We present a method to improve the lattice effective field theory description of the shape of atomic nuclei by applying unitary transformations to the eigenvectors of the Hamiltonian.
The employed unitary operator $U$ is constructed as a reflection transformation from the original and the desired wave functions.
Similarly to a derivative expansion, it can be improved systematically so that one can tune the $\langle r^n \rangle$ expectation values order by order for the two-particle system.
Moreover, the effects of $U$ in the three-particle system have been investigated.
The method might be helpful to reduce lattice artifacts in radii and electromagnetic moments of nuclei.