Answers to a few questions regarding the BMV experiment

Chiara Marletto; Vlatko Vedral

Answers to a few questions regarding the BMV experiment

T0 review · 0 major / 1 minor · reviewed 2026-05-24 · grok-4.3

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Pith's one-line read Alleged counter-examples do not refute the claim that gravity must be non-classical to mediate entanglement.

desk verdict This is a clarification note defending the 2017 BMV result against objections rather than any new derivation or data. read the letter →

arxiv 1907.08994 v1 pith:CKTHKBNW submitted 2019-07-21 quant-ph

Chiara Marletto , Vlatko Vedral This is my paper · ORCID

classification quant-ph

keywords BMVexperimentquantumgravityentanglementlocalityclassicalmediatorscounter-examples

topics Quantum Gravity

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper addresses recurring questions about the BMV experiment by showing that objections claiming gravity can create entanglement while remaining local fail to qualify as counter-examples. These objections do not satisfy the specific locality condition and definition of classicality from the 2017 argument, so the conclusion that gravity must be non-classical still holds. The authors also clarify additional subtleties in the original proposal that are often missed on first reading.

What carries the argument

The locality condition and the definition of a classical mediator from the 2017 argument, which together prohibit entanglement creation by any local classical interaction.

What would settle it

A concrete model or experiment in which a mediator satisfies the original locality condition and classical definition yet still produces entanglement between the two masses would falsify the claim.

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Extended reading notes

Core claim

Alleged counter-examples stating that gravity can create entanglement while complying with locality do not invalidate the result; the original claim that such gravity must be non-classical still stands because the proposed scenarios do not meet the locality condition and classicality definition used in the 2017 argument.

Load-bearing premise

The locality condition and definition of classicality from the 2017 argument are the correct standards to use when checking whether a proposed scenario counts as a counter-example.

Editorial extensions

If this is right

The BMV experimental proposal remains a valid test for whether gravity is classical.
No local classical field or interaction can generate the predicted entanglement in this setup.
Any mediator of the gravitational interaction that produces entanglement must fail to be classical under the stated definitions.
The result applies to any interaction mediator, not only gravity.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Similar locality-plus-classicality arguments might be used to test the quantum character of other long-range forces.
Numerical simulations of the two-mass system could make explicit whether a given classical model violates the locality condition when it attempts to entangle the particles.
The defense implies that future proposals for classical gravity theories must explicitly demonstrate how they avoid creating entanglement under the same locality rules.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Desk Editor's Note

read the letter

This paper does not introduce new physics or calculations. Marletto and Vedral are answering recurring questions about their earlier BMV proposal for testing quantum gravity via entanglement of masses, and they argue that the cited counter-examples fail because they do not meet the locality condition or the definition of a classical mediator used in the 2017 work. They also flag a few subtleties that first-time readers often miss. That is the entire contribution. The text is short and direct on those points. It gives credit to the original Bose et al. and Marletto-Vedral papers and sticks to explaining why the objections do not overturn the claim that the mediator must be non-classical. The argument is internally consistent on its own terms: if the locality and classicality criteria are applied exactly as stated in 2017, the counter-examples drop out. The main limitation is that everything rests on those prior definitions. There are no independent checks, new derivations, or external benchmarks here, so readers who already dispute the 2017 framing of locality will not be persuaded. The paper cites its own earlier result heavily, which is expected in a clarification but leaves the circularity burden on the original argument. This is useful only for people already following the BMV debate in quantum foundations. A reader outside that niche will find little to take away. It is not a load-bearing flaw, just a narrow scope. I would bring it to a reading group only if the group is actively working on that specific proposal. I would not cite it in my own work. A serious editor should still send it to peer review so the record on the objections is settled in the literature rather than left to arXiv comments.

Referee Report

0 major / 1 minor

Summary. The manuscript provides brief answers to recurring questions about the BMV experiment (Bose et al. 2017; Marletto and Vedral 2017). It focuses on alleged counter-examples claiming that gravity (or another mediator) can generate entanglement while remaining local, arguing that these examples fail to satisfy the original locality condition and definition of a classical mediator; the central claim that a non-classical mediator is required therefore stands. The paper also addresses other subtleties in the 2017 argument that are often overlooked.

Significance. If the defense of the locality and classicality conditions is correct, the clarifications strengthen the theoretical foundation of the BMV proposal for testing the quantum nature of gravity. The work supplies explicit rebuttals to common objections, which may reduce misinterpretation in future theoretical and experimental discussions of mediator-mediated entanglement.

minor comments (1)

The abstract refers to 'our result' and 'our paper (Marletto and Vedral, 2017)' without a dedicated section summarizing the precise locality condition being defended; adding a short recap of the 2017 definition (e.g., in §2) would improve self-contained readability.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript and for recommending acceptance. The report correctly identifies that the paper supplies explicit rebuttals to common objections regarding the locality and classicality conditions in the BMV proposal.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity

full rationale

The paper is a clarification responding to objections against the authors' own 2017 BMV argument. It does not introduce any new derivation, prediction, or first-principles result whose validity reduces by construction to inputs, fitted parameters, or self-citations within this manuscript. The central claim—that alleged counter-examples fail the original locality and 'classical' definitions—is defended by reference to the 2017 paper, but this is a normal citation to prior work being clarified rather than a load-bearing self-referential reduction (no equations, ansatzes, or uniqueness theorems are shown to collapse into the citation itself). No patterns from the enumerated list are exhibited with direct quotes demonstrating equivalence by construction. The paper is self-contained as a response document against external benchmarks (the objections themselves).

Assumptions & free parameters 0 free parameters · 0 assumptions · 0 invented entities

No new free parameters, axioms, or invented entities are introduced; the paper is a clarification of an existing argument.

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Cite this review

Pith. "Pith review of Answers to a few questions regarding the BMV experiment." pith.science (2026). https://pith.science/paper/CKTHKBNW

@misc{pith2026190708994,
  author       = {Pith},
  title        = {Pith review of: Answers to a few questions regarding the BMV experiment},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/CKTHKBNW}},
  note         = {Machine review of arXiv:1907.08994}
}

read the original abstract

We provide brief answers to a number of recurring questions about the BMV effect and the related experimental proposal (Bose et al., 2017; Marletto and Vedral, 2017). Some of these questions include alleged counter-examples to our result, stating that if gravity (or anything mediating the interaction) can create entanglement while complying with locality, then it must then be non-classical. Here we explain why these objections are not counter-examples and why our result still stands; we also explore a few other important subtleties often disregarded on a first read of our paper (Marletto and Vedral, 2017).

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. OpenAlex reports about 5 citations worldwide. Full citation record

Classical theories of gravity produce entanglement
quant-ph 2025-10 conditional novelty 7.0 of 10

In quantum field theory, a classical gravitational potential can entangle two superposed masses through virtual matter exchange, so gravitationally induced entanglement is not by itself proof of quantum gravity.

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Reviewed May 24, 2026 · model on record in the stance chip above.