Searching for a dipole-phonon interaction with CaO⁺ and Ca⁺

We will report our progress on searching for the dipole-phonon interaction between CaO⁺ and its axial secular motion in a CaO⁺ and Ca⁺ two-ion chain. The interaction between the dipole of a molecular ion in an ion chain and the phonon modes of the ion chain enables new tools for state preparation and measurement of molecular ions[1,2]. We have already demonstrated the near ground-state cooling of the axial motional modes of CaO⁺ via sympathetic sideband cooling with a co-trapped Ca⁺. We have also shown that the phonon state of the axial out-of-phase mode of the ion chain is maintained when the mode frequency is adiabatically ramped up or down [3]. This adiabatic ramping should allow for an adiabatic population transfer between molecular ion’s internal state and the phonon state. Experimental challenges include the mixture of molecular states at room temperature and the theoretical uncertainties in the molecular ion properties. We will discuss these challenges and present our experimental progress.

[1] W.C. Campbell & E.R. Hudson. Dipole-Phonon Quantum Logic with Trapped Polar Molecular Ions. Phys. Rev. Lett. 125, 120501 (2020).



[2] M. Mills, H. Wu, E.C. Reed, L. Qi, K.R. Brown, C. Schneider, M.C. Heaven, W.C. Campbell & E.R. Hudson. Dipole–phonon quantum logic with alkaline-earth monoxide and monosulfide cations. Phys. Chem. Chem. Phys. 22, 24964-24973 (2020).



[3] L. Qi, E.C. Reed, and K. R. Brown. Adiabatically controlled motional states of a ground-state cooled CaO⁺ and Ca⁺ trapped ion chain. arXiv preprint arXiv:2212.05105 (2022).