Sympathetic electromagnetically-induced-transparency ground state cooling of a ⁴⁰Ca⁺-²⁷Al⁺ pair in a ²⁷Al⁺ clock

Abstract We report on electromagnetically induced transparency cooling of 40Ca+ to sympathetically cool the three-dimensional secular modes of motion in a 40Ca+-27Al+ two-ion pair near the ground state. We observe simultaneous ground state cooling across all radial modes and axial modes of a 40Ca+-27Al+ ion pair, occupying a broader cooling range in frequency space over 3 MHz. The cooling time is observed to be less than 1 ms. The mean phonon number and heating rates of all motional modes are measured. This study is not only an important step for reducing the secular motion time-dilation shift uncertainty and uptime ratio of 27Al+ optical clock but is also essential for high-fidelity quantum simulations and quantum information processors using trapped ions.