---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '19401'
abstract:
- lang: eng
  text: High kinetic inductance superconductors are gaining increasing interest for
    the realisation of qubits, amplifiers and detectors. Moreover, thanks to their
    high impedance, quantum buses made of such materials enable large zero-point fluctuations
    of the voltage, boosting the coupling rates to spin and charge qubits. However,
    fully exploiting the potential of disordered or granular superconductors is challenging,
    as their inductance and, therefore, impedance at high values are difficult to
    control. Here, we report a reproducible fabrication of granular aluminium resonators
    by developing a wireless ohmmeter, which allows in situ measurements during film
    deposition and, therefore, control of the kinetic inductance of granular aluminium
    films. Reproducible fabrication of circuits with impedances (inductances) exceeding
    13 kΩ (1 nH per square) is now possible. By integrating a 7.9 kΩ resonator with
    a germanium double quantum dot, we demonstrate strong charge-photon coupling with
    a rate of gc/2π = 566 ± 2 MHz. This broadly applicable method opens the path for
    novel qubits and high-fidelity, long-distance two-qubit gates.
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
acknowledgement: 'We acknowledge Franco De Palma, Mahya Khorramshahi, Fabian Oppliger,
  Thomas Reisinger, Pasquale Scarlino and Xiao Xue for helpful discussions. We thank
  Simon Robson for proofreading 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. This research and related results were made
  possible with the support of the NOMIS Foundation and the HORIZON-RIA 101069515
  project. This research was funded in whole or in part by the Austrian Science Fund
  (FWF) https://doi.org/10.55776/P32235, https://doi.org/10.55776/I5060 and https://doi.org/10.55776/P36507.
  For Open Access purposes, the author has applied a CC BY public copyright license
  to any author accepted manuscript version arising from this submission. M.J. acknowledges
  funding from FellowQUTE 2024-01. K.R. acknowledges funding from the European Union’s
  Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant
  Agreement No. 101034413. I.M.P. acknowledges funding from the Deutsche Forschungsgemeinschaft
  (DFG - German Research Foundation) under project number 450396347 (GeHoldeQED).
  ICN2 acknowledges funding from Generalitat de Catalunya 2021SGR00457. We acknowledge
  support from CSIC Interdisciplinary Thematic Platform (PTI+) on Quantum Technologies
  (PTI-QTEP+). This research work has been funded by the European Commission - NextGenerationEU
  (Regulation EU 2020/2094), through CSIC’s Quantum Technologies Platform (QTEP).
  ICN2 is supported by the Severo Ochoa programme from Spanish MCIN/AEI (Grant No.:
  CEX2021-001214-S) and is funded by the CERCA Programme/Generalitat de Catalunya.
  Part of the present work has been performed in the framework of Universitat Autònoma
  de Barcelona Materials Science PhD programme. AGM has received funding from Grant
  RYC2021-033479-I funded by MCIN/AEI/10.13039/501100011033 and by European Union
  NextGenerationEU/PRTR. M.B. acknowledges support from SUR Generalitat de Catalunya
  and the EU Social Fund; project ref. 2020 FI 00103. The authors acknowledge the
  use of instrumentation and the technical advice provided by the Joint Electron Microscopy
  Centre at ALBA (JEMCA). ICN2 acknowledges funding from Grant IU16-014206 (METCAM-FIB)
  funded by the European Union through the European Regional Development Fund (ERDF),
  with the support of the Ministry of Research and Universities, Generalitat de Catalunya.
  ICN2 is a founding member of e-DREAM60.'
article_number: '2103'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Marian
  full_name: Janik, Marian
  id: 396A1950-F248-11E8-B48F-1D18A9856A87
  last_name: Janik
  orcid: 0009-0003-9037-8831
- first_name: Kevin Etienne Robert
  full_name: Roux, Kevin Etienne Robert
  id: 53f93ea2-803f-11ed-ab7e-b283135794ef
  last_name: Roux
- first_name: Carla N
  full_name: Borja Espinosa, Carla N
  id: 18777c01-896a-11ed-bdf8-e4851dc07d16
  last_name: Borja Espinosa
- first_name: Oliver
  full_name: Sagi, Oliver
  id: 71616374-A8E9-11E9-A7CA-09ECE5697425
  last_name: Sagi
- first_name: Abdulhamid
  full_name: Baghdadi, Abdulhamid
  id: 160D87FA-96B5-11E9-BF77-7626E6697425
  last_name: Baghdadi
- first_name: Thomas
  full_name: Adletzberger, Thomas
  id: 38756BB2-F248-11E8-B48F-1D18A9856A87
  last_name: Adletzberger
- first_name: Stefano
  full_name: Calcaterra, Stefano
  last_name: Calcaterra
- first_name: Marc
  full_name: Botifoll, Marc
  last_name: Botifoll
- first_name: Alba
  full_name: Garzón Manjón, Alba
  last_name: Garzón Manjón
- first_name: Jordi
  full_name: Arbiol, Jordi
  last_name: Arbiol
- first_name: Daniel
  full_name: Chrastina, Daniel
  last_name: Chrastina
- first_name: Giovanni
  full_name: Isella, Giovanni
  last_name: Isella
- first_name: Ioan M.
