Observation of strong and tunable light-induced dipole-dipole interactions between optically levitated nanoparticles

Arrays of optically trapped nanoparticles have emerged as a promising platform for the study of complex non-equilibrium phenomena. Analogous to atomic many-body systems, one of the crucial ingredients is the ability to precisely control the interactions between particles. However, the optical interactions studied thus far only provide conservative optical binding forces of limited tunability. Here we demonstrate a coupling mechanism that is orders of magnitude stronger and has new qualitative features. These effects arise from the previously unexplored phase coherence between the optical fields that drive the light-induced dipole-dipole interaction. In addition, polarization control allows us to observe electrostatic coupling between charged particles in the array. Our results pave the way for a fully programmable many-body system of interacting nanoparticles with tunable dissipative and nonreciprocal interactions, which are instrumental for exploring entanglement and topological phases in arrays of levitated nanoparticles.