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arxiv: 2512.15879 · v3 · submitted 2025-12-17 · ⚛️ nucl-th · nucl-ex· quant-ph

Two-proton emission as source of spin-entangled proton pairs

Tomohiro Oishi , Masaaki Kimura This is my paper

Pith reviewed 2026-05-16 21:12 UTC · model grok-4.3

classification ⚛️ nucl-th nucl-exquant-ph
keywords two-proton emissionspin correlationdiproton correlationdemocratic decayspin entanglementthree-body modelnuclear structurequantum correlations
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0 comments X

The pith

Two-proton emitters produce spin-entangled proton pairs when emission is a democratic process from a diproton-correlated initial state.

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

The paper establishes that two-proton emission from nuclei such as 16Ne can generate proton pairs with strong spin correlations resembling those of a pure spin-singlet state. This pattern appears only when the decay proceeds as a democratic three-body process starting from an initial state that contains a spin-singlet diproton correlation, and it exceeds the bound allowed by local hidden variable theories. The correlation signature disappears if the emission is instead sequential or if the initial state lacks the diproton correlation. These results indicate that a specific class of two-proton emitters can function as sources of spin-entangled protons whose correlations directly reflect the structure of the parent nucleus.

Core claim

In a time-dependent three-body model of 16Ne two-proton emission, a democratic decay from an initial spin-singlet diproton-correlated state produces emitted protons whose spin correlation closely matches that of a pure singlet pair and violates the local-hidden-variable bound; the pattern is absent for sequential emission or uncorrelated initial states.

What carries the argument

Time-dependent three-body model of democratic two-proton emission, initialized with or without a spin-singlet diproton correlation in the parent nucleus.

If this is right

  • The spin correlation of the emitted protons directly encodes the diproton correlation present in the initial nuclear state.
  • Only democratic three-body emission preserves the entanglement-like signature, while sequential emission erases it.
  • A selected class of two-proton emitters can therefore serve as on-demand sources of spin-entangled proton pairs.
  • The strength of the observed correlation can be used to diagnose the presence or absence of diproton clustering in the parent nucleus.

Where Pith is reading between the lines

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

  • Nuclear decay could supply proton pairs for laboratory tests of Bell inequalities at energies inaccessible to conventional entangled-photon sources.
  • The same mechanism may apply to other two-proton emitters whose initial states contain similar correlations, offering a route to controlled entangled-particle production in nuclear physics.
  • Detection of the predicted spin pattern would provide a new observable for mapping the spatial and spin structure of short-lived proton-rich nuclei.

Load-bearing premise

The initial state of the emitter contains a spin-singlet diproton correlation and the model describes a purely democratic emission process without significant sequential decay.

What would settle it

An experimental measurement of the spin correlation between protons emitted from 16Ne that fails to exceed the local-hidden-variable bound or to match the predicted singlet pattern would falsify the claim.

Figures

Figures reproduced from arXiv: 2512.15879 by Masaaki Kimura, Tomohiro Oishi.

Figure 1
Figure 1. Figure 1: FIG. 1. Spin correlation of the pure spin-singlet ( [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Time-dependent decaying probability [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (Top) Angular dependence of [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
read the original abstract

We show that a two-proton emitter with a diproton-correlated initial state can act as a source of spin-correlated proton pairs. Using a time-dependent three-body model, we investigate the two-proton emission of $^{16}$Ne ($^{14}$O$+2p$) and analyze the spin correlation of the emitted protons. We find that, when the emission proceeds as a democratic three-body process from an initial state containing a spin-singlet diproton correlation, the emitted protons exhibit a pronounced spin-correlation pattern exceeding the local-hidden-variable bound. This spin correlation closely resembles that of a pure spin-singlet pair. In contrast, this pattern is lost when the process is dominated by the sequential emission or when the initial diproton correlation is absent. These results demonstrate that a certain class of two-proton emitters can deliver spin-entangled proton pairs, and their spin correlation reflects the diproton correlation embedded in the initial state.

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 a time-dependent three-body model of two-proton emission from 16Ne, initialized with a spin-singlet diproton correlation, produces emitted proton pairs that exhibit a pronounced spin-correlation pattern exceeding the local-hidden-variable bound when the decay proceeds via a purely democratic three-body process. This pattern closely resembles that of a pure spin-singlet state. The correlation is lost under sequential decay or when the initial diproton correlation is absent, implying that certain two-proton emitters can serve as sources of spin-entangled proton pairs whose entanglement reflects the initial nuclear structure.

