Progress towards evaporation and sideband cooling of laser cooled CaF molecules

The wide-ranging scientific applications of ultracold molecules have inspired significant efforts in cooling and controlling molecules in the single quantum state level. Many potential applications are still hampered by the finite temperatures experimentally achieved. As temperatures are reduced further, motional decoherence rates are suppressed and fidelities increase, opening new opportunities for quantum simulations and computation. One of the most successful cooling methods for atomic species, evaporative cooling, requires a high elastic rate and large ratio of elastic to inelastic collisions. While this ratio is typically low for most molecules, using microwaves, we engineer a repulsive barrier between molecules, shielding inelastic loss and increasing the rate of elastic collisions. Using optically trapped CaF molecules, we demonstrate that the elastic rate can be increased while the inelastic loss is suppressed to reach a ratio of 50. By adiabatically lowering the trap depth to force evaporation of the hottest molecules, we were able to observe a drop in temperature of the sample when shielding was enabled compared to a control sample without shielding. Future improvements in initial density and number would allow for more effective evaporation.Evaporative cooling is useful for bulk samples, but to use molecules in single optical tweezer arrays requires single particle cooling. To this end we report progress towards sideband cooling of CaF molecules to the ground motional state of an optical tweezer.