  The subject of the work are pairs of linearly coupled PT-symmetric dimers.
Two different settings are introduced, namely, straight-coupled dimers, where
each gain site is linearly coupled to one gain and one loss site, and
cross-coupled dimers, with each gain site coupled to two lossy ones. The latter
pair with equal coupling coefficients represents a "PT-hypersymmetric"
quadrimer. We find symmetric and antisymmetric solutions in these systems,
chiefly in an analytical form, and explore the existence, stability and
dynamical behavior of such solutions by means of numerical methods. We thus
identify bifurcations occurring in the systems, including spontaneous symmetry
breaking and saddle-center bifurcations. Simulations demonstrate that evolution
of unstable branches typically leads to blowup. However, in some cases unstable
modes rearrange into stable ones.
