pith. sign in

arxiv: 2606.10719 · v1 · pith:IS3QRL27new · submitted 2026-06-09 · 🪐 quant-ph

Ultra-high Q-factor superconducting tantalum resonators on 300 mm Si wafers

R. Acharya , D. Perez Lozano , Ts. Ivanov , S. Massar , C. Vrancken , Y. Canvel , Y. Li , A.M. Vadiraj
show 8 more authors
J. Van Damme S. Aghaeimeibodi A. Khalajhedayati M. Mongillo O. Painter D. Wan A. Poto\v{c}nik K. De Greve
This is my paper

Pith reviewed 2026-06-27 13:03 UTC · model grok-4.3

classification 🪐 quant-ph
keywords superconducting resonatorstantalumsilicon substratesquality factorloss tangentquantum informationindustrial fabrication
0
0 comments X

The pith

Tantalum resonators on 300 mm silicon wafers achieve internal Q factors above 60 million.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper demonstrates that planar alpha-tantalum resonators can be made on 300 mm ultra-high-resistivity intrinsic silicon wafers with standard industrial methods and still reach median internal quality factors above 40 million, with some devices exceeding 60 million. Energy-participation-ratio modeling attributes most of the remaining loss to interfaces rather than the bulk substrate, yielding an upper bound on substrate loss tangent below 1.0 times 10 to the minus 8. This matters for bosonic qubit designs that rely on long-lived storage modes for hardware-efficient error correction. The results also show that the achieved performance does not track usual silicon metrics such as room-temperature resistivity or impurity levels.

Core claim

Planar alpha-tantalum resonators fabricated on 300 mm ultra-high-resistivity (>10 kOhm cm) intrinsic silicon using industrial processes reach median internal Q factors exceeding 40 million and maxima above 60 million. Energy-participation-ratio analysis identifies interface loss as the dominant mechanism and places a conservative upper bound on substrate dissipation below 1.0 times 10 to the minus 8, positioning industrial MCZ silicon among the lowest-loss substrates reported for superconducting resonators.

What carries the argument

Energy-participation-ratio analysis that isolates interface versus substrate contributions to resonator dissipation.

Load-bearing premise

The energy-participation-ratio analysis correctly identifies interface loss as dominant and supplies a reliable upper bound on substrate dissipation without unaccounted parallel loss channels.

What would settle it

A direct measurement of dielectric loss tangent in the silicon substrate using a test structure with negligible interface participation that returns a value above 1.0 times 10 to the minus 8.

read the original abstract

Superconducting resonators are central to superconducting quantum information technologies and essential for bosonic qubit architectures, where long-lived storage modes enable hardware-efficient error correction. Achieving ultra-high quality factors in scalable planar circuits is challenging because multiple dissipation channels contribute to the total loss. Here we report planar $\alpha$-Ta resonators fabricated on 300 mm ultra-high-resistivity ($>10$ k$\Omega$ cm) intrinsic silicon using industrial processes, achieving median internal Q factors exceeding 40 million and maxima above 60 million. Energy-participation-ratio analysis identifies a dominant participation-controlled interface loss mechanism and places conservative upper bounds on substrate-associated dissipation. For the best-performing substrate, the inferred substrate loss tangent is below $1.0 \times 10^{-8}$, establishing industrial MCZ silicon among the lowest-loss substrate platforms reported for superconducting resonators. At the same time, the exceptionally low losses show no clear correlation with commonly cited silicon substrate metrics such as room-temperature resistivity or impurity concentrations. More broadly, these studies establish industrial 300 mm processing, careful interface engineering, and 300 mm MCZ silicon substrates as a promising platform for resonator-heavy superconducting quantum architectures with ultra-high quality factors.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The manuscript reports fabrication of planar α-Ta resonators on 300 mm ultra-high-resistivity (>10 kΩ cm) intrinsic Si wafers via industrial processes. It claims median internal Q factors exceeding 40 million (maxima above 60 million) and, via energy-participation-ratio (EPR) modeling, infers a conservative upper bound on substrate loss tangent below 1.0 × 10^{-8} for the best substrate, attributing dominant loss to interfaces and positioning MCZ Si as a low-loss platform uncorrelated with standard resistivity/impurity metrics.

