Failures of the adiabatic approximation in quantum tunneling time

Abstract

In this Brief Report, we investigate the validity of the adiabatic approximation in the tunneling time problem of a two-level atomic wave packet transmitting through a laser beam. We calculate the tunneling time of ground-state atoms using adiabatic approximation and compare it to the exact solution. We find that the adiabatic solution misses an important interference dip in the tunneling time which indicates that the adiabatic approximation is not always valid although the adiabatic conditions are well satisfied.