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In the Page–Geilker experiment, radioactive-decay counts supplied a quantum random decision that determined which of two macroscopically distinct configurations of lead masses the experimenters placed around a Cavendish torsion balance. In each observed branch, the balance deflected in the direction predicted by the mass configuration recorded in that branch, with a strong correlation between the decision and the measured gravitational torque.

The unobserved alternative was the prediction of the simplest semiclassical Einstein equation, in which one classical metric is sourced by the expectation value $⟨T_{\mu \nu }⟩$ of the matter stress-energy tensor. If the universal wavefunction does not collapse, the two nearly equally weighted mass configurations both contribute to that expectation value. Their opposite torques should then largely average away, and the balance should show little branch-correlated deflection. That behavior was not seen.

The experiment was designed to go beyond earlier observations of ordinary gravity and quantum matter. It deliberately created macroscopically different mass distributions in different quantum branches and tested whether the gravitational field followed the branch actually observed or the expectation-value average over all branches. It ruled out that simplest no-collapse semiclassical coupling under the experiment's assumptions. It supplied indirect evidence for quantum gravity, while leaving more elaborate classical-quantum couplings logically possible.

Yes in both directions. The Page–Geilker experiment tests whether a classical gravitational field is sourced by the expectation value of macroscopically superposed matter configurations. The Colella–Overhauser–Werner experiment uses the Earth's effectively classical field as an external potential and therefore does not distinguish an expectation-value semiclassical source law from a quantized gravitational field.

Conversely, the Colella–Overhauser–Werner experiment directly observes coherent matter-wave interference and a gravitationally generated relative phase in a neutron wavefunction. Page and Geilker did not maintain and recombine coherent branches of the macroscopic source, and their torsion-balance measurement was not an interference experiment. Thus their experiment did not test the neutron gravitational phase effect. The experiments probe opposite sides of the coupling: quantum matter responding coherently to gravity, and gravity responding to branch-dependent quantum matter.