N. Bruckmoser

Fabrication of low-loss Josephson parametric devices

  1. K. E. Honasoge,
  2. M. Handschuh,
  3. W. K. Yam,
  4. S. Gandorfer,
  5. D. Bazulin,
  6. N. Bruckmoser,
  7. L. Koch,
  8. A. Marx,
  9. R. Gross,
  10. and K. G. Fedorov
Superconducting circuits incorporating Josephson elements represent a promising hardware platform for quantum technologies. Potential applications include scalable quantum computing,
microwave quantum networks, and quantum-limited amplifiers. However, progress in Josephson junction-based quantum technologies is facing the ongoing challenge of minimizing loss channels. This is also true for parametric superconducting devices based on nonlinear Josephson resonators. In this work, we report on the fabrication and characterization of low-loss Josephson parametric devices operated in the GHz frequency range, showing record internal quality factors. Specifically, we achieve internal quality factors significantly above 105 for both Josephson parametric converters and the Josephson parametric amplifiers at low microwave power ranging in the single-photon regime. These low-loss devices mark a significant step forward in realizing high-performance quantum circuits, enabling further advancements in superconducting quantum technologies.
arxiv pdf

Parametric multi-element coupling architecture for coherent and dissipative control of superconducting qubits

  1. G. B. P. Huber,
  2. F. A. Roy,
  3. L. Koch,
  4. I. Tsitsilin,
  5. J. Schirk,
  6. N. J. Glaser,
  7. N. Bruckmoser,
  8. C. Schweizer,
  9. J. Romeiro,
  10. G. Krylov,
  11. M. Singh,
  12. F. X. Haslbeck,
  13. M. Knudsen,
  14. A. Marx,
  15. F. Pfeiffer,
  16. C. Schneider,
  17. F. Wallner,
  18. D. Bunch,
  19. L. Richard,
  20. L. Södergren,
  21. K. Liegener,
  22. M. Werninghaus,
  23. and S. Filipp
As systems for quantum computing keep growing in size and number of qubits, challenges in scaling the control capabilities are becoming increasingly relevant. Efficient schemes to simultaneously
mediate coherent interactions between multiple quantum systems and to reduce decoherence errors can minimize the control overhead in next-generation quantum processors. Here, we present a superconducting qubit architecture based on tunable parametric interactions to perform two-qubit gates, reset, leakage recovery and to read out the qubits. In this architecture, parametrically driven multi-element couplers selectively couple qubits to resonators and neighbouring qubits, according to the frequency of the drive. We consider a system with two qubits and one readout resonator interacting via a single coupling circuit and experimentally demonstrate a controlled-Z gate with a fidelity of 98.30±0.23%, a reset operation that unconditionally prepares the qubit ground state with a fidelity of 99.80±0.02% and a leakage recovery operation with a 98.5±0.3% success probability. Furthermore, we implement a parametric readout with a single-shot assignment fidelity of 88.0±0.4%. These operations are all realized using a single tunable coupler, demonstrating the experimental feasibility of the proposed architecture and its potential for reducing the system complexity in scalable quantum processors.
arxiv pdf