Corey Rae Harrington McRae

Materials loss measurements using superconducting microwave resonators

  1. Corey Rae Harrington McRae,
  2. Haozhi Wang,
  3. Jiansong Gao,
  4. Michael Vissers,
  5. Teresa Brecht,
  6. Andrew Dunsworth,
  7. David Pappas,
  8. and Josh Mutus
The performance of superconducting circuits for quantum computing is limited by materials losses. In particular, coherence times are typically bounded by two-level system (TLS) losses
at single photon powers and millikelvin temperatures. The identification of low loss fabrication techniques, materials, and thin film dielectrics is critical to achieving scalable architectures for superconducting quantum computing. Superconducting microwave resonators provide a convenient qubit proxy for assessing performance and studying TLS loss and other mechanisms relevant to superconducting circuits such as non-equilibrium quasiparticles and magnetic flux vortices. In this review article, we provide an overview of considerations for designing accurate resonator experiments to characterize loss, including applicable types of loss, cryogenic setup, device design, and methods for extracting material and interface losses, summarizing techniques that have been evolving for over two decades. Results from measurements of a wide variety of materials and processes are also summarized. Lastly, we present recommendations for the reporting of loss data from superconducting microwave resonators to facilitate materials comparisons across the field.
arxiv pdf

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