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

O'Connor, Daniel; Fry-Bouriaux, Louis; Warburton, Paul; (2022) Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model. Physical Review A , 105 (2) , Article 022410. 10.1103/PhysRevA.105.022410. Green open access

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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.

Type: Article
Title: Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevA.105.022410
Publisher version: https://doi.org/10.1103/PhysRevA.105.022410
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher's terms and conditions.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10143388
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