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Physical Review A

Collective spontaneous emission of two atoms side-coupled to a one-dimensional semi-infinite waveguide

Guoqing Cai, Ruolin Chai, Lei Du, Mu-Tian Cheng, Yong Li

Published Apr 28, 2026• 0 citations
Publisher

Abstract

We present a theoretical investigation of collective spontaneous emission of two identical two-level atoms side-coupled to a one-dimensional semi-infinite waveguide. The presence of the waveguide boundary naturally induces a feedback interference mechanism. Our results reveal that the collective spontaneous emission rate of the two atoms can be effectively suppressed or enhanced by this interference mechanism, depending on whether the atoms are initially prepared in a symmetric or antisymmetric state. Remarkably, the maximum collective emission rate can reach twice that observed in the case of an infinite waveguide, which arises from Purcell enhancement induced by the waveguide boundary. Further analysis of the two-atom collective dynamics reveals that, under appropriate conditions, an atom-photon bound state can be formed, leading to the confinement of emitted photons within the atom-atom or atom-boundary interspace. These results offer potential applications in quantum information processing based on waveguide quantum electrodynamics.

DOI
10.1103/rxkr-t14p

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We present a theoretical investigation of collective spontaneous emission of two identical two-level atoms side-coupled to a one-dimensional semi-infinite waveguide. The presence of the waveguide boundary naturally induces a feedback interference mechanism. Our results reveal that the collective spontaneous emission rate of the two atoms can be effectively suppressed or enhanced by this interference mechanism, depending on whether the atoms are initially prepared in a symmetric or antisymmetric state. Remarkably, the maximum collective emission rate can reach twice that observed in the case of an infinite waveguide, which arises from Purcell enhancement induced by the waveguide boundary. Further analysis of the two-atom collective dynamics reveals that, under appropriate conditions, an atom-photon bound state can be formed, leading to the confinement of emitted photons within the atom-atom or atom-boundary interspace. These results offer potential applications in quantum information processing based on waveguide quantum electrodynamics.
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We investigate the spontaneous emission of a two-level system, e.g., an atom or atomlike object, coupled to a single-end, i.e., a semi-infinite, one-dimensional photonic waveguide such that one end behaves as a perfect mirror while light can pass through the opposite end with no backreflection. Through a quantum microscopic model we show that such geometry can cause nonexponential and long-lived atomic decay. Under suitable conditions, a bound atom-photon stationary state appears in the atom-mirror interspace so as to trap a considerable amount of initial atomic excitation. Yet this can be released by applying an atomic frequency shift, causing a revival of photon emission. The resilience of such effects to typical detrimental factors is analyzed.
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We consider the cooperative spontaneous emission of a system of two identical atoms interacting with the electromagnetic field in the vacuum state and in the presence of an oscillating mirror. We assume that the two atoms, one in the ground state and the other in the excited state, are prepared in a correlated (symmetric or antisymmetric) Bell-type state. We also suppose that the perfectly reflecting plate oscillates adiabatically, with the field modes satisfying the boundary conditions at the mirror surface at any given instant, so that the time dependence of the interaction Hamiltonian is entirely enclosed in the instantaneous atom-wall distance. Using time-dependent perturbation theory, we investigate the spectrum of the radiation emitted by the two-atom system, showing how the oscillation of the boundary modifies the features of the emitted spectrum, which exhibits two lateral peaks not present in the case of a static boundary. We also evaluate the transition rate to the collective ground state of the two-atom system in both cases of the superradiant (symmetric) and subradiant (antisymmetric) state. We show that it is modulated in time and that the presence of the oscillating mirror can enhance or inhibit the decay rate compared to the case of atoms in vacuum space or near a static boundary. Our results thus suggest that a dynamical (i.e., time-modulated) environment can offer further possibilities to control and manipulate radiative processes of atoms or molecules nearby, such as the cooperative decay, and strongly indicate a similar possibility for other radiative processes, for example, the resonance interaction and the energy transfer between atoms or molecules.
Abstract. In this paper, we demonstrate the application of quantum feedback control in creating desired states for atomic and photonic systems utilizing a semi-infinite waveguide coupled with multiple two-level atoms. In this approach, an initially excited atom can emit one photon into the waveguide, and the photon can be reflected by either the terminal mirror of the waveguide or other atoms, establishing various feedback loops through the coherent interactions between the atom and photon. When there are no more than two excitations in the waveguide quantum electrodynamics (QED) system, the evolution of quantum states can be effectively elucidated through the lens of random graph theory. However, this process is influenced by the environment. We propose that the environment-induced dynamics in the coherent feedback loop can be eliminated by measurement-based feedback control or coherent drives. Consequently, in the atom-waveguide interactions in open quantum systems, measurement-based feedback has the potential to modulate the quantum steady states. Additionally, the homodyne detection noise during the measurement process can induce errors upon quantum states, which can be influenced by the coherent feedback parameter designs.