  The standard axion-like particle explanation of the observed large-scale
coherent orientations of quasar polarisation vectors is ruled out by the recent
measurements of vanishing of circular polarisation. We introduce a more general
wave-packet formalism and show that, although decoherence effects between waves
of different frequencies can reduce significantly the amount of circular
polarisation, the axion-like particle hypothesis is disfavoured given the
bandwidth with which part of the observations were performed. Finally, we show
that a more sophisticated model of extragalactic fields does not lead to an
alignment of polarisations.
