Thesis
Information-theoretical witnesses of non-classicality in hybrid systems
- Abstract:
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Quantum theory is one of the most successful theories in modern physics. It has been extensively tested in the microscopic domain, always with remarkable success. Yet, these tests do not currently extend in a conclusive way to all physical systems and across all scales. This leaves open the question of whether quantum theory provides a truly universal description of reality, especially in regimes where direct experimental access is limited, such as the gravitational field or complex macroscopic biological systems.
This Thesis addresses this question through the study of hybrid systems, where a well-controlled quantum sector interacts with an unknown sector whose underlying description may or may not be quantum. It contributes to the emerging framework of information-theoretical witnesses of non-classicality, where the quantum sector is used as a probe to test the nature of the unknown system under minimal assumptions.
We first examine spatial entanglement-based witnesses, in which the ability of an unknown system to mediate entanglement between two quantum probes by local means provides a sufficient condition for its non-classicality. We extend this framework by quantitatively showing that locally mediated quantum correlations lower bound the non-commutativity of the observables of the mediator, within quantum theory.
We then introduce a novel class of single-probe temporal witnesses, where non-classicality is inferred from the temporal evolution of a probe under a global conservation law. We prove that quantum coherent evolution under such a constraint can only be mediated by a non-classical system, and propose an application to light-harvesting processes in photosynthetic complexes.
Finally, we develop a temporal entanglement-based witness. Here, the sufficient condition for the non-classicality of the unknown system is the ability to mediate temporal entanglement relative to the probe's local conserved quantity and a non-commuting observable. This result provides a temporal extension of the spatial entanglement-based witness, representing a promising route for the development of the next generation of tests to probe the universality of quantum theory in previously inaccessible fields such as gravity and biology.
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- Files:
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(Preview, Dissemination version, pdf, 3.5MB, Terms of use)
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Authors
Contributors
+ Vedral, V
- Institution:
- University of Oxford
- Division:
- MPLS
- Department:
- Physics
- Sub department:
- Atomic & Laser Physics
- Role:
- Supervisor
+ Marletto, C
- Institution:
- University of Oxford
- Division:
- MPLS
- Department:
- Physics
- Sub department:
- Atomic & Laser Physics
- Role:
- Supervisor
+ Deutsch, D
- Institution:
- University of Oxford
- Division:
- MPLS
- Department:
- Physics
- Role:
- Examiner
+ Gu, M
- Institution:
- Nanyang Technological University
- Role:
- Examiner
+ University of Oxford
More from this funder
- Funder identifier:
- https://ror.org/052gg0110
- Funding agency for:
- Di Pietra, G
- Programme:
- The Clarendon Fund Scholarship in partnership with the Oxford-Thatcher Graduate Scholarship and an Atomic and Laser Physics Studentship
- DOI:
- Type of award:
- DPhil
- Level of award:
- Doctoral
- Awarding institution:
- University of Oxford
- Language:
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English
- Keywords:
- Subjects:
- Deposit date:
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2026-10-26
- ARK identifier:
Terms of use
- Copyright holder:
- Giuseppe Di Pietra
- Copyright date:
- 2026
- Notes:
- Temporal witnesses of non-classicality in a macroscopic biological system, Tunable non-Markovian dynamics in a collision model: an application to coherent transport, and Temporal witnesses of non-classicality and conservation laws are derived from this thesis.
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