Sadman Shanto

SQuADDS: A validated design database and simulation workflow for superconducting qubit design

  1. Sadman Shanto,
  2. Andre Kuo,
  3. Clark Miyamoto,
  4. Haimeng Zhang,
  5. Vivek Maurya,
  6. Evangelos Vlachos,
  7. Malida Hecht,
  8. Chung Wa Shum,
  9. and Eli Levenson-Falk
We present an open-source database of superconducting quantum device designs that may be used as the starting point for customized devices. Each design can be generated programmatically
using the open-source Qiskit Metal package, and simulated using finite-element electromagnetic solvers. We present a robust workflow for achieving high accuracy on design simulations. Many designs in the database are experimentally validated, showing excellent agreement between simulated and measured parameters. Our database includes a front-end interface that allows users to generate „best-guess“ designs based on desired circuit parameters. This project lowers the barrier to entry for research groups seeking to make a new class of devices by providing them a well-characterized starting point from which to refine their designs.
arxiv pdf

Quasiparticle dynamics in epitaxial Al-InAs planar Josephson junctions

  1. Bassel Heiba Elfeky,
  2. William M. Strickland,
  3. Jaewoo Lee,
  4. James T. Farmer,
  5. Sadman Shanto,
  6. Azarin Zarassi,
  7. Dylan Langone,
  8. Maxim G. Vavilov,
  9. Eli M. Levenson-Falk,
  10. and Javad Shabani
Quasiparticle (QP) effects play a significant role in the coherence and fidelity of superconducting quantum circuits. The Andreev bound states of high transparency Josephson junctions
can act as low-energy traps for QPs, providing a mechanism for studying the dynamics and properties of both the QPs and the junction. We study the trapping and clearing of QPs from the Andreev bound states of epitaxial Al-InAs Josephson junctions incorporated in a superconducting quantum interference device (SQUID) galvanically shorting a superconducting resonator to ground. We use a neighboring voltage-biased Josephson junction to inject QPs into the circuit. Upon the injection of QPs, we show that we can trap and clear QPs when the SQUID is flux-biased. We examine effects of the microwave loss associated with bulk QP transport in the resonator, QP-related dissipation in the junction, and QP poisoning events. By monitoring the QP trapping and clearing in time, we study the dynamics of these processes and find a time-scale of few microseconds that is consistent with electron-phonon relaxation in our system and correlated QP trapping and clearing mechanisms. Our results highlight the QP trapping and clearing dynamics as well as the associated time-scales in high transparency Josephson junctions based fabricated on Al-InAs heterostructures.
arxiv pdf