[{"publisher":"Springer Nature","intvolume":"        16","isi":1,"type":"journal_article","DOAJ_listed":"1","citation":{"mla":"Saez Mollejo, Jaime, et al. “Exchange Anisotropies in Microwave-Driven Singlet-Triplet Qubits.” <i>Nature Communications</i>, vol. 16, 3862, Springer Nature, 2025, doi:<a href=\"https://doi.org/10.1038/s41467-025-58969-y\">10.1038/s41467-025-58969-y</a>.","ista":"Saez Mollejo J, Jirovec D, Schell YA, Kukucka J, Calcaterra S, Chrastina D, Isella G, Rimbach-Russ M, Bosco S, Katsaros G. 2025. Exchange anisotropies in microwave-driven singlet-triplet qubits. Nature Communications. 16, 3862.","ieee":"J. Saez Mollejo <i>et al.</i>, “Exchange anisotropies in microwave-driven singlet-triplet qubits,” <i>Nature Communications</i>, vol. 16. Springer Nature, 2025.","ama":"Saez Mollejo J, Jirovec D, Schell YA, et al. Exchange anisotropies in microwave-driven singlet-triplet qubits. <i>Nature Communications</i>. 2025;16. doi:<a href=\"https://doi.org/10.1038/s41467-025-58969-y\">10.1038/s41467-025-58969-y</a>","apa":"Saez Mollejo, J., Jirovec, D., Schell, Y. A., Kukucka, J., Calcaterra, S., Chrastina, D., … Katsaros, G. (2025). Exchange anisotropies in microwave-driven singlet-triplet qubits. <i>Nature Communications</i>. Springer Nature. <a href=\"https://doi.org/10.1038/s41467-025-58969-y\">https://doi.org/10.1038/s41467-025-58969-y</a>","short":"J. Saez Mollejo, D. Jirovec, Y.A. Schell, J. Kukucka, S. Calcaterra, D. Chrastina, G. Isella, M. Rimbach-Russ, S. Bosco, G. Katsaros, Nature Communications 16 (2025).","chicago":"Saez Mollejo, Jaime, Daniel Jirovec, Yona A Schell, Josip Kukucka, Stefano Calcaterra, Daniel Chrastina, Giovanni Isella, Maximilian Rimbach-Russ, Stefano Bosco, and Georgios Katsaros. “Exchange Anisotropies in Microwave-Driven Singlet-Triplet Qubits.” <i>Nature Communications</i>. Springer Nature, 2025. <a href=\"https://doi.org/10.1038/s41467-025-58969-y\">https://doi.org/10.1038/s41467-025-58969-y</a>."},"scopus_import":"1","article_number":"3862","quality_controlled":"1","has_accepted_license":"1","file_date_updated":"2025-05-05T07:08:23Z","_id":"19424","author":[{"last_name":"Saez Mollejo","id":"e0390f72-f6e0-11ea-865d-862393336714","first_name":"Jaime","full_name":"Saez Mollejo, Jaime"},{"full_name":"Jirovec, Daniel","first_name":"Daniel","orcid":"0000-0002-7197-4801","id":"4C473F58-F248-11E8-B48F-1D18A9856A87","last_name":"Jirovec"},{"full_name":"Schell, Yona A","last_name":"Schell","id":"fe39122d-06bb-11ec-a33b-9e22b40e40a5","first_name":"Yona A"},{"first_name":"Josip","id":"3F5D8856-F248-11E8-B48F-1D18A9856A87","last_name":"Kukucka","full_name":"Kukucka, Josip"},{"full_name":"Calcaterra, Stefano","last_name":"Calcaterra","first_name":"Stefano"},{"last_name":"Chrastina","first_name":"Daniel","full_name":"Chrastina, Daniel"},{"last_name":"Isella","first_name":"Giovanni","full_name":"Isella, Giovanni"},{"first_name":"Maximilian","last_name":"Rimbach-Russ","full_name":"Rimbach-Russ, Maximilian"},{"full_name":"Bosco, Stefano","first_name":"Stefano","last_name":"Bosco"},{"full_name":"Katsaros, Georgios","orcid":"0000-0001-8342-202X","id":"38DB5788-F248-11E8-B48F-1D18A9856A87","last_name":"Katsaros","first_name":"Georgios"}],"acknowledged_ssus":[{"_id":"M-Shop"},{"_id":"NanoFab"}],"publication_identifier":{"eissn":["2041-1723"]},"article_processing_charge":"Yes","date_created":"2025-03-19T13:28:12Z","acknowledgement":"We thank A. Crippa for helpful discussions. This research was supported by the Scientific Service Units of ISTA through resources provided by the MIBA Machine Shop and the Nanofabrication facility. This research and related results were made possible with the support of the NOMIS Foundation, the HORIZON-RIA 101069515 project and the FWF Projects with DOI:10.55776/F86 and DOI:10.55776/I5060. M.R.