Embargoed until 2024-10-20
Author
Date
2021Type
- Doctoral Thesis
ETH Bibliography
yes
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Abstract
Two-level systems (TLSs) are paradigmatic for quantum mechanics. The TLS description is simple, exactly solvable, and yet tremendously powerful in representing a wealth of phenomena with high precision. Being also the archetype of a quantum bit, the TLS faces a dichotomy between controlled interaction, enabling quantum operations, and uncontrolled interaction which leads to decoherence, i.e. the loss of quantum information. Hence, protection against decoherence is required.
Crystal field (CF) states of rare-earth (RE) ions doped into solids realize TLSs and offer protection, e.g. via their symmetry. In this work, the coherence and relaxation properties of two RE ions (Holmium and Terbium) doped into LiYF4 were studied.
Dipolar interaction among the TLSs in LiTbxY1-xF4 plays an ambiguous role. While close and strongly interacting Tb3+ ions form pairs with superior coherence, single ions relax and decohere quickly because of interaction. In addition, disorder can significantly decelerate interaction dynamics through localization, which enhances coherence times. Due to quasi-many-body-localization, i.e. quasi-localization of a many-body system despite the presence of interaction, coherence times were found to be enhanced by almost three orders of magnitude.
Moreover, the low-energy electronuclear Hamiltonian of Ho3+ ions in LiYF4, spectral line widths, and decoherence mechanisms were studied, contributing to the general understanding of quasi-localization in LiTbxY1-xF4.
The symmetry of the CF states is also related to magnetism. This circumstance was used to dynamically induce magnetic moments in LiTbxY1-xF4 through coherent superpositions of single and pair states. Rabi oscillations of the TLS demonstrate coherent control of the emergent dynamic moment.
Finally, an outlook is provided on the potential for universal quantum computing using the electronuclear wavefunctions of RE ions and prospects for investigating many-body physics at the example of interacting TLSs in these fascinating compounds. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000510678Publication status
publishedExternal links
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Contributors
Examiner: Aeppli, Gabriel
Examiner: Ronnøw, Henrik M.
Examiner: Coppersmith, Susan N.
Examiner: Gerber, Simon
Examiner: Müller, Markus
Examiner: Sigg, Hans
Publisher
ETH ZurichOrganisational unit
09489 - Aeppli, Gabriel / Aeppli, Gabriel
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ETH Bibliography
yes
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