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arxiv: 2604.14252 · v1 · submitted 2026-04-15 · 🪐 quant-ph

Quantum correlation tests at cosmic distances

Thomas Durt , Jean Schneider This is my paper

Pith reviewed 2026-05-10 13:53 UTC · model grok-4.3

classification 🪐 quant-ph
keywords Bell inequalityquantum entanglementpolarimeterMoon experimentcosmic distancealternative theories
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The pith

A polarimeter on the Moon would test quantum correlations over 390,000 km.

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

The paper examines the value of extending Bell inequality tests on entangled photons to the Earth-Moon distance. Current experiments have reached only 1,200 km, so this change multiplies the scale by roughly 300. The proposed setup sends one photon of an entangled pair to a polarimeter on the Moon while the other is measured on Earth. If carried out successfully, the measurements would verify whether the statistical correlations remain instantaneous and strong at that range. This would constitute a fresh check of quantum predictions and would restrict the possible range of alternative theories that assume slower or distance-dependent influences.

Core claim

The authors state that installing one polarimeter on the Moon and pairing it with a detector on Earth would enable a Bell test of entangled photon pairs across 390,000 km, thereby providing a new verification of quantum correlations and tighter constraints on alternative theories while also opening discussion of violations at still larger distances.

What carries the argument

Polarization analysis of entangled photon pairs in a Bell inequality experiment, with one analyzer placed on the Moon to extend the separation to 390,000 km.

If this is right

  • The test would constitute a new verification of quantum physics at a much larger scale.
  • It would impose stricter limits on alternative theories and interpretations of quantum correlations.
  • Bell inequalities could be violated at distances exceeding the Earth-Moon separation.

Where Pith is reading between the lines

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

  • A positive result would encourage similar tests involving other solar-system bodies or spacecraft at greater separations.
  • The technical demands of lunar timing and stability could drive improvements in space-based quantum communication systems.

Load-bearing premise

A polarimeter can be placed and operated on the Moon with the timing precision, long-term stability, and entanglement preservation needed to obtain statistically significant results without hidden decoherence or classical signaling paths.

What would settle it

Running the Earth-Moon experiment and finding that the observed correlations are consistent with local hidden-variable predictions rather than the quantum violation of Bell inequalities would show that the instantaneous correlations do not persist at that distance.

Figures

Figures reproduced from arXiv: 2604.14252 by Jean Schneider, Thomas Durt.

Figure 1
Figure 1. Figure 1: Statistically correlated projective measurements performed on polarisation states of two [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 4
Figure 4. Figure 4: Source beyond the Earth-Moon system with one detector on the moon and another one on [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
read the original abstract

It is commonly accepted that the results of measurements simultaneously realized over two entangled subsystems are statistically correlated instantaneously regardless of the distance between them. In accordance with Bell theorem, everything happens in such measurements as if there was a correlation propagating at infinite speed between the two subsystems.These correlations have been so far verified experimentally up to a distance of 1200 km. We discuss the interest and feasibility of extending this distance to 390,000 km, thus gaining a factor of 300. The idea is to install one of the polarimeters on the Moon, with the other on Earth. Such an experiment would provide a new test of Quantum Physics and allow to put higher constraints on alternative theories and interpretations. We also discuss the possibility to violate Bell inequalities beyond Earth-Moon distance.

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 proposes extending Bell inequality tests of quantum correlations to Earth-Moon distances of ~390,000 km by installing one polarimeter on the Moon and the other on Earth. It argues that this would extend current experimental records (up to 1200 km) by a factor of ~300, constitute a new test of quantum physics, impose higher constraints on alternative theories and interpretations, and discusses the possibility of such tests at even larger distances.

