Trapped ion optical clocks and tests of the equivalence principle (Dr. Ekkehard Peik)

The ¹⁷¹Yb⁺ optical clock that is based on an extremely narrow S-F electric octupole transition possesses a favorable combination of small systematic uncertainty and high sensitivity for such tests because of the strongly relativistic character of the excited state. In a comparison of two ¹⁷¹Yb⁺ single-ion clocks over six months we have experimentally demonstrated their agreement on the 10^-18 level and have improved limits on violations of local Lorentz invariance for electrons by two orders of magnitude. A future nuclear clock based on the low-energy transition in Th-229 may bring further advances in accuracy and additional opportunities for searches for new physics. Results from hyperfine spectroscopy of the Th-229 isomer have recently provided experimental data on relevant properties of this unusual nucleus.