{"publication_status":"published","alternative_title":["ISTA Thesis"],"oa":1,"language":[{"iso":"eng"}],"OA_place":"publisher","acknowledgement":"This research was supported by the Scientific Service Units of ISTA through resources provided\r\nby the MIBA Machine Shop and the Nanofabrication facility. We acknowledge the support from\r\nthe European Commission with the project Integrated Germanium Quantum Technology (with\r\nDOI:10.3030/101069515), the NOMIS Foundation, the HORIZON-RIA 101069515 project and\r\nthe FWF Projects Center for Correlated Quantum Materials and Solid State Quantum Systems:\r\nConventional and unconventional topological superconductors (with DOI:10.55776/F86) and\r\nHigh impedance circuit quantum electrodynamics with hole spins (with DOI:10.55776/I5060).\r\n","date_published":"2025-06-13T00:00:00Z","title":"Singlet-triplet qubits in planar Germanium: From exchange anisotropies to autonomous tuning ","abstract":[{"text":"Over the past century, researchers have been fascinated by the quantum nature of the\r\nphysical world, initially striving to understand its fundamental principles and consequences, and\r\neventually progressing toward engineering systems that can control and manipulate quantum\r\nproperties. Today, we stand at the dawn of the quantum technology era. While some quantum\r\ntechnologies follow well-defined roadmaps, others are still in the exciting and uncertain early\r\nstages of development. In the fields of quantum computing and quantum simulation, research\r\nis being conducted across a wide variety of platforms. Each of these demonstrates control over\r\nquantum properties but also faces challenges in scaling up to the level of a mature technology.\r\nThis thesis explores some of the fundamental properties of hole spin qubits in planar germanium.\r\nSemiconductor spin qubits are considered strong candidates for the realization of quantum\r\nprocessors, owing to their long relaxation and coherence times, as well as their compatibility\r\nwith existing semiconductor industry infrastructure. Among these, hole spin qubits in planar\r\ngermanium are particularly promising. Their advantages include a large effective mass, which\r\neases fabrication constraints; inherent protection from hyperfine noise; and strong spin-orbit\r\ninteraction, which enables fast and purely electrical control. However, spin-orbit coupling also\r\nintroduces site-dependent variability across qubits, particularly in the g-tensors and spin-flip\r\ntunneling, which might cause that the quantization axes are not aligned. In this thesis, we\r\ninvestigate the tilt between the quantization axes of two hole spins hosted in a double quantum\r\ndot as a function of both the magnetic field direction and various electrostatic configurations,\r\ndemonstrating that both parameters influence this tilt. We conclude by introducing a machine-learning-assisted routine to automatically tune baseband spin qubits. This approach may prove\r\nto be a powerful tool for characterizing spin-orbit effects and gaining deeper insight into the\r\nphysics governing spin qubit behavior.\r\n","lang":"eng"}],"doi":"10.15479/AT-ISTA-19836","publication_identifier":{"issn":["2663-337X"]},"date_updated":"2026-07-29T12:55:59Z","corr_author":"1","doi_confirm":"1","article_processing_charge":"No","_id":"19836","ddc":["530","539"],"date_created":"2025-06-13T09:01:50Z","page":"175","type":"dissertation","citation":{"ista":"Saez Mollejo J. 2025. Singlet-triplet qubits in planar Germanium: From exchange anisotropies to autonomous tuning . Institute of Science and Technology Austria.","ama":"Saez Mollejo J. Singlet-triplet qubits in planar Germanium: From exchange anisotropies to autonomous tuning . 2025. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19836\">10.15479/AT-ISTA-19836</a>","ieee":"J. Saez Mollejo, “Singlet-triplet qubits in planar Germanium: From exchange anisotropies to autonomous tuning ,” Institute of Science and Technology Austria, 2025.","chicago":"Saez Mollejo, Jaime. “Singlet-Triplet Qubits in Planar Germanium: From Exchange Anisotropies to Autonomous Tuning .” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT-ISTA-19836\">https://doi.org/10.15479/AT-ISTA-19836</a>.","apa":"Saez Mollejo, J. (2025). <i>Singlet-triplet qubits in planar Germanium: From exchange anisotropies to autonomous tuning </i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-19836\">https://doi.org/10.15479/AT-ISTA-19836</a>","short":"J. Saez Mollejo, Singlet-Triplet Qubits in Planar Germanium: From Exchange Anisotropies to Autonomous Tuning , Institute of Science and Technology Austria, 2025.","mla":"Saez Mollejo, Jaime. <i>Singlet-Triplet Qubits in Planar Germanium: From Exchange Anisotropies to Autonomous Tuning </i>. Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19836\">10.15479/AT-ISTA-19836</a>."},"degree_awarded":"PhD","department":[{"_id":"GradSch"},{"_id":"GeKa"}],"month":"06","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","day":"13","related_material":{"record":[{"relation":"part_of_dissertation","id":"19424","status":"public"}]},"tmp":{"short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png"},"status":"public","publisher":"Institute of Science and Technology Austria","file":[{"relation":"source_file","file_id":"19849","checksum":"643bfddead59857536cce4d57c775b32","access_level":"closed","file_size":59892829,"file_name":"istaustriathesis-master - Copy.zip","creator":"jsaezmol","embargo_to":"open_access","date_updated":"2026-04-01T22:30:07Z","content_type":"application/x-zip-compressed","date_created":"2025-06-16T09:38:49Z"},{"embargo":"2026-04-01","date_updated":"2026-04-01T22:30:07Z","date_created":"2025-06-18T08:50:16Z","content_type":"application/pdf","file_size":22382376,"access_level":"open_access","checksum":"e3dcb767fcc2b1787a455fdda991cefb","file_id":"19851","file_name":"SaezMollejo_PhDFinal_pdfa-1b.pdf","creator":"jsaezmol","relation":"main_file"}],"has_accepted_license":"1","acknowledged_ssus":[{"_id":"NanoFab"},{"_id":"M-Shop"}],"year":"2025","file_date_updated":"2026-04-01T22:30:07Z","oa_version":"Published Version","supervisor":[{"last_name":"Katsaros","orcid":"0000-0001-8342-202X","first_name":"Georgios","full_name":"Katsaros, Georgios","id":"38DB5788-F248-11E8-B48F-1D18A9856A87"}],"project":[{"grant_number":"101069515","name":"Integrated Germanium Quantum Technology","_id":"34c0acea-11ca-11ed-8bc3-8775e10fd452"},{"grant_number":"F8606","name":"Center for Correlated Quantum Materials and Solid State Quantum Systems: Conventional  and unconventional topological superconductors","_id":"34a66131-11ca-11ed-8bc3-a31681c6b03e"},{"grant_number":"I05060","name":"High impedance circuit quantum electrodynamics with hole spins","_id":"c0977eea-5a5b-11eb-8a69-a862db0cf4d1"}],"author":[{"full_name":"Saez Mollejo, Jaime","id":"e0390f72-f6e0-11ea-865d-862393336714","last_name":"Saez Mollejo","first_name":"Jaime"}]}