  We explore the polytope structures for genuine entanglement, biseparability
and full biseparability of multi-qubit GHZ diagonal states. We show that
biseparable GHZ diagonal states make hypersimplices, and fully biseparable
states make the convex hulls of simplices and cubes. We also compute precise
volumes for genuine entanglement, biseparability and full biseparability among
all GHZ diagonal states.
