 Impossibility of universal identical-basis perfect correlations

For two systems of equal dimension $d\ge 2$, no joint pure state guarantees equal outcome labels whenever both systems undergo the same arbitrary basic measurement. Equal outcomes in the computational basis would force $|\Psi ⟩={\sum }_j{c}_j|jj⟩$. On any two coordinates j,k, changing both bases to the real sum/difference pair makes the different-outcome amplitude $(c_j-c_k)/2$, so all coefficients must agree. Changing both to the imaginary-phase pair makes a different-outcome amplitude $(c_j+c_k)/2$, so those coefficients must also be negatives. They must all vanish, contradicting normalization. The one-dimensional case is an exception.

The requirement of all complex bases matters. A maximally entangled vector $d^{-1/2}{\sum }_j|jj⟩$ does produce matching labels if one party uses a basis and the other its coordinatewise complex conjugate basis. Conjugate-state steering from a maximally entangled pair gives this conjugation explicitly. Identical real bases are a special case, not evidence for identical arbitrary complex bases.