Inhomogeneous driving in quantum annealers can result in orders-of-magnitude improvements in performance

TL;DR

This paper demonstrates that inhomogeneous driving protocols in quantum annealers can dramatically improve their success probability in solving complex Ising problems, with potential practical and theoretical implications.

Contribution

The authors introduce a time-shift-based inhomogeneous driving protocol and experimentally show it can enhance performance by up to 10^8 times on certain problems.

Findings

Up to 10^8 times increase in success probability for some problems.

Significant performance improvements over homogeneous driving.

Potential for new insights into quantum annealer physics.

Abstract

Quantum annealers are special-purpose quantum computers that primarily target solving Ising optimization problems. Theoretical work has predicted that the probability of a quantum annealer ending in a ground state can be dramatically improved if the spin driving terms, which play a crucial role in the functioning of a quantum annealer, have different strengths for different spins; that is, they are inhomogeneous. In this paper we describe a time-shift-based protocol for inhomogeneous driving and demonstrate, using an experimental quantum annealer, the performance of our protocol on a range of hard Ising problems that have been well-studied in the literature. Compared to the homogeneous-driving case, we find that we are able to increase the probability of finding a ground state by up to $10^8 \times$ for some Weak-Strong-Cluster problem instances, and by up to $10^3 \times$ for more general spin-glass problem instances. In addition to being of practical interest as a heuristic speedup method, inhomogeneous driving may also serve as a useful tool for investigations into the physics of experimental quantum annealers.