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  • Open Access

Two-Dimensional Si Spin Qubit Arrays with Multilevel Interconnects

Sieu D. Ha, Edwin Acuna*, Kate Raach, Zachery T. Bloom, Teresa L. Brecht, James M. Chappell, Maxwell D. Choi, Justin E. Christensen, Ian T. Counts et al.

Dominic Daprano, J.P. Dodson, Kevin Eng, David J. Fialkow, Christina A. C. Garcia, Wonill Ha, Thomas R. B. Harris, nathan holman†, Isaac Khalaf, Justine W. Matten, Christi A. Peterson, Clifford E. Plesha, Matthew J. Ruiz, Aaron Smith, Bryan J. Thomas, Samuel J. Whiteley, Thaddeus D. Ladd, Michael P. Jura, Matthew T. Rakher, and Matthew G. Borselli

  • *Contact author: eacuna@hrl.com
  • †Present address: Rigetti Computing, 775 Heinz Avenue, Berkeley, CA 94710.
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PRX Quantum 6, 030327 – Published 14 August, 2025

DOI: https://doi.org/10.1103/sgn1-1t2d

Abstract

The promise of quantum computation is contingent upon physical qubits with both a low gate error rate and broad scalability. Silicon-based spins are a leading qubit platform but demonstrations to date have not utilized fabrication processes capable of extending arrays in two dimensions while maintaining complete control of individual spins. Here, we implement an interconnect process, common in semiconductor manufacturing, with multiple back-end-of-line layers, to show an extendable two-dimensional array of spins with fully controllable nearest-neighbor exchange interactions. In a device using three interconnect layers, we encode exchange-only qubits and achieve average single-qubit gate fidelities consistent with single-layer devices, including fidelities greater than 99.9%, as measured by blind randomized benchmarking. Moreover, with spin connectivity in two dimensions, we show that both linear and right-angle exchange-only qubits with high performance can be formed, enabling qubit array reconfigurability in the presence of defects. This extendable device platform demonstrates that industrial manufacturing techniques can be leveraged for scalable spin qubit technologies.

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Physics Subject Headings (PhySH)

Popular Summary

Silicon-based qubits are of interest for quantum information processing largely because of the potential to leverage complementary metal-oxide-semiconductor (CMOS) manufacturing for scaling. Silicon CMOS chips containing billions of transistors utilize many layers of nanoscale wires and vias known as interconnects to achieve contact between transistors and the external environment. However, silicon qubit chips to date have used architectures that do not leverage interconnects and cannot readily scale beyond one-dimensional arrays. Here we demonstrate an extendable two-dimensional array of silicon quantum dots fabricated using multiple interconnect layers and instantiate a spin-qubit modality called exchange only (EO), which uses three quantum dots, each with one electron, per qubit.

We fabricate a silicon qubit device with three interconnect layers to contact a 5×5 grid of gates used to control both quantum dots and charge sensors. Each spin in the two-dimensional array has quantum coherent connectivity with all nearest neighbors. Critically, we find the coherent performance metrics for all of the hosted EO spin qubits to be on par with those in single-interconnect linear arrays, and we do not observe correlations in performance with number of interconnect layers. The reconfigurability of EO qubits in such arrays will enable optimization of qubit array connectivity in a spin lattice around known defective sites.

Much work remains in these two-qubit arrays, especially in the measurement of multiqubit performance metrics and, of course, in scaling to much larger sizes.

