This IRG overcomes the limits of natural optical materials by building metamaterials from quantum clusters, particles, and quantum wells, harnessing quantum confinement, correlations, and ultimately entanglement as new levers of optical function. Mesoscale assemblies are hierarchically integrated with classical electromagnetic mode engineering to reach ultrahigh nonlinearities and ultrafast response over an unprecedented operational range, from terahertz to visible frequencies at femto-to-nanosecond timescales. First- and second-principles calculations and deep learning are used to explore and predict structure-function relationships in quantum metamaterials, and to build a closed-loop framework for their design, synthesis, and characterization.