Solution
= Solution
Charlie measures in the $X$ <basis> and sends one bit to Alice or Bob; the remaining pair becomes $|\Phi^+\rangle$ or $|\Phi^-\rangle$, corrected by a local $Z$. Alice then performs standard teleportation: CNOT from $|\xi\rangle$ to her GHZ qubit, Hadamard, two computational measurements, and sends the two outcomes to Bob, who applies the corresponding Pauli correction.