Towards optical clocks based on highly charged ions for tests of fundamental physics and improved frequency standards

Optical clocks based on highly charged ions (HCIs) offer promising avenues for exploring new physics. Among these are searches for possible time-variation of the fine structure constant, dα/dt *1/α, and tests of quantum electrodynamics (QED). In addition, HCI-based clocks offer reduced sensitivities to external perturbations such as blackbody radiation making them promising candidates for the development of high-accuracy optical frequency standards. Examples include Pr¹⁰⁺ which is predicted to have a high sensitivity to dα/dt *1/α and Ar⁹⁺ which is interesting for studies of QED ^1,2. Here we give an update on the development of a compact electron beam ion trap (EBIT) that will be used as a source of HCIs, a cryogenic radiofrequency (rf) Paul trap for clock operation, and a transport beamline designed to deliver HCIs to the Paul trap. In the future, a single Be⁺ "logic" ion will be co-trapped with an HCI "clock" ion for sympathetic cooling and quantum-logic readout operations.

[1] S. G. Porsev, et al., Phys. Rev. A 110, 042823 (2024).

[2] M. G. Kozlov, et al., Rev. Mod. Phys. 90, 045005 (2018).