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  • Open Access

Higher-order exceptional points in composite non-Hermitian systems

Jan Wiersig*

Weijian Chen

  • Institut für Physik, Otto-von-Guericke-Universität Magdeburg, Postfach 4120, D-39016 Magdeburg, Germany

  • *Contact author: jan.wiersig@ovgu.de
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Phys. Rev. Research 7, 033034 – Published 8 July, 2025

DOI: https://doi.org/10.1103/tmw5-fcph

Abstract

We show that a composite quantum system described by the tensor product of multiple systems each with a leading-order exceptional point (a non-Hermitian degeneracy at which not only eigenvalues but also eigenstates coalesce) exhibits a single leading-order exceptional point, whose order surpasses the order of any constituent exceptional point. The formation of such higher-order exceptional points does not require coupling among the subsystems. We determine explicitly the order and the spectral response strength of this exceptional point. Moreover, we observe that the energy eigenstates that do not merge are entangled. Finally, we demonstrate that general initial states disentangle during time evolution due to the presence of the higher-order exceptional point of the composite system.

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Phys. Rev. Research 7, 033034– Published 8 July, 2025
  • Received 9 April 2025
  • Accepted 16 June 2025
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