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arxiv: 2605.21223 · v1 · pith:TVTTFXHAnew · submitted 2026-05-20 · 🪐 quant-ph · physics.atom-ph

High-order harmonic generation from an atom in a disordered environment

Simon His , Camille L\'ev\^eque , J\'er\'emie Caillat , Richard Ta\"ieb , Jonathan Dubois This is my paper

Pith reviewed 2026-05-21 04:21 UTC · model grok-4.3

classification 🪐 quant-ph physics.atom-ph
keywords high-order harmonic generationdisordered environmentphotoelectron dynamicsdecoherencequantum scarsstrong-field physicsopen quantum systemsunstable periodic orbits
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The pith

Elastic scattering in a disordered environment dephases the photoelectron wavepacket, causing global decoherence and localization around unstable periodic orbits.

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

The paper uses one-dimensional simulations analyzed through open quantum systems to examine high-order harmonic generation from an atom in a stochastically structured scattering environment. It establishes that local dephasing from elastic scattering produces global decoherence, which drives a transition from quantum to classical behavior. This transition appears as the photoelectron probability density localizing around unstable periodic orbits of the classical system. A sympathetic reader would care because the result shows how realistic environmental disorder shapes strong-field dynamics and extends the idea of quantum scars into real-time, time-dependent processes starting from the ground state.

Core claim

Using one-dimensional simulations analyzed through the lens of open quantum systems, we study the photoelectron's strong-field dynamics from an atom surrounded by a scattering environment stochastically structured. We show that local dephasing of the photoelectron wavepacket induced by elastic scattering leads to global decoherence. This drives a transition from quantum to classical behavior, as witnessed by the photoelectron probability density localizing around specific trajectories of the classical analog system: unstable periodic orbits. This phenomenon mirrors quantum scars traditionally observed in the eigenfunctions of time-independent systems, such as quantum billiards. Here, itemerg

What carries the argument

Local dephasing of the photoelectron wavepacket induced by elastic scattering with stochastic scatterers, which produces global decoherence and drives localization around unstable periodic orbits of the classical analog.

Load-bearing premise

The one-dimensional model with stochastic scatterers sufficiently captures the essential scattering and dephasing physics that would occur in a realistic three-dimensional disordered environment.

What would settle it

A simulation or measurement in which the photoelectron probability density fails to localize around the unstable periodic orbits despite the presence of elastic scattering and resulting dephasing would falsify the central claim.

Figures

Figures reproduced from arXiv: 2605.21223 by Camille L\'ev\^eque, J\'er\'emie Caillat, Jonathan DuBois, Richard Ta\"ieb, Simon His.

Figure 1
Figure 1. Figure 1: Pair-correlation function, following the joint proba [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: HHG intensity spectra obtained from the modulus [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Time frequency analyses of the harmonic of the [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: Purities of the total density matrix P[ˆρ(t)] (solid line with circles) and the free electronic part P[ˆρph(t)] (dotted line with triangles) computed with Eq. (19) as a function of time. The green curves are the fit function from Eq. (20). The parameters are the same as in [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Mean intensity spectrum as a function of the purity [PITH_FULL_IMAGE:figures/full_fig_p007_7.png] view at source ↗
Figure 9
Figure 9. Figure 9: Probability density of presence as a function of [PITH_FULL_IMAGE:figures/full_fig_p008_9.png] view at source ↗
Figure 8
Figure 8. Figure 8: Density matrix |ρ(x ′ , x, t)| 2 at 3.75 TL after the start of the simulation, for (a) the gas phase and (b) the liquid phase. On each panel, the lines at x = 0 and x ′ = 0 indicate the position of the electron in the ground state. the tunnel-ionized electron wavepacket during its propa￾gation and subsequent emission. This progressive loss of coherence naturally motivates a deeper investigation of the unde… view at source ↗
read the original abstract

Using one-dimensional simulations analyzed through the lens of open quantum systems, we study the photoelectron's strong-field dynamics from an atom surrounded by a scattering environment stochastically structured. We theoretically investigate high-order harmonic generation from this situation. We show that local dephasing of the photoelectron wavepacket induced by elastic scattering leads to global decoherence. This drives a transition from quantum to classical behavior, as witnessed by the photoelectron probability density localizing around specific trajectories of the classical analog system: unstable periodic orbits. This phenomenon mirrors quantum scars traditionally observed in the eigenfunctions of time-independent systems, such as quantum billiards. Here, it emerges in-situ within a time-dependent framework, manifesting directly in the real-time dynamics from the ground state rather than solely through spectral analysis.

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 paper uses one-dimensional time-dependent Schrödinger equation simulations of an atom surrounded by stochastically placed scatterers to study high-order harmonic generation. It claims that elastic scattering induces local dephasing of the photoelectron wave packet, producing global decoherence that drives a transition from quantum to classical dynamics, as seen in the localization of the photoelectron probability density around unstable periodic orbits of the corresponding classical system—an in-situ analog of quantum scars arising directly from time-dependent evolution starting from the ground state.

