Efficient classical simulation of the Deutsch-Jozsa and Simon's algorithms

TL;DR

This paper introduces a classical simulation framework for the Deutsch-Jozsa and Simon's quantum algorithms, demonstrating they do not require quantum resources for their solutions, thus challenging assumptions about their quantum advantage.

Contribution

The authors develop an efficient classical simulation method for these quantum algorithms, showing they lack genuine quantum speed-up and providing insights into quantum-classical computational boundaries.

Findings

Classical simulation matches quantum query complexity for both problems.

Quantum algorithms for these problems do not require quantum resources.

The simulation framework is efficiently implementable on classical probabilistic Turing machines.

Abstract

A long-standing aim of quantum information research is to understand what gives quantum computers their advantage. This requires separating problems that need genuinely quantum resources from those for which classical resources are enough. Two examples of quantum speed-up are the Deutsch-Jozsa and Simon's problem, both efficiently solvable on a quantum Turing machine, and both believed to lack efficient classical solutions. Here we present a framework that can simulate both quantum algorithms efficiently, solving the Deutsch-Jozsa problem with probability 1 using only one oracle query, and Simon's problem using linearly many oracle queries, just as expected of an ideal quantum computer. The presented simulation framework is in turn efficiently simulatable in a classical probabilistic Turing machine. This shows that the Deutsch-Jozsa and Simon's problem do not require any genuinely quantum resources, and that the quantum algorithms show no speed-up when compared with their corresponding classical simulation. Finally, this gives insight into what properties are needed in the two algorithms, and calls for further study of oracle separation between quantum and classical computation.