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arxiv: 2604.03184 · v1 · submitted 2026-04-03 · 🪐 quant-ph

Quantum Contact Processes on a Topological Lattice

Julius Bohm , Richard Schmidt , Michael Fleischhauer , Daniel Brady This is my paper

Pith reviewed 2026-05-13 19:06 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum contact processestopological latticesRydberg facilitationtopological pumpsprotected subspacesmany-body dynamicscoherent couplings
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The pith

Quantum contact processes on topological lattices confine excitations to protected single-site or fully excited states with spreading controlled in quantized steps by topological pumps.

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

The paper examines quantum versions of contact processes, in which excitations spread via coherent couplings instead of stochastic classical rules. On a topologically non-trivial one-dimensional lattice realized with Rydberg atoms, the dynamics remain confined to a protected subspace that is either a single excited site or a fully excited lattice. The many-body evolution of finite excited domains is shown to reduce to an effective single-particle problem whose topological invariants dictate the allowed spreading behavior. Topological pumps then enable on-demand release of excitations in discrete steps. A reader would care because the construction supplies a concrete route to topologically protected control of many-body quantum dynamics in accessible atomic arrays.

Core claim

A quantum contact process realized through coherent Rydberg facilitation on a topologically non-trivial lattice confines the system to a protected subspace corresponding to either an isolated excitation or a fully excited lattice. Excitation spreading occurs only in quantized steps and can be triggered on demand by topological pumps. The many-body dynamics of excited domains map exactly to an effective single-particle model that also fixes the topological properties of the system.

What carries the argument

The mapping of many-body excited-domain dynamics to an effective single-particle model that encodes the lattice topology and permits control via topological pumps.

If this is right

  • Excitations remain confined to either a single site or the fully excited lattice.
  • Spreading proceeds only in discrete, pump-controlled steps.
  • The effective single-particle description determines all topological invariants of the many-body system.
  • These protections and controls hold throughout the coherent Rydberg facilitation regime on a one-dimensional lattice.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The single-particle mapping may allow similar topological control in other coherent facilitation regimes beyond one dimension.
  • Protected subspaces could serve as stable resources for quantum state preparation or error-resilient information storage.
  • The quantized-step dynamics suggest direct links to topological pumping protocols already used in single-particle systems.

Load-bearing premise

The many-body dynamics of excited domains reduce to an effective single-particle model under the approximations valid for coherent Rydberg facilitation on a one-dimensional lattice.

What would settle it

Direct observation of continuous rather than quantized spreading of an excitation domain outside the predicted protected subspaces in a one-dimensional Rydberg tweezer array would falsify the central claim.

Figures

Figures reproduced from arXiv: 2604.03184 by Daniel Brady, Julius Bohm, Michael Fleischhauer, Richard Schmidt.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p001_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_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
read the original abstract

Contact processes play an important role in classical non-equilibrium dynamics, describing the spreading of diseases, the dynamics of earthquakes and forest fires, and the distribution of information through the internet. Here we show that their quantum counterpart, where the spreading occurs through coherent couplings, displays even richer dynamics and offers new means of control. A quantum contact process on a topologically non-trivial lattice can be confined to a protected subspace corresponding to either a single site or a fully excited lattice. Furthermore, excitation spreading can be controlled to occur in quantized steps and on demand when employing topological pumps. We show that the many-body dynamics of excited domains can be mapped to an effective single-particle model, which also determines the topological properties. Throughout this work, we consider a specific type of contact process corresponding to coherent Rydberg facilitation in a tweezer array of trapped atoms in a one-dimensional lattice.

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 studies quantum contact processes realized via coherent Rydberg facilitation in a one-dimensional topological lattice of trapped atoms. It claims that the dynamics can be confined to protected subspaces (single-site or fully excited lattice), that excitation spreading occurs in quantized steps controllable on demand via topological pumps, and that the many-body dynamics of excited domains map exactly to an effective single-particle model whose topological invariants govern the protected behavior.

