Magic polarization trapping of polar molecules for tunable dipolar interactions

Ultracold polar molecules interact via the electric dipole-dipole coupling, which induces rotational transitions that entangle the individual molecules. These rotational transitions' intrinsic coherence and abundance make polar molecules an attractive platform for quantum simulation and computation. We prepare an optical tweezer array of individual NaCs molecules in the ground state of their internal and motional degrees of freedom. With < 0.5 um control over molecule position and site-selective rotational state control, we expect coherent kHz rate dipolar oscillations. Our decoherence is dominated by tweezer intensity noise due to the differential polarizability between rotational states. We reduce the difference in polarizability by three orders of magnitude by changing the tweezer polarization to a 'magic' ellipticity. We observe an order of magnitude increase in coherence time with a spin-echo pulse sequence. Due to NaCs' relatively small hyperfine coupling, we can further rotate the tweezer polarization to tune and maximize the dipolar interaction rate. The achieved coherence time should be sufficient to observe dipolar exchange interactions in adjacent molecule pairs, bringing tunable interactions to an array of individually trapped molecules.