Nonlinear constants of motion for three-level quantum systems
F. T. Hioe, Joseph H. Eberly · Physical Review A · 1982
We use the eight-dimensional coherence vector $\stackrel{\ensuremath{\rightarrow}}{\mathrm{S}}$, recently introduced for three-level quantum systems, to derive three independent nonlinear constants of motion. Two of these were known previously, but not known to be related, and the third is new.