Physics: H₂ Molecule
The H₂ Hamiltonian in minimal basis (STO-3G) has energy:
E(R) depends on bond length R.
Ground state energy ≈ −1.137 Hartree at R=0.74Å.
Variational principle: ⟨ψ|H|ψ⟩ ≥ E_ground for all |ψ⟩.
The quantum circuit prepares a trial state, the classical optimizer adjusts θ to minimize ⟨H⟩. The optimum is the ground state.