Marc Weber

Reducing the impact of radioactivity on quantum circuits in a deep-underground facility

  1. Laura Cardani,
  2. Francesco Valenti,
  3. Nicola Casali,
  4. Gianluigi Catelani,
  5. Thibault Charpentier,
  6. Massimiliano Clemenza,
  7. Ivan Colantoni,
  8. Angelo Cruciani,
  9. Luca Gironi,
  10. Lukas Grünhaupt,
  11. Daria Gusenkova,
  12. Fabio Henriques,
  13. Marc Lagoin,
  14. Maria Martinez,
  15. Giorgio Pettinari,
  16. Claudia Rusconi,
  17. Oliver Sander,
  18. Alexey V. Ustinov,
  19. Marc Weber,
  20. Wolfgang Wernsdorfer,
  21. Marco Vignati,
  22. Stefano Pirro,
  23. and Ioan M. Pop
As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information
processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor fifty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware.
arxiv pdf

Accelerating complex control schemes on a heterogeneous MPSoC platform for quantum computing

  1. Richard Gebauer,
  2. Nick Karcher,
  3. Jonas Hurst,
  4. Marc Weber,
  5. and Oliver Sander
Control and readout of superconducting quantum bits (qubits) require microwave pulses with gigahertz frequencies and nanosecond precision. To generate and analyze these microwave pulses,
we developed a versatile FPGA-based electronics platform. While basic functionality is directly handled within the FPGA, guaranteeing highest accuracy on the nanosecond timescale, more complex control schemes render impractical to implement in hardware. To provide deterministic timing and low latency with high flexibility, we developed the Taskrunner framework. It enables the execution of complex control schemes, so-called user tasks, on the real-time processing unit (RPU) of a heterogeneous Multiprocessor System-on-Chip (MPSoC). These user tasks are specified conveniently using standard C language and are compiled automatically by the MPSoC platform when loaded onto the RPU. We present the architecture of the Taskrunner framework as well as timing benchmarks and discuss applications in the field of quantum computing.
arxiv pdf

State preparation of a fluxonium qubit with feedback from a custom FPGA-based platform

  1. Richard Gebauer,
  2. Nick Karcher,
  3. Daria Gusenkova,
  4. Martin Spiecker,
  5. Lukas Grünhaupt,
  6. Ivan Takmakov,
  7. Patrick Winkel,
  8. Luca Planat,
  9. Nicolas Roch,
  10. Wolfgang Wernsdorfer,
  11. Alexey V. Ustinov,
  12. Marc Weber,
  13. Martin Weides,
  14. Ioan M. Pop,
  15. and Oliver Sander
We developed a versatile integrated control and readout instrument for experiments with superconducting quantum bits (qubits), based on a field-programmable gate array (FPGA) platform.
Using this platform, we perform measurement-based, closed-loop feedback operations with 428ns platform latency. The feedback capability is instrumental in realizing active reset initialization of the qubit into the ground state in a time much shorter than its energy relaxation time T1. We show experimental results demonstrating reset of a fluxonium qubit with 99.4% fidelity, using a readout-and-drive pulse sequence approximately 1.5μs long. Compared to passive ground state initialization through thermalization, with the time constant given by T1= 80μs, the use of the FPGA-based platform allows us to improve both the fidelity and the time of the qubit initialization by an order of magnitude.
arxiv pdf