Robust Optical Clocks for International Timescales

Short Name: ROCIT, Project Number: 18SIB05
Image of Clocks showing time around the world
Clocks showing time around the world

Tools to correct for systematic frequency shifts and enable automated validation supporting redefinition of the SI second

Advances in telecoms and GPS technologies place increasing demands on the stability and accuracy of international reference timescales. Optical clocks offer better frequency stability and timing certainty than caesium primary frequency standards, and a redefinition of the second is anticipated based on potential for orders-of-magnitude improvements to accuracy. However, optical clocks aren’t yet accepted for international timescales as monitoring and user intervention is required. Systematic frequency shifts need to be accounted for, plus automated validation is necessary.


The project targetted unattended uptimes of 80 % to 90 % over weeks for two types of optical clocks. Optical fibre and satellite links were used to compare frequencies, while traceability to the present definition of the SI second was provided by absolute frequency measurements relative to caesium primary standards. The techniques and hardware developed should lead to smaller optical clocks, while significant science and innovation impacts are expected to arise from international consistency and long-term reliability through realisation and dissemination of a new SI unit of time.


Project website
Other Participants
Ben-Gurion University of the Negev (Israel)
Centre National de la Recherche Scientifique (France)
Centrum Badan Kosmicznych Polskiej Akademii Nauk (Poland)
Gottfried Wilhelm Leibniz Universität Hannover (Germany)
Politecnico di Torino (Italy)
Université Paris 13 (France)
Uniwersytet Mikolaja Kopernika w Toruniu (Poland)