Now we have come to the interesting part where Alice, Bob, and Carol decided to adopt a quantum strategy. The three of them now share a tripartite entangled state | ψ ψ ⟩ ⟩ = 1 2 ( | 000 ⟩ ⟩ + | 111 ⟩ ⟩ ) , known as the GHZ state.