Comparison of Two Sr Optical Lattice Clocks with $10^{-17}/\sqrt{\tau}$ Level Stability

I report on the use of a state-of-the-art ultrastable laser to improve the stability of the JILA 1D and 3D $^{87}$Sr lattice clocks. The ultrastable laser system utilizes a cryogenic Silicon reference cavity with a thermal noise limited instability of $4\times10^{-17}$. By performing an asynchronous comparison betweeen the two systems along with a self comparison of each clock individually we are able to rigorously determine the stability of both clocks. We infer a clock stability at the mid-$10^{-17}/\sqrt{\tau}$ level for our 1D system and high-$10^{-17}/\sqrt{\tau}$ level for our 3D system due to dead time associated with sample preparation. The 1D result represents a new record for a clock based on a single atomic ensemble.