  We study quantum noise and decoherence induced by gravitons. We derive a
Langevin equation of geodesic deviation in the presence of gravitons. The
amplitude of noise correlations tells us that large squeezing is necessary to
detect the noise. We also consider the decoherence of spatial superpositions of
two massive particles caused by gravitons in the vacuum state and find that
gravitons could give a relevant contribution to the decoherence. The
decoherence induced by gravitons would offer new vistas to test quantum gravity
in tabletop experiments.
