LSPE-SWIPE only. Ratio between the mean angular power spectrum of either pure B modes only (solid lines) or E–B leakage residuals (dashed lines) after having applied the iterative B decomposition correction and that of corresponding input maps. The cases with 1 (red), 2 (blue), 4 (magenta), and 9 (green) iterations are shown. 200 different realisations of CMB have been considered, including lensing and a primordial tensor signal with r = 0.01. The trend of dashed lines highlights the reduction of E–B leakage residuals obtained by performing the iterations. The trend of solid lines, instead, the loss of power suffered due to the B–E leakage when applying the iterative B decomposition. A binning scheme of Δℓ = 3 for ℓ ≤ 4, Δℓ = 6 for 5 ≤ ℓ ≤ 28, and Δℓ = 15 for ℓ ≥ 29 is employed. The error-bars highlight the uncertainty on the mean at 1σ, estimated from the dispersion of the angular power spectra of the simulations divided by . Readers can refer to the main text for details.