Dold, Gavin Patrick;
(2020)
milliKelvin ESR of rare-earth doped crystals using superconducting resonators.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Rare-earth doped crystals have proven to be of considerable interest for quantum information processing, with demonstrations of quantum memories and the potential for coherent microwave–optical conversion as part of a quantum network. By interfacing these rare-earth based technologies with superconducting devices, they can complement existing technologies — which form the basis of many state-of-the-art quantum computers — forming a hybrid quantum information processing architecture exhibiting the advantages of fast superconducting processors alongside the extended coherence time and frequency conversion available from rare-earths. This thesis demonstrates the suitability of a widely used rare-earth doped crystal, yttrium orthosilicate (Y2SiO5 or YSO) doped with 145Nd or with 171Yb, as a substrate for fabrication of superconducting resonators. Designs for these resonators are presented with simulations of their electromagnetic modes, and their fabrication detailed. These devices are cooled to milliKelvin temperatures in a dilution refrigerator in order to investigate properties of the device and its coupling to electron spin transitions within the substrate where a coupling rate of the order gens/2π =1.2–7.1 MHz is observed. Dielectric loss due to two-level systems is measured with a loss-tangent tan δ = 4*10−6, and a coupling between resonator and spins is observed to have a high cooperativity C = 8–250. The superconducting resonator is then used to perform pulsed spectroscopy of electron spin resonance (ESR) transitions in the high-cooperativity regime, measuring two-pulse coherence times of T2 = (409 ± 14) μs for 200 ppm 145Nd:Y2SiO5 and T2 = (1170 ± 90) μs for 50 ppm 171Yb:Y2SiO5. Chirped pulses are used to invert spin magnetisation and drive arbitrary rotations, enabling the measurement of relaxation dynamics and Rabi oscillations. Dynamical decoupling sequences are explored as a method for extending coherence time. Experiments exploiting coherence-enhancing 'near-ZEFOZ' transitions in 171Yb are proposed, and continuous-wave measurements are used to demonstrate the working principle of such a scheme.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | milliKelvin ESR of rare-earth doped crystals using superconducting resonators |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author [year]. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/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. |
| Keywords: | Rare-earths, Quantum technologies, Superconducting resonators, milliKelvin, Electron spin resonance, ESR, Neodymium, Ytterbium, Rare-earth doped crystals, Yttrium Orthosilicate |
| 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 > London Centre for Nanotechnology |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10098757 |
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