Rodrigo Benevides

Loss Mechanisms in High-coherence Multimode Mechanical Resonators Coupled to Superconducting Circuits

  1. Raquel Garcia Belles,
  2. Alexander Anferov,
  3. Lukas F. Deeg,
  4. Loris Colicchio,
  5. Arianne Brooks,
  6. Tom Schatteburg,
  7. Maxwell Drimmer,
  8. Ines C. Rodrigues,
  9. Rodrigo Benevides,
  10. Marco Liffredo,
  11. Jyotish Patidar,
  12. Oleksandr Pshyk,
  13. Matteo Fadel,
  14. Luis Guillermo Villanueva,
  15. Sebastian Siol,
  16. Gerhard Kirchmair,
  17. and Yiwen Chu
Circuit quantum acoustodynamics (cQAD) devices have a wide range of applications in quantum science, all of which depend crucially on the quantum coherence of the mechanical subsystem.
In this context, high-overtone bulk acoustic-wave resonators (HBARs) are particularly promising, since they have shown very high quality factors with negligible dephasing. However, the introduction of piezoelectric films, which are necessary for coupling to a superconducting circuit, can lead to additional loss channels, such as surface scattering and two-level systems (TLS). Here, we study the acoustic dissipation of HBAR resonators in cQAD systems and find that the defect density of the piezoelectric material and its interface with the bulk are limiting factors for the coherence. We measure acoustic modes with phonon lifetimes up to 400 μs and lifetime-limited coherence times approaching one millisecond in the quantum regime. When coupled to a superconducting qubit, this leads to a hybrid system with a large quantum coherence cooperativity of CT2=1.1×105. These results represent a new milestone for the performance of cQAD devices and offer concrete paths forward for further improvements.
arxiv pdf

Quasiparticle dynamics in a superconducting qubit irradiated by a localized infrared source

  1. Rodrigo Benevides,
  2. Maxwell Drimmer,
  3. Giacomo Bisson,
  4. Francesco Adinolfi,
  5. Uwe von Lüpke,
  6. Hugo Michiel Doeleman,
  7. Gianluigi Catelani,
  8. and Yiwen Chu
A known source of decoherence in superconducting qubits is the presence of broken Cooper pairs, or quasiparticles. These can be generated by high-energy radiation, either present in
the environment or purposefully introduced, as in the case of some hybrid quantum devices. Here, we systematically study the properties of a transmon qubit under illumination by focused infrared radiation with various powers, durations, and spatial locations. Despite the high energy of incident photons, our observations agree well with a model of low-energy quasiparticle dynamics dominated by trapping. This technique can be used for understanding and potentially mitigating the effects of high-energy radiation on superconducting circuits with a variety of geometries and materials.
arxiv pdf