Application of generalized Hellmann-Feynman theorem in deriving internal energy of some Hamiltonians in quantum optics

摘要

In this paper, after introducing the generalized Hellmann-Feyiinian (or Feynmau-IIellinann) theorem (GHFT) for mixed-state ensemble average, we apply GHFT to deriving the internal energy of some Hamiltonian systems in quantum optics. The ensemble average energy contributed from each separated term involved in the Hamiltonian is also considered. We thus develop an alternate approach for deriving the internal energy.