Molecular Quantum Computations on a Protein

We present the implementation of a fragment-based, quantum-centric supercomputing workflow for computing molecular electronic structure using quantum hardware. The workflow is applied to predict the relative energies of two conformers of the 303-atom Trp-cage miniprotein. The methodology employs wave function-based embedding (EWF) as the underlying fragmentation framework, in which all atoms in the system are explicitly included in the configuration interaction (CI) simulations. We employ sample-based quantum diagonalization (SQD) solver for challenging fragments and full configuration interaction (FCI) solver for trivial fragments. The EWF-(FCI,SQD) results are compared against EWF-MP2 and EWF-CCSD benchmarks. The impact of fragmentation on the predicted relative energies of the Trp-cage conformers is further evaluated by comparison with unfragmented RI-MP2 and DLPNO-CCSD calculations. The results demonstrate that large-scale electronic configuration interaction (CI) simulations of protein systems containing hundreds or even thousands of atoms can be realized through the combined use of quantum and classical computing resources.