Mustafa Bal

Overlap junctions for superconducting quantum electronics and amplifiers

  1. Mustafa Bal,
  2. Junling Long,
  3. Ruichen Zhao,
  4. Haozhi Wang,
  5. Sungoh Park,
  6. Corey Rae Harrington McRae,
  7. Tongyu Zhao,
  8. Russell E. Lake,
  9. Daniil Frolov,
  10. Roman Pilipenko,
  11. Silvia Zorzetti,
  12. Alexander Romanenko,
  13. and David P. Pappas
Due to their unique properties as lossless, nonlinear circuit elements, Josephson junctions lie at the heart of superconducting quantum information processing. Previously, we demonstrated
a two-layer, submicrometer-scale overlap junction fabrication process suitable for qubits with long coherence times. Here, we extend the overlap junction fabrication process to micrometer-scale junctions. This allows us to fabricate other superconducting quantum devices. For example, we demonstrate an overlap-junction-based Josephson parametric amplifier that uses only 2 layers. This efficient fabrication process yields frequency-tunable devices with negligible insertion loss and a gain of ~ 30 dB. Compared to other processes, the overlap junction allows for fabrication with minimal infrastructure, high yield, and state-of-the-art device performance.
arxiv pdf

Kinetic Inductance Traveling Wave Amplifiers For Multiplexed Qubit Readout

  1. Leonardo Ranzani,
  2. Mustafa Bal,
  3. Kin Chung Fong,
  4. Guilhem Ribeill,
  5. Xian Wu,
  6. Junling Long,
  7. Hsiang-Sheng Ku,
  8. Robert P. Erickson,
  9. David Pappas,
  10. and Thomas A. Ohki
We describe a kinetic inductance traveling-wave (KIT) amplifier suitable for superconducting quantum information measurements and characterize its wideband scattering and noise properties.
We use mechanical microwave switches to calibrate the four amplifier scattering parameters up to the device input and output connectors at the dilution refrigerator base temperature and a tunable temperature load to characterize the amplifier noise. Finally, we demonstrate the high fidelity simultaneous dispersive readout of two superconducting transmon qubits. The KIT amplifier provides low-noise amplification of both readout tones with readout fidelities in excess of 89% and negligible effect on qubit lifetime and coherence.
arxiv pdf