Applications of quantum computing to real materials: quantum simulations of conducting polymers
File(s)
Author(s)
Sticher, Lorenzo Friedrich Carlo
Type
Thesis or dissertation
Abstract
Electronic structure theory is considered an extremely promising application of both near-term and fault-tolerant quantum computers. The variational quantum eigensolver (VQE) has been studied extensively as an algorithm for solving simple chemical systems on noisy quantum devices. However, given the current constraints of these devices, benchmarks have focused mostly on lattice and small molecular systems. The gap between realistic, useful electronic structure simulations and current idealised benchmark systems remains large. With this thesis we aim to bridge this gap, by considering simulations of trans-polyacetylene (TPA) as benchmark system. This system is industrially relevant and displays non-trivial physics, but is also importantly modelled by the relatively simple Su-Schrieffer-Heeger (SSH) model.
Using VQE simulations of the SSH model, we assess the feasibility of quantum computing from the viewpoint of an electronic structure practitioner. A particular emphasis rests on the calculation of molecular forces, an understudied application, but of great importance in realistic electronic structure calculations. Throughout our work, we find that within our implementation the shot- and circuit-noise present on realistic quantum devices impose limitations on VQE simulations of SSH that put them beyond the scope of current algorithmic and hardware capabilities. Analysing our calculations with a particular focus on the (in-)applicability of the variational principle in realistic calculations, we find that the consideration of molecular forces is crucial to appropriately evaluating the feasibility of VQE for realistic electronic structure calculations. Furthermore, we find that the SSH description of TPA provides a valuable benchmark for assessing the performance of and guiding future improvements in both algorithms and hardware.
Using VQE simulations of the SSH model, we assess the feasibility of quantum computing from the viewpoint of an electronic structure practitioner. A particular emphasis rests on the calculation of molecular forces, an understudied application, but of great importance in realistic electronic structure calculations. Throughout our work, we find that within our implementation the shot- and circuit-noise present on realistic quantum devices impose limitations on VQE simulations of SSH that put them beyond the scope of current algorithmic and hardware capabilities. Analysing our calculations with a particular focus on the (in-)applicability of the variational principle in realistic calculations, we find that the consideration of molecular forces is crucial to appropriately evaluating the feasibility of VQE for realistic electronic structure calculations. Furthermore, we find that the SSH description of TPA provides a valuable benchmark for assessing the performance of and guiding future improvements in both algorithms and hardware.
Version
Open Access
Date Issued
2026-01-31
Date Awarded
2026-08-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Haynes, Peter
Kim, Myung Shik
Knolle, Johannes
Publisher Department
Department of Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)