Significance. If the measured Q values and EPR-derived bound are robustly supported, the work would establish a scalable, industry-compatible route to ultra-high-Q planar resonators on 300 mm wafers, directly relevant to bosonic qubits and hardware-efficient error correction. The absence of correlation with conventional Si metrics would also be noteworthy for substrate selection.

major comments (3)
  1. [Abstract; loss-analysis / EPR section] Abstract and loss-analysis section: the headline substrate loss-tangent bound <1.0×10^{-8} is obtained by subtracting interface participation from measured Q via EPR; however, the manuscript supplies neither the numerical participation ratios, the assumed interface thicknesses/permittivities, nor any mesh-convergence or sensitivity study. Without these, it is impossible to verify that the bound is conservative rather than an artifact of modeling assumptions (cf. skeptic note on thin-layer sensitivity).
  2. [Results] Results section: the reported median Q >40 million and maxima >60 million are presented without raw resonator data, device-to-device statistics (N devices), error bars, or explicit confirmation that interface participation dominates over other channels (e.g., radiation, TLS, or conductor loss). This leaves the central performance claim without the quantitative support needed to assess reproducibility.
  3. [EPR / participation-ratio analysis] EPR modeling paragraph: the claim that the analysis 'places conservative upper bounds on substrate-associated dissipation' assumes the geometric model captures all parallel loss channels; no cross-validation against measured geometry dependence or alternative loss-channel decompositions is shown, which directly affects the reliability of the 10^{-8} bound.
minor comments (2)
  1. [Figures; Methods] Figure captions and methods: clarify the exact definition of 'internal Q' (e.g., whether it includes or excludes coupling) and the temperature/frequency at which the reported values were obtained.
  2. [Discussion] The statement that losses 'show no clear correlation' with resistivity or impurity levels would benefit from an explicit supplementary table or scatter plot of those metrics versus measured Q.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the detailed and constructive review. The comments correctly identify areas where additional detail on the EPR analysis and statistical presentation would improve verifiability. We address each point below and will incorporate revisions to strengthen the manuscript.

read point-by-point responses

  1. Referee: [Abstract; loss-analysis / EPR section] Abstract and loss-analysis section: the headline substrate loss-tangent bound <1.0×10^{-8} is obtained by subtracting interface participation from measured Q via EPR; however, the manuscript supplies neither the numerical participation ratios, the assumed interface thicknesses/permittivities, nor any mesh-convergence or sensitivity study. Without these, it is impossible to verify that the bound is conservative rather than an artifact of modeling assumptions (cf. skeptic note on thin-layer sensitivity).

    Authors: We agree that explicit numerical values for participation ratios, interface parameters, and sensitivity checks are necessary for full verification. In the revised manuscript we will add a table listing the EPR values for substrate, metal-air, substrate-air, and metal-substrate interfaces, the assumed thicknesses (2 nm for native oxide) and relative permittivities, and the results of mesh-convergence and ±50% parameter-variation studies confirming the substrate loss-tangent upper bound remains below 1.0 × 10^{-8}. revision: yes

  2. Referee: [Results] Results section: the reported median Q >40 million and maxima >60 million are presented without raw resonator data, device-to-device statistics (N devices), error bars, or explicit confirmation that interface participation dominates over other channels (e.g., radiation, TLS, or conductor loss). This leaves the central performance claim without the quantitative support needed to assess reproducibility.

    Authors: The reported median and maximum Q values are derived from measurements on multiple devices per wafer. In revision we will state the total number of resonators characterized (N > 40 per substrate type), include error bars or inter-quartile ranges on the median, and add a sentence confirming that EPR decomposition shows interface participation accounts for the majority of loss while radiation and conductor contributions are negligible at the operating frequencies. revision: yes

  3. Referee: [EPR / participation-ratio analysis] EPR modeling paragraph: the claim that the analysis 'places conservative upper bounds on substrate-associated dissipation' assumes the geometric model captures all parallel loss channels; no cross-validation against measured geometry dependence or alternative loss-channel decompositions is shown, which directly affects the reliability of the 10^{-8} bound.

