Related papers: On possible ways for future redefinition of the SI…
The current SI second based on the atomic hyperfine transition in the ground state of 133Cs is expected to be replaced by a new definition based on optical frequency standards, whose estimated uncertainty has now been established two orders…
The current definition of the SI second based on the Cs ground state hyperfine transition is expected to be replaced by a new definition based on optical frequency standards in the next decade. Several options are currently under…
The rapid increase in accuracy and stability of optical atomic clocks compared to the caesium atomic clock as primary standard of time and frequency asks for a future re-definition of the second in the International System of Units (SI).…
The atomic transitions employed in the best of today's optical clocks are a strong foundation for the upcoming redefinition of the SI second. Including multiple transitions in the definition offers increased accuracy, a robust diversity of…
Some 50~years ago, physicists, and after them the entire world, started to found their time reference on atomic properties instead of motions of the Earth that have been in use since the origin. Far from being an arrival point, this…
A new definition of the SI second based on optical transitions is expected to be adopted within the next 10 years. Several options for this redefinition are currently under consideration. Among them, a definition based on several…
The current definition of the SI second is based on the 133Cs ground-state hyperfine transition in the microwave domain, with the most accurate realizations achieving fractional frequency uncertainties of about (1-2)E16. In contrast,…
In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femto-second optical frequency combs have enabled a rapid development of…
The pursuit of ever more precise measures of time and frequency is likely to lead to the eventual redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on a microwave…
Advantages and disadvantages of fixation of fundamental physical constants' values for definition of SI units are considered. The case with a new definition of the mass unit on the base of a fixed value of the Avogadro constant is studied…
We report the first contribution to the international atomic time (TAI) based on a secondary representation of the SI second. This work is done with the LNE-SYRTE FO2-Rb fountain frequency standard using the $^{87}$Rb ground state hyperfine…
A brief description of the main methods for determining the fine structure constant is given. It is shown that the exact value of the fine structure constant is important for the new International System of Units (SI) and for fundamental…
We consider microwave hyperfine transitions in the ground state of cesium and rubidium atoms which are presently used as the primary and the secondary frequency standards. The atoms are confined in an optical lattice generated by a…
Optical clocks are not only powerful tools for prime fundamental research, but are also deemed for the re-definition of the SI base unit second as they now surpass the performance of caesium atomic clocks in both accuracy and stability by…
A two-photon transition in laser-cooled and trapped calcium atoms is proposed as the atomic reference in an optical frequency standard. An efficient scheme for interrogation of the frequency standard is described, and the sensitivity of the…
Progress in realizing the SI second had multiple technological impacts and enabled to further constraint theoretical models in fundamental physics. Caesium microwave fountains, realizing best the second according to its current definition…
We derive an expression for the magnetic blackbody shift of hyperfine transitions such as the cesium primary reference transition which defines the second. The shift is found to be a complicated function of temperature, and has a T^2…
We present a theoretical analysis of the Stark effect in the hyperfine structure of the cesium ground-state. We have used third order perturbation theory, including diagonal and off-diagonal hyperfine interactions, and have identified terms…
Plans are underway to redefine the International System of Units (SI) around 2018. The New SI specifies the values of certain physical constants to define units. This article explains the New SI in a way that could be used to present it to…
The four SI base units are proposed to be redefined in two stages: first, the kilogram, mole and ampere should be defined, and then the kelvin. To realize the redefinition of a base unit of the SI in terms of fundamental physical constant…