AC0∘MOD2 lower bounds for the Boolean Inner Product

AC0∘MOD2 circuits are AC0 circuits augmented with a layer of parity gates just above the input layer. We study AC0∘MOD2 circuit lower bounds for computing the Boolean Inner Product functions. Recent works by Servedio and Viola (ECCC TR12-144) and Akavia et al. (ITCS 2014) have highlighted this problem as a frontier problem in circuit complexity that arose both as a first step towards solving natural special cases of the matrix rigidity problem and as a candidate for constructing pseudorandom generators of minimal complexity. We give the first superlinear lower bound for the Boolean Inner Product function against AC0∘MOD2 of depth four or greater. Specifically, we prove a superlinear lower bound for circuits of arbitrary constant depth, and an Ω˜(n2) lower bound for the special case of depth-4 AC0∘MOD2.