We study the time evolution of a quantum system under the adiabatic condition using the path integral formulation. We reobtain Berry's phase for systems with nondegenerate and degenerate energy spectra, recovering the well-known results on the literature, and we verify the behavior of the phases under a change of basis of the energy instantaneous eigenstates. We also present a simple derivation of the Adiabatic Theorem[1] using the current notation. We have a comparative summary between the
Schrodinger's and the Heisenberg's pictures when the quantum system is driven by a time-dependent hamiltonian and we show how to aply the Adiabatic Theorem to any operator in the Heisenberg's picture that evolves under adiabactic conditions.
An alternative interpretation of the quantum adiabatic approximation is presented. This interpretation is based on the ideas originally advocated by David Bohm in his quest for establishing a hidden variable alternative to quantum mechanics. It indicates that the validity of the quantum adiabatic approximation is a sufficient condition for the separability of the quantum action function in the time variable. The implications of this interpretation for Berry’s adiabatic phase and its semi-classical limit are also discussed. Probably one of the best recognized applications of the quantum adiabatic approximation [1, 2] is in Berry’s derivation of the adiabatic geometrical phases [3]. Following Berry’s, by now, classical article on the adiabatic geometric phase [3], Hannay proposed a classical analogue of Berry’s phase [4] and Berry [5] and Anandan [6] explored the semiclassical limit of Berry’s phase and the classical analogue of the general, non-adiabatic geometric phase [7], respectively. The purpose of this note is to provide an alternative interpretation of the quantum adiabatic approximation which yields a natural approach to study the semi-classical limit of this approximation and consequently Berry’s phase.