Raman sideband cooling of molecules in an optical tweezer array to the 3-D motional ground state

Ultracold polar molecules are potentially interesting for quantum information processing and searches for physics beyond the Standard Model (BSM). Laser cooling to ultracold temperatures is an established technique for trapped diatomic and triatomic molecules. Further cooling of the molecules to near the motional ground state in a trap is crucial for reducing dephasing, which can limit gate fidelity and BSM searches. In this work, we demonstrate Raman sideband cooling of CaF molecules in optical tweezers to near their motional ground state, with average motional occupation quantum numbers of n_x=0.16(12), n_y=0.17(17) (radial directions), n_z=0.22(16) (axial direction) and a 3-D motional ground state probability of 54±18%. This points the way increased molecular coherence times in optical tweezers for robust quantum computation and simulation applications.