As shown on the right, for the quantum correlation of spin (assuming 100% detection efficiency), the prediction of local hidden variable theory is represented by solid line, and the prediction of quantum mechanics is represented by dotted line. Assuming that the angle θ between the two straight axes is between the above basic angles, the establishment of the local hidden variable theory means that the quantum correlation changes linearly. However, according to the theory of quantum mechanics, quantum correlation should change at the angle of cosine cos θ.