Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2512.15879 · Physics Letters B

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

Tomohiro Oishi, Masaaki Kimura

nucl-thnucl-exquant-phSubmitted Dec 17, 2025• Announced Dec 19, 2025• 0 citations• Revised Apr 10, 2026 (v3)
v1 · Dec 17, 2025v2 · Jan 13, 2026v3 · Apr 10, 2026
arXivHTMLPDF

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.

Comments
Accepted in PLB. Previous title: Entangled two-proton emission from 16Ne and its sensitivity to diproton correlation. 6 pages, 1 table, 5 figures

Related papers

Diproton correlation and two-proton emission from proton-rich nuclei

Oishi, Tomohiro

Open-print version of dissertation thesis. This thesis focuses on the relation between the diproton correlation and the two-proton emission with quantum entanglement. For this purpose, I developed a time-dependent three-body (proton-proton-core) model, where one Cooper pair of protons move inside the mean-field potential. The time-dependent calculation based on the three-body model provides an intuitive way to describe the quantum dynamics of the entangled fermionic pair. It has been shown that, by considering the Cooper-pairing correlation in the initial state of the two protons, (i) the experimental 2p-decay width of Be-6 is well reproduced, and (ii) the two protons are emitted mainly as a diproton-like cluster with the spin-singlet configuration in the early stage of the emission. Hence, the two-proton emission can provide an access to the diproton correlation. This thesis presented the first step to theoretically investigate the diproton correlation as well as quantum entanglement in the time-dependent radioactive emission. [NOTE] In this open-print version, several Figures were inevitably eliminated, because of the copyright and/or file-size problems. Several minor corrections have been done, but without changing the scientific discussions, results, and conclusions from the original version in 2014.

arXiv:2303.10529•Mar 19, 2023•0 citations

Spin correlation in two-proton emission from 6Be

Tomohiro Oishi

This paper presents a theoretical evaluation of spin correlation in the two-proton (2 p ) radioactive emission . The three-body model of 6 Be with the proton-proton interaction, which is adjusted to reproduce the experimental energy release, is utilized. Time-dependent calculations are performed to compute the coupled-spin state of the emitted two protons. The spin-correlation function S as the Clauser-Horne-Shimony-Holt (CHSH) indicator is evaluated as | S | ≅ 2.65 . Namely, the 2 p -spin correlation beyond the limit of local-hidden-variable (LHV) theory is suggested. This correlation is sensitive to the proton-proton interaction. The short-lived (broad-width) 2 p state has the weaker spin correlation. In parallel, the core-proton interactions do not harm this correlation during the time-dependent decaying process. The CHSH measurement can be a novel probe into the effective nuclear interaction inside finite systems. Two-proton emitters can provide a testing field for the identical-particle entanglement.

arXiv:2407.11136•Physics Letters B•Feb 26, 2025•4 citations

Spin-State Teleportation and Tests of EPR Correlations Using 151 MeV Entangled Protons

Henryk Witała

We discuss the feasibility of quantum spin-state teleportation in a three-proton system at an energy of 151 MeV, where, similarly to the low-energy case, a single Bell-state term dominates the proton-proton scattering matrix. We find that, in contrast to the low-energy regime, where unpolarized proton-proton scattering produces strongly entangled outgoing proton pairs, at higher energies a pair of protons, each with an energy of $151$~MeV, must be produced in an unpolarized, exclusive proton-deuteron breakup reaction under complete final-state-interaction kinematics. The subsequent interaction of one of the entangled protons with a polarized hydrogen target triggers, as in the low-energy case, the teleportation process, whereby the polarization of the target proton is transferred to the second member of the entangled pair within the very narrow angular region of strong entanglement centered around a laboratory scattering angle of $45^\circ$. We also find that scattering one member of a strongly correlated proton pair forming a Bell state from an unpolarized hydrogen target leads to Einstein-Podolsky-Rosen-like correlations between the polarization of the scattered proton and that of the unscattered second entangled proton. The polarization of the scattered proton varies with its scattering angle. An identical polarization, following the angular dependence of thepolarization of the first proton, is induced in the second member of the pair, whose initial polarization was zero and whose momentum remains unchanged. The sign of the polarization of the second proton is determined by the sign of the spin correlation in the Bell state.

