= Polarization correlations of the Psi-plus Bell state
{title2=$E(\alpha,\beta)=-\cos2(\alpha+\beta)$}
For $|\Psi^+\rangle=(|01\rangle+|10\rangle)/\sqrt2$, the <Pauli operator> correlations are $\langle XX\rangle=1$, $\langle ZZ\rangle=-1$, and $\langle XZ\rangle=\langle ZX\rangle=0$. Substituting the <measurement of linear photon polarization> into $\langle M(\alpha)\otimes M(\beta)\rangle$ gives $\sin2\alpha\sin2\beta-\cos2\alpha\cos2\beta=-\cos2(\alpha+\beta)$. In particular, opposite physical angles give perfect anticorrelation. The sum of angles here depends on this choice of <Bell state> and basis conventions.
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