Towards Doppler laser cooling of trapped Ba+ ions to near the ground state

Here, we present a route to achieve near ground state cooling of all motional modes using the same lasers and transitions to eventually bring the ions very close to their motional ground states by sideband cooling. Based on a past study of Doppler cooling of Ca^+ ions on a dipolar forbidden transition, we have recently theoretically looked more careful into strategies for more optimizing such cooling schemes for Ba^+ ions in the near future, applying muliti-watt lasers to drive the 2^S_1/2 – 2^D_3/2,5/2 transitions. Besides for many quantum technology applications of trapped ions leading to a much-reduced laser infrastructure, the presented cooling scheme enables complete background-free optical qubit readout in the blue-green through two-photon excitation in the orange and infrared.