Baity, P. G. , Maclean, C., Seferai, V. , Bronstein, J., Shu, Y., Hemakumara, T. and Weides, M. (2024) Circle fit optimization for resonator quality factor measurements: point redistribution for maximal accuracy. Physical Review Research, 6(1), 013329. (doi: 10.1103/PhysRevResearch.6.013329)
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Abstract
The control of material loss mechanisms is playing an increasingly important role for improving coherence times of superconducting quantum devices. Such material losses can be characterized through the measurement of planar superconducting resonators, which reflect losses through the resonance's quality factor Qₗ. The resonance quality factor consists of both internal (material) losses as well as coupling losses when resonance photons escape back into the measurement circuit. The combined losses are then described as Qₗ⁻¹l=Re{Q꜀⁻¹}+Qᵢ⁻¹, where Q꜀ and Qᵢ reflect the coupling and internal quality factors of the resonator, respectively. To separate the relative contributions of Qᵢ and Q꜀ to Qₗ, diameter-correcting circle fits use algebraic or geometric means to fit the resonance signal on the complex plane. However, such circle fits can produce varied results, so to address this issue, we use a combination of simulation and experiment to determine the reliability of a fitting algorithm across a wide range of quality factor values from Qᵢ≪Q꜀ to Q꜀≪Qᵢ. In addition, we develop a measurement protocol that can not only reduce fitting errors by factors ≳2 but also mitigates the influence of the measurement background on the fit results. This technique can be generalized for other resonance systems beyond superconducting resonators.
| Item Type: | Articles |
|---|---|
| Additional Information: | This work was supported by Innovate UK (QTools, Grant No. 79373, and FABU, Grant No. 50868); the EPSRC Oxford Quantum Computing Hub EP/T001062/1; and the FET Open initiative from the European Union’s Horizon 2020 program under Grant No. 899561. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Bronstein, Dr Joe and Weides, Professor Martin and Seferai, Valentino and Maclean, Mr Connor and Baity, Dr Paul |
| Authors: | Baity, P. G., Maclean, C., Seferai, V., Bronstein, J., Shu, Y., Hemakumara, T., and Weides, M. |
| College/School: | College of Science and Engineering > School of Engineering College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering |
| Journal Name: | Physical Review Research |
| Publisher: | American Physical Society |
| ISSN: | 2643-1564 |
| ISSN (Online): | 2643-1564 |
| Published Online: | 27 March 2024 |
| Copyright Holders: | Copyright © 2024 The Authors |
| First Published: | First published in Physical Review Research 6(1):013329 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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