Parameter estimation for mixed states from a single copy
arXiv:quant-ph/0702211 · doi:10.1103/PhysRevA.75.062101
Abstract
Given a single copy of a mixed state of the form ρ=λρ_1+(1-λ)ρ_2, what is the optimal measurement to estimate the parameter λ, if ρ_1 and ρ_2 are known? We present a general strategy to obtain the optimal measurements employing a Bayesian estimator. The measurements are chosen to minimize the deviation between the estimated- and the true value of λ. We explicitly determine the optimal measurements for a general two-dimensional system and for important higher dimensional cases.
9 pages, 3 figures, v2: small changes, to appear in PRA