Electron–photon field dynamics: numerically exact calculations of multi-state molecule systems interacting with a single-mode coherent photon field Original Research Article

We perform numerically exact calculations of quantum dynamics for an arbitrary molecule model system composed of M states interacting with a single-mode photon field. Two- and three-state molecule systems interacting with a single-mode coherent photon field are considered. The time development of molecular and photon density matrices and the entropy of a molecule is investigated in order to understand the dynamics of molecule–photon field systems. We also examine the quantum phase properties (cos2 φ (〈cos2 φ̂〉) and Δ cos2 φ(≡〈cos2 φ̂〉−〈cos φ̂〉2)) of photon field systems by using Pegg–Barnett phase operator (φ̂), and elucidate the relations among the collapses and revivals phenomena of molecular ground-state populations and time-development behavior in quantum phase of photon field. It is predicted for multi-state molecule systems with equivalent energy intervals that variations in their transition moments remarkably affect the quantum phase distribution of the external single-mode photon field and the features of time development of molecular and photon density matrices.