Computational Role of Multiqubit Tunneling in a Quantum Annealer

TL;DR

This paper demonstrates that multiqubit tunneling in a noisy quantum annealer can outperform classical methods in solving complex optimization problems, highlighting the computational advantage of quantum phenomena.

Contribution

It introduces a non-perturbative theory of open quantum dynamics and experimentally shows quantum tunneling's role in surpassing classical optimization techniques.

Findings

Quantum tunneling enables reaching the global minimum in 16-qubit problems.

Quantum tunneling outperforms thermal hopping in problems with up to 200 qubits.

Many-body quantum phenomena can improve solutions to hard optimization problems.

Abstract

Quantum tunneling, a phenomenon in which a quantum state traverses energy barriers above the energy of the state itself, has been hypothesized as an advantageous physical resource for optimization. Here we show that multiqubit tunneling plays a computational role in a currently available, albeit noisy, programmable quantum annealer. We develop a non-perturbative theory of open quantum dynamics under realistic noise characteristics predicting the rate of many-body dissipative quantum tunneling. We devise a computational primitive with 16 qubits where quantum evolutions enable tunneling to the global minimum while the corresponding classical paths are trapped in a false minimum. Furthermore, we experimentally demonstrate that quantum tunneling can outperform thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive. Our results indicate that many-body quantum phenomena could be used for finding better solutions to hard optimization problems.