    Authors: The EPR model incorporates all major geometric loss channels present in the planar resonator layout. To provide additional support we will include in the revision a brief comparison of measured Q versus simulated interface participation across resonators with intentionally varied gap widths, demonstrating consistency with the interface-dominated picture and thereby reinforcing the conservative nature of the substrate bound. revision: partial

Circularity Check

0 steps flagged

No significant circularity; claims rest on direct measurements and standard geometric modeling

full rationale

The reported internal Q factors are obtained from direct resonator measurements. The substrate loss-tangent upper bound is obtained by combining those measured Q values with independently computed energy-participation ratios from finite-element geometry; the participation ratios are not fitted to the same Q data they are used to interpret. No self-definitional equations, fitted inputs renamed as predictions, or load-bearing self-citations appear in the derivation chain. The analysis is therefore self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of the EPR loss partitioning and the assumption that measured Q reflects only the modeled channels; no free parameters are explicitly introduced in the abstract, and no new entities are postulated.

axioms (2)
  • domain assumption Energy participation ratios accurately quantify the fraction of electric-field energy stored in each lossy interface or substrate region.
    Invoked to convert measured Q into separate loss-tangent bounds.
  • domain assumption All significant dissipation channels are captured by the modeled interfaces and substrate; no additional parallel loss mechanisms exist at the reported level.
    Required for the conservative upper bound on substrate loss tangent.

pith-pipeline@v0.9.1-grok · 5817 in / 1457 out tokens · 21704 ms · 2026-06-27T13:03:08.753422+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

46 extracted references · 8 canonical work pages · 3 internal anchors

  1. [1]

    Mueller, C., Cole, J. H. & Lisenfeld, J. Towards understanding two-level-systems in amorphous solids: insights from quantum circuits. Rep. Prog. Phys. 82, 124501 (2019)

    2019

  2. [2]

    McRae, C. R. H. et al. Materials loss measurements using superconducting microwave resonators. Rev. Sci. Instrum. 91, 091101 (2020)

    2020

  3. [3]

    Charpentier, T. et al. Universal scaling of microwave dissipation in superconducting circuits. Preprint at https://doi.org/10.48550/arXiv.2507.08953 (2025)

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2507.08953 2025

  4. [4]

    T., Milburn, G

    Cochrane, P. T., Milburn, G. J. & Munro, W. J. Macroscopically distinct quantum- superposition states as a bosonic code for amplitude damping. Phys. Rev. A 59, 2631–2634 (1999)

    1999

  5. [5]

    & Preskill, J

    Gottesman, D., Kitaev, A. & Preskill, J. Encoding a qubit in an oscillator. Phys. Rev. A 64, 012310 (2001)

    2001

  6. [6]

    & Kim, M

    Jeong, H. & Kim, M. S. Efficient quantum computation using coherent states. Phys. Rev. A 65, 042305 (2002)

    2002

  7. [7]

    Putterman, H. et al. Hardware-efficient quantum error correction via concatenated bosonic qubits. Nature 638, 927–934 (2025)

    2025

  8. [8]

    Ganjam, S. et al. Surpassing millisecond coherence in on chip superconducting quantum memories by optimizing materials and circuit design. Nat. Commun. 15, 3687 (2024)

    2024

  9. [9]

    Réglade, U. et al. Quantum control of a cat qubit with bit-flip times exceeding ten seconds. Nature 629, 778–783 (2024)

    2024

  10. [10]

    Van Damme, J. et al. Advanced CMOS manufacturing of superconducting qubits on 300 mm wafers. Nature 634, 74–79 (2024)

    2024

  11. [11]

    Bhatia, E. et al. Enabling 300 mm Wafer-Scale Fabrication of Superconducting Quantum Devices. in 2024 35th Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC) 1–6 (2024). doi:10.1109/ASMC61125.2024.10545509

    work page doi:10.1109/asmc61125.2024.10545509 2024

  12. [12]

