  Current and planned observations of the cosmic microwave background (CMB)
polarization anisotropies, with their ever increasing number of detectors, have
reached a potential accuracy that requires a very demanding control of
systematic effects. While some of these systematics can be reduced in the
design of the instruments, others will have to be modeled and hopefully
accounted for or corrected a posteriori. We propose QuickPol, a quick and
accurate calculation of the full effective beam transfer function and of
temperature to polarization leakage at the power spectra level, as induced by
beam imperfections and mismatches between detector optical and electronic
responses. All the observation details such as exact scanning strategy,
imperfect polarization measurements, and flagged samples are accounted for. Our
results are validated on Planck high frequency instrument (HFI) simulations. We
show how the pipeline can be used to propagate instrumental uncertainties up to
the final science products, and could be applied to experiments with rotating
half-wave plates.
