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).