We give a natural filtration F on QH(G/B), which respects the quantum product structure. Its associated graded algebra
GrF(QH(G/B)) is isomorphic to the tensor product of QH(G/P) and a corresponding graded algebra of QH(P/B) after localization.
When the quantum parameter goes to zero, this specializes to the filtration on H(G/B) from the Leray spectral sequence
associated to the fibration P/B -> G/B −> G/P.