Tensor-power reduction of PBR overlap ($⟨{\psi }_1^{\otimes n}|{\psi }_2^{\otimes n}⟩=⟨{\psi }_1|{\psi }_2{⟩}^n$)

If two pure quantum states overlap by $(1/\sqrt{2}{)}^{1/n}$, their $n$-copy states have overlap $1/\sqrt{2}$. Each block spans an effective qubit, with orthonormal basis $e_0={\Psi }_1$ and $e_1=\sqrt{2}{\Psi }_2-{\Psi }_1$. Applying the two-block PBR exclusion measurement for zero and plus uses $2n$ independently prepared copies. A common single-copy ontic overlap of positive mass remains positive under this finite tensor power.