Harald Schnatz

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Optical clocks show unprecedented accuracy, surpassing that of previously available clock systems by more than one order of magnitude. Precise intercomparisons will enable a variety of experiments, including tests of fundamental quantum physics and cosmology and applications in geodesy and navigation. Well-established, satellite-based techniques for(More)
—Two 171 Yb + single-ion optical frequency standards operating at 688 THz (436 nm) are compared in order to investigate systematic frequency shifts in the subhertz range. In the absence of externally applied perturbations, a mean relative frequency difference of 3.8 · 10 −16 is observed. Using a femtosecond frequency comb generator based on an Er 3+-doped(More)
The optical calcium frequency standards of PTB and NIST ⋆ Lesétalons de fréquence optique au calcium de la PTB et du NIST Abstract We describe the current status of the Ca optical frequency standards with laser-cooled neutral atoms realized in two different laboratories for the purpose of developing a possible future optical atomic clock. Frequency(More)
—We stabilize a microwave oscillator at 9.6 GHz to an optical clock laser at 344 THz by using a fiber-based femto-second laser frequency comb as a transfer oscillator. With a second frequency comb, we independently measure the instability of the microwave source with respect to another optical clock laser frequency at 456 THz. The total fractional frequency(More)
Precision comparisons of different atomic frequency standards over a period of a few years can be used for a sensitive search for temporal variations of fundamental constants. We present recent frequency measurements of the 688 THz transition in the 171 Yb + ion. For this transition frequency a record over six years is now available, showing that a possible(More)
Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10(-17) via a newly(More)