Exposedness of Choi type entanglement witnesses and applications to   lengths of separable states
  We present a large class of indecomposable exposed positive linear maps between three dimensional matrix algebras. We also construct two qutrit separable states with lengths ten in the interior of their dual faces. With these examples, we show that the length of a separable state may decrease strictly when we mix it with another separable state. 
Kil-Chan Ha and Seung-Hyeok Kye
quant-ph math.OA