  We study the interaction between gravitational waves and quantum matter such
as Bose-Einstein condensates, super-fluid Helium, or ultra-cold solids,
explicitly taking into account the changes of the trapping potential induced by
the gravitational wave. As a possible observable, we consider the change of
energy due to the gravitational wave, for which we derive rigorous bounds in
terms of kinetic energy and particle number. Finally, we discuss implications
for possible experimental tests.
