Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model

Abstract

Quantum annealing in the transverse-field Ising model (TFIM) with open-system dynamics is known to use thermally assisted tunneling to drive computation. However, it is still subject to debate whether quantum systems in the presence of decoherence are more useful than those using classical dynamics to drive computation. We contribute to this debate by introducing the perturbed ferromagnetic chain (PFC), a chain of frustrated subsystems where the degree of frustration scales inversely with the perturbation introduced by a tunable parameter. This gives us an easily embeddable gadget whereby problem hardness can be tuned for systems of constant size. We outline the properties of the PFC and compare classical spin-vector Monte Carlo (SVMC) variants with the adiabatic quantum master equation. We demonstrate that SVMC methods get trapped in the exponentially large first-excited-state manifold when solving this frustrated problem, whereas evolution using quantum dynamics remains in the lowest energy eigenstates. This results in significant differences in ground-state probability when using either classical or quantum annealing dynamics in the TFIM.

Mapping State Transition Susceptibility in Quantum Annealing

“…Alongside expanding its possible application domains, understanding the dynamics of how the D-Wave quantum annealers sample problems has been a subject of research [60][61][62][63][64]. For example, one of the examples of a notable property of quantum annealing in the transverse field Ising model is that it does not sample ground states fairly for optimization problems which have multiple optimal solutions [65][66][67][68][69][70][71][72].…”