Super-quantum states in SU(2) invariant $3 \times N$ level systems

Abstract: Nonclassicality of quantum states is expressed in many shades, the most stringent of them being a new standard introduced recently in [Phys. Rev. A 89, 062110 (2014)]. This is accomplished by expanding the notion of local hidden variables (LHV) to generalised local hidden variables (GLHV), which renders many nonlocal states also classical. We investigate these super-quantum states (called exceptional in [Phys. Rev. A 89, 062110 (2014)]) in the family of $SU(2)$ invariant $3 \times N$ level systems. We show that all super-quantum states admit a universal geometrical description, and that they are most likely to lie on a line segment in the manifold, irrespective of the value of $N$. We also show that though the super - quantum states can be highly mixed, its relative rank with respect to the uniform state is always less than that of a state which admits a GLHV description.