arXiv:2608.28325•Aug 28, 2026•0 citations

Separating entanglement at emission from femtoscopic correlations

Isaac Vidaña

We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin-$\frac{1}{2}$ particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical $Λ$ hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.

nucl-thCross-listedarXiv:2610.14358•Oct 13, 2026•0 citations

Teleportation in Proton Systems Revisited

Henryk Witała

We discuss the peculiarities of scattering in a three-proton system induced by the presence of an entangled proton-proton Bell-like state in the initial configuration. We formulate the problem using the standard spin formalism of nuclear physics in order to follow in detail the reaction pathways leading to the teleportation of a quantum-mechanical state within this system. By performing numerical simulations of the system and calculations based on a realistic nucleon-nucleon potential, we evaluate the relevant spin observables and search for a simple, experimentally feasible signal that could provide clear evidence of quantum teleportation. For the case in which proton 2, belonging to the entangled proton pair 23, interacts with hydrogen target 1, thereby triggering the teleportation process, we find clear evidence of teleportation through measurements of the final polarization of proton 3', even for small values of the polarization of target proton 1. The dominant component of this polarization is transferred almost entirely from target proton 1 to proton 3 in the angular region characterized by strong entanglement. For an unpolarized target proton 1, quantum teleportation is no longer possible. The only unambiguous signature of the residual quantum correlations would be provided by measurements of the spin correlations within the strongly entangled final-state proton pair 1'2'. Indirect evidence may also be obtained from measurements of the polarization of proton 2' in the final state, although the corresponding effectis relatively weak.

arXiv:2606.14171•Jun 12, 2026•0 citations

Two-particle correlations via quasi-deterministic analyzer model

Dalton, Bill

We introduce a quasi-deterministic eigenstate transition model of analyzers in which the final eigenstate is selected by initial conditions. We combine this analyzer model with causal spin coupling to calculate both proton-proton and photon-photon correlations, one particle pair at a time. The calculated correlations exceed the Bell limits and show excellent agreement with the measured correlations of [M. Lamehi-Rachti and W. Mittig, Phys. Rev. D 14 (10), 2543 (1976)] and [ A. Aspect, P. Grangier and G. Rogers, Phys. Rev. Lett. 49 91 (1982)] respectively. We discuss why this model exceeds the Bell type limits.

