  Effective Field Theory techniques are used to study the leading order quantum
corrections to the gravitational wave backreaction. The effective stress-energy
tensor is calculated and it is shown that it has a non-vanishing trace that
contributes to the cosmological constant. By comparing the result obtained with
LIGO's data, the first bound on the amplitude of the massive mode is found:
$\epsilon < 1.4\times 10^{-33}$.
