David Olaya

Identifying Materials-Level Sources of Performance Variation in Superconducting Transmon Qubits

  1. Akshay A. Murthy,
  2. Mustafa Bal,
  3. Michael J. Bedzyk,
  4. Hilal Cansizoglu,
  5. Randall K. Chan,
  6. Venkat Chandrasekhar,
  7. Francesco Crisa,
  8. Amlan Datta,
  9. Yanpei Deng,
  10. Celeo D. Matute Diaz,
  11. Vinayak P. Dravid,
  12. David A. Garcia-Wetten,
  13. Sabrina Garattoni,
  14. Sunil Ghimire,
  15. Dominic P. Goronzy,
  16. Sebastian de Graaf,
  17. Sam Haeuser,
  18. Mark C. Hersam,
  19. Dieter Isheim,
  20. Kamal Joshi,
  21. Richard Kim,
  22. Saagar Kolachina,
  23. Cameron J. Kopas,
  24. Matthew J. Kramer,
  25. Ella O. Lachman,
  26. Jaeyel Lee,
  27. Peter G. Lim,
  28. Andrei Lunin,
  29. William Mah,
  30. Jayss Marshall,
  31. Josh Y. Mutus,
  32. Jin-Su Oh,
  33. David Olaya,
  34. David P. Pappas,
  35. Joong-mok Park,
  36. Ruslan Prozorov,
  37. Roberto dos Reis,
  38. David N. Seidman,
  39. Zuhawn Sung,
  40. Makariy Tanatar,
  41. Mitchell J. Walker,
  42. Jigang Wang,
  43. Haotian Wu,
  44. Lin Zhou,
  45. Shaojiang Zhu,
  46. Anna Grassellino,
  47. and Alexander Romanenko
The Superconducting Materials and Systems (SQMS) Center, a DOE National Quantum Information Science Research Center, has conducted a comprehensive and coordinated study using superconducting
transmon qubit chips with known performance metrics to identify the underlying materials-level sources of device-to-device performance variation. Following qubit coherence measurements, these qubits of varying base superconducting metals and substrates have been examined with various nondestructive and invasive material characterization techniques at Northwestern University, Ames National Laboratory, and Fermilab as part of a blind study. We find trends in variations of the depth of the etched substrate trench, the thickness of the surface oxide, and the geometry of the sidewall, which when combined, lead to correlations with the T1 lifetime across different devices. In addition, we provide a list of features that varied from device to device, for which the impact on performance requires further studies. Finally, we identify two low-temperature characterization techniques that may potentially serve as proxy tools for qubit measurements. These insights provide materials-oriented solutions to not only reduce performance variations across neighboring devices, but also to engineer and fabricate devices with optimal geometries to achieve performance metrics beyond the state-of-the-art values.
arxiv pdf

Single Flux Quantum-Based Digital Control of Superconducting Qubits in a Multi-Chip Module

  1. Chuan-Hong Liu,
  2. Andrew Ballard,
  3. David Olaya,
  4. Daniel R. Schmidt,
  5. John Biesecker,
  6. Tammy Lucas,
  7. Joel Ullom,
  8. Shravan Patel,
  9. Owen Rafferty,
  10. Alexander Opremcak,
  11. Kenneth Dodge,
  12. Vito Iaia,
  13. Tianna McBroom,
  14. Jonathan L Dubois,
  15. Pete F. Hopkins,
  16. Samuel P. Benz,
  17. Britton L. T. Plourde,
  18. and Robert McDermott
The single flux quantum (SFQ) digital superconducting logic family has been proposed for the scalable control of next-generation superconducting qubit arrays. In the initial implementation,
SFQ-based gate fidelity was limited by quasiparticle (QP) poisoning induced by the dissipative on-chip SFQ driver circuit. In this work, we introduce a multi-chip module architecture to suppress phonon-mediated QP poisoning. Here, the SFQ elements and qubits are fabricated on separate chips that are joined with In bump bonds. We use interleaved randomized benchmarking to characterize the fidelity of SFQ-based gates, and we demonstrate an error per Clifford gate of 1.2(1)%, an order-of-magnitude reduction over the gate error achieved in the initial realization of SFQ-based qubit control. We use purity benchmarking to quantify the contribution of incoherent error at 0.96(2)%; we attribute this error to photon-mediated QP poisoning mediated by the resonant mm-wave antenna modes of the qubit and SFQ-qubit coupler. We anticipate that a straightforward redesign of the SFQ driver circuit to limit the bandwidth of the SFQ pulses will eliminate this source of infidelity, allowing SFQ-based gates with fidelity approaching theoretical limits, namely 99.9% for resonant sequences and 99.99% for more complex pulse sequences involving variable pulse-to-pulse separation.
arxiv pdf