  Quantum gravity is expected to contain descriptions of semiclassical
spacetime geometries in quantum superpositions. To date, no framework for
modelling such superpositions has been devised. Here, we provide a new
phenomenological description for the response of quantum probes (i.e.
Unruh-deWitt detectors) on a spacetime manifold in quantum superposition. By
introducing an additional control degree of freedom, one can assign a Hilbert
space to the spacetime, allowing it to exist in a superposition of spatial or
curvature states. Applying this approach to static de Sitter space, we discover
scenarios in which the effects produced by the quantum spacetime are
operationally indistinguishable from those induced by superpositions of Rindler
trajectories in Minkowski spacetime. The distinguishability of such quantum
spacetimes from superpositions of trajectories in flat space reduces to the
equivalence or non-equivalence of the field correlations between the superposed
amplitudes.