  full_name: Pop, Ioan M.
  last_name: Pop
- first_name: Georgios
  full_name: Katsaros, Georgios
  id: 38DB5788-F248-11E8-B48F-1D18A9856A87
  last_name: Katsaros
  orcid: 0000-0001-8342-202X
citation:
  ama: Janik M, Roux KER, Borja Espinosa CN, et al. Strong charge-photon coupling
    in planar germanium enabled by granular aluminium superinductors. <i>Nature Communications</i>.
    2025;16. doi:<a href="https://doi.org/10.1038/s41467-025-57252-4">10.1038/s41467-025-57252-4</a>
  apa: Janik, M., Roux, K. E. R., Borja Espinosa, C. N., Sagi, O., Baghdadi, A., Adletzberger,
    T., … Katsaros, G. (2025). Strong charge-photon coupling in planar germanium enabled
    by granular aluminium superinductors. <i>Nature Communications</i>. Springer Nature.
    <a href="https://doi.org/10.1038/s41467-025-57252-4">https://doi.org/10.1038/s41467-025-57252-4</a>
  chicago: Janik, Marian, Kevin Etienne Robert Roux, Carla N Borja Espinosa, Oliver
    Sagi, Abdulhamid Baghdadi, Thomas Adletzberger, Stefano Calcaterra, et al. “Strong
    Charge-Photon Coupling in Planar Germanium Enabled by Granular Aluminium Superinductors.”
    <i>Nature Communications</i>. Springer Nature, 2025. <a href="https://doi.org/10.1038/s41467-025-57252-4">https://doi.org/10.1038/s41467-025-57252-4</a>.
  ieee: M. Janik <i>et al.</i>, “Strong charge-photon coupling in planar germanium
    enabled by granular aluminium superinductors,” <i>Nature Communications</i>, vol.
    16. Springer Nature, 2025.
  ista: Janik M, Roux KER, Borja Espinosa CN, Sagi O, Baghdadi A, Adletzberger T,
    Calcaterra S, Botifoll M, Garzón Manjón A, Arbiol J, Chrastina D, Isella G, Pop
    IM, Katsaros G. 2025. Strong charge-photon coupling in planar germanium enabled
    by granular aluminium superinductors. Nature Communications. 16, 2103.
  mla: Janik, Marian, et al. “Strong Charge-Photon Coupling in Planar Germanium Enabled
    by Granular Aluminium Superinductors.” <i>Nature Communications</i>, vol. 16,
    2103, Springer Nature, 2025, doi:<a href="https://doi.org/10.1038/s41467-025-57252-4">10.1038/s41467-025-57252-4</a>.
  short: M. Janik, K.E.R. Roux, C.N. Borja Espinosa, O. Sagi, A. Baghdadi, T. Adletzberger,
    S. Calcaterra, M. Botifoll, A. Garzón Manjón, J. Arbiol, D. Chrastina, G. Isella,
    I.M. Pop, G. Katsaros, Nature Communications 16 (2025).
corr_author: '1'
date_created: 2025-03-16T23:01:23Z
date_published: 2025-03-01T00:00:00Z
date_updated: 2025-09-30T11:03:35Z
day: '01'
ddc:
- '530'
department:
- _id: GeKa
- _id: JoFi
- _id: M-Shop
doi: 10.1038/s41467-025-57252-4
ec_funded: 1
external_id:
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  - '2407.03079'
  isi:
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month: '03'
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oa_version: Published Version
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  grant_number: '101069515'
  name: Integrated Germanium Quantum Technology
- _id: 237B3DA4-32DE-11EA-91FC-C7463DDC885E
  call_identifier: FWF
  grant_number: P32235
  name: Towards scalable hut wire quantum devices
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  grant_number: I05060
  name: High impedance circuit quantum electrodynamics with hole spins
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  name: Merging spin and superconducting qubits in planar Ge
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  call_identifier: H2020
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publication: Nature Communications
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title: Strong charge-photon coupling in planar germanium enabled by granular aluminium
  superinductors
tmp:
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  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
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...
