Theoretical survey of unconventional quantum annealing methods applied to adifficult trial problem

TL;DR

This paper surveys unconventional quantum annealing techniques applied to a challenging artificial problem, demonstrating potential improvements in solution time scaling and guiding future quantum speedup research.

Contribution

It provides a theoretical overview of various novel quantum annealing modifications and evaluates their effectiveness on a difficult problem, highlighting promising directions for quantum speedup.

Findings

All methods improve solution time scaling in some regimes

Comparison helps identify promising quantum annealing paths

Potential for quantum speedup over classical algorithms

Abstract

We consider a range of unconventional modifications to Quantum Annealing (QA), applied to an artificial trial problem with continuously tunable difficulty. In this problem, inspired by "transverse field chaos" in larger systems, classical and quantum methods are steered toward a false local minimum. To go from this local minimum to the global minimum, all N spins must flip, making this problem exponentially difficult to solve. We numerically study this problem by using a variety of new methods from the literature: inhomogeneous driving, adding transverse couplers, and other types of coherent oscillations in the transverse field terms (collectively known as RFQA). We show that all of these methods improve the scaling of the time to solution (relative to the standard uniform sweep evolution) in at least some regimes. Comparison of these methods could help identify promising paths towards a demonstrable quantum speedup over classical algorithms in solving some realistic problems with near-term quantum annealing hardware.