Sympathetic Electromagnetically-Induced-Transparency Laser Cooling of Motional Modes in an Ion Chain

We use electromagnetically-induced-transparency laser cooling to cool motional modes of a linear ion chain. As a demonstration, we apply electromagnetically-induced-transparency cooling on ²⁴Mg⁺ ions to cool the axial modes of a ⁹Be⁺-²⁴Mg⁺ ion pair and a ⁹Be⁺-²⁴Mg⁺-²⁴Mg⁺-⁹Be⁺ ion chain, thereby sympathetically cooling the ⁹Be⁺ ions. Compared to previous implementations of conventional Raman sideband cooling, we achieve approximately an order-of-magnitude reduction in the duration required to cool the modes to near the ground state and significant reduction in required laser intensity.