  We examine a macroscopic system in a quantum superposition of two spatially
separated localized states as a detector for a stream of weakly interacting
relativistic particles. We do this using the explicit example of neutrinos with
MeV-scale energy scattering from a solid object via neutral-current
neutrino-nucleus scattering. Presuming the (anti-)neutrino source to be a
nuclear fission reactor, we utilize the estimated flux and coherent elastic
neutrino-nucleus cross section to constrain the spatial separation ${\Delta}$x
and describe the temporal evolution of the sensing system. Particularly, we
find that a potentially measurable relative phase between quantum superposed
components is obtained for a single gram scale mass placed in a superposition
of spatial components separated by $10^{-14}$m under sufficient cooling and
background suppression.
