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Research . 2026
License: CC BY
Data sources: Datacite
ZENODO
Research . 2026
License: CC BY
Data sources: Datacite
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The Fano Monogamy Paradox: Irreducible Three-Body Entanglement and the Tripartite Hardy Impossible Event

Authors: Buckley, Ian R. C.;

The Fano Monogamy Paradox: Irreducible Three-Body Entanglement and the Tripartite Hardy Impossible Event

Abstract

Monogamy of entanglement states that quantum correlations cannot be freely shared: if two parties are maximally entangled, neither can be entangled with a third. The Fano plane $\mathrm{PG}(2,2)$ appears to violate this principle — its Hamiltonian ground state simultaneously correlates all seven directed triples. Hardy's paradox is a complementary phenomenon: four conditions on a multi-qubit state force the classically impossible conclusion $P(Z_+,\ldots,Z_+) = 0$, yet quantum mechanics permits $P(Z_+,\ldots,Z_+) > 0$. Both are well-understood within standard quantum mechanics; neither was ever mysterious to quantum theory itself. This paper identifies a single necessary condition that unifies both phenomena: irreducible three-body entanglement, as measured by the Coffman–Kundu–Wootters three-tangle $\tau_3$. The Fano monogamy apparent paradox dissolves once one observes that $C(i,j) 0$ for Fano-line triples — the correlations are triangular, not pairwise. For the tripartite Hardy impossible event ($N=3$), we show numerically that $\tau_3 > 0$ is a necessary condition: no W-class or product state ($\tau_3 = 0$) satisfies all four Hardy conditions simultaneously, confirmed across 54 independent free-state optimisations (JAX/Adam, A100 GPU). The open question — whether this is provable algebraically — is stated explicitly. The novel contribution is the connection between the Dür–Vidal–Cirac entanglement classification and Hardy-type nonlocality: GHZ-class states ($\tau_3 > 0$) can exhibit the tripartite impossible event; W-class states cannot. Within the Adelic Simplicial Architecture (ASA), both phenomena share a further geometric explanation: the octonion associator $|\mathcal{A}(e_i,e_j,e_k)| = 0$ on Fano-line triples and $|\mathcal{A}| = 2$ elsewhere is the algebraic signature of the same triangular irreducibility, connecting the monogamy resolution and the Hardy condition to the associator firewall of the companion papers on the Spacelike Associator Paradox and Hardy's Paradox and the Fano Associator.

Keywords

Octonions, Quantum Nonlocality, Monogamy of Entanglement, Fano Plane, W State, Tripartite Entanglement, CKW Inequality, Non-Associative Algebra, Entanglement Classification, GHZ State, Quantum Contextuality, Hardy's Paradox, Adelic Simplicial Architecture, Three-Tangle, Dür-Vidal-Cirac Classification

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average