Classification of four-qubit states by means of a stochastic local operation and the classical communication invariant and semi-invariants
Dafa Li, Xiangrong Li, Hongtao Huang, Xinxin Li · Physical Review A · 2007
We show there are at least 28 distinct true stochastic local operations and classical communication (SLOCC) entanglement classes for four qubits by means of SLOCC invariant and semi-invariants and derive the number of degenerate SLOCC classes for $n$ qubits.