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arxiv: 2604.12739 · v1 · submitted 2026-04-14 · 🪐 quant-ph · cond-mat.mes-hall· physics.optics

Decoherence Resilience of the Non-Hermitian Skin Effect

Kunkun Wang , Lei Xiao , Stefano Longhi , Peng Xue This is my paper

Pith reviewed 2026-05-10 14:49 UTC · model grok-4.3

classification 🪐 quant-ph cond-mat.mes-hallphysics.optics
keywords non-Hermitian skin effectdecoherencedephasingamplitude dampingquantum walksdirectional transportopen quantum systems
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The pith

The non-Hermitian skin effect survives dephasing and can be enhanced by it even in the fully incoherent regime.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines whether the non-Hermitian skin effect, in which dissipation drives directional bulk-to-boundary transport, can withstand or benefit from environmental decoherence. Researchers implement this in photonic quantum walks and introduce controlled dephasing or amplitude damping at tunable strengths and orders. Dephasing preserves the directional transport all the way to complete incoherence and produces faster drift than purely coherent evolution. Amplitude damping instead yields suppression or persistence depending on whether it precedes or follows the non-Hermitian loss operator. These results indicate that certain forms of noise can be turned to advantage for controlled transport in open systems.

Core claim

In photonic quantum walks realizing non-Hermitian dynamics, the skin effect that concentrates probability at one boundary persists under dephasing decoherence through the fully incoherent limit and produces larger drift velocities than coherent evolution; for amplitude damping the outcome is order-dependent, with preceding damping eliminating the effect in the incoherent limit while subsequent damping permits persistence and enhancement at strong loss.

What carries the argument

Photonic quantum walks with independently tunable dephasing and amplitude-damping channels applied before or after the non-Hermitian loss operator, used to track the evolution of asymmetric probability distributions that signal the skin effect.

Load-bearing premise

The two engineered decoherence channels in the photonic walk fully represent the relevant environmental interactions and introduce no additional effects that would change the observed skin-effect behavior.

What would settle it

Measurement of drift velocities under strong dephasing that remain equal to or smaller than the coherent case, or complete disappearance of boundary accumulation in the fully incoherent limit regardless of damping order, would falsify the reported resilience.

Figures

Figures reproduced from arXiv: 2604.12739 by Kunkun Wang, Lei Xiao, Peng Xue, Stefano Longhi.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: a-c, increasing the damping strength gradually reduces the spatial asymmetry of the walker distribution, indicating that amplitude damping suppresses the NHSE. However, even in the fully incoherent limit, a clear directional transport per￾sists. This behavior is quantitatively captured by the center￾of-mass evolution. As shown in Fig. 4d, the drift velocity de￾creases monotonically with increasing damping … view at source ↗
read the original abstract

Decoherence and dissipation, arising from unavoidable interactions with the environment, can exert a dual influence on transport in physical systems, suppressing coherent propagation while inducing diffusion and mitigating localization in disordered systems. Non-Hermitian physics reveals a qualitatively different scenario, in which structured dissipation can induce directional bulk-to-boundary transport, known as the non-Hermitian skin effect (NHSE), that remains robust against disorder. Whether such transport can persist, be enhanced or hindered under decoherence, remains a largely open question. Here we experimentally address this question using photonic quantum walks with two tunable prototypical decoherence channels, dephasing and amplitude damping. Under dephasing, the NHSE survives up to the fully incoherent regime and is observed to even be enhanced by dephasing, yielding drift velocities that exceed those of coherent dynamics. By contrast, amplitude damping shows a pronounced order dependence: applied before the non-Hermitian loss operator, it suppresses and ultimately eliminates the NHSE in the fully incoherent limit; applied afterward, the NHSE persists and can be enhanced at sufficiently large loss strengths. Our work bridges quantum and classical non-Hermitian dynamics, demonstrates the resilience of the NHSE to decoherence, and opens avenues for harnessing decoherence to enhance directional transport in noisy, nonequilibrium systems.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript experimentally investigates the resilience of the non-Hermitian skin effect (NHSE) to decoherence using photonic discrete-time quantum walks. It demonstrates that dephasing preserves the NHSE up to the fully incoherent regime and can enhance drift velocities beyond coherent dynamics, while amplitude damping exhibits a pronounced dependence on whether it is applied before or after the non-Hermitian loss operator, suppressing the NHSE in one ordering but allowing persistence or enhancement in the other.

