title: Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km.
abstract: We have demonstrated a direct frequency comparison between two ⁸⁷Sr lattice clocks operated in intercontinentally separated laboratories in real time. Two-way satellite time and frequency transfer technique, based on the carrier-phase, was employed for a direct comparison, with a baseline of 9000 km between Japan and Germany. A frequency comparison was achieved for 83,640 s, resulting in a fractional difference of (1.1±1.6)×10⁻¹⁵, where the statistical part is the largest contributor to the uncertainty. This measurement directly confirms the agreement of the two optical frequency standards on an intercontinental scale.
authors.forename: H
authors.initials: H
authors.lastname: Hachisu
authors.forename: M
authors.initials: M
authors.lastname: Fujieda
authors.forename: S
authors.initials: S
authors.lastname: Nagano
authors.forename: T
authors.initials: T
authors.lastname: Gotoh
authors.forename: A
authors.initials: A
authors.lastname: Nogami
authors.forename: T
authors.initials: T
authors.lastname: Ido
authors.forename: St
authors.initials: S
authors.lastname: Falke
authors.forename: N
authors.initials: N
authors.lastname: Huntemann
authors.forename: C
authors.initials: C
authors.lastname: Grebing
authors.forename: B
authors.initials: B
authors.lastname: Lipphardt
authors.forename: Ch
authors.initials: Ch
authors.lastname: Lisdat
authors.forename: D
authors.initials: D
authors.lastname: Piester