Chen, Hongxiang;
(2025)
Application of variational algorithms in quantum computation.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Variational quantum algorithms are a class of techniques that are particularly suitable for near-term applications and borrow many ideas from classical variational methods in quantum chemistry and machine learning. We developed variational quantum algorithms to improve error-correcting codes as well as modelling quantum mechanical systems, hence looking at both the long-term and short-term perspectives in quantum computing. For error correction, we designed an algorithm that generates logical gates when encoding and decoding circuits are given as input. We demonstrated its capability in numerical simulations and generated non-trivial logical gates for small-size errorcorrecting codes. For modelling quantum mechanical systems, we considered an approach based on the Green function, which describes the response of the system to external perturbations. We adapted traditional formulae for the Green function so that they can be computed on near-term quantum hardware, and we conducted both numerical and experimental studies on IBM prototype quantum processors for proof-of-principle demonstrations. Our results highlighted the limitations of the approach, and we suggested potential alternatives.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Application of variational algorithms in quantum computation |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS 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 Computer Science UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10205621 |
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