  Electronic states in 2D materials can exhibit pseudospin degrees of freedom,
which allow for unique carrier-field interaction scenarios. Here, we
investigate ultrafast sublattice pseudospin relaxation in graphene by means of
polarization-resolved photoluminescence spectroscopy. Comparison with
microscopic Boltzmann simulations allows to determine a lifetime of the
optically aligned pseudospin distribution of $12\pm 2\,\text{fs}$. This
experimental approach extends the toolbox of graphene pseudospintronics,
providing novel means to investigate pseudospin dynamics in active devices or
under external fields.