---
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abstract:
- lang: eng
  text: "High kinetic inductance superconductors are gaining increasing interest for\r\nthe
    realisation of qubits, amplifiers and detectors. Moreover, thanks to their\r\nhigh
    impedance, quantum buses made of such materials enable large zero-point\r\nfluctuations
    of the voltage, boosting the coupling rates to spin and charge\r\nqubits. However,
    fully exploiting the potential of disordered or granular\r\nsuperconductors is
    challenging, as their inductance and, therefore, impedance\r\nat high values are
    difficult to control. Here we have integrated a granular\r\naluminium resonator,
    having a characteristic impedance exceeding the resistance\r\nquantum, with a
    germanium double quantum dot and demonstrate strong\r\ncharge-photon coupling
    with a rate of $g_\\text{c}/2\\pi= (566 \\pm 2)$ MHz. This\r\nwas achieved due
    to the realisation of a wireless ohmmeter, which allows\r\n\\emph{in situ} measurements
    during film deposition and, therefore, control of\r\nthe kinetic inductance of
    granular aluminium films. Reproducible fabrication of\r\ncircuits with impedances
    (inductances) exceeding 13 k$\\Omega$ (1 nH per square)\r\nis now possible. This
    broadly applicable method opens the path for novel qubits\r\nand high-fidelity,
    long-distance two-qubit gates."
acknowledged_ssus:
- _id: M-Shop
- _id: NanoFab
acknowledgement: "We acknowledge Franco De Palma, Mahya Khorramshahi, Fabian Oppliger,
  Thomas Reisinger, Pasquale Scarlino and Xiao Xue for helpful discussions. This research
  was supported by the Scientific Service Units of ISTA through resources provided
  by the MIBA Machine Shop and the Nanofabrication facility. This research and related
  results were made possible with the support of the NOMIS Foundation, the HORIZON-RIA
  101069515 project, the FWF Projects with DOI:10.55776/P32235, DOI:10.55776/I5060
  and DOI:10.55776/P36507. IMP acknowledges funding from the Deutsche Forschungsgemeinschaft
  (DFG – German Research Foundation) under project number 450396347 (GeHoldeQED).
  ICN2 acknowledges funding from Generalitat de Catalunya 2021SGR00457. We acknowledge
  support from CSIC Interdisciplinary Thematic Platform (PTI+) on Quantum Technologies
  (PTI-QTEP+). This research work has been funded by the European Commission – NextGenerationEU
  (Regulation EU 2020/2094), through CSIC’s\r\nQuantum Technologies Platform (QTEP).
  ICN2 is supported by the Severo Ochoa program from Spanish MCIN/AEI (Grant No.:
  CEX2021-001214-S) and is funded by the CERCA Programme/Generalitat de Catalunya.
  Part of the present work has been performed in the framework of Universitat Autònoma
  de Barcelona Materials Science PhD program. AGM has received funding from Grant
  RYC2021-033479-I funded by MCIN/AEI/10.13039/501100011033 and by European Union
  NextGenerationEU/PRTR. M.B. acknowledges support from SUR Generalitat de Catalunya
  and the EU Social Fund; project ref. 2020 FI 00103. The authors\r\nacknowledge the
  use of instrumentation and the technical advice provided by the Joint Electron Microscopy
  Center at ALBA (JEMCA). ICN2 acknowledges funding from Grant IU16-014206 (METCAM-FIB)
  funded by the European Union through the European Regional Development\r\nFund (ERDF),
  with the support of the Ministry of Research and Universities, Generalitat de Catalunya.
  ICN2 is a founding member of e-DREAM [60]."
article_number: '2407.03079'
article_processing_charge: No
arxiv: 1
author:
- first_name: Marian
  full_name: Janik, Marian
  id: 396A1950-F248-11E8-B48F-1D18A9856A87
  last_name: Janik
  orcid: 0009-0003-9037-8831
- first_name: Kevin Etienne Robert
  full_name: Roux, Kevin Etienne Robert
  id: 53f93ea2-803f-11ed-ab7e-b283135794ef
  last_name: Roux
- first_name: Carla N
  full_name: Borja Espinosa, Carla N
  id: 18777c01-896a-11ed-bdf8-e4851dc07d16
  last_name: Borja Espinosa
- first_name: Oliver
  full_name: Sagi, Oliver
  id: 71616374-A8E9-11E9-A7CA-09ECE5697425
  last_name: Sagi
- first_name: Abdulhamid
  full_name: Baghdadi, Abdulhamid
  id: 160D87FA-96B5-11E9-BF77-7626E6697425
  last_name: Baghdadi
- first_name: Thomas
  full_name: Adletzberger, Thomas
  id: 38756BB2-F248-11E8-B48F-1D18A9856A87
  last_name: Adletzberger
- first_name: Stefano
  full_name: Calcaterra, Stefano
  last_name: Calcaterra
- first_name: Marc
  full_name: Botifoll, Marc
  last_name: Botifoll
- first_name: Alba Garzón
  full_name: Manjón, Alba Garzón
  last_name: Manjón
- first_name: Jordi
  full_name: Arbiol, Jordi
  last_name: Arbiol
- first_name: Daniel
  full_name: Chrastina, Daniel
  last_name: Chrastina
- first_name: Giovanni
  full_name: Isella, Giovanni
  last_name: Isella
- first_name: Ioan M.
