Progress towards laser-free mixed-species coupled-mode gates with a near-motional-frequency oscillating magnetic field gradient

Quantum logic operations that exchange information between different co-trapped charged species – atoms, molecules, or other particles – can enable precise preparation, control, and measurement of the ‘data’ species via the ‘helper’ species, even if the data species lacks easy cooling or readout. Adding laser-free entanglement operations based on microwave and radiofrequency magnetic fields and field gradients to such a system enables processing on the data and helper species with no lasers while all non-unitary operations for the data species are realized indirectly by dissipatively coupling to the helper species. However, the need for a relatively close charge-to-mass ratio match between the helper and data species restricts the choice of helper species. A poor match means imbalanced motional mode participations, especially in the radial modes used in many laser-free gate implementations, which drastically slows down mixed-species entangling operations. This can be mitigated by introducing tunable coupling between different motional modes, speeding up quantum logic operations mediated by the hybridized modes of such a mixed-species ion crystal. We present progress towards a laser-free mixed-species entangling gate mediated by coupled motional modes, which uses multiple microwave and radiofrequency oscillating fields and field gradients.