Francesco De Dominicis

A Cryogenic Muon Tagging System Based on Kinetic Inductance Detectors for Superconducting Quantum Processors

  1. Ambra Mariani,
  2. Laura Cardani,
  3. Mustafa Bal,
  4. Nicola Casali,
  5. Ivan Colantoni,
  6. Angelo Cruciani,
  7. Giorgio Del Castello,
  8. Daniele Delicato,
  9. Francesco De Dominicis,
  10. Matteo del Gallo Raccagiovine,
  11. Matteo Folcarelli,
  12. Sabrina Garattoni,
  13. Anna Grassellino,
  14. Mehmood Khan Yasir Raja,
  15. Valerio Pettinacci,
  16. Alberto Ressa,
  17. Tanay Roy,
  18. Marco Vignati,
  19. and David v Zanten
Ionizing radiation has emerged as a potential limiting factor for superconducting quantum processors, inducing quasiparticle bursts and correlated errors that challenge fault-tolerant
operation. Atmospheric muons are particularly problematic due to their high energy and penetration power, making passive shielding ineffective. Therefore, monitoring the real-time muon flux is crucial to guide the development of alternative error-correction or protection strategies. We present the design, simulation, and first operation of a cryogenic muon-tagging system based on Kinetic Inductance Detectors (KIDs) for integration with superconducting quantum processors. The system consists of two KIDs arranged in a vertical stack and operated at ~20 mK. Monte Carlo simulations based on Geant4 guided the prototype design and provided reference expectations for muon-tagging efficiency and accidental coincidences due to ambient γ-rays. We measured a muon-induced coincidence rate among the top and bottom detectors of (192 ± 9) × 10−3 events/s, in excellent agreement with the Monte Carlo prediction. The prototype achieves a muon-tagging efficiency of about 90% with negligible dead time. These results demonstrate the feasibility of operating a muon-tagging system at millikelvin temperatures and open the path toward its integration with multi-qubit chips to veto or correct muon-induced errors in real time.
arxiv pdf

Evaluating radiation impact on transmon qubits in above and underground facilities

  1. Francesco De Dominicis,
  2. Tanay Roy,
  3. Ambra Mariani,
  4. Mustafa Bal,
  5. Nicola Casali,
  6. Ivan Colantoni,
  7. Francesco Crisa,
  8. Angelo Cruciani,
  9. Fernando Ferroni,
  10. Dounia L Helis,
  11. Lorenzo Pagnanini,
  12. Valerio Pettinacci,
  13. Roman M Pilipenko,
  14. Stefano Pirro,
  15. Andrei Puiu,
  16. Alexander Romanenko,
  17. David v Zanten,
  18. Shaojiang Zhu,
  19. Anna Grassellino,
  20. and Laura Cardani
Superconducting qubits can be sensitive to abrupt energy deposits caused by cosmic rays and ambient radioactivity. Previous studies have focused on understanding possible correlated
effects over time and distance due to cosmic rays. In this study, for the first time, we directly compare the response of a transmon qubit measured initially at the Fermilab SQMS above-ground facilities and then at the deep underground Gran Sasso Laboratory (INFN-LNGS, Italy). We observe same average qubit lifetime T1 of roughly 80 microseconds at above and underground facilities. We then apply a fast decay detection protocol and investigate the time structure, sensitivity and relative rates of triggered events due to radiation versus intrinsic noise, comparing above and underground performance of several high-coherence qubits. Using gamma sources of variable activity we calibrate the response of the qubit to different levels of radiation in an environment with minimal background radiation. Results indicate that qubits respond to a strong gamma source and it is possible to detect particle impacts. However, when comparing above and underground results, we do not observe a difference in radiation induced-like events for these sapphire and niobium-based transmon qubits. We conclude that the majority of these events are not radiation related and to be attributed to other noise sources which by far dominate single qubit errors in modern transmon qubits.
arxiv pdf