V. I. Chichkov

States dressing analysis in a transmon-transmon-bus system

  1. P. A. Gladilovich,
  2. R.A. Migdisov,
  3. A.V. Sabluk,
  4. P.S. Burtsev,
  5. N.N. Abramov,
  6. N.Y. Rudenko,
  7. V. I. Chichkov,
  8. and N. A. Maleeva
The multi-qubit gates fidelity of superconducting quantum processors can be limited due to the dressing of computational states by noncomputational ones. Here, we experimentally and
analytically investigate a transmon-transmon-bus system where the computational states dressing is tunable over a broad range. We estimate the dressing using three methods: a full three-element model, an effective mode approach, and an unperturbed mode approach. The obtained results highlight the importance of the accurate estimation and control of the computational states dressing in order to optimize gates on superconducting platform.
arxiv pdf

Effect of Etching Methods on Dielectric Losses in Transmons

  1. T. A. Chudakova,
  2. G. S. Mazhorin,
  3. I. V. Trofimov,
  4. N. Yu. Rudenko,
  5. A. M. Mumlyakov,
  6. A. S. Kazmina,
  7. E. Yu. Egorova,
  8. P. A. Gladilovich,
  9. M. V.Chichkov,
  10. N. A. Maleeva,
  11. M. A. Tarkhov,
  12. and V. I. Chichkov
Superconducting qubits are considered as a promising platform for implementing a fault tolerant quantum computing. However, surface defects of superconductors and the substrate leading
to qubit state decoherence and fluctuations in qubit parameters constitute a significant problem. The amount and type of defects depend both on the chip materials and fabrication procedure. In this work, transmons produced by two different methods of aluminum etching: wet etching in a solution of weak acids and dry etching using a chlorine-based plasma are experimentally studied. The relaxation and coherence times for dry-etched qubits are more than twice as long as those for wet-etched ones. Additionally, the analysis of time fluctuations of qubit frequencies and relaxation times, which is an effective method to identify the dominant dielectric loss mechanisms, indicates a significantly lower impact of two-level systems in the dry-etched qubits compared to the wet-etched ones.
arxiv pdf