Superradiant decay in non-Markovian waveguide quantum electrodynamics

An array of initially excited emitters coupled to a one-dimensional waveguide exhibits superradiant decay under the Born-Markov approximation, manifested as a coherent burst of photons in the output field. In this work, we employ tensor-network methods to investigate its non-Markovian dynamics induced by finite time delays in photon exchange among the emitters. We find that the superradiant burst breaks into a structured train of correlated photons, each intensity peak corresponding to a specific photon number. We quantify the emitter-photon and emitter-emitter entanglement generated during this process and show that the latter emerges in the long-time limit, as part of the excitation becomes trapped within the emitters’ singlet subspace. We finally consider the decay of the system’s most radiant state, the symmetric Dicke state, and show that time delay can lead to decay rates exceeding those predicted by the Markovian approximation. The authors consider an array of two-level quantum emitters, coupled to a one-dimensional waveguide, and use tensor-network methods to investigate non-Markovian effects induced by finite time delays in photon exchange. In superradiant emission, they observe how delay effects entail burst breakdown, generation of entanglement between emitters and photons and among emitters, and asymptotic excitation trapping.