Post-fabrication frequency tuning in superconducting transmon qubits

Visa enkel post
dc.contributor.authorToselli, Maurizio
dc.contributor.departmentChalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2)sv
dc.contributor.departmentChalmers University of Technology / Department of Microtechnology and Nanoscience (MC2)en
dc.contributor.examinerBylander, Jonas
dc.contributor.supervisorNylander, Andreas
dc.contributor.supervisorTancredi, Giovanna
dc.date.accessioned2024-09-03T04:49:54Z
dc.date.available2024-09-03T04:49:54Z
dc.date.issued
dc.date.submitted
dc.description.abstractThis thesis presents a study on the manipulation of the normal state resistance RN of Al/AlOx/Al Josephson junctions using electrical DC signals. The goal is to develop a post-fabrication method for tuning the frequency of transmon qubits in superconducting quantum processors. This method aims to correct initial fabrication uncertainties and mitigate frequency collisions to scale up the number of qubits. The project initially focused on a precise, non-intrusive technique to measure RN at room temperature, which is directly related to the qubit plasma frequency f01 through the Ambegaokar-Baratoff relation. Subsequently, the natural aging of two types of devices, thin-oxide and thick-oxide junctions, was studied. Thin-oxide junctions proved less stable, exhibiting a resistance increase of more than 30% within the first two weeks after fabrication, compared to the 3% to 4% observed in thickoxide junctions. A procedure was then developed to deliberately increase RN at room temperature using high DC voltage biases, achieving increases of nearly 20% for thin-oxide devices and about 10% for thick-oxide ones. This demonstrates the potential for correcting fabrication variations on a wafer-level scale. An essential finding was the delayed resistance increase after manipulation, suggesting the need for further studies to better understand and control this effect. Theoretical modeling and simulations also revealed that the applied voltage plays a crucial role beyond simply delivering localized heat to the junction. Finally, a technology demonstration performed with a new experimental setup specifically designed to address individual qubits validated this method on a working quantum processor, providing a proof of concept. The results showed frequency shifts of several hundred megahertz after manipulation, without compromising qubit lifetimes. Despite a systematic overestimation of the final frequencies, likely due to the delayed resistance increase, this thesis successfully demonstrates a promising frequency tuning method and suggests future optimization and implementation directions.
dc.identifier.coursecodeMCCX04
dc.identifier.urihttp://hdl.handle.net/20.500.12380/308503
dc.language.isoeng
dc.setspec.uppsokPhysicsChemistryMaths
dc.subjectfrequency tuning method, transmon qubit, Josephson junction, super conducting quantum computing, electrical measurements, junction aging
dc.titlePost-fabrication frequency tuning in superconducting transmon qubits
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster's Thesisen
dc.type.uppsokH
local.programmeÖvrigt, MSc
Ladda ner
Original bundle
Visar 1 - 1 av 1
Bild (thumbnail)
Namn:
Post-fabrication Frequency Tuning in Superconducting Transmon Qubits.pdf
Storlek:
31.16 MB
Format:
Adobe Portable Document Format
Beskrivning:
Ladda ner
License bundle
Visar 1 - 1 av 1
Bild (thumbnail)
Namn:
license.txt
Storlek:
2.35 KB
Format:
Item-specific license agreed upon to submission
Beskrivning:
Ladda ner
Samling
Examensarbeten för masterexamen