Diagonal cases of the Krenn–Gu perfect-matching quantum-graph problem
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The Krenn–Gu perfect-matching model asks which colored quantum graphs can represent the required multiparticle states in linear optics. The diagonal cases set the number N of particles equal to the local dimension d, here N=d=4, 6 or 10. Existence or impossibility must be stated for a specified coefficient domain.
Why it matters and what counts as progress
Why it matters: These graph constructions encode possibilities and obstructions for producing high-dimensional Greenberger–Horne–Zeilinger (GHZ) states using linear optics.
What counts as progress: Construct a graph satisfying the perfect-matching requirements, or prove impossibility in a new case with its coefficient domain specified. A theorem for real, complex or restricted coefficients must not be silently transferred to the other settings.
How the problem developed
- 2017 · Problem formulation [1]
Mario Krenn, Xuemei Gu, and Anton Zeilinger Introduced quantum experiments represented by coherent superpositions of perfect matchings in graphs.
- 2019 · Open problem [2]
Mario Krenn, Xuemei Gu, and Matthias Soltész Developed structural questions about perfect matchings inspired by the quantum-graph model.
- 28 May 2026 · Reported claim [3]
Google DeepMind AlphaProof Nexus The paper reports resolving several monochromatic quantum-graph conjectures for N=d in {4,6,10}; it does not specify that every complex-weighted diagonal case is covered.
AI contribution
Advancing Mathematics Research with AI-Driven Formal Proof Search
The AlphaProof Nexus report says its agent ruled out monochromatic quantum graphs for the diagonal four-, six- and ten-particle cases N=d=4, 6 and 10 in the Krenn–Gu perfect-matching model.
Sources
- Krenn, Gu, and Zeilinger, Quantum experiments and graphs: multiparty states as coherent superpositions of perfect matchings
- Krenn, Gu, and Soltész, Questions on the Structure of Perfect Matchings inspired by Quantum Physics
- AlphaProof Nexus quantum-optics results
- Krenn, monochromatic quantum-graph cases
- Later separate quantum-graph Lean result
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