Search

Grover's algorithm, orginally conceived as a means of searching an unordered database, can also be used to extract solutions from the result sets generated by quantum computations. The Grover algorithm exploits the concept of an oracle function, which abstracts the process of matching a search item (returning 1 for a match and 0 otherwise), where searching for 1 target item in a search space of size $N$ scales as $\mathcal{O}(\sqrt{N})$ oracle queries. In this article, we explore the idea of associating a separate oracle with each bit of the matching condition, obtaining multiple partial oracle functions which can be tested independently. Exploring this idea leads to a multi-stage hybrid search algorithm, whose performance can fall within a wide range, anywhere between $\mathcal{O}(\sqrt{N})$ (same as Grover) or $\mathcal{O}(\log(N))$. The algorithm is validated against the simplest kind of search scenario, where the incoming index bits are scrambled using a permutation operation.