An energetic perspective on rapid quenches in quantum annealing

TL;DR

This paper develops analytical tools to understand and improve rapid quench dynamics in quantum annealing, offering insights into energy behavior, local dynamics, and heuristic parameter estimation for better quantum optimization performance.

Contribution

It introduces new methods for analyzing rapid quenches, including energy analysis, local dynamics detection, and heuristic parameter estimation, enhancing quantum annealing understanding.

Findings

Monotonic quenches outperform random guessing.

Pre-annealing improves quantum walk performance.

Tools enable heuristic Hamiltonian parameter estimation.

Abstract

There are well developed theoretical tools to analyse how quantum dynamics can solve computational problems by varying Hamiltonian parameters slowly, near the adiabatic limit. On the other hand, there are relatively few tools to understand the opposite limit of rapid quenches, as used in quantum annealing and (in the limit of infinitely rapid quenches) in quantum walks. In this paper, we develop several tools which are applicable in the rapid quench regime. Firstly, we analyse the energy expectation value of different elements of the Hamiltonian. From this, we show that monotonic quenches, where the strength of the problem Hamiltonian is consistently increased relative to fluctuation (driver) terms, will yield a better result on average than random guessing. Secondly, we develop methods to determine whether dynamics will occur locally under rapid quench Hamiltonians, and identify cases where a rapid quench will lead to a substantially improved solution. In particular, we find that a technique we refer to as "pre-annealing" can significantly improve the performance of quantum walks. We also show how these tools can provide efficient heuristic estimates for Hamiltonian parameters, a key requirement for practical application of quantum annealing.