An Almost-Quadratic Lower Bound for Quantum Formula Size
Vwani Roychowdhury, Farrokh Vatan · arXiv (Cornell University) · 1999
We show that Nechiporuk's method for proving lower bound for Boolean formulas can be extended to the quantum case. This leads to an n^2 / log^2 n lower bound for quantum formulas computing an explicit function. The only known previous explicit lower bound for quantum formulas (by Yao) states that the majority function does not have a linear-size quantum formula.