Significance. If the reported qualitative contrasts and order dependence hold under quantitative scrutiny, the work provides direct experimental evidence bridging quantum and classical non-Hermitian transport, establishes decoherence resilience of the NHSE, and suggests practical routes to harness environmental noise for directional transport in open systems. The photonic platform's tunability of two distinct Lindblad channels is a notable strength for isolating channel-specific effects.

major comments (2)
  1. [Results section on dephasing] Results on dephasing (likely §4 or equivalent): the claim that drift velocities exceed coherent dynamics requires explicit comparison of extracted velocities with error bars against the coherent baseline; without this, the 'enhancement' assertion rests on qualitative observation alone and cannot be assessed for statistical significance.
  2. [Methods and amplitude-damping results] Amplitude-damping order-dependence experiments: the manuscript must clarify how the two application orders are realized in the discrete-step protocol (e.g., interleaving of loss operator and damping channel) to ensure the observed suppression vs. persistence is not an artifact of the specific pulse sequence or timing.
minor comments (2)
  1. [Figure captions] Figure captions should explicitly state the number of experimental realizations, binning procedure for probability distributions, and fitting method used to extract drift velocities.
  2. [Throughout] Notation for the non-Hermitian loss operator and the two Lindblad channels should be unified between the abstract, main text, and supplementary material to avoid ambiguity in the order-dependence discussion.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript, positive assessment of its significance, and recommendation for minor revision. We address each major comment below and have revised the manuscript to incorporate the suggested improvements.

read point-by-point responses

  1. Referee: [Results section on dephasing] Results on dephasing (likely §4 or equivalent): the claim that drift velocities exceed coherent dynamics requires explicit comparison of extracted velocities with error bars against the coherent baseline; without this, the 'enhancement' assertion rests on qualitative observation alone and cannot be assessed for statistical significance.

    Authors: We agree that quantitative support with error bars is required to rigorously establish the enhancement. While the original figures display the qualitative trend, we have revised the dephasing results section to include a new panel (or supplementary figure) reporting the extracted drift velocities with error bars obtained from multiple independent experimental runs. These values are directly compared to the coherent-dynamics baseline, and the text has been updated to reference the statistical significance of the observed enhancement. revision: yes

  2. Referee: [Methods and amplitude-damping results] Amplitude-damping order-dependence experiments: the manuscript must clarify how the two application orders are realized in the discrete-step protocol (e.g., interleaving of loss operator and damping channel) to ensure the observed suppression vs. persistence is not an artifact of the specific pulse sequence or timing.

    Authors: We appreciate this request for clarification. In the revised Methods section we now explicitly describe the two orders: the 'before' configuration applies the amplitude-damping channel immediately prior to the non-Hermitian loss operator in each discrete time step, while the 'after' configuration applies the damping channel immediately after the loss operator. A schematic of the pulse sequence and timing for both orderings has been added to demonstrate that the reported suppression versus persistence arises from the intended channel ordering rather than from any implementation artifact. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely experimental observations

full rationale

The paper reports direct experimental measurements in a photonic discrete-time quantum walk realizing non-Hermitian evolution plus two Lindblad channels (dephasing and amplitude damping). No mathematical derivation, fitted parameter, or prediction is claimed; the central results (NHSE survival/enhancement under dephasing, order-dependent suppression under amplitude damping) are read out from observed probability distributions and drift velocities. The work contains no self-citation load-bearing steps, no ansatz smuggling, and no reduction of outputs to inputs by construction. The experimental protocol is self-contained against the stated observables.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

The central claim rests on the experimental platform faithfully realizing the non-Hermitian skin effect under controlled decoherence; no new entities are postulated and the only free parameters are the experimentally tuned decoherence strengths.

free parameters (2)
  • dephasing strength
    Tunable experimental parameter controlling the level of phase randomization applied to the quantum walk.
  • amplitude damping strength
    Tunable experimental parameter controlling the probability leakage applied before or after the non-Hermitian loss.
axioms (1)
  • domain assumption The photonic quantum walk with added loss operator accurately models the non-Hermitian skin effect in the presence of the two specified decoherence channels.
    Invoked throughout the experimental design and interpretation.

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    See Supplemental Material for more details. AcknowledgementsThis work is supported by the National Key R&D Program of China (Grant No. 2023YFA1406701) and the National Natural Science Foundation of China (Grant Nos. 12025401, 92265209, 12474352 and 92476106). S.L. acknowledges the Spanish Agencia Estatal de Investigacion (Grant No. MDM-2017-0711). K.K.W. ...

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