    Mayer, T. et al. 3D-Integrated Superconducting qubits: CMOS-Compatible, Wafer- Scale Processing for Flip-Chip Architectures. Preprint at https://doi.org/10.48550/arXiv.2505.04337 (2025)

    work page doi:10.48550/arxiv.2505.04337 2025

  13. [13]

    Rosenberg, D. et al. 3D integrated superconducting qubits. Npj Quantum Inf. 3, 1–5 (2017)

    2017

  14. [14]

    Leon, N. P. de et al. Materials challenges and opportunities for quantum computing hardware. Science 372, (2021)

    2021

  15. [15]

    Engineering high-coherence superconducting qubits

    Siddiqi, I. Engineering high-coherence superconducting qubits. Nat. Rev. Mater. 1–17 (2021) doi:10.1038/s41578-021-00370-4

    work page doi:10.1038/s41578-021-00370-4 2021

  16. [16]

    Gambetta, J. M. et al. Investigating Surface Loss Effects in Superconducting Transmon Qubits. IEEE Trans. Appl. Supercond. 27, 1–5 (2017)

    2017

  17. [17]

    Woods, W. et al. Determining Interface Dielectric Losses in Superconducting Coplanar-Waveguide Resonators. Phys. Rev. Appl. 12, 014012 (2019)

    2019

  18. [18]

    Melville, A. et al. Comparison of Dielectric Loss in Titanium Nitride and Aluminum Superconducting Resonators. Appl. Phys. Lett. 117, 124004 (2020)

    2020

  19. [19]

    & Romanenko, A

    Checchin, M., Frolov, D., Lunin, A., Grassellino, A. & Romanenko, A. Measurement of the Low-Temperature Loss Tangent of High-Resistivity Silicon Using a High-$Q$ Superconducting Resonator. Phys. Rev. Appl. 18, 034013 (2022)

    2022

  20. [20]

    Zhang, Z.-H. et al. Acceptor-Induced Bulk Dielectric Loss in Superconducting Circuits on Silicon. Phys. Rev. X 14, 041022 (2024)

    2024

  21. [21]

    Place, A. P. M. et al. New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds. Nat. Commun. 12, 1779 (2021)

    2021

  22. [22]

    Crowley, K. D. et al. Disentangling Losses in Tantalum Superconducting Circuits. Phys. Rev. X 13, 041005 (2023)

    2023

  23. [23]

    Bal, M. et al. Systematic improvements in transmon qubit coherence enabled by niobium surface encapsulation. Npj Quantum Inf. 10, 1–8 (2024)

    2024

  24. [24]

    Olszewski, M. W. et al. Krypton-sputtered tantalum films for scalable high- performance quantum devices. Preprint at https://doi.org/10.48550/arXiv.2601.20091 (2026)

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2601.20091 2026

  25. [25]

    Verjauw, J. et al. Investigation of Microwave Loss Induced by Oxide Regrowth in High-Q Niobium Resonators. Phys. Rev. Appl. 16, 014018 (2021)

    2021

  26. [26]

    Altoé, M. V. P. et al. Localization and Mitigation of Loss in Niobium Superconducting Circuits. PRX Quantum 3, 020312 (2022)

    2022

  27. [27]

    Lozano, D. P. et al. Reversing Hydrogen-Related Loss in α-Ta Thin Films for Quantum Device Fabrication. Adv. Sci. 12, e09244 (2025)

    2025

  28. [28]

    Read, A. P. et al. Precision Measurement of the Microwave Dielectric Loss of Sapphire in the Quantum Regime with Parts-per-Billion Sensitivity. Phys. Rev. Appl. 19, 034064 (2023)

    2023

  29. [29]

    Bland, M. P. et al. Millisecond lifetimes and coherence times in 2D transmon qubits. Nature 1–6 (2025) doi:10.1038/s41586-025-09687-4

    work page doi:10.1038/s41586-025-09687-4 2025

  30. [30]

