  Weak gravitational lensing by intervening large-scale structure induces a
distinct signature in the cosmic microwave background (CMB) that can be used to
reconstruct the weak-lensing displacement map. Estimators for individual
  Fourier modes of this map can be combined to produce an estimator for the
lensing-potenial power spectrum. The naive estimator for this quantity will be
biased upwards by the uncertainty associated with reconstructing individual
modes; we present an iterative scheme for removing this bias. The variance and
covariance of the lensing-potenial power spectrum estimator are calculated and
evaluated numerically in a
  $\Lambda$CDM universe for Planck and future polarization-sensitive CMB
experiments.
