Suppose a particle has 50% probability of being at location $A$, and 50% probability being at location $B$ (see double slit experiment). According to QM the particle is at both $A$ and $B$ at the same time, so is there a force of gravity between the two particle superpositions? Is there *self*-gravity when a wave-function reaches over a finite distance?

I cannot seem to wrap my head around this. Is the gravity a proportional fraction of the entire mass based on the probabilities. How do you combine a wavefunction with [Gauss' law of gravity](http://en.wikipedia.org/wiki/Gauss%27_law_for_gravity)? I have being trying to think about self-gravity for a long time now.