Indexed on: 18 Oct '17Published on: 18 Oct '17Published in: arXiv - Quantum Physics
According to the geometric characterization of measurement assemblages and local hidden state (LHS) models, we propose a steering criterion which is both necessary and sufficient for two-qubit states under arbitrary measurement sets. A quantity S is introduced to describe the required local resources to reconstruct a measurement assemblage for two-qubit states. We show that the quantity S can be regarded as a quantification of steerability and be used to find out optimal LHS models. Finally we propose a method to generate unsteerable states, and construct some two-qubit states which are entangled but unsteerable under all projective measurements.