DMRG for Multi-Component Quantum Systems: A Symmetry-Aware and Unified Framework

Recent advances in high-resolution spectroscopy and cavity quantum technologies have driven growing interest in multicomponent quantum chemistry, where electronic degrees of freedom are treated on an equal footing with other quantum particles. Here, we present a unified symmetry-aware density matrix renormalization group (DMRG) framework for multicomponent quantum chemistry. By decoupling physical model specification from tensor-network representation and numerical optimization, new multicomponent models are introduced through symmetry quantum numbers, local basis, and operators, without modifying the underlying tensor algorithms. Built upon a mature tensor infrastructure, the framework provides a reusable symmetry-aware numerical engine, allowing new models to be implemented through concise Python-level specifications while fully reusing the optimized computational backend. The framework is demonstrated through symmetry-adapted nuclear-electronic orbital (NEO) and cavity quantum electrodynamics (CQED) DMRG calculations, yielding accurate electronic structures, excited-state energies, and polaritonic properties. This work establishes a reusable and extensible computational framework for symmetry-aware multicomponent quantum chemistry.