Six conditions uniquely force δP(i)=ε(P_QM(i)-1/n)F(x). Sign reversal at P_QM=1/n is exact and forced by normalization. Positivity bound -1≤εF≤1/(n-1) proved. Testable at ε=10⁻³ in 27 seconds on a transmon qubit (T₂=200μs). No decoherence model produces a zero fixed at 1/n under state sweep.