LG/CY correspondence: the state space isomorphism

We prove the classical mirror symmetry conjecture for the mirror pairs constructed by Berglund, H"ubsch, and Krawitz. Our main tool is a cohomological LG/CY correspondence which provides a degree-preserving isomorphism between the cohomology of finite quotients of Calabi-Yau hypersurfaces inside a weighted projective space and the Fan-Jarvis-Ruan-Witten state space of the associated Landau-Ginzburg singularity theory.