  When neutrinos propagate over long distances, the mass eigenstate components
of a flavor eigenstate will become spatially separated due to their different
group velocities. This can happen over terrestrial distance scales if the
neutrino energy is of order MeV and if the neutrino is localized (in a quantum
mechanical sense) to subatomic scales. For example, if the Heisenberg
uncertainty in the neutrino position is below 0.01 Angstrom, neutrino
decoherence can be observed in reactor neutrinos using a large liquid
scintillator detector.
