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Active Quantum Flocks

Reyhaneh Khasseh1,2, Sascha Wald3, Roderich Moessner2, Christoph A. Weber4,2, and Markus Heyl1,2

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Phys. Rev. Lett. 135, 248302 – Published 10 December, 2025

DOI: https://doi.org/10.1103/rd46-hr3q

Abstract

Flocks of animals represent a prominent archetype of collective behavior in the macroscopic classical world, where the constituents, such as birds, concertedly perform motions and actions as if being one single entity. Here, we address the so far open question of whether flocks can also form in the microscopic world at the quantum level. For that purpose, we introduce the concept of active quantum matter by formulating a class of models of active quantum particles on a one-dimensional lattice. We provide both analytical and large-scale numerical evidence that these systems can give rise to quantum flocks. A key finding is that these quantum flocks exhibit distinct quantum properties by developing strong quantum coherence over long distances. We propose that quantum flocks could be experimentally observed in Rydberg atom arrays.

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Phys. Rev. Lett. 135, 248302– Published 10 December, 2025
  • Received 5 June 2025
  • Accepted 14 November 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. Open access publication funded by the Max Planck Society.

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