  There are discernible and fundamental differences between clocks, waves and
physical states in classical physics. These fundamental concepts find a common
expression in the context of quantum physics in gravitational fields; matter
and light waves, quantum states and oscillator clocks become quantum synonymous
through the Planck-Einstein-de Broglie relations and the equivalence principle.
With this insight, gravitational effects on quantum systems can be simply and
accurately analyzed. Apart from providing a transparent framework for
conceptual and quantitative thinking on matter waves and quantum states in a
gravitational field, we address and resolve with clarity the recent
controversial discussions on the important issue of the relation and the
crucial difference between gravimetery using atom interferometers and the
measurement of gravitational time dilation.
