{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/340365"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/340365","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Dispersive Readout and Spin-State Spectroscopy of Industrially-Fabricated Silicon Quantum Dots","abstract":"Encouraged by the promise of large-scale quantum computing, this thesis focuses on reliable and scalable readout of spin qubits in gate-defined silicon complementary metal-oxide-semiconductor quantum dots. In particular, this thesis studies the spin states and Pauli spin blockade (PSB) physics of silicon quantum dots using scalable gate-based dispersive sensing and magnetic-field-assisted energy spectroscopy. In the first part of the thesis, I present an expanded description of the PSB-physics of a tunnel-coupled silicon double quantum dot defined in the corners of a split-gate transistor. Using gate-based magnetospectroscopy and by developing a quantum capacitance model for reconstruction of quantum dot energy spectra, I report successive steps of PSB and PSB-lifting involving spin states with total spin angular momentum up to S = 3. More particularly, I discover the formation of a hybridized spin quintet state and the presence of triplet-quintet and quintet-septet PSB. This enables studies of the quintet relaxation dynamics from which I find a characteristic relaxation time of T1 ~ 4 μs. Subsequently, I present an experimental observation of a new, highly prevalent PSB-lifting mechanism in a silicon double quantum dot due to incoherent tunneling between different spin manifolds. Through dispersively-detected magnetospectroscopy of the double quantum dot in 16 charge configurations, I find the mechanism to be energy-level selective and non- reciprocal for neighbouring charge configurations. Additionally, I report a large coupling of different electron spin manifolds of 7.90 μeV, the largest reported to date, indicating an enhanced spin-orbit coupling which may enable all-electrical qubit control. Finally, I introduce Pulse Assembler, a software tool developed to aid execution of spin qubit control experiments. Designed to combine the strengths of the Qiskit, Pulse lib and QCoDeS software packages, Pulse Assembler introduces a JSON-file-based representation of qubit control pulses that allows parametrisation of any pulse parameter. As a result, pulse parameter sweeps can be implemented in just a few lines of code.","abstract_html":"Encouraged by the promise of large-scale quantum computing, this thesis focuses on reliable and scalable readout of spin qubits in gate-defined silicon complementary metal-oxide-semiconductor quantum dots. In particular, this thesis studies the spin states and Pauli spin blockade (PSB) physics of silicon quantum dots using scalable gate-based dispersive sensing and magnetic-field-assisted energy spectroscopy. In the first part of the thesis, I present an expanded description of the PSB-physics of a tunnel-coupled silicon double quantum dot defined in the corners of a split-gate transistor. Using gate-based magnetospectroscopy and by developing a quantum capacitance model for reconstruction of quantum dot energy spectra, I report successive steps of PSB and PSB-lifting involving spin states with total spin angular momentum up to S = 3. More particularly, I discover the formation of a hybridized spin quintet state and the presence of triplet-quintet and quintet-septet PSB. This enables studies of the quintet relaxation dynamics from which I find a characteristic relaxation time of T1 ~ 4 μs. Subsequently, I present an experimental observation of a new, highly prevalent PSB-lifting mechanism in a silicon double quantum dot due to incoherent tunneling between different spin manifolds. Through dispersively-detected magnetospectroscopy of the double quantum dot in 16 charge configurations, I find the mechanism to be energy-level selective and non- reciprocal for neighbouring charge configurations. Additionally, I report a large coupling of different electron spin manifolds of 7.90 μeV, the largest reported to date, indicating an enhanced spin-orbit coupling which may enable all-electrical qubit control. Finally, I introduce Pulse Assembler, a software tool developed to aid execution of spin qubit control experiments. Designed to combine the strengths of the Qiskit, Pulse lib and QCoDeS software packages, Pulse Assembler introduces a JSON-file-based representation of qubit control pulses that allows parametrisation of any pulse parameter. As a result, pulse parameter sweeps can be implemented in just a few lines of code.","abstract_has_math":false,"creators":["Lundberg, Theodor William"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Sirringhaus, Henning","Robinson, Jason WA","Gonzalez-Zalba, M Fernando"],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-12-01","date_published":"2021-12-01","updated_at":"2026-07-22T22:24:11Z","subjects":["dispersive readout","magnetospectroscopy","Pauli spin blockade","quantum computing","quantum dot","silicon","spin qubit"],"languages":["eng"],"rights":[],"rights_urls":["http://purl.org/NET/rdflicense/allrightsreserved"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.87803","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Sirringhaus, Henning","Robinson, Jason WA","Gonzalez-Zalba, M Fernando"]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 688539; EPSRC Cambridge NanoDTC, EP/L015978/1"]},{"key":"dc:creator","label":"Author","values":["Lundberg, Theodor William"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2021-12-01"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/340365"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["dispersive readout","magnetospectroscopy","Pauli spin blockade","quantum computing","quantum dot","silicon","spin qubit"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["http://purl.org/NET/rdflicense/allrightsreserved"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["10.17863/CAM.87803"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://www.repository.cam.ac.uk/bitstreams/6037e740-d251-4a0c-80eb-6e3b4b63bb63/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Encouraged by the promise of large-scale quantum computing, this thesis focuses on reliable and scalable readout of spin qubits in gate-defined silicon complementary metal-oxide-semiconductor quantum dots. 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Subsequently, I present an experimental observation of a new, highly prevalent PSB-lifting mechanism in a silicon double quantum dot due to incoherent tunneling between different spin manifolds. Through dispersively-detected magnetospectroscopy of the double quantum dot in 16 charge configurations, I find the mechanism to be energy-level selective and non- reciprocal for neighbouring charge configurations. Additionally, I report a large coupling of different electron spin manifolds of 7.90 μeV, the largest reported to date, indicating an enhanced spin-orbit coupling which may enable all-electrical qubit control. Finally, I introduce Pulse Assembler, a software tool developed to aid execution of spin qubit control experiments. Designed to combine the strengths of the Qiskit, Pulse lib and QCoDeS software packages, Pulse Assembler introduces a JSON-file-based representation of qubit control pulses that allows parametrisation of any pulse parameter. 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Subsequently, I present an experimental observation of a new, highly prevalent PSB-lifting mechanism in a silicon double quantum dot due to incoherent tunneling between different spin manifolds. Through dispersively-detected magnetospectroscopy of the double quantum dot in 16 charge configurations, I find the mechanism to be energy-level selective and non- reciprocal for neighbouring charge configurations. Additionally, I report a large coupling of different electron spin manifolds of 7.90 μeV, the largest reported to date, indicating an enhanced spin-orbit coupling which may enable all-electrical qubit control. Finally, I introduce Pulse Assembler, a software tool developed to aid execution of spin qubit control experiments. Designed to combine the strengths of the Qiskit, Pulse lib and QCoDeS software packages, Pulse Assembler introduces a JSON-file-based representation of qubit control pulses that allows parametrisation of any pulse parameter. 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