Superradiant decay in non-Markovian Waveguide Quantum Electrodynamics

TL;DR

This paper investigates how finite time delays in photon exchange affect superradiant decay in waveguide QED, revealing structured photon emission, entanglement dynamics, and enhanced decay rates beyond Markovian predictions.

Contribution

It introduces tensor-network methods to study non-Markovian effects, showing structured photon trains and entanglement growth in superradiant decay.

Findings

Superradiant burst breaks into correlated photon train

Emitter-emitter entanglement emerges over time

Time delay can increase decay rates beyond Markovian limits

Abstract

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.