Miikka Koistinen

A Superconducting Qubit-Resonator Quantum Processor with Effective All-to-All Connectivity

  1. Michael Renger,
  2. Jeroen Verjauw,
  3. Nicola Wurz,
  4. Amin Hosseinkhani,
  5. Caspar Ockeloen-Korppi,
  6. Wei Liu,
  7. Aniket Rath,
  8. Manish J. Thapa,
  9. Florian Vigneau,
  10. Elisabeth Wybo,
  11. Ville Bergholm,
  12. Chun Fai Chan,
  13. Bálint Csatári,
  14. Saga Dahl,
  15. Rakhim Davletkaliyev,
  16. Rakshyakar Giri,
  17. Daria Gusenkova,
  18. Hermanni Heimonen,
  19. Tuukka Hiltunen,
  20. Hao Hsu,
  21. Eric Hyyppä,
  22. Joni Ikonen,
  23. Tyler Jones,
  24. Shabeeb Khalid,
  25. Seung-Goo Kim,
  26. Miikka Koistinen,
  27. Anton Komlev,
  28. Janne Kotilahti,
  29. Vladimir Kukushkin,
  30. Julia Lamprich,
  31. Alessandro Landra,
  32. Lan-Hsuan Lee,
  33. Tianyi Li,
  34. Per Liebermann,
  35. Sourav Majumder,
  36. Janne Mäntylä,
  37. Fabian Marxer,
  38. Arianne Meijer - van de Griend,
  39. Vladimir Milchakov,
  40. Jakub Mrożek,
  41. Jayshankar Nath,
  42. Tuure Orell,
  43. Miha Papič,
  44. Matti Partanen,
  45. Alexander Plyushch,
  46. Stefan Pogorzalek,
  47. Jussi Ritvas,
  48. Pedro Figuero Romero,
  49. Ville Sampo,
  50. Marko Seppälä,
  51. Ville Selinmaa,
  52. Linus Sundström,
  53. Ivan Takmakov,
  54. Brian Tarasinski,
  55. Jani Tuorila,
  56. Olli Tyrkkö,
  57. Alpo Välimaa,
  58. Jaap Wesdorp,
  59. Ping Yang,
  60. Liuqi Yu,
  61. Johannes Heinsoo,
  62. Antti Vepsäläinen,
  63. William Kindel,
  64. Hsiang-Sheng Ku,
  65. and Frank Deppe
In this work we introduce a superconducting quantum processor architecture that uses a transmission-line resonator to implement effective all-to-all connectivity between six transmon
qubits. This architecture can be used as a test-bed for algorithms that benefit from high connectivity. We show that the central resonator can be used as a computational element, which offers the flexibility to encode a qubit for quantum computation or to utilize its bosonic modes which further enables quantum simulation of bosonic systems. To operate the quantum processing unit (QPU), we develop and benchmark the qubit-resonator conditional Z gate and the qubit-resonator MOVE operation. The latter allows for transferring a quantum state between one of the peripheral qubits and the computational resonator. We benchmark the QPU performance and achieve a genuinely multi-qubit entangled Greenberger-Horne-Zeilinger (GHZ) state over all six qubits with a readout-error mitigated fidelity of 0.86.
arxiv pdf

Long-distance transmon coupler with CZ gate fidelity above 99.8%

  1. Fabian Marxer,
  2. Antti Vepsäläinen,
  3. Shan W. Jolin,
  4. Jani Tuorila,
  5. Alessandro Landra,
  6. Caspar Ockeloen-Korppi,
  7. Wei Liu,
  8. Olli Ahonen,
  9. Adrian Auer,
  10. Lucien Belzane,
  11. Ville Bergholm,
  12. Chun Fai Chan,
  13. Kok Wai Chan,
  14. Tuukka Hiltunen,
  15. Juho Hotari,
  16. Eric Hyyppä,
  17. Joni Ikonen,
  18. David Janzso,
  19. Miikka Koistinen,
  20. Janne Kotilahti,
  21. Tianyi Li,
  22. Jyrgen Luus,
  23. Miha Papic,
  24. Matti Partanen,
  25. Jukka Räbinä,
  26. Jari Rosti,
  27. Mykhailo Savytskyi,
  28. Marko Seppälä,
  29. Vasilii Sevriuk,
  30. Eelis Takala,
  31. Brian Tarasinski,
  32. Manish J. Thapa,
  33. Francesca Tosto,
  34. Natalia Vorobeva,
  35. Liuqi Yu,
  36. Kuan Yen Tan,
  37. Juha Hassel,
  38. Mikko Möttönen,
  39. and Johannes Heinsoo
Tunable coupling of superconducting qubits has been widely studied due to its importance for isolated gate operations in scalable quantum processor architectures. Here, we demonstrate
a tunable qubit-qubit coupler based on a floating transmon device which allows us to place qubits at least 2 mm apart from each other while maintaining over 50 MHz coupling between the coupler and the qubits. In the introduced tunable-coupler design, both the qubit-qubit and the qubit-coupler couplings are mediated by two waveguides instead of relying on direct capacitive couplings between the components, reducing the impact of the qubit-qubit distance on the couplings. This leaves space for each qubit to have an individual readout resonator and a Purcell filter needed for fast high-fidelity readout. In addition, the large qubit-qubit distance reduces unwanted non-nearest neighbor coupling and allows multiple control lines to cross over the structure with minimal crosstalk. Using the proposed flexible and scalable architecture, we demonstrate a controlled-Z gate with (99.81±0.02)% fidelity.
arxiv pdf