Classical and Quantum Approaches to Reduced Basis Methods for Impurity Solvers

Impurity models are a central constituent of embedding frameworks such as dynamical mean-field theory (DMFT) and the ghost Gutzwiller approximation (gGA), where they act as simpler auxiliary systems representing realistic materials. Because they are correlated, solving for their ground state and dynamics remains a many-body problem, but their electron correlations are usually confined to a small part of the system, which makes them amenable to approximate treatments. Norman Hogan discusses solvers being developed for multi-orbital impurity models, including quantum computing approaches, reduced basis methods and the intersection of the two. Efficient and reliable solvers make it possible to explore the phases of multi-orbital impurity models, which are interesting in their own right, and accelerate the most expensive step in embedding frameworks, offering a pathway toward functional materials design.