Quantum engineering with a tweezer array of ultracold CaF molecule*

Ultracold polar molecules trapped in programmable tweezer arrays are emerging as a promising system for quantum information processing and quantum simulation, due to their intrinsic electric dipole moment and intricate internal structures. The long-lived molecular rotational states provide robust qubit states, and molecules can exchange rotational excitations via dipolar interactions, producing long-range spin-exchange Hamiltonians with tunable spatial anisotropy. These interactions have been used to generate on-demand entanglement via two-qubit (two-molecule) gates, but a primary limitation in the gate fidelity has been the decoherence caused by thermal motion of the molecules [Science 382,1138-1143(2023)]].

Here, we report improvement in the coherence of the dipolar interactions and two-qubit gates by cooling an array of calcium monofluoride (CaF) molecules to near their motional ground state. Furthermore, we present progress towards creating a two-dimensional array of  molecules. The ability to create arbitrary patterns of CaF molecules in 2D, combined with the precise single-site control offered by the optical tweezer platform and tunable entangling interactions, opens the door to probing strongly-interacting many-body quantum phases. 

Finally, we highlight enhancement of molecular density and number through the implementation of a “conveyor-belt” MOT, which further optimizes the system for a range of applications utilizing high-density, optically trapped ultracold molecules, including precision measurement and the production of degenerate quantum gasses.