_version_ 1866914521298239488
author Pizzocaro, Marco
Zyskind, Clara
Amy-Klein, Anne
Benkler, Erik
Bize, Sebastien
Calonico, Davide
Cantin, Etienne
Chardonnet, Christian
Clivati, Cecilia
Condio, Stefano
Curtis, E. Anne
Donadello, Simone
Dörscher, Sören
Feng, Chen-Hao
Filzinger, Melina
Gaudron, Jacques-Olivier
Godun, Rachel M.
Goti, Irene
Hill, Ian R.
Huang, Wei
Huntemann, Nils
Johnson, Matthew
Klose, Joshua
Kronjäger, Jochen
Kuhl, Alexander
Targat, Rodolphe Le
Levi, Filippo
Lipphardt, Burghard
Lisdat, Christian
Lodewyck, Jerome
Lopez, Olivier
Margolis, Helen S.
Mazouth-Laurol, Maxime
Mura, Alberto
Pointard, Benjamin
Pottie, Paul-Eric
Risaro, Matias
Robertson, Billy I.
Schioppo, Marco
Stahl, Kilian
Steinel, Martin
Tofful, Alexandra
Tønnes, Mads
Tunes, Jacob
author_facet Pizzocaro, Marco
Zyskind, Clara
Amy-Klein, Anne
Benkler, Erik
Bize, Sebastien
Calonico, Davide
Cantin, Etienne
Chardonnet, Christian
Clivati, Cecilia
Condio, Stefano
Curtis, E. Anne
Donadello, Simone
Dörscher, Sören
Feng, Chen-Hao
Filzinger, Melina
Gaudron, Jacques-Olivier
Godun, Rachel M.
Goti, Irene
Hill, Ian R.
Huang, Wei
Huntemann, Nils
Johnson, Matthew
Klose, Joshua
Kronjäger, Jochen
Kuhl, Alexander
Targat, Rodolphe Le
Levi, Filippo
Lipphardt, Burghard
Lisdat, Christian
Lodewyck, Jerome
Lopez, Olivier
Margolis, Helen S.
Mazouth-Laurol, Maxime
Mura, Alberto
Pointard, Benjamin
Pottie, Paul-Eric
Risaro, Matias
Robertson, Billy I.
Schioppo, Marco
Stahl, Kilian
Steinel, Martin
Tofful, Alexandra
Tønnes, Mads
Tunes, Jacob
contents Optical clocks have achieved remarkable estimated fractional frequency uncertainties reaching the $10^{-18}$ level and below, enabling applications in fundamental physics, general relativity, and geodesy. However, the challenge of verifying the international consistency of optical clocks remains critical as efforts intensify toward redefining the SI second based on an optical transition or transitions. We report on a two-month international clock comparison campaign involving seven optical clocks in four national metrology institutes (INRIM, LNE-OP, NPL, and PTB) connected via the optical fiber network established in Europe. The campaign resulted in optical frequency ratios with uncertainties ranging from $7.7\times10^{-18}$ to $6.1\times10^{-17}$. Among the results, the $^{171}$Yb$^+$(E3) clocks at NPL and PTB demonstrated agreement within an uncertainty of $7.7\times10^{-18}$, marking the first international verification of two independently developed optical clocks below one part in $10^{17}$. The operation of the $^{199}$Hg clock at LNE-OP (formerly LNE-SYRTE) resulted in frequency ratios with improved uncertainties with $^{171}$Yb$^+$(E3), $^{171}$Yb, and $^{87}$Sr optical clocks. These results provide input for the redefinition of the second and underscore how fiber-linked clock networks can advance metrology and scientific applications.
format Preprint
id arxiv_https___arxiv_org_abs_2604_27963
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle International Optical Clock Comparison Using the European Optical Fiber Network
Pizzocaro, Marco
Zyskind, Clara
Amy-Klein, Anne
Benkler, Erik
Bize, Sebastien
Calonico, Davide
Cantin, Etienne
Chardonnet, Christian
Clivati, Cecilia
Condio, Stefano
Curtis, E. Anne
Donadello, Simone
Dörscher, Sören
Feng, Chen-Hao
Filzinger, Melina
Gaudron, Jacques-Olivier
Godun, Rachel M.
Goti, Irene
Hill, Ian R.
Huang, Wei
Huntemann, Nils
Johnson, Matthew
Klose, Joshua
Kronjäger, Jochen
Kuhl, Alexander
Targat, Rodolphe Le
Levi, Filippo
Lipphardt, Burghard
Lisdat, Christian
Lodewyck, Jerome
Lopez, Olivier
Margolis, Helen S.
Mazouth-Laurol, Maxime
Mura, Alberto
Pointard, Benjamin
Pottie, Paul-Eric
Risaro, Matias
Robertson, Billy I.
Schioppo, Marco
Stahl, Kilian
Steinel, Martin
Tofful, Alexandra
Tønnes, Mads
Tunes, Jacob
Atomic Physics
Optics
Optical clocks have achieved remarkable estimated fractional frequency uncertainties reaching the $10^{-18}$ level and below, enabling applications in fundamental physics, general relativity, and geodesy. However, the challenge of verifying the international consistency of optical clocks remains critical as efforts intensify toward redefining the SI second based on an optical transition or transitions. We report on a two-month international clock comparison campaign involving seven optical clocks in four national metrology institutes (INRIM, LNE-OP, NPL, and PTB) connected via the optical fiber network established in Europe. The campaign resulted in optical frequency ratios with uncertainties ranging from $7.7\times10^{-18}$ to $6.1\times10^{-17}$. Among the results, the $^{171}$Yb$^+$(E3) clocks at NPL and PTB demonstrated agreement within an uncertainty of $7.7\times10^{-18}$, marking the first international verification of two independently developed optical clocks below one part in $10^{17}$. The operation of the $^{199}$Hg clock at LNE-OP (formerly LNE-SYRTE) resulted in frequency ratios with improved uncertainties with $^{171}$Yb$^+$(E3), $^{171}$Yb, and $^{87}$Sr optical clocks. These results provide input for the redefinition of the second and underscore how fiber-linked clock networks can advance metrology and scientific applications.
title International Optical Clock Comparison Using the European Optical Fiber Network
topic Atomic Physics
Optics
url https://arxiv.org/abs/2604.27963