Significance. If realized with sufficient fidelity, the proposal would extend the spatial scale of Bell tests by two orders of magnitude, offering a concrete way to further close the locality loophole and potentially tighten bounds on local realistic models or superluminal signaling. The manuscript correctly identifies the scaling motivation from prior experiments but does not quantify the gain in constraints.

major comments (2)
  1. [Abstract] Abstract: The claim that the experiment would 'put higher constraints on alternative theories and interpretations' is not supported by any quantitative analysis, such as estimates of improved bounds on hypothetical influence speeds, required visibility thresholds, or how the 300-fold distance increase affects the statistical power to rule out alternatives.
  2. [Main text (feasibility discussion)] Main text (feasibility discussion): No error budget, timing synchronization requirements (sub-nanosecond precision needed to close the locality loophole over the ~1.28 s light-travel time), polarization stability, entanglement preservation estimates, source brightness, or coincidence window are provided. These omissions make it impossible to assess whether the central claim of a statistically significant Bell test at lunar distances is viable.
minor comments (2)
  1. The manuscript would benefit from citing specific prior works on lunar laser ranging or space-based quantum communication to ground the technical discussion.
  2. Clarify assumptions about lunar infrastructure (e.g., whether new hardware deployment is required) to make the feasibility discussion more precise.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our proposal for Bell tests at Earth-Moon distances. The feedback highlights opportunities to strengthen the quantitative aspects and technical discussion. We address each major comment below and have revised the manuscript to incorporate additional analysis and details.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The claim that the experiment would 'put higher constraints on alternative theories and interpretations' is not supported by any quantitative analysis, such as estimates of improved bounds on hypothetical influence speeds, required visibility thresholds, or how the 300-fold distance increase affects the statistical power to rule out alternatives.

    Authors: We agree that the original claim would be strengthened by quantitative support. The factor-of-300 distance increase extends the light-travel time to ~1.28 s, providing a substantially larger window for independent, space-like separated measurement settings and thereby closing the locality loophole more robustly than prior experiments (up to 1200 km). This directly constrains any hypothetical finite-speed influence or local realistic model to speeds at least 10^5 times c (depending on exact timing margins), far beyond current bounds. The required visibility for a CHSH violation remains ~70%, unchanged from shorter-distance tests, while statistical power scales with achievable coincidence rates (which modern sources can maintain). We have added a dedicated paragraph with these estimates in the revised manuscript. revision: yes

  2. Referee: [Main text (feasibility discussion)] Main text (feasibility discussion): No error budget, timing synchronization requirements (sub-nanosecond precision needed to close the locality loophole over the ~1.28 s light-travel time), polarization stability, entanglement preservation estimates, source brightness, or coincidence window are provided. These omissions make it impossible to assess whether the central claim of a statistically significant Bell test at lunar distances is viable.

    Authors: The manuscript is a concise conceptual proposal rather than a full technical design study. We acknowledge that additional specifics improve assessability. In revision we have added a feasibility section with order-of-magnitude estimates: sub-nanosecond timing is achievable via existing lunar laser ranging and atomic-clock synchronization; polarization stability follows from demonstrated satellite links with active compensation; entanglement preservation is feasible given vacuum propagation and low-loss Earth-side optics. A source rate of ~10^6 pairs/s with a ~10 ns coincidence window (adjusted for propagation) yields sufficient statistics in hours of integration. An outline error budget is now included, supported by references to lunar quantum-communication studies. revision: yes

Circularity Check

0 steps flagged

No derivations or self-referential predictions; proposal is self-contained

full rationale

The manuscript is a conceptual proposal for extending Bell tests to Earth-Moon distances. It cites prior experimental verifications up to 1200 km but contains no equations, fitted parameters, predictions, or derivation chains that reduce to the paper's own inputs or self-citations. Feasibility is discussed qualitatively without any self-definitional steps, fitted-input predictions, or load-bearing self-citation chains. The central claim rests on external experimental benchmarks and standard quantum mechanics rather than internal circular reductions.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The proposal rests on the standard assumption that quantum mechanics predicts distance-independent correlations for entangled states, with no new free parameters, axioms, or postulated entities introduced.

axioms (1)
  • domain assumption Bell theorem implies that entangled measurements exhibit correlations as if propagating at infinite speed, independent of distance.
    Invoked in the opening paragraph to justify extending the test.

pith-pipeline@v0.9.0 · 5412 in / 1213 out tokens · 30673 ms · 2026-05-10T13:53:40.477829+00:00 · methodology

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Reference graph

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