We shall continue and expand our investigations of the fundamental aspects of quantum theory and gravitation, with a view towards experimental applications on the one hand and obtaining theoretical insights on the other hand. We shall try to (1) obtain new quantum effects, possibly involving gravity, with experimental consequences, (2) resolve paradoxes arising from effects we have previously discovered, which may lead to new effects, (3) obtain greater insight into the quantum measurement problem and its possible relation to quantum gravity, and (4) investigate quantum geometry, in particular its relation to supersymmetry.