  In this work, we provide a detailed analysis of the issue of encoding of
quantum information which is invariant with respect to arbitrary Lorentz
transformations. We significantly extend already known results and provide
compliments where necessary. In particular, we introduce novel schemes for
invariant encoding which utilize so-called pair-wise helicity -- a physical
parameter characterizing pairs of electric-magnetic charges. We also introduce
new schemes for ordinary massive and massless particles based on states with
fixed total momentum, in contrast to all protocols already proposed, which
assumed equal momenta of all the particles involved in the encoding scheme.
Moreover, we provide a systematic discussion of already existing protocols and
show directly that they are invariant with respect to Lorentz transformations
drawn according to any distribution, a fact which was not manifestly shown in
previous works.
