Optical atomic clocks represent the state of the art in the frontier of modern measurement
science. In this article a detailed review on the development of optical atomic clocks that are …

Optical atomic clocks, due to their unprecedented stability,–and uncertainty,,–, are already
being used to test physical theories, and herald a revision of the International System of …

A list of standard reference frequency values (LoF) of quantum transitions from the
microwave to the optical regime has been recommended by the International Committee for …

The last decade has witnessed tremendous progress in research on optical frequency
metrology. Optical frequency standards using optical lattice and single-ion trap technologies …

The pursuit of ever more precise measures of time and frequency motivates redefinition of
the second in terms of an optical atomic transition. To ensure continuity with the current …

Since 1967, the second as the base unit of time in the International System of Units (SI) is
defined via an unperturbed hyperfine transition in atomic caesium [1] that is interrogated by …

We have measured the absolute frequency of the optical lattice clock based on 87 Sr at PTB
with an uncertainty of $3.9\times {{10}^{-16}} $ using two caesium fountain clocks. This is …

Optical clocks are not only powerful tools for prime fundamental research, but are also
deemed for the redefinition of the SI base unit “second,” as they now surpass the …

Optical lattice clocks are at the forefront of frequency metrology. Both the instability and
systematic uncertainty of these clocks have been reported to be two orders of magnitude …

We report on a series of 42 measurements of the transition frequency of the 429 THz (5 s 2)
S 0 1–(5 s 5 p) P 0 3 line in Sr 87 taken over three years from 2017 to 2019. They were …