Article Text

References (28)

  1. G. Burkard, T. D. Ladd, J. M. Nichol, A. Pan, and J. R. Petta, Semiconductor spin qubits, Rev. Mod. Phys. 95, 025003 (2023).
  2. N. D. Stuyck, A. Saraiva, W. Gilbert, J. C. Pardo, R. Li, C. C. Escott, K. D. Greve, S. Voinigescu, D. J. Reilly, and A. S. Dzurak, CMOS compatibility of semiconductor spin qubits, ArXiv:2409.03993 [cond-mat.mes-hall].
  3. B. Bertrand, B. Martinez, J. Li, B. C. Paz, V. Millory, V. Labracherie, L. Brévard, H. Sahin, G. Roussely, A. Sarrazin, T. Meunier, M. Vinet, Y.-M. Niquet, B. Brun, R. Maurand, S. De Franceschi, and H. Niebojewski, in 2023 International Electron Devices Meeting (IEDM) (IEEE, San Francisco, CA, 2023), pp. 1–4.
  4. A. M. J. Zwerver, A. M. J. Zwerver, T. Krähenmann, T. F. Watson, L. Lampert, H. C. George, R. Pillarisetty, S. A. Bojarski, P. Amin, S. V. Amitonov, J. M. Boter, R. Caudillo, D. Correas-Serrano, J. P. Dehollain, G. Droulers, E. M. Henry, R. Kotlyar, M. Lodari, F. Lüthi, D. J. Michalak, B. K. Mueller, S. Neyens, J. Roberts, N. Samkharadze, G. Zheng, O. K. Zietz, G. Scappucci, M. Veldhorst, L. M. K. Vandersypen, and J. S. Clarke, Qubits made by advanced semiconductor manufacturing, Nat. Electron. 5, 184 (2022).
  5. A. Elsayed, M. M. K. Shehata, C. Godfrin, S. Kubicek, S. Massar, Y. Canvel, J. Jussot, G. Simion, M. Mongillo, D. Wan, B. Govoreanu, I. P. Radu, R. Li, P. Van Dorpe, and K. De Greve, Low charge noise quantum dots with industrial CMOS manufacturing, npj Quantum Inf. 10, 70 (2024).
  6. S. G. J. Philips, M. T. Mądzik, S. V. Amitonov, S. L. de Snoo, M. Russ, N. Kalhor, C. Volk, William I. L. Lawrie, D. Brousse, L. Tryputen, B. P. Wuetz, A. Sammak, M. Veldhorst, G. Scappucci, and L. M. K. Vandersypen, Universal control of a six-qubit quantum processor in silicon, Nature 609, 919 (2022).
  7. F. Borsoi, N. W. Hendrickx, V. John, S. Motz, F. van Riggelen, A. Sammak, S. L. de Snoo, G. Scappucci, and M. Veldhorst, Shared control of a 16 semiconductor quantum dot crossbar array, Nat. Nanotechnol. 19, 21 (2024).
  8. W. Ha, S. D. Ha, M. D. Choi, Y. Tang, A. E. Schmitz, M. P. Levendorf, K. Lee, J. M. Chappell, T. S. Adams, D. R. Hulbert, E. Acuna, R. S. Noah, J. W. Matten, M. P. Jura, J. A. Wright, M. T. Rakher, and M. G. Borselli, A flexible design platform for Si/SiGe exchange-only qubits with low disorder, Nano Lett. 22, 1443 (2022).
  9. A. J. Weinstein, M. D. Reed, A. M. Jones, R. W. Andrews, D. Barnes, J. Z. Blumoff, L. E. Euliss, K. Eng, B. Fong, S. D. Ha, R. R. Hulbert, C. Jackson, M. Jura, T. E. Keating, J. Kerckhoff, A. A. Kiselev, J. Matten, G. Sabbir, A. Smith, J. Wright, M. T. Rakher, T. D. Ladd, and M. G. Borselli, Universal logic with encoded spin qubits in silicon, Nature 615, 817 (2023).
