Ultralight dark matter detection with trapped-ion interferometry

We explore how recent advances in the manipulation of single-ion wave packets open new avenues for detecting weak magnetic fields sourced by ultralight dark matter. A trapped ion in a “Schrödinger’s cat” state can be prepared with its spin and motional degrees of freedom entangled and be used as a matter-wave interferometer that is sensitive to the Aharonov-Bohm-like phase shift accumulated by the ion over its trajectory. The result of the spin-motion entanglement is a parametrically enhanced sensitivity to weak magnetic fields as compared with an unentangled ion in a trap. Taking into account the relevant boundary conditions, we demonstrate that a single trapped ion can probe unexplored regions of kinetically mixed dark-photon dark matter parameter space in the 10 − 15 eV ≲ m A ′ ≲ 10 − 14 eV mass window. We also show how such a table-top quantum device will also serve as a complementary probe of axionlike particle dark matter in the same mass window.