title: Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination.
abstract: Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the1S0-3P0clock transition in an ultracold gas of173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Clivati
authors.forename: Giacomo
authors.initials: G
authors.lastname: Cappellini
authors.forename: Lorenzo F
authors.initials: LF
authors.lastname: Livi
authors.forename: Francesco
authors.initials: F
authors.lastname: Poggiali
authors.forename: Mario Siciliani
authors.initials: MS
authors.lastname: de Cumis
authors.forename: Marco
authors.initials: M
authors.lastname: Mancini
authors.forename: Guido
authors.initials: G
authors.lastname: Pagano
authors.forename: Matteo
authors.initials: M
authors.lastname: Frittelli
authors.forename: Alberto
authors.initials: A
authors.lastname: Mura
authors.forename: Giovanni A
authors.initials: GA
authors.lastname: Costanzo
authors.forename: Filippo
authors.initials: F
authors.lastname: Levi
authors.forename: Davide
authors.initials: D
authors.lastname: Calonico
authors.forename: Leonardo
authors.initials: L
authors.lastname: Fallani
authors.forename: Jacopo
authors.initials: J
authors.lastname: Catani
authors.forename: Massimo
authors.initials: M
authors.lastname: Inguscio