Super-Polynomial Quantum Speed-ups for Boolean Evaluation Trees with Hidden Structure

We give a quantum algorithm for evaluating a class of boolean formulas (such as NAND trees and 3-majority trees) on a restricted set of inputs. Due to the structure of the allowed inputs, our algorithm can evaluate a depth n tree using O(n2+logω) queries, where ω is independent of n and depends only on the type of subformulas within the tree. We also prove a classical lower bound of nΩ(log logn) queries, thus showing a (small) super-polynomial speed-up.