  We compute one-loop corrections to the power spectrum of the curvature
perturbation in single-field slow-roll inflation arising from gravitons and
inflaton interactions. The quantum corrections due to gravitons to the power
spectrum of the inflaton field are computed around the time of horizon crossing
and their effect on the curvature perturbation is obtained on superhorizon
scales through the delta-N formalism. We point out that one-loop corrections
from the tensor modes are of the same magnitude as those coming from scalar
self-interactions, therefore they cannot be neglected in a self-consistent
calculation.