-R. acknowledges support from the Netherlands Organization of Scientific Research (NWO) under Veni grant VI.Veni.212.223. The\r\nResearch of S.B. and M.R.-R. was sponsored in part by the Army Research Office and was accomplished under Award Number: W911NF-23-1-0110. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.","department":[{"_id":"GeKa"}],"related_material":{"record":[{"relation":"research_data","id":"19409","status":"public"},{"status":"public","id":"19836","relation":"dissertation_contains"}],"link":[{"relation":"research_data","url":"https://ista.ac.at/en/news/the-shadow-of-an-electron/","description":"News on ISTA website"}]},"OA_place":"publisher","publication":"Nature Communications","project":[{"grant_number":"101069515","_id":"34c0acea-11ca-11ed-8bc3-8775e10fd452","name":"Integrated Germanium Quantum Technology"},{"name":"Center for Correlated Quantum Materials and Solid State Quantum Systems: Conventional  and unconventional topological superconductors","_id":"34a66131-11ca-11ed-8bc3-a31681c6b03e","grant_number":"F8606"},{"name":"High impedance circuit quantum electrodynamics with hole spins","_id":"c0977eea-5a5b-11eb-8a69-a862db0cf4d1","grant_number":"I05060"},{"_id":"262116AA-B435-11E9-9278-68D0E5697425","name":"Hybrid Semiconductor - Superconductor Quantum Devices"}],"year":"2025","volume":16,"article_type":"original","external_id":{"arxiv":["2408.03224"],"pmid":["40274808"],"isi":["001475587400022"]},"title":"Exchange anisotropies in microwave-driven singlet-triplet qubits","day":"24","file":[{"file_name":"2025_NatureComm_SaezMollejo.pdf","file_size":1548756,"success":1,"checksum":"13fe84cddc9d4e47213bf17acdac70d7","file_id":"19645","date_created":"2025-05-05T07:08:23Z","relation":"main_file","content_type":"application/pdf","access_level":"open_access","creator":"dernst","date_updated":"2025-05-05T07:08:23Z"}],"corr_author":"1","license":"https://creativecommons.org/licenses/by/4.0/","arxiv":1,"date_updated":"2026-05-02T22:31:13Z","oa_version":"Published Version","language":[{"iso":"eng"}],"oa":1,"OA_type":"gold","month":"04","tmp":{"short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","doi":"10.1038/s41467-025-58969-y","pmid":1,"ddc":["530"],"abstract":[{"text":"Hole spin qubits are rapidly emerging as the workhorse of semiconducting quantum processors because of their large spin-orbit interaction, enabling fast all-electric operations at low power. However, spin-orbit interaction also causes non-uniformities in devices, resulting in locally varying qubit energies and site-dependent anisotropies. While these anisotropies can be used to drive single-spins, if not properly harnessed, they can hinder the path toward large-scale quantum processors. Here, we report on microwave-driven singlet-triplet qubits in planar germanium and use them to investigate the anisotropy of two spins in a double quantum dot. We show two distinct operating regimes depending on the magnetic field direction. For in-plane fields, the two spins are largely anisotropic, and electrically tunable, which enables to measure all the available transitions; coherence times exceeding 3 $\\mu$s are extracted. For out-of-plane fields, they have an isotropic response but preserve the substantial energy difference required to address the singlet-triplet qubit. Even in this field direction, where the qubit lifetime\r\nis strongly