P. Campana

Kinetic Inductance Traveling Wave Parametric Amplifiers Near the Quantum Limit: Methodology and Characterization

  1. L. Howe,
  2. A. Giachero,
  3. M. Vissers,
  4. P. Campana,
  5. J. Wheeler,
  6. J. Gao,
  7. J. Austermann,
  8. J. Hubmayr,
  9. A. Nucciotti,
  10. and J. Ullom
We present a detailed simulation and design framework for realizing traveling wave parametric amplifiers (TWPAs) using the nonlinear kinetic inductance of disordered superconductors
— in our case niobium-titanium-nitride (NbTiN). These kinetic inductance TWPAs (KITs) operate via three-wave mixing (3WM) to achieve high broadband gain and near-quantum-limited (nQL) noise. Representative fabricated devices — realized using an inverted microstrip (IMS), dispersion-engineered, artificial transmission line — demonstrate power gains above 25 dB, bandwidths beyond 3 GHz, and achieve ultimate system noise levels of 1.1 quanta even when operated with no magnetic shielding. These performance metrics are competitive with state-of-the-art Josephson-junction-based TWPAs but involve simpler fabrication and able to providing three orders of magnitude higher dynamic range (IIP1=−68 dBm, IIP3=−55 dBm), and high magnetic field resilience — making KITs an attractive technology for highly multiplexed readout of quantum information and superconducting detector systems.
arxiv pdf

Transmon qubit modeling and characterization for Dark Matter search

  1. R. Moretti,
  2. D. Labranca,
  3. P. Campana,
  4. R. Carobene,
  5. M. Gobbo,
  6. M. A. Castellanos-Beltran,
  7. D. Olaya,
  8. P. F. Hopkins,
  9. L. Banchi,
  10. M. Borghesi,
  11. A. Candido,
  12. H. A. Corti,
  13. A. D'Elia,
  14. M. Faverzani,
  15. E. Ferri,
  16. A. Nucciotti,
  17. L. Origo,
  18. A. Pasquale,
  19. A. S. Piedjou Komnang,
  20. A. Rettaroli,
  21. S. Tocci,
  22. S. Carrazza,
  23. C. Gatti,
  24. and A. Giachero
This study presents the design, simulation, and experimental characterization of a superconducting transmon qubit circuit prototype for potential applications in dark matter detection
experiments. We describe a planar circuit design featuring two non-interacting transmon qubits, one with fixed frequency and the other flux tunable. Finite-element simulations were employed to extract key Hamiltonian parameters and optimize component geometries. The qubit was fabricated and then characterized at 20 mK, allowing for a comparison between simulated and measured qubit parameters. Good agreement was found for transition frequencies and anharmonicities (within 1\% and 10\% respectively) while coupling strengths exhibited larger discrepancies (30\%). We discuss potential causes for measured coherence times falling below expectations (T1∼1-2 \textmu s) and propose strategies for future design improvements. Notably, we demonstrate the application of a hybrid 3D-2D simulation approach for energy participation ratio evaluation, yielding a more accurate estimation of dielectric losses. This work represents an important first step in developing planar Quantum Non-Demolition (QND) single-photon counters for dark matter searches, particularly for axion and dark photon detection schemes.
arxiv pdf