---
OA_place: repository
OA_type: green
_id: '22619'
abstract:
- lang: eng
  text: Planar germanium is currently the only semiconducting platform where high-coherence
    spin qubits and proximity-induced superconductivity have each been demonstrated.
    Recent research into spin qubits in Ge/SiGe heterostructures has focused on increasing
    the thickness of the SiGe capping layer, reporting improvements in the electrostatic
    noise levels. Meanwhile, heterostructures with thinner capping layers remain rather
    unexplored, despite the potential advantages for proximity-induced superconductivity.
    Here, we study a Ge/SiGe heterostructure with a thin SiGe cap d - 4nm and investigate
    its viability to host low-noise quantum dots. To keep the thermal budget compatible
    with superconducting layers, low-temperature oxide deposition processes were developed
    and implemented for the gate dielectrics. The charge noise level of the fabricated
    devices is estimated to be 1.8  +- 1.0 μeV/ square HZ⁠, comparable to devices
    fabricated on shallow heterostructures (⁠ d - 20nm⁠) with high-temperature deposited
    oxides. Low charge noise levels, together with the straightforward integration
    of superconductors, make this heterostructure an attractive platform for prototyping
    hybrid semiconducting–superconducting devices.
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
acknowledgement: 'We sincerely thank Nick van Loo, Greg Mazur, Dhananjay Joshi, and
  Srijit Goswami for their inputs on low-temperature HfOx deposition; Matias Urdampilleta
  and Daniel Jirovec for discussions; and Kristen Léonard for the careful reading
  of the manuscript. This research was supported by the Scientific Service Units of
  ISTA through resources provided by the Miba Machine Shop and the Nanofabrication
  facility. The authors acknowledge support from the NOMIS Foundation; the European
  Innovation Council Pathfinder Grant No. 101115315 (QuKiT); the FWF Projects with
  DOI:10.55776/F86, DOI:10.55776/PAT7682124, and DOI:10.55776/P36507; and the HE-MSCA-PF
  project with DOI:10.3030/101150858. ICN2 is supported by the Severo Ochoa Program
  from Spanish MCIN/AEI (Grant No.: CEX2021-001214-S) and is funded by the CERCA Program/Generalitat
  de Catalunya. ICN2 acknowledges funding from Generalitat de Catalunya (No. 2021SGR00457).
  We acknowledge support from the CSIC Interdisciplinary Thematic Platform (PTI+)
  on Quantum Technologies (PTI-QTEP+).'
article_number: '033505'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Maksim
  full_name: Borovkov, Maksim
  id: 1fd0975f-8b61-11ed-b69e-d149334f28c5
  last_name: Borovkov
- first_name: Yona A
  full_name: Schell, Yona A
  id: fe39122d-06bb-11ec-a33b-9e22b40e40a5
  last_name: Schell
- first_name: Dina
  full_name: Sokolova, Dina
  id: 2d2d62f8-72f0-11ef-b75a-8ec3e8a60032
  last_name: Sokolova
- first_name: Kevin Etienne Robert
  full_name: Roux, Kevin Etienne Robert
  id: 53f93ea2-803f-11ed-ab7e-b283135794ef
  last_name: Roux
- first_name: Paul
  full_name: Falthansl-Scheinecker, Paul
  id: 85b43b21-15b2-11ec-abd3-e2c252cc2285
  last_name: Falthansl-Scheinecker
- first_name: Giorgio
  full_name: Fabris, Giorgio
  id: 298cf6f3-1ff6-11ee-9fa6-d94cfa0b3352
  last_name: Fabris
- first_name: Devashish C
  full_name: Shah, Devashish C
  id: de191434-4e7e-11ef-bf4b-9a056fc19fc3
  last_name: Shah
  orcid: 0009-0007-5829-7707
- first_name: Jaime
  full_name: Saez Mollejo, Jaime
  id: e0390f72-f6e0-11ea-865d-862393336714
  last_name: Saez Mollejo
