Modern Michelson-Morley Experiment using Cryogenic Optical Resonators

We report on a new test of Lorentz invariance performed by comparing the resonance frequencies of two orthogonal cryogenic optical resonators subject to Earth’s rotation over $\sim 1\mathrm{y}\mathrm{r}$. For a possible anisotropy of the speed of light $c$, we obtain ${\Delta }_{\theta }c/c_0=(2.6\pm 1.7)\times {10}^{-15}$. Within the Robertson-Mansouri-Sexl (RMS) test theory, this implies an isotropy violation parameter $\beta -\delta -\frac{1}{2}=(-2.2\pm 1.5)\times {10}^{-9}$, about 3 times lower than the best previous result. Within the general extension of the standard model of particle physics, we extract limits on seven parameters at accuracies down to ${10}^{-15}$, improving the best previous result by about 2 orders of magnitude.