According to Equation (???), \[\begin{align}\begin{aligned} \Big(\langle \psi_1 | \langle 0 | \hat{U}^\dagger \Big) \Big(\hat{U} | \psi_2 \rangle |0\rangle \Big) &= \Big(\langle \psi_1| \l...According to Equation (???), (⟨ψ1|⟨0|ˆU†)(ˆU|ψ2⟩|0⟩)=(⟨ψ1|⟨ψ1|e−iϕ1)(eiϕ2|ψ2⟩|ψ2⟩)=e−i(ϕ1−ϕ2)(⟨ψ1|ψ2⟩)2. Here, ϕ1 and ϕ2 are the phase factors from Equation (???) for the two ch…