Precision Measurement of the Hydrogen 1S-2S Frequency via a 920-km Fiber Link

Arthur Matveev, Christian G. Parthey, Katharina Predehl, Janis Alnis, Axel Beyer, Ronald Holzwarth,* Thomas Udem, Tobias Wilken, Nikolai Kolachevsky, Michel Abgrall, Daniele Rovera, Christophe Salomon, Philippe Laurent, Gesine Grosche, Osama Terra, Thomas Legero, Harald Schnatz, Stefan Weyers, Brett Altschul, and Theodor W. Hansch Max-Planck-Institut fur Quantenoptik, 85748 Garching, Germany LNE-SYRTE, Observatoire de Paris, 61 avenue de l’Observatoire, 75014 Paris, France Laboratoire Kastler-Brossel, CNRS, 75231 Paris, France Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208, USA (Received 4 March 2013; published 6 June 2013)