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

Abstract

The ${}^{1}S_0$-${}^{3}P_0$ clock transition frequency ${\nu }_{\mathrm{Sr}}$ 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 $1\times {10}^{-15}$ level makes ${\nu }_{\mathrm{Sr}}$ 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 $\alpha$, electron-proton mass ratio $\mu$, 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 $\alpha$ and $\mu$.