  For a compact locally symmetric space $\XG$ of non-positive curvature, we
consider sequences of normalized joint eigenfunctions which belong to the
principal spectrum of the algebra of invariant differential operators. Using an
$h$-\psdiff\ calculus on $\XG$, we define and study lifted quantum limits as
weak$^*$-limit points of Wigner distributions. The Helgason boundary values of
the eigenfunctions allow us to construct Patterson--Sullivan distributions on
the space of Weyl chambers. These distributions are asymptotic to lifted
quantum limits and satisfy additional invariance properties, which makes them
useful in the context of quantum ergodicity. Our results generalize results for
compact hyperbolic surfaces obtained by Anantharaman and Zelditch.
