Direct frequency comparison of intercontinentally separated Sr lattice clocks using carrier-phase two-way satellite frequency transfer

Two strontium lattice clocks, one in Japan and the other in Germany were directly compared by a two-way satellite frequency transfer technique that utilizes the carrier phase of the transmitted signal. The comparison has resulted in a fractional difference of 1.1(1.6)×10
^-15
, directly confirming the frequency agreement on an intercontinental scale.