Jason Walter

Quantum Computer Controlled by Superconducting Digital Electronics at Millikelvin Temperature

  1. Jacob Bernhardt,
  2. Caleb Jordan,
  3. Joseph Rahamim,
  4. Alex Kirchenko,
  5. Karthik Bharadwaj,
  6. Louis Fry-Bouriaux,
  7. Katie Porsch,
  8. Aaron Somoroff,
  9. Kan-Ting Tsai,
  10. Jason Walter,
  11. Adam Weis,
  12. Meng-Ju Yu,
  13. Mario Renzullo,
  14. Daniel Yohannes,
  15. Igor Vernik,
  16. Oleg Mukhanov,
  17. and Shu Jen Han
Current superconducting quantum computing platforms face significant scaling challenges, as individual signal lines are required for control of each qubit. This wiring overhead is a
result of the low level of integration between control electronics at room temperature and qubits operating at millikelvin temperatures, which raise serious doubts among technologists about whether utility-scale quantum computers can be built. A promising alternative is to utilize cryogenic, superconducting digital control electronics that coexist with qubits. Here, we report the first multi-qubit system integrating this technology. The system utilizes digital demultiplexing, breaking the linear scaling of control lines to number of qubits. We also demonstrate single-qubit fidelities above 99%, and up to 99.9%. This work is a critical step forward in realizing highly scalable chip-based quantum computers.
arxiv pdf

Flip-Chip Packaging of Fluxonium Qubits

  1. Aaron Somoroff,
  2. Patrick Truitt,
  3. Adam Weis,
  4. Jacob Bernhardt,
  5. Daniel Yohannes,
  6. Jason Walter,
  7. Konstantin Kalashnikov,
  8. Raymond A. Mencia,
  9. Igor V. Vernik,
  10. Oleg Mukhanov,
  11. Maxim G. Vavilov,
  12. and Vladimir E. Manucharyan
The strong anharmonicity and high coherence times inherent to fluxonium superconducting circuits are beneficial for implementing quantum information processors. In addition to requiring
high-quality physical qubits, a quantum processor needs to be assembled in a manner that reduces crosstalk and decoherence. In this letter, we report work on fluxonium qubits packaged in a flip-chip architecture. Here, the fluxonium qubits are embedded in a multi-chip module (MCM), where a classical control and readout chip is bump-bonded to the quantum chip. The modular approach allows for improved connectivity between qubits and control/readout elements, and separate fabrication processes. We demonstrate that this configuration does not degrade the fluxonium qubit performance, and identify the main decoherence mechanisms to improve on the reported results.
arxiv pdf