arXiv:quant-ph/0101053•Jan 12, 2001•1 citation
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^{16}16Ne (14^{14}14O+2p+2p+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.
Open-print version of dissertation thesis. This thesis focuses on the relation between the diproton correlation and the two-proton emission with quantum entanglement. For this purpose, I developed a time-dependent three-body (proton-proton-core) model, where one Cooper pair of protons move inside the mean-field potential. The time-dependent calculation based on the three-body model provides an intuitive way to describe the quantum dynamics of the entangled fermionic pair. It has been shown that, by considering the Cooper-pairing correlation in the initial state of the two protons, (i) the experimental 2p-decay width of Be-6 is well reproduced, and (ii) the two protons are emitted mainly as a diproton-like cluster with the spin-singlet configuration in the early stage of the emission. Hence, the two-proton emission can provide an access to the diproton correlation. This thesis presented the first step to theoretically investigate the diproton correlation as well as quantum entanglement in the time-dependent radioactive emission. [NOTE] In this open-print version, several Figures were inevitably eliminated, because of the copyright and/or file-size problems. Several minor corrections have been done, but without changing the scientific discussions, results, and conclusions from the original version in 2014.
This paper presents a theoretical evaluation of spin correlation in the two-proton (2 p ) radioactive emission . The three-body model of 6 Be with the proton-proton interaction, which is adjusted to reproduce the experimental energy release, is utilized. Time-dependent calculations are performed to compute the coupled-spin state of the emitted two protons. The spin-correlation function S as the Clauser-Horne-Shimony-Holt (CHSH) indicator is evaluated as | S | ≅ 2.65 . Namely, the 2 p -spin correlation beyond the limit of local-hidden-variable (LHV) theory is suggested. This correlation is sensitive to the proton-proton interaction. The short-lived (broad-width) 2 p state has the weaker spin correlation. In parallel, the core-proton interactions do not harm this correlation during the time-dependent decaying process. The CHSH measurement can be a novel probe into the effective nuclear interaction inside finite systems. Two-proton emitters can provide a testing field for the identical-particle entanglement.
We discuss the feasibility of quantum spin-state teleportation in a three-proton system at an energy of 151 MeV, where, similarly to the low-energy case, a single Bell-state term dominates the proton-proton scattering matrix. We find that, in contrast to the low-energy regime, where unpolarized proton-proton scattering produces strongly entangled outgoing proton pairs, at higher energies a pair of protons, each with an energy of 151151151~MeV, must be produced in an unpolarized, exclusive proton-deuteron breakup reaction under complete final-state-interaction kinematics. The subsequent interaction of one of the entangled protons with a polarized hydrogen target triggers, as in the low-energy case, the teleportation process, whereby the polarization of the target proton is transferred to the second member of the entangled pair within the very narrow angular region of strong entanglement centered around a laboratory scattering angle of 45∘45^\circ45∘. We also find that scattering one member of a strongly correlated proton pair forming a Bell state from an unpolarized hydrogen target leads to Einstein-Podolsky-Rosen-like correlations between the polarization of the scattered proton and that of the unscattered second entangled proton. The polarization of the scattered proton varies with its scattering angle. An identical polarization, following the angular dependence of thepolarization of the first proton, is induced in the second member of the pair, whose initial polarization was zero and whose momentum remains unchanged. The sign of the polarization of the second proton is determined by the sign of the spin correlation in the Bell state.
We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin-12\frac{1}{2}21​ particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical ΛΛΛ hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.
We discuss the peculiarities of scattering in a three-proton system induced by the presence of an entangled proton-proton Bell-like state in the initial configuration. We formulate the problem using the standard spin formalism of nuclear physics in order to follow in detail the reaction pathways leading to the teleportation of a quantum-mechanical state within this system. By performing numerical simulations of the system and calculations based on a realistic nucleon-nucleon potential, we evaluate the relevant spin observables and search for a simple, experimentally feasible signal that could provide clear evidence of quantum teleportation. For the case in which proton 2, belonging to the entangled proton pair 23, interacts with hydrogen target 1, thereby triggering the teleportation process, we find clear evidence of teleportation through measurements of the final polarization of proton 3', even for small values of the polarization of target proton 1. The dominant component of this polarization is transferred almost entirely from target proton 1 to proton 3 in the angular region characterized by strong entanglement. For an unpolarized target proton 1, quantum teleportation is no longer possible. The only unambiguous signature of the residual quantum correlations would be provided by measurements of the spin correlations within the strongly entangled final-state proton pair 1'2'. Indirect evidence may also be obtained from measurements of the polarization of proton 2' in the final state, although the corresponding effectis relatively weak.
We introduce a quasi-deterministic eigenstate transition model of analyzers in which the final eigenstate is selected by initial conditions. We combine this analyzer model with causal spin coupling to calculate both proton-proton and photon-photon correlations, one particle pair at a time. The calculated correlations exceed the Bell limits and show excellent agreement with the measured correlations of [M. Lamehi-Rachti and W. Mittig, Phys. Rev. D 14 (10), 2543 (1976)] and [ A. Aspect, P. Grangier and G. Rogers, Phys. Rev. Lett. 49 91 (1982)] respectively. We discuss why this model exceeds the Bell type limits.