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  • Open Access

Unraveling Superradiance: Entanglement and Mutual Information in Collective Decay

Xin H. H. Zhang1,2,3,*, Daniel Malz4, and Peter Rabl1,2,3

  • *Contact author: physicsxinzhang@gmail.com
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Phys. Rev. Lett. 135, 033602 – Published 16 July, 2025

DOI: https://doi.org/10.1103/qbfk-zrzc

Abstract

We study the collective decay of an initially inverted ensemble of two-level emitters in two distinct scenarios: when coupled to a squeezed photonic reservoir and when interacting with a one-dimensional waveguide. Using a quantum-state diffusion approach to unravel the emission process, we investigate entanglement and classical correlations along individual quantum trajectories over time. This numerical analysis shows that despite an initial buildup of entanglement and a significant amount of entanglement due to either spin squeezing or dark states at late times, the essential features of the superradiant burst are well described by averages over fully factorizable states. We explain this observation in terms of an almost complete factorization of all 2-local observables, which we identify as a generic property of superradiant decay. Based on this insight, we provide a purely classical theory for the burst in squeezed superradiance, which is both intuitive and exact for a large number of emitters. Moreover, we find that our numerical approach also performs well in the presence of subradiant states, which dominate the slow residual decay of nonuniform ensembles at late times.

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Phys. Rev. Lett. 135, 033602– Published 16 July, 2025
  • Received 21 May 2025
  • Accepted 26 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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