Pseudomode approach to Fano effect in dissipative cavity quantum electrodynamics

TL;DR

This paper presents a pseudomode approach to analyze the Fano effect in dissipative cavity QED, revealing its non-Markovian origin and unifying the description of interference phenomena.

Contribution

It introduces a pseudomode method to derive the spectral function and master equation, clarifying the Fano effect's origin in cavity QED systems.

Findings

Spectral function includes a constant and non-Lorentzian part forming the Fano profile.

The constant term is crucial for a Lindblad master equation and relates to Fano interference.

Unified framework for Fano effect in single-mode cavity QED established.

Abstract

We study the Fano effect in dissipative cavity quantum electrodynamics, which originates from the interference between the emitter's direct radiation and that mediated by a cavity mode. Starting from a two-level system coupled to a structured reservoir, we show that a quantum master equation previously derived within the Born-Markov approximation can be rederived by introducing a single auxiliary mode via pseudomode approach. We identify the corresponding spectral function of the system--environment interaction and demonstrate that it consists of a constant and a non-Lorentzian contribution forming the Fano profile. The constant term is shown to be essential for obtaining a Lindblad master equation and is directly related to the rate associated with this Fano interference. Furthermore, by applying Fano diagonalization to a common-environment setup including an explicit cavity mode, we independently derive the same spectral function in the strongest-interference regime. Our results establish a unified framework for describing the Fano effect in single-mode cavity QED systems and clarify its non-Markovian origin encoded in the spectral function.