Interspecies clock comparison below $5\times 10^{-18}$ uncertainty with a transportable clock

Chetan Vishwakarma, Ingo Nosske, Tim Lücke +6

We report a measurement of the optical frequency ratio between the ${}^2{\mathrm{S}}_{1/2}(F=0)$--${}^2{\mathrm{F}}_{7/2}(F=3)$ electric-octupole (E3) transition of ${}^{171}$Yb${}^{+}$ and…