Atomic clocks and fundamental tests
Prof. Ekkehard Peik (Physikalisch-Technische Bundesanstalt (PTB))

Time and Frequency are the most precisely measurable physical quantities, thanks to atomic clocks based on laser-cooled and trapped atoms and ions.
Caesium clocks now realize the SI second with a relative uncertainty in the low 1E-16 range and the new generation of optical atomic clocks permits frequency comparisons to 18 significant digits. I will give an overview with an emphasis on optical clocks with trapped ions. The variety of atomic systems that are being studied allows for tests of fundamental physics, like a search for temporal variations of fundamental constants.