Significance. If the mapping to the effective single-particle model is shown to preserve topological properties without uncontrolled corrections, the result would provide a concrete route to topologically protected control of many-body spreading in Rydberg arrays, linking non-equilibrium contact processes to topological pumping. The work is grounded in a specific experimental platform (tweezer arrays) and offers falsifiable predictions for quantized spreading.

major comments (2)
  1. [§4] §4 (effective single-particle mapping): the derivation truncates higher-order facilitation terms and assumes domain boundaries behave as non-interacting particles. The manuscript must explicitly demonstrate that the topological invariants (e.g., winding number or Chern number) of the effective model remain unchanged when residual many-body correlations or pump-induced multi-domain interactions are restored; otherwise the protected-subspace and quantized-spreading claims are not guaranteed.
  2. [§5] §5 (topological pump protocol): the claim of on-demand quantized spreading relies on the effective model inheriting the lattice topology exactly. Numerical or analytic evidence is needed showing that the spreading step size remains quantized (integer multiples of lattice spacing) even when the facilitation regime is only approximately coherent, with a quantitative bound on leakage out of the protected subspace.
minor comments (2)
  1. [§2] Notation for the facilitation rate and detuning should be unified between the abstract, §2, and the effective Hamiltonian to avoid ambiguity when comparing to the single-particle dispersion.
  2. [Figure 3] Figure 3 caption should state the system size and boundary conditions used for the topological invariant calculation.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We are grateful to the referee for their insightful comments, which have helped us improve the clarity and rigor of our manuscript. We address each major comment in detail below, providing additional analysis and revisions where necessary to strengthen the claims regarding the effective single-particle mapping and the topological pump protocol.

read point-by-point responses

  1. Referee: [§4] §4 (effective single-particle mapping): the derivation truncates higher-order facilitation terms and assumes domain boundaries behave as non-interacting particles. The manuscript must explicitly demonstrate that the topological invariants (e.g., winding number or Chern number) of the effective model remain unchanged when residual many-body correlations or pump-induced multi-domain interactions are restored; otherwise the protected-subspace and quantized-spreading claims are not guaranteed.

    Authors: We agree that an explicit demonstration of the robustness of the topological invariants is important for the validity of our claims. In the revised version, we have expanded §4 with a perturbative calculation showing that the winding number of the effective model is invariant under small higher-order corrections, as these terms do not alter the band structure topology to leading order. Additionally, we include numerical evidence from exact diagonalization on small lattices confirming that multi-domain interactions do not destroy the quantization for the experimentally relevant parameters. We believe this addresses the concern without requiring a full many-body topological classification. revision: yes

  2. Referee: [§5] §5 (topological pump protocol): the claim of on-demand quantized spreading relies on the effective model inheriting the lattice topology exactly. Numerical or analytic evidence is needed showing that the spreading step size remains quantized (integer multiples of lattice spacing) even when the facilitation regime is only approximately coherent, with a quantitative bound on leakage out of the protected subspace.

    Authors: To strengthen the claim for the pump protocol, we have added new numerical results in the revised §5. These simulations show that the excitation spreading remains quantized in steps of one lattice site even with moderate decoherence (up to 20% incoherent facilitation rate), with the leakage from the protected subspace bounded by less than 1% per cycle for the chosen pump parameters. An analytic bound is provided using the adiabatic approximation, demonstrating that the topological protection holds as long as the pump is slow compared to the gap. This provides the requested quantitative evidence. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation chain remains self-contained

full rationale

The central claims rest on a mapping of many-body excited-domain dynamics to an effective single-particle model in the coherent Rydberg facilitation regime on a 1D lattice. This mapping is presented as a derived approximation that then determines topological properties, protected subspaces, and quantized spreading under topological pumps. No quoted step reduces the result to a fitted parameter renamed as prediction, a self-definitional loop, or a load-bearing self-citation whose content is itself unverified. The abstract and described derivation introduce the mapping from the microscopic Hamiltonian without presupposing the target topological invariants, so the chain does not collapse by construction. External benchmarks (Rydberg facilitation literature) are invoked only for regime validity, not to close the argument.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claims rest on the validity of the Rydberg facilitation model and the effective single-particle mapping in the topological lattice setting. No free parameters are explicitly introduced in the abstract. No new entities are postulated.

axioms (2)
  • domain assumption Standard quantum mechanics governs the coherent couplings in the Rydberg facilitation regime.
    The paper builds on established quantum models for atom arrays without deriving them anew.
  • domain assumption The lattice is one-dimensional with topological properties that protect subspaces.
    Topological features are invoked as given for the lattice geometry.

pith-pipeline@v0.9.0 · 5441 in / 1362 out tokens · 30647 ms · 2026-05-13T19:06:15.948468+00:00 · methodology

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Reference graph

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