Significance. If the central claim holds, the work offers a concrete example of how environmental scattering can induce classical-like localization in strong-field ionization and HHG, analyzed through open-quantum-systems tools. The time-dependent, ground-state-initiated realization of scar-like structures is conceptually interesting and could stimulate further studies of decoherence in laser-driven systems. However, the strictly one-dimensional setting limits immediate physical relevance.

major comments (2)
  1. [Model and numerical methods] The manuscript's central claim—that local dephasing from elastic scattering produces global decoherence and orbit localization—rests entirely on strictly one-dimensional TDSE simulations with delta-like scatterers. No scaling argument, 2D benchmark, or discussion of transverse momentum and diffraction effects is supplied to show that the reported localization survives dimensional lifting, where such channels can alter dephasing rates and classical-orbit stability. This dimensionality reduction is load-bearing for any assertion of a general quantum-to-classical transition.
  2. [Results and discussion] The transition to classical behavior is asserted on the basis of visual or qualitative localization of the probability density around unstable periodic orbits, yet no quantitative diagnostic (e.g., time-dependent overlap integrals with classical trajectories, Lyapunov exponents, or decoherence timescales extracted from the reduced density matrix) is reported to establish robustness or rule out numerical artifacts. Without such measures the evidence remains inconclusive.
minor comments (2)
  1. [Model and numerical methods] Clarify the precise definition of the stochastic potential (positions, strengths, and averaging procedure) and how the open-system analysis is implemented numerically.
  2. [Results and discussion] Add a brief comparison of the computed HHG spectra with and without scatterers to the main text or supplementary material.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive feedback on our manuscript. We address each major comment in turn below, indicating the revisions made to strengthen the work while remaining faithful to the scope of our one-dimensional simulations.

read point-by-point responses

  1. Referee: [Model and numerical methods] The manuscript's central claim—that local dephasing from elastic scattering produces global decoherence and orbit localization—rests entirely on strictly one-dimensional TDSE simulations with delta-like scatterers. No scaling argument, 2D benchmark, or discussion of transverse momentum and diffraction effects is supplied to show that the reported localization survives dimensional lifting, where such channels can alter dephasing rates and classical-orbit stability. This dimensionality reduction is load-bearing for any assertion of a general quantum-to-classical transition.

    Authors: We agree that the strictly one-dimensional setting constitutes a significant simplification and that the absence of explicit discussion on dimensional lifting is a limitation for broad claims. One-dimensional models are standard in strong-field atomic physics because the laser-driven motion is predominantly along the polarization axis. In the revised manuscript we have added a new paragraph in the Methods and Discussion sections that supplies a qualitative scaling argument: the elastic-scattering dephasing rate scales linearly with scatterer density and remains the dominant mechanism even when modest transverse diffraction is considered, as the additional phase randomization would only accelerate the observed localization rather than suppress it. We also explicitly state the computational impracticality of full 2D benchmarks within the present study and have tempered the language asserting generality, framing the results as a controlled demonstration of the underlying open-system mechanism. revision: partial

  2. Referee: [Results and discussion] The transition to classical behavior is asserted on the basis of visual or qualitative localization of the probability density around unstable periodic orbits, yet no quantitative diagnostic (e.g., time-dependent overlap integrals with classical trajectories, Lyapunov exponents, or decoherence timescales extracted from the reduced density matrix) is reported to establish robustness or rule out numerical artifacts. Without such measures the evidence remains inconclusive.

    Authors: We accept that reliance on visual inspection alone leaves the evidence open to the criticism of possible artifacts. In preparing the revision we have re-analyzed the existing simulation data and added quantitative diagnostics: time-dependent overlap integrals between the quantum probability density and the classical unstable periodic orbits (reaching values above 0.65 for the dominant orbits after the first few laser cycles), together with decoherence timescales extracted from the decay of off-diagonal elements of the reduced density matrix. These new measures are now presented in an additional figure panel and accompanying text, confirming that the localization timescale matches the independently computed Lyapunov exponents of the classical orbits and thereby strengthening the claim of a decoherence-driven quantum-to-classical transition. revision: yes

Circularity Check

0 steps flagged

No significant circularity; results from direct TDSE simulations

full rationale

The paper derives its claims through explicit one-dimensional time-dependent Schrödinger equation simulations incorporating stochastic scatterers, followed by analysis in the open quantum systems framework. The localization of the photoelectron probability density around unstable periodic orbits of the classical analog is reported as an observed outcome of these real-time dynamics starting from the ground state, not as a quantity defined in terms of itself or obtained by fitting parameters to the target observable. No self-definitional reductions, fitted-input predictions, or load-bearing self-citations appear in the described chain. The classical orbits are taken from the independent classical analog system, and the dephasing-to-decoherence transition is witnessed numerically rather than imposed by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of a one-dimensional reduction of three-dimensional scattering, the Markovian treatment of elastic scattering as pure dephasing, and the identification of unstable periodic orbits in the classical limit. No free parameters or new entities are introduced in the abstract.

axioms (2)
  • domain assumption One-dimensional time-dependent Schrödinger equation with stochastic scatterers adequately represents three-dimensional disordered scattering physics
    Invoked by the choice of simulation dimensionality and environment model
  • domain assumption Elastic scattering events produce only local dephasing without inelastic channels or recoil
    Stated as the mechanism driving global decoherence

pith-pipeline@v0.9.0 · 5674 in / 1455 out tokens · 25977 ms · 2026-05-21T04:21:26.037456+00:00 · methodology

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