  The subject of this paper is the big quantum cohomology rings of symplectic
isotropic Grassmannians $\text{IG}(2, 2n)$. We show that these rings are
regular. In particular, by "generic smoothness", we obtain a conceptual proof
of generic semisimplicity of the big quantum cohomology for $\text{IG}(2, 2n)$.
Further, by a general result of Claus Hertling, the regularity of these rings
implies that they have a description in terms of isolated hypersurface
singularities, which we show in this case to be of type $A_{n-1}$. By the
homological mirror symmetry conjecture, these results suggest the existence of
a very special full exceptional collection in the derived category of coherent
sheaves on $\text{IG}(2, 2n)$. Such a collection is constructed in the appendix
by Alexander Kuznetsov.
