English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The rapid increase in accuracy and stability of optical atomic clockscompared to the caesium atomic clock as primary standard of time and frequencyasks for a future re-definition of the second in the International System ofUnits (SI). The status of the optical clocks based on either single ions inradio-frequency traps or on neutral atoms stored in an optical lattice isdescribed with special emphasis of the current work at thePhysikalisch-Technische Bundesanstalt (PTB). Besides the development andoperation of different optical clocks with estimated fractional uncertaintiesin the 10^-18 range, the supporting work on ultra-stable lasers as coreelements and the means to compare remote optical clocks via transportablestandards, optical fibers, or transportable clocks is reported. Finally, theconditions, methods and next steps are discussed that are the prerequisites fora future re-definition of the second.

Towards a Re-definition of the Second Based on Optical Atomic Clocks