Figure 2

(a) Level scheme of the Rydberg ⁸⁸Sr⁺ ion. The levels nD_3/2 and n′P_1/2 are Rydberg levels. Two laser fields are applied which drive the transitions |1〉 ↔ |2〉 and |2〉 ↔ |3〉 with Rabi frequencies Ω_1,2 and detunings Δ_2,3. The quadrupole field couples the levels |2〉 and |4〉 with peak Rabi frequency Ω. This transition oscillates with radio trap frequency ω. The level |4〉 has an energy shift Δ₄. (b) Using the effective picture, the system is reduced to three state ladder system with rescaled Rabi frequencies \({{\rm{\Omega }}^{\prime} }_{1,2}\) and detunings \({{\rm{\Omega }}^{\prime} }_{2}\).