  10. E. Acuna, J. D. Broz, K. Shyamsundar, A. B. Mei, C. P. Feeney, V. Smetanka, T. Davis, K. Lee, M. D. Choi, B. Boyd, J. Suh, W. Ha, C. Jennings, A. S. Pan, D. S. Sanchez, M. D. Reed, and J. R. Petta, Coherent control of a triangular exchange-only spin qubit, Phys. Rev. Appl. 22, 044057 (2024).
  11. J. Z. Blumoff, A. S. Pan, T. E. Keating, R. W. Andrews, D. W. Barnes, T. L. Brecht, E. T. Croke, L. E. Euliss, J. A. Fast, C. A. Jackson, A. M. Jones, J. Kerckhoff, R. K. Lanza, K. Raach, B. J. Thomas, R. Velunta, A. J. Weinstein, T. D. Ladd, K. Eng, M. G. Borselli, A. T. Hunter, and M. T. Rakher, Fast and high-fidelity state preparation and measurement in triple-quantum-dot spin qubits, PRX Quantum 3, 010352 (2022).
  12. D. P. DiVincenzo, D. Bacon, J. Kempe, G. Burkard, and K. B. Whaley, Universal quantum computation with the exchange interaction, Nature 408, 339 (2000).
  13. R. W. Andrews, C. Jones, M. D. Reed, A. M. Jones, S. D. Ha, M. P. Jura, J. Kerckhoff, M. Levendorf, S. Meenehan, S. T. Merkel, A. Smith, B. Sun, A. J. Weinstein, M. T. Rakher, T. D. Ladd, and M. G. Borselli, Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit, Nat. Nanotechnol. 14, 747 (2019).
  14. A. M. Jones, E. J. Pritchett, E. H. Chen, T. E. Keating, R. W. Andrews, J. Z. Blumoff, L. A. De Lorenzo, K. Eng, S. D. Ha, A. A. Kiselev, S. M. Meenehan, S. T. Merkel, J. A. Wright, L. F. Edge, R. S. Ross, M. T. Rakher, M. G. Borselli, and A. T. Hunter, Spin-blockade spectroscopy of Si/Si-Ge quantum dots, Phys. Rev. Appl. 12, 014026 (2019).
  15. Y. P. Kandel, H. Qiao, S. Fallahi, G. C. Gardner, M. J. Manfra, and J. M. Nichol, Coherent spin-state transfer via Heisenberg exchange, Nature 573, 553 (2019).
  16. M. D. Reed, B. M. Maune, R. W. Andrews, M. G. Borselli, K. Eng, M. P. Jura, A. A. Kiselev, T. D. Ladd, S. T. Merkel, I. Milosavljevic, E. J. Pritchett, M. T. Rakher, R. S. Ross, A. E. Schmitz, A. Smith, J. A. Wright, M. F. Gyure, and A. T. Hunter, Reduced sensitivity to charge noise in semiconductor spin qubits via symmetric operation, Phys. Rev. Lett. 116, 110402 (2016).
  17. F. Martins, F. K. Malinowski, P. D. Nissen, E. Barnes, S. Fallahi, G. C. Gardner, M. J. Manfra, C. M. Marcus, and F. Kuemmeth, Noise suppression using symmetric exchange gates in spin qubits, Phys. Rev. Lett. 116, 116801 (2016).
  18. M. Badaroglu, in 2021 IEEE International Roadmap for Devices and Systems Outbriefs (IEEE, 2021), pp. 01–38.
  19. A. Pirati, R. Peeters, D. Smith, S. Lok, M. van Noordenburg, R. van Es, E. Verhoeven, H. Meijer, A. Minnaert, J.-W. van der Horst, H. Meiling, J. Mallmann, C. Wagner, J. Stoeldraijer, G. Fisser, J. Finders, C. Zoldesi, U. Stamm, H. Boom, D. Brandt, D. Brown, I. Fomenkov, and M. Purvis, in Extreme Ultraviolet (EUV) Lithography VII, edited by E. M. Panning, International Society for Optics and Photonics (SPIE, 2016), Vol. 9776, p. 97760A.
  20. J. Cunningham, The use and evaluation of yield models in integrated circuit manufacturing, IEEE Trans. Semicond. Manuf. 3, 60 (1990).
