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arXiv:2602.16032

Multi-emitter oscillating bound states in Waveguide QED

Sergi Terradas-Briansó, Carlos A. González-Gutiérrez, Iván Huarte, David Zueco, Luis Martin-Moreno

quant-phSubmitted Feb 17, 2026• Announced Feb 19, 2026• 0 citations
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Abstract

Waveguide quantum electrodynamics platforms have emerged as promising candidates for exploring and implementing non-Markovian quantum phenomena. In this work, we investigate the formation and dynamics of superpositions of bound states in a cavity array waveguide coupled to two spatially separated quantum emitters. By tuning the system parameters, we show that spontaneous emission can drive the system into non-local equilibrium states in which both photonic and emitter populations exhibit persistent oscillations. These states arise from the coexistence of bound states embedded in the energy continuum and bound states outside it, leading to hybrid oscillatory modes. We analytically derive the conditions required for the emergence of these states, numerically simulate their formation through spontaneous emission, and predict their long-time behaviour. Our results demonstrate that such bound-state superpositions enable the generation of emitter-emitter interaction through free evolution, while supporting oscillatory breathing modes of the photon density between the emitters.

Comments
7 pages, 4 figures

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Abstract Giant quantum emitters, whose effective size is comparable to the wavelength of the resonant radiation they couple to, give rise to interference effects and non-Markovian dynamics that lie beyond the scope of the standard Weisskopf–Wigner approximation. Here we study minimal models of giant emitters coupled to cavity–array waveguides and identify symmetric configurations where the dynamics can be solved exactly. This allows us to capture the emergence of bound states both inside and outside the photonic continuum, and to demonstrate the possibility of engineering their coherent superpositions. Our results provide analytical insight into non-Markovian light–matter interaction and suggest a feasible implementation using superconducting circuit platforms.