Nonclassicality thresholds for multiqubit states: Numerical analysis

States that strongly violate Bell’s inequalities are required in many quantum-informational protocols as, for example, in cryptography, secret sharing, and the reduction of communication complexity. We investigate families of such states with a numerical method which allows us to reveal nonclassicality even without direct knowledge of Bell’s inequalities for the given problem. An extensive set of numerical results is presented and discussed.

Figure 1

The bars represent, for several families of quantum states, the critical visibilities, which are necessary to falsify a local realistic description in two setting experiments. The additional line in some cases corresponds to the value of the critical visibility in a three-setting experiment.