CMB EE power spectra for various reionization models. The green dashed line shows the ﹩{\rm{\tanh }}(z)﹩ model with ﹩{z}_{{\rm{re}}}=8﹩, yielding a total τ = 0.057. The red and blue dashed lines show equivalent ﹩{\rm{\tanh }}(z)﹩ models with τ of 0.079 and 0.091, respectively. The red and blue solid lines show fiducial ﹩{\rm{\tanh }}(z)﹩ + Pop III.1 reionization models with z_flash = 20 and 25 that also yield τ of 0.079 and 0.091, respectively. The shaded region around the red solid line shows a cosmic-variance-limited error range to the z_flash = 20 model, assuming 70% sky coverage, i.e., a reasonable approximation for expected LiteBIRD uncertainties. The gray circles and error bars show the Planck NPIPE data (Planck Collaboration Int. LVII 2020; M. Tristram et al. 2021).