Scientists from China have brought the redefinition of seconds as a unit of time closer.
Scientists from China have created a unique optical clock that is so accurate that the error in its course is only one second in 7 billion years. Described in the scientific journal Metrologia, the achievement paves the way for a revision of the definition of the second as the main unit of time measurement.
Researchers from the University of Science and Technology of China used super-cold strontium atoms and high-power laser beams to create a clock with a stability level and an error of less than five quintillionths. Thus, China became the second country after the United States to achieve such time accuracy.
Optical clock based on strontium.
Physicist Pan Jianwei, head of the research team, emphasized that their achievement marked the beginning of the formation of a global network of optical clocks. This approach opens the door to new horizons in scientific research, including testing fundamental physical theories, detecting gravitational waves, and searching for dark matter.
Currently, the record holder for accuracy among optical watches based on strontium remains the clock of the University of Colorado at Boulder. They are slightly superior to their Chinese competitor, and their work is more stable.
Optical clocks have great potential for use in the vital infrastructure of the future. They can significantly improve the accuracy of global navigation satellite systems, help create highly secure communication networks based on quantum key distribution, improve synchronization and efficiency of power grids, and play a key role in national defense and security.
Currently, the definition of a second is based on a caesium-based frequency reference. However, the possibilities for improving the accuracy of such watches are limited. In recent years, researchers have developed optical clocks that use laser light to excite electronic transitions and exhibit characteristics two orders of magnitude higher than their microwave-powered predecessors.
However, in order to replace the existing time standard with optical clocks in the future, at least three laboratories in the world must have optical clocks with stability below 5 quintillion and uncertainty below 2 quintillion. These are key performance and reliability indicators for an optical watch.
In their work, a group of Chinese scientists cooled strontium-87 atoms to a temperature of several micro-Kelvin and placed them in a one-dimensional lattice created using intersecting laser beams. Then they used a super-stable laser to interact with trapped strontium-87 atoms and initiate a so-called clock transition, which is characterized by high stability and accuracy.
The scientists also performed frequency measurements between two independent clocks, which demonstrated that the stability of individual clocks is on the order of 2.2 quintillion. The total uncertainty of the system as a whole was 4.4 quintillionths, which is equivalent to a deviation of one second every 7.2 billion years, the authors concluded.
The team plans to make comparisons between optical clocks built on different types of atom, such as strontium-87 and ytterbium-171. The research was supported by the Ministry of Science and Technology and Anhui Province, as well as other financial agencies, and builds on previous work on quantum simulations of super-cold atoms.
Scientists from China have created a unique optical clock that is so accurate that the error in its course is only one second in 7 billion years. Described in the scientific journal Metrologia, the achievement paves the way for a revision of the definition of the second as the main unit of time measurement.
Researchers from the University of Science and Technology of China used super-cold strontium atoms and high-power laser beams to create a clock with a stability level and an error of less than five quintillionths. Thus, China became the second country after the United States to achieve such time accuracy.
Optical clock based on strontium.
Physicist Pan Jianwei, head of the research team, emphasized that their achievement marked the beginning of the formation of a global network of optical clocks. This approach opens the door to new horizons in scientific research, including testing fundamental physical theories, detecting gravitational waves, and searching for dark matter.
Currently, the record holder for accuracy among optical watches based on strontium remains the clock of the University of Colorado at Boulder. They are slightly superior to their Chinese competitor, and their work is more stable.
Optical clocks have great potential for use in the vital infrastructure of the future. They can significantly improve the accuracy of global navigation satellite systems, help create highly secure communication networks based on quantum key distribution, improve synchronization and efficiency of power grids, and play a key role in national defense and security.
Currently, the definition of a second is based on a caesium-based frequency reference. However, the possibilities for improving the accuracy of such watches are limited. In recent years, researchers have developed optical clocks that use laser light to excite electronic transitions and exhibit characteristics two orders of magnitude higher than their microwave-powered predecessors.
However, in order to replace the existing time standard with optical clocks in the future, at least three laboratories in the world must have optical clocks with stability below 5 quintillion and uncertainty below 2 quintillion. These are key performance and reliability indicators for an optical watch.
In their work, a group of Chinese scientists cooled strontium-87 atoms to a temperature of several micro-Kelvin and placed them in a one-dimensional lattice created using intersecting laser beams. Then they used a super-stable laser to interact with trapped strontium-87 atoms and initiate a so-called clock transition, which is characterized by high stability and accuracy.
The scientists also performed frequency measurements between two independent clocks, which demonstrated that the stability of individual clocks is on the order of 2.2 quintillion. The total uncertainty of the system as a whole was 4.4 quintillionths, which is equivalent to a deviation of one second every 7.2 billion years, the authors concluded.
The team plans to make comparisons between optical clocks built on different types of atom, such as strontium-87 and ytterbium-171. The research was supported by the Ministry of Science and Technology and Anhui Province, as well as other financial agencies, and builds on previous work on quantum simulations of super-cold atoms.