  full_name: Pop, Ioan M.
  last_name: Pop
- first_name: Georgios
  full_name: Katsaros, Georgios
  id: 38DB5788-F248-11E8-B48F-1D18A9856A87
  last_name: Katsaros
  orcid: 0000-0001-8342-202X
citation:
  ama: Janik M, Roux KER, Borja Espinosa CN, et al. Strong charge-photon coupling
    in planar germanium enabled by granular  aluminium superinductors. <i>arXiv</i>.
    doi:<a href="https://doi.org/10.48550/arXiv.2407.03079">10.48550/arXiv.2407.03079</a>
  apa: Janik, M., Roux, K. E. R., Borja Espinosa, C. N., Sagi, O., Baghdadi, A., Adletzberger,
    T., … Katsaros, G. (n.d.). Strong charge-photon coupling in planar germanium enabled
    by granular  aluminium superinductors. <i>arXiv</i>. <a href="https://doi.org/10.48550/arXiv.2407.03079">https://doi.org/10.48550/arXiv.2407.03079</a>
  chicago: Janik, Marian, Kevin Etienne Robert Roux, Carla N Borja Espinosa, Oliver
    Sagi, Abdulhamid Baghdadi, Thomas Adletzberger, Stefano Calcaterra, et al. “Strong
    Charge-Photon Coupling in Planar Germanium Enabled by Granular  Aluminium Superinductors.”
    <i>ArXiv</i>, n.d. <a href="https://doi.org/10.48550/arXiv.2407.03079">https://doi.org/10.48550/arXiv.2407.03079</a>.
  ieee: M. Janik <i>et al.</i>, “Strong charge-photon coupling in planar germanium
    enabled by granular  aluminium superinductors,” <i>arXiv</i>. .
  ista: Janik M, Roux KER, Borja Espinosa CN, Sagi O, Baghdadi A, Adletzberger T,
    Calcaterra S, Botifoll M, Manjón AG, Arbiol J, Chrastina D, Isella G, Pop IM,
    Katsaros G. Strong charge-photon coupling in planar germanium enabled by granular 
    aluminium superinductors. arXiv, 2407.03079.
  mla: Janik, Marian, et al. “Strong Charge-Photon Coupling in Planar Germanium Enabled
    by Granular  Aluminium Superinductors.” <i>ArXiv</i>, 2407.03079, doi:<a href="https://doi.org/10.48550/arXiv.2407.03079">10.48550/arXiv.2407.03079</a>.
  short: M. Janik, K.E.R. Roux, C.N. Borja Espinosa, O. Sagi, A. Baghdadi, T. Adletzberger,
    S. Calcaterra, M. Botifoll, A.G. Manjón, J. Arbiol, D. Chrastina, G. Isella, I.M.
    Pop, G. Katsaros, ArXiv (n.d.).
corr_author: '1'
date_created: 2024-09-26T09:50:43Z
date_published: 2024-07-03T00:00:00Z
date_updated: 2026-04-29T22:30:21Z
day: '03'
department:
- _id: GeKa
- _id: GradSch
- _id: JoFi
doi: 10.48550/arXiv.2407.03079
external_id:
  arxiv:
  - '2407.03079'
language:
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main_file_link:
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  url: https://doi.org/10.48550/arXiv.2407.03079
month: '07'
oa: 1
oa_version: Preprint
project:
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  grant_number: '101069515'
  name: Integrated Germanium Quantum Technology
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  call_identifier: FWF
  grant_number: P32235
  name: Towards scalable hut wire quantum devices
- _id: bd8bd29e-d553-11ed-ba76-f0070d4b237a
  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
publication: arXiv
publication_status: draft
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title: Strong charge-photon coupling in planar germanium enabled by granular  aluminium
  superinductors
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