New Limits on Coupling of Fundamental Constants to Gravity UsingSr87Optical Lattice Clocks

Abstract

The $^{1}S_{0}$-$^{3}P_{0}$ clock transition frequency ${\ensuremath{\nu}}_{\mathrm{Sr}}$ in neutral $^{87}\mathrm{Sr}$ has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ level makes ${\ensuremath{\nu}}_{\mathrm{Sr}}$ the best agreed-upon optical atomic frequency. We combine periodic variations in the $^{87}\mathrm{Sr}$ clock frequency with $^{199}\mathrm{Hg}^{+}$ and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant $\ensuremath{\alpha}$, electron-proton mass ratio $\ensuremath{\mu}$, and light quark mass. Furthermore, after $^{199}\mathrm{Hg}^{+}$, $^{171}\mathrm{Yb}^{+}$, and H, we add $^{87}\mathrm{Sr}$ as the fourth optical atomic clock species to enhance constraints on yearly drifts of $\ensuremath{\alpha}$ and $\ensuremath{\mu}$.