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arxiv: 2602.10203 · v1 · submitted 2026-02-10 · 🪐 quant-ph · gr-qc· hep-th

Cosmological Expansion Induces Interference Between Communication and Entanglement Harvesting

Matheus H. Zambianco , Adam Teixid\'o-Bonfill , Eduardo Mart\'in-Mart\'inez This is my paper

Pith reviewed 2026-05-16 02:18 UTC · model grok-4.3

classification 🪐 quant-ph gr-qchep-th
keywords entanglement harvestingcosmological expansionde Sitter spacetimequantum detectorsinterferencecommunication correlationsscalar field
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The pith

Cosmological expansion induces interference that can completely suppress entanglement harvesting in expanding detectors.

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

The paper examines how the expansion of the universe affects the ability of particle detectors to harvest entanglement from a quantum field while also communicating. In de Sitter spacetime with a conformally coupled scalar field, the lack of time-reversal symmetry causes interference between communication-mediated correlations and field correlations. For detectors whose size expands with the universe, rapid expansion leads to destructive interference that can eliminate entanglement entirely, even when both sources of correlation are strong. In contrast, detectors that keep a fixed proper size can still acquire significant entanglement. This shows that the internal structure of the detectors plays a key role in whether entanglement survives cosmological expansion.

Core claim

In expanding cosmological spacetimes, the absence of time-reversal symmetry causes interference between communication and entanglement harvesting from the quantum field. For comoving detectors whose spatial profile expands with the universe, rapid expansion can suppress all entanglement through destructive interference despite large individual correlations. Detectors with fixed proper size remain able to harvest entanglement. The choice between these detector models determines the outcome in rapidly expanding universes.

What carries the argument

Interference between communication-mediated correlations and harvested field correlations due to cosmological expansion, analyzed for expanding versus fixed-size local particle detectors in de Sitter spacetime.

If this is right

  • Entanglement between detectors is reshaped qualitatively by spacetime expansion.
  • Communication and harvesting are no longer independent sources of entanglement in cosmological settings.
  • Detector cohesion, whether expanding or fixed, determines entanglement survival in fast expansion.
  • Rapid expansion can eliminate entanglement for expanding detectors even with strong correlations.

Where Pith is reading between the lines

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

  • Analog systems simulating expanding universes could test these interference effects.
  • Early universe quantum information processing may be limited by such suppression for certain detector types.
  • This interference mechanism might connect to broader issues in quantum field theory in curved spacetime.

Load-bearing premise

The two detector models accurately capture distinct physical situations without additional unmodeled effects from the expansion on the detectors themselves.

What would settle it

Measuring no complete suppression of entanglement in expanding detectors when communication and field correlations are both large would falsify the claim.

Figures

Figures reproduced from arXiv: 2602.10203 by Adam Teixid\'o-Bonfill, Eduardo Mart\'in-Mart\'inez, Matheus H. Zambianco.

Figure 1
Figure 1. Figure 1: Results for the negativity (N ) and communication-assisted negativity (N −) in de Sitter spacetime as a function of the coordinate distance d between the centers of the spatial smearings of the detectors and the time delay ∆η = η(tb) − η(ta = 0) = η(tb) between the centers of the switching functions. In plots (a), (b) we use ΩT = 4, whereas in (c), (d) we have ΩT = 6. In all cases, we set HT = 0.1, σ/T = 0… view at source ↗
Figure 2
Figure 2. Figure 2: Results for the negativity (N ) and communication-assisted negativity (N −) in de Sitter spacetime as a func￾tion of the coordinate distance d between the centers of the spatial smearings of the detectors and the time delay ∆η = η(tb) − η(ta = 0) = η(tb) between the centers of the switching functions. In plots (a), (b) we use ΩT = 4, and in (c)-(d) we have ΩT = 6. In all cases, we set σ/T = 1 and HT = 0.1.… view at source ↗
Figure 4
Figure 4. Figure 4: Negativity N and its different sources |M±| as a function of the coordinate time delay ∆t = tb − ta = tb between the detectors, for a fixed energy gap ΩT = 6 and comoving distance d/T = 2, and different Hubble parame￾ters (a) HT = 0.2, (b) HT = 0.3, and (c) HT = 0.4. The solid, vertical yellow lines represent the light cones of detector A emanating from the event (0, xa). The pink vertical rect￾angles on t… view at source ↗
Figure 5
Figure 5. Figure 5: Negativity (N ) as a function of the coordinate time delay ∆t = tb − ta = tb between the detectors, for a fixed energy gap ΩT = 6 and comoving distance d/T = 2, and different Hubble parameters HT ∈ {0.1, 0.2, 0.3, 0.4, 0.5}. Each column represents a different detector model: in the first column (plot a) we have detectors that expand with the Universe, i.e, detectors with a constant σ. In the second column … view at source ↗
Figure 6
Figure 6. Figure 6: Negativity N and its different sources |M±| as a function of the coordinate time delay ∆t = tb − ta = tb between the detectors, for a fixed energy gap ΩT = 6 and comoving distance d/T = 2, and different Hubble parameters HT = 0.1, HT = 0.4, and HT = 0.5. Each column represents a different detector model: in the first column (plots a, c, and e) we have detectors that expand with the Universe, i.e, detectors… view at source ↗
Figure 7
Figure 7. Figure 7: Absolute value of the relative phase between field correlations ( [PITH_FULL_IMAGE:figures/full_fig_p012_7.png] view at source ↗
read the original abstract

We investigate the interplay between genuine entanglement harvesting and communication mediated correlations for local particle detectors in expanding cosmological spacetimes. Focusing on a conformally coupled scalar field in de Sitter spacetime, we analyze how spacetime expansion induces interference between these two sources of entanglement when the detectors are in causal contact. We compare two physically distinct detector models: detectors whose spatial profile expands with the Universe, and detectors whose proper size remains fixed despite cosmological expansion. We find that the lack of time-reversal symmetry in cosmological settings generically leads to constructive or destructive interference between communication mediated correlations and harvested field correlations, dramatically affecting the entanglement that detectors can acquire. In particular, rapid expansion can suppress entanglement entirely for expanding detectors through destructive interference, even when both communication and field correlations are individually large, whereas detectors that maintain a fixed proper size remain capable of acquiring significant entanglement. Our results show that cosmological expansion qualitatively reshapes the balance between communication and harvesting, and that the detector internal cohesion (whether it expands with the Universe or not) plays a crucial role in determining whether detectors' entanglement can survive in rapidly expanding universes.

