title: A clock network for geodesy and fundamental science.
abstract: Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10(-17) via a newly established phase-coherent frequency link connecting Paris and Braunschweig using 1,415 km of telecom fibre. The remote comparison is limited only by the instability and uncertainty of the strontium lattice clocks themselves, with negligible contributions from the optical frequency transfer. A fractional precision of 3 × 10(-17) is reached after only 1,000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than any previous long-distance clock comparison. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second.
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: C
authors: C
authors: Lisdat
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: G
authors: G
authors: Grosche
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: N
authors: N
authors: Quintin
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: C
authors: C
authors: Shi
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: S M F
authors: SM
authors: Raupach
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: C
authors: C
authors: Grebing
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: D
authors: D
authors: Nicolodi
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.|LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: F
authors: F
authors: Stefani
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: A
authors: A
authors: Al-Masoudi
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: S
authors: S
authors: Dörscher
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: S
authors: S
authors: Häfner
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: J-L
authors: JL
authors: Robyr
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: N
authors: N
authors: Chiodo
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: S
authors: S
authors: Bilicki
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: E
authors: E
authors: Bookjans
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: A
authors: A
authors: Koczwara
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: S
authors: 0000-0002-2393-5701
authors: S
authors: Koke
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: A
authors: A
authors: Kuhl
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: F
authors: F
authors: Wiotte
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: F
authors: 0000-0003-2719-5592
authors: F
authors: Meynadier
authors: Réseau National de télécommunications pour la Technologie, l'Enseignement et la Recherche, 23-25 Rue Daviel, 75013 Paris, France.
authors: E
authors: E
authors: Camisard
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: M
authors: M
authors: Abgrall
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: M
authors: M
authors: Lours
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: T
authors: T
authors: Legero
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: H
authors: H
authors: Schnatz
authors: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors: U
authors: U
authors: Sterr
authors: Institut für Erdmessung, Leibniz Universität Hannover, Schneiderberg 50, 30167 Hannover, Germany.
authors: H
authors: H
authors: Denker
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: C
authors: C
authors: Chardonnet
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: Y
authors: Y
authors: Le Coq
authors: Laboratoire Photonique, Numérique et Nanosciences, UMR 5298 Institut d'Optique Graduate School, CNRS, and Université de Bordeaux, 1 Rue F. Mitterrand, 33400 Talence, France.
authors: G
authors: G
authors: Santarelli
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: A
authors: A
authors: Amy-Klein
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: R
authors: R
authors: Le Targat
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: J
authors: 0000-0003-0808-6964
authors: J
authors: Lodewyck
authors: Laboratoire de Physique des Lasers, Université Paris 13, Sorbonne Paris Cité, CNRS, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France.
authors: O
authors: O
authors: Lopez
authors: LNE-SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University of Paris 06, 61 Avenue de l'Observatoire, 75014 Paris, France.
authors: P-E
authors: PE
authors: Pottie