RQC Seminar

290th RQC Seminar

• Speaker

  Mr. Kazuki Kobayashi
  ( Shizuoka University )

• Date

  16:00-17:00, (4:00 p.m.- 5:00 p.m.) Tuesday, July 14, 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

  Identifying the Spectral Function Underlying the Fano Effect in a Single-Mode Cavity QED System

• Inquiries

  norilab_rqc_assist[at]ml.riken.jp

Abstract
The Fano effect arises from the interference between a direct transition from a discrete state to a continuum and an indirect transition to the same continuum mediated by another discrete state. In recent years, several quantum master equations (QMEs) incorporating the Fano effect have been proposed for cavity quantum electrodynamics (QED) systems. For Fano effects arising from the interaction between two coupled cavity modes, Markovian embedding approaches have clarified the spectral functions that characterize the environmental memory effects. In contrast, for Fano effects originating from the interference between an emitter's direct radiation and that mediated by a single cavity mode, existing Fano-type QMEs have been derived within the Born-Markov approximation, while the spectral function underlying the Fano effect has remained unclear.

In this work, we identify the spectral function underlying the Fano-type QME in a single-mode cavity QED system from the perspective of Markovian embedding. Starting from an emitter coupled to a structured reservoir, we show that the QME can be derived by introducing a single auxiliary mode through the pseudomode approach. We identify the corresponding spectral function of the system-environment interaction and show that it consists of a constant contribution and a non-Lorentzian contribution, whose interplay gives rise to the Fano profile. The constant contribution represents a Markovian background and is essential for obtaining a Lindblad-type QME. Furthermore, by applying Fano diagonalization to an emitter-cavity system coupled to common and independent reservoirs, we independently derive the same spectral function. These results reveal the non-Markovian origin of the Fano effect in a single-mode cavity QED system and show how it is encoded in the spectral function of the structured reservoir.