A Quantum Algorithm for the Commutativity of Finite Dimensional Algebras

A quantum procedure for testing the commutativity of a finite dimensional algebra is introduced. This algorithm, based on Grover's quantum search, is shown to provide a quadratic speed-up (when the number of queries to the algebra multiplication constants is considered) over any classical algorithm (both deterministic and randomized) with equal success rate and shown to be optimal among the class of probabilistic quantum query algorithms. This algorithm can also be readily adapted to test commutativity and hermiticity of square matrices, again with quadratic speed-up. The results of the experiments carried out on a quantum computer simulator and on one of IBM's 5-qubit quantum computers are presented.