Measurement-induced nonlocality in the W and Greenberger–Horne–Zeilinger superposition states*
Lin Qina), Bai Yan-Kuib), Ye Ming-Yonga)†, Lin Xiu-Mina)
       
N ( ρ a | b ) of the two-qubit reduced state of the n -qubit W–GHZ state varies as a function of cos 2 θ , which does not vary with the relative phase φ although ρ ab depends on φ . For any fixed θ not equal to π /2, i.e., cos 2 θ ≠ 0, N ( ρ a | b ) will decrease as n increases.