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Institute’s Seminar

Institute’s Seminar

Towards Frequency Metrology of the Optical Hyperfine Structure of Highly Charged Ions Using Quantum Logic

Peter Micke
BASE Collaboration, CERN, Geneva

Highly charged ions (HCI) are extreme atoms with favorable properties for the study of fundamental physics and the search for new physics [1]. They feature a simple atomic structure due to a small number of bound electrons, strong electromagnetic fields to which the electrons are exposed, and a low sensitivity to external perturbing fields [2]. Recent developments such as Coulomb crystallization [3], the application of quantum logic [4], and algorithmic ground-state cooling [5] have made HCI accessible for use in the most accurate measurement devices: optical atomic clocks, which today reach fractional uncertainties of 10-18.

In this talk, I will briefly review how we overcame all previous obstacles to realize the first optical atomic clock based on an HCI. I will present our frequency ratio measurement of the ground-state fine-structure transition in Ar13+ at 441 nm against the electric-octupole transition in 171Yb+ at a fractional uncertainty of about 1x10-16, limited by statistics and improving the previous uncertainty level by eight orders of magnitude [6]. By comparing the transition frequencies of the two isotopes 40Ar13+ and 36Ar13+, we determined the isotope shift with a relative uncertainty of 5.7x10-11, an improvement of nine orders of magnitude that resolves the QED nuclear recoil contribution [6]. In the second part of my talk, I will discuss how the measurement concept can be extended to optical hyperfine-structure transitions which are available in heavy hydrogen-like or lithium-like HCI.

  1. M. S. Safronova et al., Rev. Mod. Phys. 90, 025008 (2018)
  2. M. G. Kozlov et al., Rev. Mod. Phys. 90, 045005 (2018)
  3. L. Schmöger et al., Science 347, 1233–1236 (2015)
  4. P. Micke et al., Nature 578, 60–65 (2020)
  5. S. A. King et al., Phys. Rev. X 11, 041049 (2021)
  6. S. A. King et al., Nature (in print)
Seminar room HI-Jena, Fröbelstieg 3