Atomic Clocks for Geodesy

TL;DR

Optical atomic clocks with unprecedented accuracy are advancing geodetic measurements and fundamental physics tests by enabling precise gravitational potential sensing and height referencing.

Contribution

This review highlights recent progress in optical atomic clocks and their potential applications in geodesy, emphasizing technological developments for portable, reliable devices.

Findings

Atomic clocks now achieve relative frequency inaccuracies below 10^-17.

Comparison of optical frequency standards can reach 10^-18 accuracy.

Potential for cm-level height determination in geodesy using atomic clocks.

Abstract

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.