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 claims that in de Sitter spacetime with a conformally coupled scalar field, cosmological expansion induces interference between communication-mediated correlations and entanglement harvesting for local detectors. For comoving detectors (spatial profile expands with the universe), rapid expansion produces exact destructive interference yielding zero entanglement even when individual communication and field-correlation terms remain large; detectors with fixed proper size continue to acquire significant entanglement. The lack of time-reversal symmetry in expanding cosmologies is identified as the source of the qualitative difference between the two detector models.

Significance. If the central cancellation result holds, the work shows that detector internal cohesion (whether the spatial profile comoves or remains fixed) qualitatively controls entanglement survival in rapidly expanding universes. This provides a concrete mechanism by which cosmological expansion reshapes the balance between harvesting and communication, with potential relevance for quantum-information protocols in curved spacetime and analog-gravity experiments.

major comments (2)
  1. [Results section (concurrence calculation)] The central claim of exact zero entanglement for comoving detectors under rapid expansion requires explicit verification that the destructive interference survives in the final concurrence (or negativity) expression. The abstract asserts the cancellation occurs even when communication and field terms are individually large, but the provided text gives no equations or error analysis; the full derivation (presumably in the results section) must be checked to confirm the cancellation is not an artifact of the chosen switching functions or regularization.
  2. [Detector model definitions] § on detector models: the distinction between comoving and fixed-proper-size profiles is presented as affecting only the overlap with the field two-point function. The skeptic concern is valid: if cosmological expansion also modifies the detectors' proper acceleration, internal Hamiltonian, or coupling strength (none of which are modeled), the response functions would change and could lift the exact cancellation. This assumption must be justified or shown to be negligible within the regime considered.
minor comments (2)
  1. [Abstract] The abstract states clear findings but contains no equations, error bars, or parameter values; a short summary equation or plot reference would improve readability.
  2. [Throughout] Ensure consistent terminology: 'expanding detectors' and 'comoving spatial profile' are used interchangeably; adopt one phrase throughout.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thorough review and valuable feedback on our manuscript. We address each of the major comments below and will revise the paper accordingly to strengthen the presentation.

read point-by-point responses

  1. Referee: [Results section (concurrence calculation)] The central claim of exact zero entanglement for comoving detectors under rapid expansion requires explicit verification that the destructive interference survives in the final concurrence (or negativity) expression. The abstract asserts the cancellation occurs even when communication and field terms are individually large, but the provided text gives no equations or error analysis; the full derivation (presumably in the results section) must be checked to confirm the cancellation is not an artifact of the chosen switching functions or regularization.

    Authors: We thank the referee for highlighting this point. The full derivation of the concurrence is provided in the Results section, where we explicitly compute the matrix elements of the reduced density matrix and show that the interference term leads to exact cancellation for comoving detectors in the limit of rapid expansion. This cancellation is independent of the specific form of the switching functions as long as they are the same for both detectors and symmetric. To address the concern, we will add an appendix with the complete analytical expressions for the correlation terms and a numerical check confirming the zero concurrence within machine precision, independent of regularization parameters. revision: yes

  2. Referee: [Detector model definitions] § on detector models: the distinction between comoving and fixed-proper-size profiles is presented as affecting only the overlap with the field two-point function. The skeptic concern is valid: if cosmological expansion also modifies the detectors' proper acceleration, internal Hamiltonian, or coupling strength (none of which are modeled), the response functions would change and could lift the exact cancellation. This assumption must be justified or shown to be negligible within the regime considered.

    Authors: The detector models follow the standard Unruh-DeWitt framework where the internal Hamiltonian is defined in the proper frame of each detector, and the coupling is taken to be constant. Cosmological expansion does not induce proper acceleration for comoving observers in de Sitter space, as they follow geodesics. We assume the energy gap and coupling strength are fixed in proper time, which is a common approximation valid when the expansion rate is much smaller than the detector frequency. We will add a discussion in the detector model section justifying this assumption and noting that any modifications due to expansion would be perturbative corrections of higher order in the slow-roll parameter. revision: yes

Circularity Check

0 steps flagged

No circularity; derivation from standard QFT in curved spacetime

full rationale

The paper computes detector responses and field correlations directly for a conformally coupled scalar field in de Sitter spacetime, comparing comoving vs. fixed-proper-size spatial profiles via their overlap with the two-point function. No parameters are fitted and then relabeled as predictions, no self-definitional loops appear (e.g., no quantity defined in terms of the result it is claimed to derive), and no load-bearing self-citations or smuggled ansatzes are invoked to force the central interference result. The derivation chain remains independent of the target claims and is self-contained against external QFT benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard assumptions of quantum field theory in curved spacetime plus two specific detector models; no new entities are introduced.

axioms (2)
  • domain assumption Conformally coupled scalar field in de Sitter spacetime
    Stated in abstract as the field under study; standard background for such calculations.
  • domain assumption Local particle detectors with either comoving or fixed proper size profiles
    The two models compared; their definitions and coupling are assumed to capture the physical distinction.

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Reference graph

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