[time-nuts] Paper tip: Atomic Clocks for Geodesy

[Ole Petter Ronningen]

Hi, all

I just stumbled across a nice review paper from last year: (
https://arxiv.org/ftp/arxiv/papers/1803/1803.01585.pdf) that perhaps others
will find interesting.

Primarily geared towards geodesy as the title indicates, but it also looks
at several techniques of interest to time-nuts, such as optical clocks and
state of the art time transfer. Also I enjoyed the reminder/example of why
precision in timing matters..

The full abstract of the paper:

We review experimental progress on optical atomic clocks and frequency
transfer, and consider the prospects of using these technologies for
geodetic measurements. Today, optical atomic frequency standards have
reached relative frequency inaccuracies below 10-17, opening new fields of
fundamental and applied research. The dependence of atomic frequencies on
the gravitational potential makes atomic clocks ideal candidates for the
search for deviations in the predictions of Einstein's general relativity,
tests of modern unifying theories and the development of new gravity field
sensors. In this review, we introduce the concepts of optical atomic clocks
and present the status of international clock development and comparison.
Besides further improvement in stability and accuracy of today's best
clocks, a large effort is put into increasing the reliability and
technological readiness for applications outside of specialized
laboratories with compact, portable devices. With relative frequency
uncertainties of 10-18, comparisons of optical frequency standards are
foreseen to contribute together with satellite and terrestrial data to the
precise determination of fundamental height reference systems in geodesy
with a resolution at the cm-level. The long-term stability of atomic
standards will deliver excellent long-term height references for geodetic
measurements and for the modelling and understanding of our Earth.

Enjoy,
Ole