Characterizing resources for multiparameter estimation of SU(2) and SU(1,1) unitaries

Quantum 10, 2130 (2026). https://doi.org/10.22331/q-2026-06-08-2130 We analyze the task of estimating a multi-parameter unitary belonging to the $SU(2)$ or $SU(1,1)$ groups, in a two-bosonic-mode scenario and investigate the scaling of the precision in terms of the total particle number. For the $SU(2)$ case, the total particle number is conserved by the evolution and we discuss optimal states in fixed-$n$ subspaces, identifying eigenstates of $J_z^2$ as useful resources, even allowing simultane