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arXiv:2011.06245 · Physical Review Research

Theory of Fano effect in cavity quantum electrodynamics

Makoto Yamaguchi, Alexey Lyasota, Tatsuro Yuge

Published Jan 13, 2021• 17 citations
arXivHTMLPDF

Abstract

We propose a Markovian quantum master equation that can describe the Fano effect directly, by assuming a standard cavity quantum electrodynamics system.The framework allows us to generalize the Fano formula, applicable over the weak-and strong-coupling regimes with pure dephasing.A formulation of its emission spectrum is also given in a consistent manner.We then find that the interference responsible for the Fano effect is robust against pure dephasing.This is counterintuitive because the impact of interference is, in general, severely reduced by decoherence processes.Our approach thus provides a basis for theoretical treatments of the Fano effect and insights into the quantum interference in open quantum systems.

DOI
10.1103/physrevresearch.3.013037

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We propose a Markovian quantum master equation that can describe the Fano effect directly, by assuming a standard cavity quantum electrodynamics system.The framework allows us to generalize the Fano formula, applicable over the weak-and strong-coupling regimes with pure dephasing.A formulation of its emission spectrum is also given in a consistent manner.We then find that the interference responsible for the Fano effect is robust against pure dephasing.This is counterintuitive because the impact of interference is, in general, severely reduced by decoherence processes.Our approach thus provides a basis for theoretical treatments of the Fano effect and insights into the quantum interference in open quantum systems.
We study the Fano effect in dissipative cavity quantum electrodynamics (QED), 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 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 a spectral profile of the Fano form. The constant contribution represents a Markovian background and is essential for obtaining a Lindblad master equation. Furthermore, by applying Fano diagonalization to an atom--cavity system coupled to common and independent reservoirs, we independently derive the same spectral function and clarify its physical origin. Our results provide a unified description of the Fano effect in single-mode cavity QED systems and reveal its non-Markovian origin encoded in the spectral function of the structured reservoir.
The Fano effect arising from the interference between two dissipation channels of the radiation continuum enables tuning of the photon statistics. Understanding the role of the Fano effect and exploiting it to achieve strong photon correlations are of both fundamental and applied significance. We present an analytical description of Fano-enhanced photon correlations based on cavity quantum electrodynamics to show that the Fano effect in atom-cavity systems can improve the degree of antibunching by over four orders of magnitude. The enhancement factors and the optimal conditions are explicitly given, and found to relate to the Fano parameter q. Remarkably, the Fano enhancement manifests robustness against the decoherence processes and can survive in the weak coupling regime. We expect our work to provide insight to tuning the photon statistics through the Fano effect, which offers a new, to the best of our knowledge, route to enhance the photon correlations, as well as the possibility of generating nonclassical light in a wider diversity of systems without the need of a strong light-matter interaction.
This paper renders two main results. One is a unified quantum master equation, which satisfies the detailed-balance relation and can serve as a convenient starting formulation to study the dissipative dynamics in a variety of systems in quantum optics and solid-state physics. Another is based on the proposed quantum master equation to study cavity quantum electrodynamics in the presence of T1{T}_{1}T1​ energy relaxation and pure T2{T}_{2}T2​ dephasing. Demonstrated in detail is also the effect of cavity field--absorber interaction on dissipation, which is neglected in the conventional theory.
Vacuum induced coherence in a strongly coupled cavity consisting of a three-level system is studied theoretically. The effects of the strong coupling to electromagnetic field vacuum are examined by solution of an open-system quantum master equation. The numerical results show that the system exhibits population trapping, and the numerical results are interpreted with analytical expressions derived from a new basis in the weak excitation regime. We further show that the generated effects can be probed with weak external fields. Moreover, it is shown that the induced coherence can be controlled by the applied field parameters like field detuning. Finally, we study the trapping dynamics in the strong field excitation regime, and also demonstrate that a recently proposed asymmetric pumping regime (limited to the weak coupling regime) can remove the radiative decay of coherent Rabi oscillations, with both weak and strong excitation fields.
We derive analytical formulas for the forward emission and side emission spectra of cavity-modified single-photon sources, as well as the corresponding normal-mode oscillations in the cavity quantum electrodynamics strong-coupling regime. We investigate the effects of pure dephasing, treated in the phase-diffusion model based on a Wiener-Levy process, on the emission spectra and normal-mode oscillations. We also extend our previous calculation of quantum efficiency to include the pure dephasing process. All results are obtained in the Weisskopf-Wigner approximation for an impulse-excited emitter. We find that the spectra are broadened, the depths of the normal-mode oscillations are reduced and the quantum efficiency is decreased in the presence of pure dephasing.
We theoretically analyze the resonance fluorescence of a solid-state cavity quantum electrodynamics (QED) system that consists of a quantum dot and a cavity. We clarify the effects of pure dephasing by investigating the elastic and inelastic scattering probabilities, the fluorescence power spectrum, and the energy exchange with the environment. Pure dephasing interactions with the environment both enhance nonresonant coupling between the dot and the cavity and enable the pump light to continuously absorb energy from the environment under appropriate conditions.