affected by nuclear spins, we find 400 ns coherence times. Our work adds a valuable tool to investigate and harness the anisotropy of spin qubits and can be implemented in any large-scale NxN device, facilitating the path towards scalable quantum processors.","lang":"eng"}],"publication_status":"published","status":"public","date_published":"2025-04-24T00:00:00Z"},{"month":"06","tmp":{"short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","doi":"10.15479/AT-ISTA-19836","supervisor":[{"first_name":"Georgios","orcid":"0000-0001-8342-202X","last_name":"Katsaros","id":"38DB5788-F248-11E8-B48F-1D18A9856A87","full_name":"Katsaros, Georgios"}],"ddc":["530","539"],"abstract":[{"lang":"eng","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"}],"publication_status":"published","status":"public","date_published":"2025-06-13T00:00:00Z","day":"13","file":[{"file_name":"istaustriathesis-master - Copy.zip","file_size":59892829,"checksum":"643bfddead59857536cce4d57c775b32","file_id":"19849","date_created":"2025-06-16T09:38:49Z","embargo_to":"open_access","relation":"source_file","content_type":"application/x-zip-compressed","access_level":"closed","creator":"jsaezmol","date_updated":"2026-04-01T22:30:07Z"},{"creator":"jsaezmol","access_level":"open_access","embargo":"2026-04-01","date_updated":"2026-04-01T22:30:07Z","content_type":"application/pdf","relation":"main_file","checksum":"e3dcb767fcc2b1787a455fdda991cefb","date_created":"2025-06-18T08:50:16Z","file_id":"19851","file_name":"SaezMollejo_PhDFinal_pdfa-1b.pdf","file_size":22382376}],"corr_author":"1","oa_version":"Published Version","alternative_title":["ISTA Thesis"],"date_updated":"2026-04-28T13:29:28Z","oa":1,"language":[{"iso":"eng"}],"acknowledged_ssus":[{"_id":"NanoFab"},{"_id":"M-Shop"}],"publication_identifier":{"issn":["2663-337X"]},"article_processing_charge":"No","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_created":"2025-06-13T09:01:50Z","department":[{"_id":"GradSch"},{"_id":"GeKa"}],"related_material":{"record":[{"relation":"part_of_dissertation","id":"19424","status":"public"}]},"degree_awarded":"PhD","page":"175","OA_place":"publisher","project":[{"name":"Integrated Germanium Quantum Technology","_id":"34c0acea-11ca-11ed-8bc3-8775e10fd452","grant_number":"101069515"},{"grant_number":"F8606","_id":"34a66131-11ca-11ed-8bc3-a31681c6b03e","name":"Center for Correlated Quantum Materials and Solid State Quantum Systems: Conventional  and unconventional topological superconductors"},{"_id":"c0977eea-5a5b-11eb-8a69-a862db0cf4d1","name":"High impedance circuit quantum electrodynamics with hole spins","grant_number":"I05060"}],"year":"2025","title":"Singlet-triplet qubits in planar Germanium : From exchange anisotropies to autonomous tuning ","publisher":"Institute of Science and Technology Austria","type":"dissertation","citation":{"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.","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>","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>.","ista":"Saez Mollejo J. 2025. Singlet-triplet qubits in planar Germanium : From exchange anisotropies to autonomous tuning . Institute of Science and Technology Austria.","ieee":"J. Saez Mollejo, “Singlet-triplet qubits in planar Germanium : From exchange anisotropies to autonomous tuning ,” Institute of Science and Technology Austria, 2025."},"has_accepted_license":"1","_id":"19836","file_date_updated":"2026-04-01T22:30:07Z","author":[{"full_name":"Saez Mollejo, Jaime","first_name":"Jaime","id":"e0390f72-f6e0-11ea-865d-862393336714","last_name":"Saez Mollejo"}]}]