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.
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