Quantum Search Algorithm with more Reliable Behaviour using Partial Diffusion

Abstract

In this paper, we will define a quantum operator that performs the inversion about the mean only on a subspace of the system (partial diffusion operator). This operator is used in a quantum search algorithm that runs in O(N/M) for searching an unstructured list of size N with M matches such that, 1 ⩽ M ⩽ N. We will show that the performance of the algorithm is more reliable than known fixed operator quantum search algorithms especially for multiple matches where we can get a solution after a single iteration with probability over 90% if the number of matches is approximately more than one‐third of the search space. A performance comparison with Grover’s algorithm will be provided.