Karol Kowalski, Pacific Northwest National Laboratory (PNNL)

Novel and predictive modeling tools for overcoming exponential computational barriers in computational chemistry are needed to describe chemical transformations that involve challenging quasi-degenerate electronic states. These states are commonly encountered in modeling chemical processes related to catalysis, actinide chemistry, nitrogen fixation, and energy storage materials.  We have recently developed rigorous many-body coupled-cluster downfolding techniques to address these challenges and to represent many-body quantum problems in reduced-size active spaces.  To illustrate the performance of  DUCC formalisms based on finite commutator expansions, we will provide results obtained with the Quantum Phase Estimator (QPE) and Variational Quantum Eigensolver (VQE) for benchmark molecular systems described by Gaussian and plane-wave basis sets. We also discuss perspectives of integrating the downfolding formalism with recently developed quantum algorithms for connected moments expansions and executing combined workflow on quantum hardware to describe properties of the ground and excited electronic states.