Yi, Bin;
(2023)
Quantum Entanglement and Quantum Causal Analysis.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
In this thesis, I consider two broad areas: the generation and verification of entanglement between large masses, and the analysis of causality in quantum dynamics. While the former is an extension of quantum mechanics in hitherto unexplored regimes such as for large masses and gravity, the latter provides a tool to probe quantum mechanics in complex networks. The first part of the thesis introduces a new methodology, namely, "spatial qubits", to the study of non-classicality of macroscopic objects. Essentially, it allows one to treat a continuous variable system as an effective qubit. This offers us a way to detect the entanglement between a spin and a path in a Stern-Gerlach apparatus, which has never been verified to date. We offer a way to observe it. It also enables one to observe the entanglement between two neutral large masses induced by the Casimir interaction. This works in a regime of non-Gaussian states of the two masses, and can evidence the quantum nature of macroscopic forces. As a separate application, we apply the same technique to witness the quantum nature of gravity via a table-top experiment. This approach has the advantage of not requiring ancillary degrees of freedom such as spins, as well as not requiring a precise closure of an interferometer, to evidence the entanglement. However, here we find it necessary to prepare a highly position squeezed state of a mechanical system. The other part of the thesis adopts concepts from classical causal analysis to the quantum regime. In particular, we generalize the notion of Liang-Kleeman information flow to quantum networks. The key feature of this theory is that an intervention is applied to the system and then the resulting changes on the target are observed. Causal influence is then quantified by relevant quantum entropic quantities such as the von Neumann entropy and quantum relative entropy. The presence of entanglement in the quantum domain uniquely manifests itself through some counterintuitive flows of information which we exemplify in small networks.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Quantum Entanglement and Quantum Causal Analysis |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. 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 UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10166674 |
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