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  • Open Access

Lindbladian versus Postselected non-Hermitian Topology

Alexandre Chaduteau*, Derek K. K. Lee, and Frank Schindler

  • *Contact author: alexandre.chaduteau20@imperial.ac.uk
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Phys. Rev. Lett. 136, 016603 – Published 6 January, 2026

DOI: https://doi.org/10.1103/ljvt-w6hw

Abstract

The recent topological classification of non-Hermitian “Hamiltonians” is usually interpreted in terms of pure quantum states that decay or grow with time. However, many-body systems with loss and gain are typically better described by mixed-state open quantum dynamics, which only correspond to pure-state non-Hermitian dynamics upon a postselection of measurement outcomes. Since postselection becomes exponentially costly with particle number, we here investigate to what extent the most important example of non-Hermitian topology can survive without it: the non-Hermitian skin effect and its relationship to a bulk winding number in one spatial dimension. After defining the winding number of the Lindbladian superoperator for a quadratic fermion system, we systematically relate it to the winding number of the associated postselected non-Hermitian Hamiltonian. We prove that the two winding numbers are equal (opposite) in the absence of gain (loss), and provide a physical explanation for this relationship. When both loss and gain are present, the Lindbladian winding number typically remains quantized and non-zero, though it can change sign at a phase transition separating the loss and gain-dominated regimes. This transition, which leads to a reversal of the Lindbladian skin effect localization, is rendered invisible by postselection. We also identify a case where removing postselection induces a skin effect from otherwise topologically trivial non-Hermitian dynamics.

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Phys. Rev. Lett. 136, 016603– Published 6 January, 2026
  • Received 23 July 2025
  • Revised 16 October 2025
  • Accepted 16 December 2025
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