Speaker
Description
Singly ionized lutetium ($^{176}$Lu$^+$) has a unique level structure that provides multiple clock transitions. In combination with hyperfine averaging, two of these transitions ($^1{S}_0$ – ${}^3D_1$ & $^1{S}_0$ – ${}^3D_2$) present both a long lifetime and low sensitivity to the electromagnetic environment, which allows high performance clock operation on both transitions. Recently we have demonstrated clock comparison on the $^1{S}_0$ – ${}^3D_1$ at the low $10^{-18}$ level limited by clock stability, with an error budget that supports the capability to go well beyond $10^{-18}$.
The relative ease at which we are able to establish agreement between two independent frequency references is attractive both for applications and establishing a laboratory frequency reference. We discuss the advantages that lutetium offers with an emphasis on the unique possibilities afforded by the existence of two transitions within the one system. In particular, a frequency ratio measured within the one system provides an independent metric that can validate performance claims made on a single transition.
