We have used that the first two cumulants are the mean κ 1 = ⟨∆u⟩ p = µ and the variance κ 2 = var p (∆u) = σ 2 . Consequently, the KL divergence, Eq. ( ), is given by a sum of the higher-order cumulants. The leading term is half the variance. For small errors in the energy, |∆u| ≪ 1, the cumulants of order n = 3 and higher can be ignored,