Robustness of Entanglement for Bell Decomposable States
  We propose a simple geometrical approach for finding the robustness of entanglement for Bell decomposable states of 2 otimes 2 quantum systems. It is shown that the robustness of entanglement is equal to the concurrence. We also present an analytical expression for two separable states that wipe out all entanglement of these states. Finally the random robustness of these states is also obtained. 
S.J. Akhtarshenas, M.A. Jafarizadeh