An Exact Quantum Query Algorithm Beyond Parity using Maiorana-McFarland (MM) type Bent functions.
Chandra Sekhar Mukherjee, Subhamoy Maitra
Abstract
The Exact Quantum Query model is the least explored query model, and almost all of the functions for which non-trivial query algorithms exist are symmetric in nature. In this paper we explore the Maiorana-McFarland(MM) type Bent functions, defined on all even $n$ variables. The (classical) Deterministic Query Complexity ($D(f)$) of all functions in this class is $n$. In this regard we construct an $\frac{n}{2} + \lceil \frac{n}{8} \rceil$ query exact quantum algorithm that is not a parity decision tree and evaluates a non-symmetric subclass of MM type Bent functions on $n$ variables consisting of $\left(2^{\lfloor \frac{n}{4} \rfloor}!\right)\left(2^{\lceil \frac{n}{4} \rceil}!\right) 2^{2^{\lfloor \frac{n}{4} \rfloor}}$ functions. Finally we also extend this technique for functions defined on odd values of $n$ using the Bent concatenation method. To the best of our knowledge, this is the first algorithm beyond parity for a general class of non-symmetric functions.