Realization of a timescale with an accurate optical lattice clock

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 performance of cesium atomic clocks in both accuracy and stability by more than an order of magnitude. However, an important obstacle in this transition has so far been the limited reliability of optical clocks, which made a continuous realization of a timescale impractical. In this paper, we demonstrate how this situation can be resolved and show that a timescale based on an optical clock can be established that is superior to one based on even the best cesium fountain clocks. The paper also gives further proof of the international consistency of strontium lattice clocks on the 10(-16) accuracy level, which is another prerequisite for a change in the definition of the second. (C) 2016 Optical Society of America