Symmetric three-qubit-state invariants
Alexander Meill, DAVID A. MEYER · Physical Review A · 2017
For pure symmetric three-qubit states there are only three algebraically independent entanglement measures; one choice is the pairwise concurrence $\mathcal{C}$, the three-tangle $\ensuremath{\tau}$, and the Kempe invariant $\ensuremath{\kappa}$. Using a canonical form for symmetric $n$-qubit states derived from their Majorana representation, we derive the explicit achievable region of triples $(\mathcal{C},\ensuremath{\tau},\ensuremath{\kappa})$.