Optical clock network tracks tidal variations of the gravity potential
Abstract
Gravity affects the passage of time, as described by General Relativity. On Earth, the rate of a clock as seen by a fixed observer changes by about one part in 1016 per metre in height. Chronometric levelling exploits this effect to directly measure differences in gravity potential by comparing distant clocks. It has been proposed as a complementary approach to established geodetic techniques for linking height reference systems and monitoring the terrestrial gravity potential. Experimental demonstrations have to date focused primarily on static potential differences. Yet, the potentials of the Moon, the Sun and other celestial bodies as well as the Earth's response to their tidal forcing change clock rates by several 10−17, providing a predictable test signal to demonstrate optical clock networks resolving small variations in relativistic time dilation. Here, we report chronometric observations of time-varying gravity potential differences using a network of optical clocks and phase-stabilized fibre links in Europe. Two distinct geographical configurations, with baselines of about 800 km each, result in different combinations of diurnal and semidiurnal tidal components. One comparison uses a transportable optical clock as a remote sensor. The measured rate shifts track the tidal variations, resolving the predicted signal within 1 d of measurement and agreeing with model predictions. These results extend experimental chronometric levelling from static to dynamic potential differences and highlight the need to account for the time dependence of relativistic time dilation in frequency metrology. They also open the prospect for quantum clock networks with improved stability and availability to move beyond known tides and monitor other gravity potential variations, such as those arising from surface deformation and mass redistribution in geologically or volcanically active regions.
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BibTeX
@misc{stahl2026optical,
title = {{Optical clock network tracks tidal variations of the gravity potential}},
author = {Kilian Stahl and Ingo Nosske and Chetan Vishwakarma and Tim Lücke and Joshua Klose and Erik Benkler and Alexander Kuhl and Shambo Mukherjee and Thomas Legero and Jochen Kronjäger and Uwe Sterr and Christian Lisdat and Sören Dörscher and Chen-Hao Feng and Matthew Y. H. Johnson and Jacques-Olivier Gaudron and Wei Huang and Jacob Tunesi and Xi Zhang and Marco Schioppo and Adam L. Parke and Ian R. Hill and Heiner Denker and Biplab Dutta and Etienne Cantin and Olivier Lopez and Anne Amy-Klein and Christian Chardonnet and Benjamin Pointard and Rodolphe Le Targat and Jérôme Lodewyck and Paul-Eric Pottie and Ichiro Ushijima and Masao Takamoto and Hidetoshi Katori and Yogeshwar B. Kale and Stefano Condio and Irene Goti and Tommaso Petrucciani and Cecilia Clivati and Simone Donadello and Filippo Levi and Davide Calonico and Marco Pizzocaro},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.39635},
eprint = {2610.39635},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.39635},
}
RIS
TY - UNPB
TI - Optical clock network tracks tidal variations of the gravity potential
AU - Kilian Stahl
AU - Ingo Nosske
AU - Chetan Vishwakarma
AU - Tim Lücke
AU - Joshua Klose
AU - Erik Benkler
AU - Alexander Kuhl
AU - Shambo Mukherjee
AU - Thomas Legero
AU - Jochen Kronjäger
AU - Uwe Sterr
AU - Christian Lisdat
AU - Sören Dörscher
AU - Chen-Hao Feng
AU - Matthew Y. H. Johnson
AU - Jacques-Olivier Gaudron
AU - Wei Huang
AU - Jacob Tunesi
AU - Xi Zhang
AU - Marco Schioppo
AU - Adam L. Parke
AU - Ian R. Hill
AU - Heiner Denker
AU - Biplab Dutta
AU - Etienne Cantin
AU - Olivier Lopez
AU - Anne Amy-Klein
AU - Christian Chardonnet
AU - Benjamin Pointard
AU - Rodolphe Le Targat
AU - Jérôme Lodewyck
AU - Paul-Eric Pottie
AU - Ichiro Ushijima
AU - Masao Takamoto
AU - Hidetoshi Katori
AU - Yogeshwar B. Kale
AU - Stefano Condio
AU - Irene Goti
AU - Tommaso Petrucciani
AU - Cecilia Clivati
AU - Simone Donadello
AU - Filippo Levi
AU - Davide Calonico
AU - Marco Pizzocaro
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.39635
UR - https://arxiv.org/abs/2610.39635
AB - Gravity affects the passage of time, as described by General Relativity. On Earth, the rate of a clock as seen by a fixed observer changes by about one part in 10^16 per metre in height. Chronometric levelling exploits this effect to directly measure differences in gravity potential by comparing distant clocks. It has been proposed as a complementary approach to established geodetic techniques for linking height reference systems and monitoring the terrestrial gravity potential. Experimental demonstrations have to date focused primarily on static potential differences. Yet, the potentials of the Moon, the Sun and other celestial bodies as well as the Earth's response to their tidal forcing change clock rates by several 10^−17, providing a predictable test signal to demonstrate optical clock networks resolving small variations in relativistic time dilation. Here, we report chronometric observations of time-varying gravity potential differences using a network of optical clocks and phase-stabilized fibre links in Europe. Two distinct geographical configurations, with baselines of about 800 km each, result in different combinations of diurnal and semidiurnal tidal components. One comparison uses a transportable optical clock as a remote sensor. The measured rate shifts track the tidal variations, resolving the predicted signal within 1 d of measurement and agreeing with model predictions. These results extend experimental chronometric levelling from static to dynamic potential differences and highlight the need to account for the time dependence of relativistic time dilation in frequency metrology. They also open the prospect for quantum clock networks with improved stability and availability to move beyond known tides and monitor other gravity potential variations, such as those arising from surface deformation and mass redistribution in geologically or volcanically active regions.
ER -