Strong monogamy conjecture for multiqubit entanglement: The four-qubit   case
  We investigate the distribution of bipartite and multipartite entanglement in multiqubit states. In particular we define a set of monogamy inequalities sharpening the conventional Coffman-Kundu-Wootters constraints, and we provide analytical proofs of their validity for relevant classes of states. We present extensive numerical evidence validating the conjectured strong monogamy inequalities for arbitrary pure states of four qubits. 
Bartosz Regula, Sara Di Martino, Soojoon Lee, Gerardo Adesso
quant-ph cond-mat.stat-mech math-ph math.MP