RQC Seminar

199th RQC Seminar

• Speaker

  Mr. Samuel Napoli
  ( University of Messina, Italy )

• Date

  16:00-17:00 (4:00 p.m. - 5:00 p.m.), May 26, 2025 (Friday)

• Venue

  Hybrid(ZOOM・ Wako Main Research 3F 345-347 Seminar Room / 研究本館3階 セミナー室 (345-347) (C01))

• Title

  Circuit QED Spectra in the Ultrastrong Coupling Regime : How They Differ from Cavity QED Spectra

• Inquiries

  norilab_rqc_assist[at]ml.riken.jp

Abstract
Cavity quantum electrodynamics (QED) studies the interaction between resonator-confined radiation and natural atoms or other formally equivalent quantum excitations, under conditions where the quantum nature of photons is relevant. Phenomena studied in cavity QED can also be explored using superconducting artificial atoms and microwave photons in superconducting resonators. These circuit QED systems offer the possibility to reach the ultrastrong coupling regime with individual artificial atoms, unlike their natural counterparts. In this regime, the light-matter coupling strength reaches a considerable fraction of the bare resonance frequencies in the system. Here, we provide a careful analysis of both incoherent and coherent spectra in circuit QED systems consisting of a flux qubit interacting with an LC resonator [1]. Despite these systems can be effectively described by the quantum Rabi model, as the corresponding cavity QED ones, we find distinctive features, depending on how the system is coupled to the output port, which become evident in the ultrastrong coupling regime.

[1] S. Napoli et al., Circuit QED Spectra in the Ultrastrong Coupling Regime: How They Differ from Cavity QED, arXiv: 2408.16558