We show here that the Λ and V configurations of three-level atomic
systems, while they have recently been shown to be equivalent for many
important physical quantities when driven with classical fields [M. B. Plenio,
Phys. Rev. A \textbf{62}, 015802 (2000)], are no longer equivalent when coupled
via a quantum field. We analyze the physical origin of such behavior and show
how the equivalence between these two configurations emerges in the
semiclassical limit.Comment: 4 pages, 1 figure. To appear as Brief Report in Physical Review