Highly Charged Ion Optical Clocks to Test Fundamental Physics
Piet O. Schmidt (MPI für Dynamik und Selbstorganisation)

Highly charged ions (HCI) have many favorable properties for tests of fundamental physics and as potential next-generation optical atomic frequency standards. However, up until recently the most accurate laser spectroscopy on any HCI was performed on the 17 Hz wide fine-structure transition in Ar13+ with 400 MHz resolution, lagging almost twelve orders of magnitude behind state-of-the-art optical clocks. We present the first coherent laser spectroscopy of an HCI using techniques developed in the context of quantum information processing with trapped ions. A novel quantum algorithmic cooling scheme has been developed and implemented, which reduces motional shifts to below the 10-18 level. We have performed an absolute frequency measurement, including a full error budget for the Ar13+ HCI clock, which demonstrates that HCI optical clocks with systematic uncertainty below 10-18 become feasible. Finally, prospects for 5th force tests based on isotope shift spectroscopy of Ca+/Ca14+ isotopes and the high-sensitivity search for a variation of the fine-structure constant using HCI will be presented. This work paves the way towards optical clocks based on highly charged ions with a high sensitivity to a change in fundamental constants and other tests of beyond standard model physics.