In my research this morning, I came across a collection of interesting articles from the 1970s where researchers observed a shift in the phase of a neutron's quantum wave function because of a change in the gravitational potential. This is similar to the Aharanov-Bohm effect, but using a gravitational rather than an electromagnetic potential. If you're a university student like myself, all the journal links below should be accessible via your university's library. The experiment design is described in Experimental Test of Gravitationally Induced Quantum Interference The results of the experiment are presented in: Observation of Gravitationally Induced Quantum Interference Another similar experiment by the same researchers was described in: Observation of a Phase Shift of a Neutron Due to Precession in a Magnetic Field For a nice primer of all things Aharanov-Bohm with reference to the above mentioned experiments, see Reviews of Modern Physics: The quantum effe...