Relativistic Quantum Simulation of Hydrogen Sulfide for Hydrogen Energy via Hybrid Quantum-Classical Algorithms

We present a relativistic quantum simulation framework for modeling hydrogen sulfide (H2S) decomposition relevant to hydrogen energy applications. The approach integrates Dirac-Coulomb relativistic quantum chemistry with the variational quantum eigensolver (VQE), implemented on a hybrid quantum-classical architecture. Using quantum algorithms based on Jordan-Wigner encoding and relativistic integrals, we simulate ground-state energies and potential energy surfaces for H2, H2O, and H2S molecules. Results demonstrate that the relativistic VQE correctly reproduces known energy shifts and molecular trends. Optimizer performance, energy variance, and Pauli term complexity are also evaluated. The findings offer insight into scalable quantum simulations of chemically and physically significant systems involving heavy atoms.