Gabriel Cutter

Adaptive Spectroscopy of Fast Two-Level-System Dynamics in Superconducting Qubits

  1. Fabrizio Berritta,
  2. David Pahl,
  3. Lukas Pahl,
  4. William P. Banner,
  5. Gabriel Cutter,
  6. Jan A. Krzywda,
  7. Spencer Weeden,
  8. Shravan Patel,
  9. Paul Buttles,
  10. Stanislav Eilhart,
  11. Michael Gingras,
  12. Bethany M. Niedzielski,
  13. Robert McDermott,
  14. Mollie E. Schwartz,
  15. Kyle Serniak,
  16. Max Hays,
  17. Jeffrey A. Grover,
  18. and William D. Oliver
Parasitic two-level-system (TLS) defects are a major source of energy relaxation and temporal instability in superconducting quantum processors. Our sub-second adaptive spectroscopy
reveals telegraphic switching of TLSs with a characteristic timescale of a few seconds and spectral diffusion with diffusivity D≈0.9 MHz2/s. These timescales are about 3×102 times faster than what is observed in conventional nonadaptive spectroscopy, which typically requires hours of measurement time. We resolve such fast dynamics on a field-programmable gate array (FPGA)-based controller that enables measurement of frequency- and time-resolved relaxations with sub-second temporal resolution in flux-tunable superconducting qubits. We observe similar defect dynamics across multiple qubits in independently fabricated devices measured in different laboratories. We correlate TLS-induced fluctuations with gate-level errors using randomized benchmarking. Our results reveal a previously inaccessible regime of frequency-resolved TLS dynamics and redefine the timescales relevant to TLS-aware characterization and calibration of superconducting quantum processors.
arxiv pdf

Driven-dissipative entanglement of distant giant atoms

  1. Aziza Almanakly,
  2. Ariadna Soro,
  3. Alejandro Vivas-Viaña,
  4. Beatriz Yankelevich,
  5. Caspar Groiseau,
  6. David Pahl,
  7. Junyoung An,
  8. Gabriel Cutter,
  9. Michael E. Gingras,
  10. Bethany M. Niedzielski,
  11. Hannah Stickler,
  12. Renée DePéncier Piñero,
  13. Mollie E. Schwartz,
  14. Kyle Serniak,
  15. Max Hays,
  16. Jeffrey A. Grover,
  17. Anton Frisk Kockum,
  18. and William D. Oliver
Quantum interconnects distribute entanglement via controlled light-matter interactions for quantum computing and sensing applications. Many entanglement generation schemes use coherent,
reversible interactions that require precisely calibrated pulses to execute. In contrast, driven-dissipative protocols use a continuous-wave drive in the presence of correlated dissipation to stabilize entanglement in protected (dark) states. However, the same dissipation that generates the entanglement also limits its utility once the stabilization protocol ends. Here, we engineer a superconducting system of two giant artificial atoms coupled sequentially to a waveguide, with tunable individual and correlated dissipation enabled by interference between coupling points. Continuously driving the atoms through the waveguide exploits correlated dissipation to generate remote entanglement. We then tune the qubit frequencies in situ to suppress individual dissipation and thereby preserve the entanglement, achieving a Bell-state fidelity F = 0.89 +/- 0.02. This demonstration indicates that the driven dissipation of giant atoms is a viable approach for distributing entanglement across quantum networks.
arxiv pdf