- first_name: Rodolfo
  full_name: Previdi, Rodolfo
  id: bc4ea1dc-00ce-11ec-8a4e-b325ca8b9876
  last_name: Previdi
- first_name: Inas
  full_name: Taha, Inas
  last_name: Taha
- first_name: Aziz
  full_name: Genç, Aziz
  last_name: Genç
- first_name: Jordi
  full_name: Arbiol, Jordi
  last_name: Arbiol
- first_name: Stefano
  full_name: Calcaterra, Stefano
  last_name: Calcaterra
- first_name: Afonso De Cerdeira
  full_name: Oliveira, Afonso De Cerdeira
  last_name: Oliveira
- first_name: Daniel
  full_name: Chrastina, Daniel
  last_name: Chrastina
- first_name: Giovanni
  full_name: Isella, Giovanni
  last_name: Isella
- first_name: Anton
  full_name: Bubis, Anton
  id: 1f6212b5-f795-11ec-9c0c-de4780302890
  last_name: Bubis
- first_name: Georgios
  full_name: Katsaros, Georgios
  id: 38DB5788-F248-11E8-B48F-1D18A9856A87
  last_name: Katsaros
  orcid: 0000-0001-8342-202X
citation:
  ama: Borovkov M, Schell YA, Sokolova D, et al. Low-noise quantum dots in ultra-shallow
    Ge/SiGe heterostructures for prototyping hybrid semiconducting–superconducting
    devices. <i>Applied Physics Letters</i>. 2026;129(3). doi:<a href="https://doi.org/10.1063/5.0333142">10.1063/5.0333142</a>
  apa: Borovkov, M., Schell, Y. A., Sokolova, D., Roux, K. E. R., Falthansl-Scheinecker,
    P., Fabris, G., … Katsaros, G. (2026). Low-noise quantum dots in ultra-shallow
    Ge/SiGe heterostructures for prototyping hybrid semiconducting–superconducting
    devices. <i>Applied Physics Letters</i>. AIP Publishing. <a href="https://doi.org/10.1063/5.0333142">https://doi.org/10.1063/5.0333142</a>
  chicago: Borovkov, Maksim, Yona A Schell, Dina Sokolova, Kevin Etienne Robert Roux,
    Paul Falthansl-Scheinecker, Giorgio Fabris, Devashish C Shah, et al. “Low-Noise
    Quantum Dots in Ultra-Shallow Ge/SiGe Heterostructures for Prototyping Hybrid
    Semiconducting–Superconducting Devices.” <i>Applied Physics Letters</i>. AIP Publishing,
    2026. <a href="https://doi.org/10.1063/5.0333142">https://doi.org/10.1063/5.0333142</a>.
  ieee: M. Borovkov <i>et al.</i>, “Low-noise quantum dots in ultra-shallow Ge/SiGe
    heterostructures for prototyping hybrid semiconducting–superconducting devices,”
    <i>Applied Physics Letters</i>, vol. 129, no. 3. AIP Publishing, 2026.
  ista: Borovkov M, Schell YA, Sokolova D, Roux KER, Falthansl-Scheinecker P, Fabris
    G, Shah DC, Saez Mollejo J, Previdi R, Taha I, Genç A, Arbiol J, Calcaterra S,
    Oliveira ADC, Chrastina D, Isella G, Bubis A, Katsaros G. 2026. Low-noise quantum
    dots in ultra-shallow Ge/SiGe heterostructures for prototyping hybrid semiconducting–superconducting
    devices. Applied Physics Letters. 129(3), 033505.
  mla: Borovkov, Maksim, et al. “Low-Noise Quantum Dots in Ultra-Shallow Ge/SiGe Heterostructures
    for Prototyping Hybrid Semiconducting–Superconducting Devices.” <i>Applied Physics
    Letters</i>, vol. 129, no. 3, 033505, AIP Publishing, 2026, doi:<a href="https://doi.org/10.1063/5.0333142">10.1063/5.0333142</a>.
  short: M. Borovkov, Y.A. Schell, D. Sokolova, K.E.R. Roux, P. Falthansl-Scheinecker,
    G. Fabris, D.C. Shah, J. Saez Mollejo, R. Previdi, I. Taha, A. Genç, J. Arbiol,
    S. Calcaterra, A.D.C. Oliveira, D. Chrastina, G. Isella, A. Bubis, G. Katsaros,
    Applied Physics Letters 129 (2026).
corr_author: '1'
das_tickbox: '1'
dataavailabilitystatement: The data that support the findings of this study are openly
  available in Institute of Science and Technology repository at http://doi.org/10.15479/AT-ISTA-22242,
  Ref. 50.