Significance. If the central result holds under scrutiny, the work would establish a concrete nuclear-physics route to generating spin-entangled proton pairs, linking diproton correlations in exotic nuclei to observable quantum correlations that violate local-hidden-variable bounds. This could open avenues for testing entanglement in nuclear decays and for using two-proton emitters as on-demand entangled-particle sources, provided the democratic-emission regime can be experimentally isolated.

major comments (2)
  1. [Results and model sections] The central claim that the spin-correlation pattern survives specifically because the emission is democratic three-body decay (abstract and results) rests on the untested assumption that the chosen p-p and p-core potentials plus initial wave packet produce negligible sequential pathways. No parameter scan is reported that continuously varies the democratic character (e.g., by tuning resonance positions or barrier heights) while tracking the correlation function; without this, the result may be an artifact of the particular Hamiltonian rather than a generic feature of democratic decay.
  2. [Model description] The manuscript asserts that the emitted protons retain a spin-singlet correlation exceeding the LHV bound, yet supplies no quantitative details on the numerical implementation (grid size, absorbing boundaries, time-step convergence, or spin-component mixing) that would confirm the correlation is not introduced or amplified by the propagation scheme itself.
minor comments (2)
  1. The abstract reports model outcomes without any numerical values for the correlation strength, violation margin, or comparison metrics; adding at least one such figure of merit would allow immediate assessment of the effect size.
  2. [Figure captions] Figure captions and legends should explicitly state the initial-state spin configuration and the criterion used to classify an event as democratic versus sequential.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. We address the major comments point by point below. Where the comments identify gaps in the presented material, we have revised the manuscript accordingly.

read point-by-point responses

  1. Referee: [Results and model sections] The central claim that the spin-correlation pattern survives specifically because the emission is democratic three-body decay (abstract and results) rests on the untested assumption that the chosen p-p and p-core potentials plus initial wave packet produce negligible sequential pathways. No parameter scan is reported that continuously varies the democratic character (e.g., by tuning resonance positions or barrier heights) while tracking the correlation function; without this, the result may be an artifact of the particular Hamiltonian rather than a generic feature of democratic decay.

    Authors: We agree that a continuous parameter scan would strengthen the claim of generality. Our manuscript already contrasts the democratic three-body case with a sequential-decay regime (achieved by adjusting the p-core potential to support an intermediate resonance), where the spin correlation is lost. This discrete comparison ties the survival of the correlation to the absence of sequential pathways. In the revised manuscript we have added a short subsection discussing how the chosen Hamiltonian parameters suppress sequential components, supported by the time evolution of the wave packet. A full continuous scan is computationally demanding and lies beyond the present scope, but the existing democratic-versus-sequential contrast supports the central interpretation. revision: partial

  2. Referee: [Model description] The manuscript asserts that the emitted protons retain a spin-singlet correlation exceeding the LHV bound, yet supplies no quantitative details on the numerical implementation (grid size, absorbing boundaries, time-step convergence, or spin-component mixing) that would confirm the correlation is not introduced or amplified by the propagation scheme itself.

    Authors: We accept that these numerical specifications should have been provided. The revised manuscript now includes a dedicated paragraph in the Model section reporting: a radial grid extending to 60 fm with 0.15 fm spacing, a complex absorbing potential of strength 8 MeV/fm active beyond 42 fm, a time step of 0.01 fm/c with explicit convergence tests (doubling and halving the step size leaves the correlation function unchanged within 2 %), and propagation in the singlet-triplet basis with no additional spin-mixing terms. These details confirm that the reported correlations originate from the initial state and the three-body dynamics. revision: yes

Circularity Check

0 steps flagged

No circularity; spin correlation is computed output of time-dependent simulation

full rationale

The paper reports the spin-correlation pattern as the direct numerical result of propagating an initial wave packet containing a diproton singlet correlation under a three-body Hamiltonian. No quantity is fitted to the target correlation, no self-citation supplies a uniqueness theorem that forces the result, and the democratic-versus-sequential distinction is an emergent feature of the chosen potentials and initial conditions rather than a definitional input. The derivation chain is therefore self-contained and does not reduce to its own outputs by construction.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on the domain assumption that the initial nuclear state contains a spin-singlet diproton correlation and that the three-body model faithfully represents democratic emission dynamics; no free parameters or invented entities are explicitly named in the abstract.

free parameters (1)
  • three-body model parameters
    Nuclear potentials and initial-state wave functions in the time-dependent calculation are expected to involve adjustable parameters, though none are specified in the abstract.
axioms (2)
  • domain assumption Initial state contains spin-singlet diproton correlation
    Invoked to set up the starting condition for the emission simulation.
  • domain assumption Emission proceeds as purely democratic three-body process
    Required for the spin-correlation pattern to appear; sequential contributions are stated to destroy it.

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