical uncertainty of 7×10−18. The differential BBR shift is used to calculate the static differential polarizability and the result is found to be in excellent agreement with our previous measurement using a different method. This work suggests that the BBR shift of optical clocks can be suppressed well in a liquid-nitrogen environment. Systems similar to what is presented here can also be used to suppress the BBR shift significantly in other types of optical clocks, such as Yb+, Sr+, Yb, Sr, etc.
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记者4月14日从中科院精密测量院了解到，该院研究团队成功研制不确定度达3×10-18的钙离子光频标，即105亿年偏差不到1秒，使我国拥有了国际上第五种不确定度指标达到10-18量级的光频标。相关成果近日在《应用物理评论》上发表。

当前世界测量精度最高的物理量是光频，最高精度已达10-18量级。其中原子光频标是光频精密测量的典型代表，是目前准确度最高的原子频标。截止目前，国际上仅有锶原子光频标(美国天体物理联合实验室JILA、日本东京大学)、镱原子光频标(美国国家标准与技术研究院NIST)、铝离子光频标(NIST)、以及镱离子光频标(德国联邦物理技术研究院PTB)等四种原子光频标的不确定度达到了10-18量级。
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相关科研人员表示，在基础研究领域，光频标极低的不确定度有助于提高基本物理量定义、基本物理常数测量和基本物理定律检验等的精度，以及推进新物理的发现。在应用研究领域，在时间基准、相对论大地测量、导航定位等方面具有广泛的应用场景。
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J

JebKerman

Junior Member
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SanWenYu said:
I was wondering about the same, in particular the "national defense" part. Unfortunately, the prof. did not elaborate.

My uneducated guess would be that submarines under water and underground constructions, for example, can change the gravity field.
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Accurate map of local gravitational fields is extremely important for increasing accuracy of ballistic missiles and other things relying on inertial navigation.
 
Strangelove

Strangelove

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Huawei Technologies Co is continuing its drive for development of the OpenEuler operating system as part of its broader push to solve China's lack of homegrown operating systems for fundamental digital technologies.

The OpenEuler is designed for enterprise customers and can be used in devices such as servers, cloud computing and edge computing. Last year, Huawei donated the Euler operating system to the OpenAtom Foundation, a major open source foundation in China, to become an open-source OS.

Jiang Dayong, director of the OpenEuler Community, said the OpenEuler open source community has attracted more than 8,000 developers and 330 partners such as chip makers, software companies and hardware makers. At present, the cumulative installed capacity of OpenEuler is more than 1.3 million sets in industries such as finance, transportation and telecom, which has passed the ecological inflection point.

Jiang expected about 2 million sets of OpenEuler to be newly installed in 2022.
 
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