We present the use of algorithms and code coupling strategies to model neutral excitations in complex heterogeneous materials to provide a description of light activated processes for energy sustainability and quantum information science. First, we describe the simulation of excitons using density matrix perturbation theory, where an interoperability strategy between the first principles molecular dynamics Qbox (http://qboxcode.org/) code, the many-body perturbation theory WEST (http://west-code.org/) code and Tensorflow enables us to evaluate the dielectric screening from first principles with a finite field method or with a surrogate model obtained with machine learning. Second, we focus on the simulation of neutral excitations that take place in localized regions within a material, e.g., color centers. Using input from density functional theory, code coupling allows us to define and solve an effective Hamiltonian that describes the low-lying excitations of a defect embedded in a periodic crystal. These examples benefit from the use of the latest developments in high-performance computing architectures, which include pre-exascale capable machines and quantum processors.
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