  Inflationary gravitational waves (GW) contribute to the curl component in the
polarization of the CMB. Cosmic shear--gravitational lensing of the CMB--
converts a fraction of the dominant gradient polarization to the curl
component. Higher-order correlations can be used to map the cosmic shear and
subtract this contribution to the curl. Arcminute resolution will be required
to pursue GW amplitudes smaller than those accessible by Planck. The finite
cutoff in CMB power at small scales leads to a minimum detectable GW amplitude
corresponding to an inflation energy near 10^15 GeV.
