RQC Seminar

270th RQC Seminar

• Speaker

  Mr. Oleksandr Kitsenko
  ( V.N. Karazin Kharkiv National University )

• Date

  16:00-17:00, (4:00 p.m.-5:00 p.m.) Monday, May 11, 2026

• Venue

  Hybrid( Zoom,
  345-347 Seminar Room, 3F, Main Research Building, Wako Campus / 和光地区 研究本館3階 セミナー室 (345-347) (C01))

• Title

  Quantum reflectometry: quantum and tunneling capacitances, Sisyphus and Hermes resistances

• Inquiries

  norilab_rqc_assist[at]ml.riken.jp

Abstract
When a classical resonator is coupled to a quantum system, its capacitance, inductance, and resistance are modified. The effective capacitance and inductance include geometric, quantum, and tunneling components, while the effective resistance is composed of Sisyphus and Hermes contributions. By probing the resonator's response, one can access the state of the quantum system. Such reflectometry is usually studied in situations where all characteristic times of the quantum system are much shorter than the resonator's period, in which case only stationary quantum states are probed.
We explore how both isolated and open two- and multi-level systems interact with classical resonator and how they can be effectively represented by an impedance that is directly measurable. To rigorously determine the effective response of a quantum system, we quantize the qubit/qudit-resonator system and apply perturbation theory. We show that the quantum capacitance originates from the curvature of the energy levels, while the tunneling capacitance appears when relaxation, temperature or resonant microwave driving is taken into consideration. The corresponding contributions to the effective resistance are the relaxation-defined Sisyphus resistance and the decoherence-defined Hermes resistance. Our theoretical framework can be applied to describe any quantum system coupled to any classical resonator.