Year: 2026
Type: preprint
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 $10^{16}$ 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.
Source: arXiv (Cornell University)
Authors: Stahl, Kilian, Nosske, Ingo, Vishwakarma, Chetan, Lücke, Tim, Klose, Joshua, Benkler, Erik, Kuhl, Alexander, Mukherjee, Shambo, Legero, Thomas, Kronjäger, Jochen, Sterr, Uwe, Lisdat, Christian, Dörscher, Sören, Feng, Chen-Hao, Johnson, Matthew Y. H., Gaudron, Jacques-Olivier, Huang, Wei, Tunesi, Jacob, Zhang, Xi, Schioppo, Marco, Parke, Adam L., Hill, Ian R., Denker, Heiner, Dutta, Biplab, Cantin, Etienne, Lopez, Olivier, Amy-Klein, Anne, Chardonnet, Christian, Pointard, Benjamin, Targat, Rodolphe Le, Lodewyck, Jérôme, Pottie, Paul-Eric, Ushijima, Ichiro, Takamoto, Masao, Katori, Hidetoshi, Kale, Yogeshwar B., Condio, Stefano, Goti, Irene, Petrucciani, Tommaso, Clivati, Cecilia, Donadello, Simone, Levi, Filippo, Calonico, Davide, Pizzocaro, Marco
Institutions: Physikalisch-Technische Bundesanstalt, National Physical Laboratory, Leibniz University Hannover, Centre National de la Recherche Scientifique, Université Sorbonne Paris Nord, Laboratoire de physique des lasers, Observatoire de Paris, Laboratoire Temps Espace, RIKEN, The University of Tokyo, RIKEN Center for Advanced Photonics, University of Birmingham, Istituto Nazionale di Ricerca Metrologica, Université de Lille, Université Paris Sciences et Lettres, Sorbonne Université
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: Equipex, European Commission, Deutsche Forschungsgemeinschaft, Volkswagen Foundation, Agence Nationale de la Recherche, Istituto Nazionale di Ricerca Metrologica, HORIZON EUROPE Framework Programme, Engineering and Physical Sciences Research Council, Japan Science and Technology Agency, RIKEN, JST-Mirai Program, European Metrology Programme for Innovation and Research
Awards: International Clock and Oscillator Networking - ICON, FOR 5456: Uhrenmetrologie: Die ZEIT als neue Variable in der Geodäsie, G4285572622, EXC 2123: QuantumFrontiers Licht und Materie an der Quantengrenze, RESEAU FIBRE METROLOGIQUE A VOCATION EUROPEENNE +, G5546255241, Time-frequency shared service on optical fibre network, SFB 1227: Designte Quantenzustände der Materie (DQmat) Herstellung, Manipulation und Detektion für metrologische Anwendungen und Tests fundamentaler Physik, G714411183, G745383156, クラウド光格子時計による時空間情報基盤の構築, G8205597137, G865028186, G9000276246
OpenAlex ID: W7224940901