Multiparameter quantum metrology for general and adaptive strategies

arXiv:2611.01027v1 Announce Type: new Abstract: We develop a conic-programming framework for multiparameter estimation of quantum processes under different classes of sensing strategies. Estimation precision depends on the choice of input probe state and measurement and, when a channel is used multiple times, on the arrangement of channel uses and intermediate controls. We specify different strategy classes through linear normalization constraints on generalized measurements, and formulate the local estimation problem using linear constraints and a linear objective function. We show that the separable-cone program gives the exact precision limit under the local estimation conditions considered here, while cone relaxations yield Cram\'er-Rao-type lower bounds.