Fig. 5. Cost analysis in QCT.

(A) Dependence on the signal photon number n_S of the total error probability (p_err), false positive (p₀₁), and false negative (p₁₀). The maximum likelihood postprocessing used in this case minimizes p_err. The reference process is considered strongly peaked around the value τ₀ = 0.8, while the defective one is chosen uniformly distributed with mean $\overline{\mathrm{\tau }}=0.9$ and half-width δ = 0.09. (B) A situation similar to that of (A) is considered, but we use a biased maximum likelihood postprocessing with bias coefficient b = 0.6 (see the main text for details). (C) We fix photon number to n_S = 500 and analyze the dependence of the cost C on b. All the other parameters are equal to those of the previous panels. (D) Optimum value of b as a function of S.