The 27th General Conference of Weights and Measures (CGPM) adopted the resolution on the “future redefinition of the second,” which aims to redefine the unit of time using optical clocks.
A research team led by Prof. CHANG Hong and Prof. WU Wenjun from the National Time Service Center (NTSC) of the Chinese Academy of Sciences developed a 87Sr optical clock (NTSC-Sr1).
They found that the systematic uncertainty and frequency stability of NTSC-Sr1 were 5.1×10-17 and 6.6×10-16 (τ/s)-0.5, respectively. Using the Hydrogen maser to link the International Atomic Time (TAI), they found that the absolute frequency of the clock transition was measured with an uncertainty of 4.1×10-16.
The results were published in Metrologia on Jan. 23.
The researchers measured the absolute frequency of a Sr-87 optical lattice clock, making a link to primary frequency standards through the international atomic time scale. “These measurements are important ahead of the redefinition of the SI second in order to build confidence in the performance of optical frequency standards around the world,” said a reviewer of Metrologia.
According to Prof. CHANG Hong, the research team will carry out NTSC-Sr1 to participate in the calculation of TAI in order to cope with the change of the international definition of “second” and ensure the independence, safety and reliability of China’s time standard.