Progress towards laser-free mixed-species gates with a near-motional frequency oscillating gradient

The choice of ion species for trapped ion quantum processors involves tradeoffs – lighter ions can enable faster interactions and have good qubit coherence times, but the laser wavelengths required for species such as Be⁺, Mg⁺, and Al⁺ are deep in the ultraviolet. The need for ultraviolet lasers can be reduced by performing entangling operations with microwave and rf magnetic field gradients instead, and such interactions have demonstrated high fidelities and improved speeds in recent years. Quantum logic state preparation and readout, together with sympathetic cooling, can eliminate the need for qubit species lasers by incorporating a helper species. However, the choice of helper species is limited because large mass disparities between species can make trapping and loading difficult and impact the efficiency of sympathetic cooling. Combining laser-free entangling gates with sympathetic cooling and quantum logic-based state preparation and readout allows us to take advantage of a lighter qubit ion species without requiring ultraviolet lasers. The addition of tunable parametric coupling between motional modes helps to speed up sympathetic cooling and laser-free entangling operations between ions with imbalanced mode participation. We present progress towards a mixed-ion species laser-free entangling gate with a near-motional oscillating gradient and tunable parametric motional-mode coupling.