  Benchmarking a high-precision quantum operation is a big challenge for many
quantum systems in the presence of various noises as well as control errors.
Here we propose an $O(1)$ benchmarking of a dynamically corrected rotation by
taking the quantum advantage of a squeezed spin state in a spin-1 Bose-Einstein
condensate. Our analytical and numerical results show that tiny rotation
infidelity, defined by $1-F$ with $F$ the rotation fidelity, can be calibrated
in the order of $1/N^2$ by only several measurements of the rotation error for
$N$ atoms in an optimally squeezed spin state. Such an $O(1)$ benchmarking is
possible not only in a spin-1 BEC but also in other many-spin or many-qubit
systems if a squeezed or entangled state is available.
