The stabilizer group for an
n-qubit state
∣ϕ⟩ is the set of all invertible local operators (ILO)
g=g1⊗g2⊗⋯⊗gn, $ g_i\in \mathcal{GL}(2,\mathbb{C})$ such that
∣ϕ⟩=g∣ϕ⟩. Recently, G. Gour
et al. \cite{GKW} presented that almost all
n-qubit state
∣ψ⟩ own a trivial stabilizer group when
n≥5. In this article, we consider the case when the stabilizer group of an
n-qubit symmetric pure state
∣ψ⟩ is trivial. First we show that the stabilizer group for an n-qubit symmetric pure state
∣ϕ⟩ is nontrivial when
n≤4. Then we present a class of
n-qubit symmetric states
∣ϕ⟩ with the trivial stabilizer group. At last, we prove that an
n-qubit symmetric pure state owns a trivial stabilizer group when its diversity number is bigger than 5, which confirms the main result of \cite{GKW} partly.
The stabilizer group for an
n-qubit state
∣ϕ⟩ is the set of all invertible local operators (ILO)
g=g1⊗g2⊗⋯⊗gn, $ g_i\in \mathcal{GL}(2,\mathbb{C})$ such that
∣ϕ⟩=g∣ϕ⟩. Recently, G. Gour
et al. \cite{GKW} presented that almost all
n-qubit state
∣ψ⟩ own a trivial stabilizer group when
n≥5. In this article, we consider the case when the stabilizer group of an
n-qubit symmetric pure state
∣ψ⟩ is trivial. First we show that the stabilizer group for an n-qubit symmetric pure state
∣ϕ⟩ is nontrivial when
n≤4. Then we present a class of
n-qubit symmetric states
∣ϕ⟩ with the trivial stabilizer group. At last, we prove that an
n-qubit symmetric pure state owns a trivial stabilizer group when its diversity number is bigger than 5, which confirms the main result of \cite{GKW} partly.
We refine recent local unitary entanglement classification for symmetric pure states of
n qubits (that is, states invariant under permutations of qubits) using local unitary stabilizer subgroups and Majorana configurations. Stabilizer subgroups carry more entanglement distinguishing power than do the stabilizer subalgebras used in our previous work. We extend to mixed states recent results about local operations on pure symmetric states by showing that if two symmetric density operators are equivalent by a local unitary operation, then they are equivalent via a local unitary operation that is the {\em same} in each qubit. A geometric consequence, used in our entanglement classification, is that two symmetric pure states are local unitary equivalent if and only if their Majorana configurations can be interchanged by a rotation of the Bloch sphere.