date_created: 2026-08-02T22:01:53Z
date_published: 2026-07-20T00:00:00Z
date_updated: 2026-08-03T11:08:39Z
day: '20'
department:
- _id: GeKa
- _id: GradSch
- _id: NanoFab
doi: 10.1063/5.0333142
external_id:
  arxiv:
  - '2602.21363'
fulldoi: https://doi.org/10.1063/5.0333142
intvolume: '       129'
issue: '3'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.48550/arXiv.2602.21363
month: '07'
oa: 1
oa_version: Preprint
project:
- _id: bdc2ca30-d553-11ed-ba76-cf164a5bb811
  grant_number: '101115315'
  name: Quantum bits with Kitaev Transmons
- _id: 34a66131-11ca-11ed-8bc3-a31681c6b03e
  grant_number: F8606
  name: 'Center for Correlated Quantum Materials and Solid State Quantum Systems:
    Conventional  and unconventional topological superconductors'
- _id: 5b9e579c-ab3d-11f0-914f-88754c5b5a3f
  grant_number: PAT 7682124
  name: Superconducting spin qubits in planar Ge
- _id: bd8bd29e-d553-11ed-ba76-f0070d4b237a
  grant_number: P36507
  name: Merging spin and superconducting qubits in planar Ge
- _id: 8ea8abf7-16d5-11f0-9cad-c41e56ec8bb3
  grant_number: '101150858'
  name: Realization and Manipulation of a Planar hybrid superconducting Andreev spin
    qubit in Germanium
publication: Applied Physics Letters
publication_identifier:
  eissn:
  - 1077-3118
  issn:
  - 0003-6951
publication_status: published
publisher: AIP Publishing
quality_controlled: '1'
related_material:
  record:
  - id: '22242'
    relation: research_data
    status: public
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: yes
title: Low-noise quantum dots in ultra-shallow Ge/SiGe heterostructures for prototyping
  hybrid semiconducting–superconducting devices
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 129
year: '2026'
...
---
APC_amount: 6828 EUR
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '17202'
abstract:
- lang: eng
  text: Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions
    have recently emerged as building blocks for hybrid quantum circuits. In this
    study, we present a gatemon fabricated in planar Germanium. We induce superconductivity
    in a two-dimensional hole gas by evaporating aluminum atop a thin spacer, which
    separates the superconductor from the Ge quantum well. The Josephson junction
    is then integrated into an Xmon circuit and capacitively coupled to a transmission
    line resonator. We showcase the qubit tunability in a broad frequency range with
    resonator and two-tone spectroscopy. Time-domain characterizations reveal energy
    relaxation and coherence times up to 75 ns. Our results, combined with the recent
    advances in the spin qubit field, pave the way towards novel hybrid and protected
    qubits in a group IV, CMOS-compatible material.
acknowledged_ssus:
- _id: ScienComp
- _id: M-Shop
- _id: NanoFab
acknowledgement: "We acknowledge Lucas Casparis, Jeroen Danon, Valla Fatemi, Morten
  Kjaergard and Javad Shabani for their valuable insights and comments. This research
  was supported by the Scientific Service Units of ISTA through resources provided
  by the MIBA Machine Shop\r\nand the Nanofabrication facility. This research and
  related results were made possible with the support of the NOMIS Foundation and
  the FWF Projects with DOI:10.55776/I5060 and DOI:10.55776/P36507. We also acknowledge
  the NextGenerationEU PRIN project\r\n2022A8CJP3 (GAMESQUAD) for partial financial
  support."
article_number: '6400'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Oliver
  full_name: Sagi, Oliver
  id: 71616374-A8E9-11E9-A7CA-09ECE5697425
  last_name: Sagi
- first_name: Alessandro
  full_name: Crippa, Alessandro
  id: 1F2B21A2-F6E7-11E9-9B82-F7DBE5697425
  last_name: Crippa
  orcid: 0000-0002-2968-611X
- first_name: Marco
  full_name: Valentini, Marco
  id: C0BB2FAC-D767-11E9-B658-BC13E6697425
  last_name: Valentini
- first_name: Marian
  full_name: Janik, Marian
  id: 396A1950-F248-11E8-B48F-1D18A9856A87
  last_name: Janik
  orcid: 0009-0003-9037-8831
- first_name: Levon
  full_name: Baghumyan, Levon
  id: 7aa1f788-b527-11ee-aa9e-e6111a79e0c7