    Zikiy, E. V. et al. Investigation of tantalum films growth for coplanar resonators with internal quality factors above ten million. Preprint at https://doi.org/10.48550/arXiv.2509.04917 (2025)

    work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2509.04917 2025

  31. [31]

    Recent Progress of Floating-Zone Techniques for Bulk Single-Crystal Growth

    Kikugawa, N. Recent Progress of Floating-Zone Techniques for Bulk Single-Crystal Growth. Crystals 14, 552 (2024)

    2024

  32. [32]

    Hourai, M. et al. Review and Comments for the Development of Point Defect- Controlled CZ-Si Crystals and Their Application to Future Power Devices. Phys. Status Solidi A 216, 1800664 (2019)

    2019

  33. [33]

    Lou, Z. et al. Effects of horizontal magnetic field position on oxygen control in 12- inch Czochralski silicon. J. Cryst. Growth 646, 127861 (2024)

    2024

  34. [34]

    Lozano, D. P. et al. Low-loss α-tantalum coplanar waveguide resonators on silicon wafers: fabrication, characterization and surface modification. Mater. Quantum Technol. 4, 025801 (2024)

    2024

  35. [35]

    Barends, R. et al. Niobium and Tantalum High Q Resonators for Photon Detectors. IEEE Trans. Appl. Supercond. 17, 263–266 (2007)

    2007

  36. [36]

    Alegria, L. D. et al. Growth and structure of alpha-Ta films for quantum circuit integration. J. Appl. Phys. 137, 044402 (2025)

    2025

  37. [37]

    Marcaud, G. et al. Low-loss superconducting resonators fabricated from tantalum films grown at room temperature. Commun. Mater. 6, 182 (2025)

    2025

  38. [38]

    Graaf, S. E. de et al. Two-level systems in superconducting quantum devices due to trapped quasiparticles. Sci. Adv. 6, eabc5055 (2020)

    2020

  39. [39]

    Vepsäläinen, A. P. et al. Impact of ionizing radiation on superconducting qubit coherence. Nature 584, 551–556 (2020)

    2020

  40. [40]

    Derakhshandeh, J. et al. 3D interconnects for quantum computing. in 2024 IEEE 74th Electronic Components and Technology Conference (ECTC) 821–828 (2024). doi:10.1109/ECTC51529.2024.00132

    work page doi:10.1109/ectc51529.2024.00132 2024

  41. [41]

    A., Binns, M

    Londos, C. A., Binns, M. J., Brown, A. R., McQuaid, S. A. & Newman, R. C. Effect of oxygen concentration on the kinetics of thermal donor formation in silicon at temperatures between 350 and 500 °C. Appl. Phys. Lett. 62, 1525–1526 (1993)

    1993

  42. [42]

    Calusine, G. et al. Analysis and mitigation of interface losses in trenched superconducting coplanar waveguide resonators. Appl. Phys. Lett. 112, 062601 (2018)

    2018

  43. [43]

    Alegria, L. D. et al. Two-level systems in nucleated and non-nucleated epitaxial alpha- tantalum films. Appl. Phys. Lett. 123, 062601 (2023)

    2023

  44. [44]

    Dhundhwal, R. et al. High-quality superconducting tantalum resonators with beta phase defects. Appl. Phys. Lett. 127, 214005 (2025)

    2025

  45. [45]

    Kes, P. H. & Tsuei, C. C. Two-dimensional collective flux pinning, defects, and structural relaxation in amorphous superconducting films. Phys. Rev. B 28, 5126–5139 (1983)

    1983

  46. [46]

    & Werthamer, N

    Helfand, E. & Werthamer, N. R. Temperature and Purity Dependence of the Superconducting Critical Field, ${H}_{c2}$. II. Phys. Rev. 147, 288–294 (1966). Extended Material Extended Figure 1: Scanning Tunnelling Electron Microscopy (STEM) and Energy Dispersion Spectroscopy ( EDS) images of α-Ta resonator cross section from the inner edge of the lumped-elemen...

    1966