  21. R. Kube, H. Bracht, J. L. Hansen, A. N. Larsen, E. E. Haller, S. Paul, and W. Lerch, Composition dependence of Si and Ge diffusion in relaxed Si1−xGex alloys, J. Appl. Phys. 107, 073520 (2010).
  22. P. Batude, L. Brunet, C. Fenouillet-Beranger, F. Andrieu, J.-P. Colinge, D. Lattard, E. Vianello, S. Thuries, O. Billoint, P. Vivet, C. Santos, B. Mathieu, B. Sklenard, C.-M. V. Lu, J. Micout, F. Deprat, E. A. Mercado, F. Ponthenier, N. Rambal, M.-P. Samson, M. Cassé, S. Hentz, J. Arcamone, G. Sicard, L. Hutin, L. Pasini, A. Ayres, O. Rozeau, R. Berthelon, F. Nemouchi, P. Rodriguez, J.-B. Pin, D. Larmagnac, A. Duboust, V. Ripoche, S. Barraud, N. Allouti, S. Barnola, C. Vizioz, J.-M. Hartmann, S. Kerdiles, P. A. Alba, S. Beaurepaire, V. Beugin, F. Fournel, P. Besson, V. Loup, R. Gassilloud, F. Martin, X. Garros, F. Mazen, B. Previtali, C. Euvrard-Colnat, V. Balan, C. Comboroure, M. Zussy, Mazzocchi, O. Faynot, and M. Vinet, in 2017 IEEE International Electron Devices Meeting (IEDM) (IEEE, San Francisco, CA, 2017), pp. 3.1.1–3.1.4.
  23. D. M. Zajac, T. M. Hazard, X. Mi, E. Nielsen, and J. R. Petta, Scalable gate architecture for a one-dimensional array of semiconductor spin qubits, Phys. Rev. Appl. 6, 054013 (2016).
  24. J. I. Colless, A. C. Mahoney, J. M. Hornibrook, A. C. Doherty, H. Lu, A. C. Gossard, and D. J. Reilly, Dispersive readout of a few-electron double quantum dot with fast rf gate sensors, Phys. Rev. Lett. 110, 046805 (2013).
  25. A. West, B. Hensen, A. Jouan, T. Tanttu, C.-H. Yang, A. Rossi, M. F. Gonzalez-Zalba, F. Hudson, A. Morello, D. J. Reilly, and A. S. Dzurak, Gate-based single-shot readout of spins in silicon, Nat. Nanotechnol. 14, 437 (2019).
  26. B. Sun, T. Brecht, B. H. Fong, M. Akmal, J. Z. Blumoff, T. A. Cain, F. W. Carter, D. H. Finestone, M. N. Fireman, W. Ha, A. T. Hatke, R. M. Hickey, C. A. C. Jackson, I. Jenkins, A. M. Jones, A. Pan, D. R. Ward, A. J. Weinstein, S. J. Whiteley, P. Williams, M. G. Borselli, M. T. Rakher, and T. D. Ladd, Full-permutation dynamical decoupling in triple-quantum-dot spin qubits, PRX Quantum 5, 020356 (2024).
  27. F. Setiawan, H.-Y. Hui, J. P. Kestner, X. Wang, and S. D. Sarma, Robust two-qubit gates for exchange-coupled qubits, Phys. Rev. B 89, 085314 (2014).
  28. J. D. Chadwick, G. G. Guerreschi, F. Luthi, M. T. Mądzik, F. A. Mohiyaddin, P. Prabhu, A. T. Schmitz, A. Litteken, S. Premaratne, N. C. Bishop, A. Y. Matsuura, and J. S. Clarke, Short two-qubit pulse sequences for exchange-only spin qubits in two-dimensional layouts, Phys. Rev. A 111, 052616 (2025).

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PRX Quantum 6, 030327– Published 14 August, 2025
  • Received 25 February 2025
  • Accepted 26 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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