= CHSH axes for an entangled pure two-qubit state
{c}
{title2=$S=2\sqrt{1+s^2}$}
For the <Schmidt-basis Pauli correlation tensor>, choose Alice's axes $\mathbf e_z,\mathbf e_x$ and Bob's $(\mathbf e_z\pm s\mathbf e_x)/\sqrt{1+s^2}$. The <CHSH inequality> expression is $2\sqrt{1+s^2}$. It exceeds two exactly when both <Schmidt coefficients> are nonzero, reaching $2\sqrt2$ for maximal <quantum entanglement>. A <product state> gives $s=0$ and saturates rather than violates the inequality.
Back to article page
