Ground State Laser Cooling of Trapped Atoms Using Electromagnetically Induced Transparency

A laser cooling method for trapped atoms is presented which achieves ground state cooling by exploiting quantum interference in a Λ-shaped arrangement of atomic levels driven by two lasers.¹ The scheme is technically simpler than existing methods of sideband cooling, yet it can be significantly more efficient, in particular when several motional modes are involved. We have applied the method to a single Calcium ion in a Paul trap,² coupling a single laser to the Zeeman structure of its S_1/2 → P_1/2 dipole transition at 397 nm. We have achieved more than 90% ground-state occupation probability. By suitably tuning the laser parameters, we obtain simultaneous ground-state cooling of two oscillator modes. This is of great practical importance for the implementation of quantum logic schemes with trapped ions.