  last_name: Baghumyan
- first_name: Giorgio
  full_name: Fabris, Giorgio
  id: 298cf6f3-1ff6-11ee-9fa6-d94cfa0b3352
  last_name: Fabris
- first_name: Lucky
  full_name: Kapoor, Lucky
  id: 84b9700b-15b2-11ec-abd3-831089e67615
  last_name: Kapoor
  orcid: 0000-0001-8319-2148
- first_name: Farid
  full_name: Hassani, Farid
  id: 2AED110C-F248-11E8-B48F-1D18A9856A87
  last_name: Hassani
  orcid: 0000-0001-6937-5773
- first_name: Johannes M
  full_name: Fink, Johannes M
  id: 4B591CBA-F248-11E8-B48F-1D18A9856A87
  last_name: Fink
  orcid: 0000-0001-8112-028X
- first_name: Stefano
  full_name: Calcaterra, Stefano
  last_name: Calcaterra
- first_name: Daniel
  full_name: Chrastina, Daniel
  last_name: Chrastina
- first_name: Giovanni
  full_name: Isella, Giovanni
  last_name: Isella
- first_name: Georgios
  full_name: Katsaros, Georgios
  id: 38DB5788-F248-11E8-B48F-1D18A9856A87
  last_name: Katsaros
  orcid: 0000-0001-8342-202X
citation:
  ama: Sagi O, Crippa A, Valentini M, et al. A gate tunable transmon qubit in planar
    Ge. <i>Nature Communications</i>. 2024;15. doi:<a href="https://doi.org/10.1038/s41467-024-50763-6">10.1038/s41467-024-50763-6</a>
  apa: Sagi, O., Crippa, A., Valentini, M., Janik, M., Baghumyan, L., Fabris, G.,
    … Katsaros, G. (2024). A gate tunable transmon qubit in planar Ge. <i>Nature Communications</i>.
    Springer Nature. <a href="https://doi.org/10.1038/s41467-024-50763-6">https://doi.org/10.1038/s41467-024-50763-6</a>
  chicago: Sagi, Oliver, Alessandro Crippa, Marco Valentini, Marian Janik, Levon Baghumyan,
    Giorgio Fabris, Lucky Kapoor, et al. “A Gate Tunable Transmon Qubit in Planar
    Ge.” <i>Nature Communications</i>. Springer Nature, 2024. <a href="https://doi.org/10.1038/s41467-024-50763-6">https://doi.org/10.1038/s41467-024-50763-6</a>.
  ieee: O. Sagi <i>et al.</i>, “A gate tunable transmon qubit in planar Ge,” <i>Nature
    Communications</i>, vol. 15. Springer Nature, 2024.
  ista: Sagi O, Crippa A, Valentini M, Janik M, Baghumyan L, Fabris G, Kapoor L, Hassani
    F, Fink JM, Calcaterra S, Chrastina D, Isella G, Katsaros G. 2024. A gate tunable
    transmon qubit in planar Ge. Nature Communications. 15, 6400.
  mla: Sagi, Oliver, et al. “A Gate Tunable Transmon Qubit in Planar Ge.” <i>Nature
    Communications</i>, vol. 15, 6400, Springer Nature, 2024, doi:<a href="https://doi.org/10.1038/s41467-024-50763-6">10.1038/s41467-024-50763-6</a>.
  short: O. Sagi, A. Crippa, M. Valentini, M. Janik, L. Baghumyan, G. Fabris, L. Kapoor,
    F. Hassani, J.M. Fink, S. Calcaterra, D. Chrastina, G. Isella, G. Katsaros, Nature
    Communications 15 (2024).
corr_author: '1'
date_created: 2024-07-04T11:40:45Z
date_published: 2024-07-30T00:00:00Z
date_updated: 2026-04-07T13:01:55Z
day: '30'
ddc:
- '530'
department:
- _id: GeKa
- _id: JoFi
- _id: GradSch
doi: 10.1038/s41467-024-50763-6
external_id:
  arxiv:
  - '2403.16774'
  isi:
  - '001281271000022'
  pmid:
  - '39080279'
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language:
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month: '07'
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oa_version: Published Version
pmid: 1
project:
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  grant_number: P36507
  name: Merging spin and superconducting qubits in planar Ge
- _id: c0977eea-5a5b-11eb-8a69-a862db0cf4d1
  grant_number: I05060
  name: High impedance circuit quantum electrodynamics with hole spins
- _id: 262116AA-B435-11E9-9278-68D0E5697425
  name: Hybrid Semiconductor - Superconductor Quantum Devices
- _id: 3AC91DDA-15DF-11EA-824D-93A3E7B544D1
  call_identifier: FWF
  name: FWF Open Access Fund
publication: Nature Communications
publication_identifier:
  eissn:
  - 2041-1723
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
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    url: https://doi.org/10.1038/s41467-024-53910-1
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title: A gate tunable transmon qubit in planar Ge
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...