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Two players share the Bell state ∣Φ+⟩=(∣00⟩+∣11⟩)/2|\Phi^+\rangle = (|00\rangle + |11\rangle)/\sqrt{2}. Alice measures ZZ (input 0) or XX (input 1); Bob measures (Z+X)/2(Z+X)/\sqrt{2} (input 0) or (Z−X)/2(Z-X)/\sqrt{2} (input 1). The CHSH value is S=⟨Φ+∣(Z⊗B0+Z⊗B1+X⊗B0−X⊗B1)∣Φ+⟩S = \langle\Phi^+| (Z\otimes B_0 + Z\otimes B_1 + X\otimes B_0 - X\otimes B_1) |\Phi^+\rangle, and the optimal win probability of the CHSH game is 1/2+S/81/2 + S/8. What is this win probability?