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arXiv:2601.19857 · Entropy

Symmetric and Antisymmetric Quantum States from Graph Structure and Orientation

Matheus R. de Jesus, Eduardo O. C. Hoefel, Renato M. Angelo

quant-phSubmitted Jan 27, 2026• Announced Jan 28, 2026• 0 citations• Revised May 4, 2026 (v2)
v1 · Jan 27, 2026v2 · May 4, 2026
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Abstract

Graph states provide a powerful framework for describing multipartite entanglement in quantum information science. In their standard formulation, graph states are generated by controlled-$Z$ interactions and naturally encode symmetric exchange properties. Here we establish a precise correspondence between graph topology and exchange symmetry by proving that a graph state is fully symmetric under particle permutations if and only if the underlying graph is complete. We then introduce a generalized graph-based construction using a non-commutative two-qudit gate, denoted $GR$, which requires directed edges and an explicit vertex ordering. We show that complete directed graphs generate fully antisymmetric multipartite states when endowed with appropriate orientations. Together, these results provide a unified graph-theoretic description of bosonic and fermionic exchange symmetry based on graph completeness and edge orientation.

Journal reference
Entropy 28(4), 386 (2026)
DOI
10.3390/e28040386
Comments
13 pages, 4 figures

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Graph states provide a powerful framework for describing multipartite entanglement in quantum information science. In their standard formulation, graph states are generated by controlled-ZZZ interactions and naturally encode symmetric exchange properties. Here we establish a precise correspondence between graph topology and exchange symmetry by proving that a graph state is fully symmetric under particle permutations if and only if the underlying graph is complete. We then introduce a generalized graph-based construction using a non-commutative two-qudit gate, denoted GRGRGR, which requires directed edges and an explicit vertex ordering. We show that complete directed graphs generate fully antisymmetric multipartite states when endowed with appropriate orientations. Together, these results provide a unified graph-theoretic description of bosonic and fermionic exchange symmetry based on graph completeness and edge orientation.
Entanglement of multipartite systems is studied based on exchange symmetry under the permutation group SN{S}_{N}SN​. With the observation that symmetric property under the exchange of two constituent states and their separability are intimately linked, we show that antisymmetric (fermionic) states are necessarily globally entangled, while symmetric (bosonic) states are either globally entangled or fully separable and possess essentially identical states in all the constituent systems. It is also shown that there cannot exist a fully separable state which is orthogonal to all symmetric states, and that full separability of states does not survive under total symmetrization unless the states are originally symmetric. Besides, anyonic states permitted under the braid group BN{B}_{N}BN​ must also be globally entangled. Our results reveal that exchange symmetry is actually sufficient for pure states to become globally entangled or fully separable.
Bosons and fermions are defined by their exchange properties and the underlying symmetries determine the structure of the corresponding state spaces. For two particles there are two possible exchange symmetries, resulting in symmetric or antisymmetric behaviour, but when exploring multiparticle systems also quantum states with chiral symmetries appear. In this work we demonstrate that chiral symmetries lead to extremal forms of quantum entanglement. More precisely, we show that subspaces with this symmetry are highly entangled with respect to the geometric measure of entanglement, leading to observables which can be useful for entanglement characterization. Along the way, we develop a simple method to solve the problem of genuine multiparticle entanglement for unitarily invariant three-particle states and use it to identify genuine multipartite entangled states whose partial transposes with respect to all bipartitions are positive. Finally, we consider generalizations with less symmetry and discuss potential applications.
Efficient representations of multipartite quantum states play a fundamental role in quantum information theory, providing both conceptual insight and practical tools for characterizing entanglement. Motivated by the axiomatic framework for graph states [Phys. Rev. A 85, 062313 (2012)] and its subsequent extension to hypergraph states [Phys. Rev. A 87, 022311 (2013)], we introduce an axiomatic construction of \emph{matroid states}, a new family of multipartite quantum states associated with matroids. Our constructions are based on a set of axioms analogous to those that define graph and hypergraph states, yielding a consistent quantum representation of arbitrary matroids. Two ways of constructing matroid states are proposed: the first is defined in terms of circuits, and the second in terms of independent sets. In both approaches, we establish the existence of universal global operators that satisfy desirable properties such as locality, symmetry, commutativity, and are associated with the combinatorial structure of matroids. Furthermore, we establish a hierarchy connecting graph, matroid, and hypergraph states within a unified framework. Additionally, we show how to obtain an arbitrary graph state by applying suitable families of matroid states, whose corresponding operators are the generators of the stabilizer subgroup of the graph state. These results identify matroid theory as a natural combinatorial language for the efficient description of multipartite quantum states and open new perspectives for the investigation of quantum entanglement and related combinatorial structures.
Abstract The entanglement properties of quantum states associated with directed graphs are investigated. Using a measure derived from the Fubini–Study metric, multipartite entanglement is quantitatively related to the local connectivity of the graph. In Entanglement in Directed Graph States (2025), arXiv:2505.10716, it is demonstrated that the vertex degree distribution fully determines this entanglement measure and remains invariant under vertex relabeling, highlighting its topological character. As a consequence, the measure depends only on the total degree of each vertex, making it independent of the distinction between incoming and outgoing edges. This framework is applied to several specific graph structures, including hierarchical networks, neural network–inspired graphs, full binary tree and linear bridged cycle graphs, demonstrating how their combinatorial properties influence entanglement distribution. These results provide a geometric perspective on quantum correlations in complex systems, offering potential applications in the design and analysis of quantum networks.
A graph-theoretical framework for quantum mechanics is developed in which observables and symmetry operators are incorporated into a single complete bi-coloured graph. The proposed Symmetry/Observables Quantum Graph (SOQG) treats Hamiltonians, observables, conserved quantities, and unitary symmetry transformations on equal footing as operators acting on a common Hilbert space. The vertices of the graph represent operators, while the colours of the edges are determined by their commutation relations: commuting operators are connected by maroon edges and non-commuting operators by teal edges. The resulting structure constitutes a finite Ramsey graph that provides a combinatorial representation of operator compatibility. The formalism is applied to several representative quantum systems, including a particle in a central potential, a charged particle in a uniform magnetic field, and a particle in a homogeneous external field. In each case, monochromatic cliques identify maximal compatibility sectors containing both observables and symmetry operators, thereby revealing the interplay between conserved quantities and dynamical symmetries. It is further shown that coloured-graph automorphisms generally differ from the physical symmetry group of the underlying quantum system, leading to the notion of second-order graph symmetry. The SOQG is proved to be invariant under simultaneous unitary transformations of all operators and therefore represents intrinsic properties of the operator algebra rather than a particular Hilbert-space representation. The graph-theoretical structure is analysed using Ramsey theory and the Mantel–Turán extremal theorem, which provide rigorous conditions for the appearance of mutually compatible and mutually incompatible operator subsets. The framework is subsequently generalized to parameter-dependent Symmetry/Observables Quantum Graphs (PSOQGs), whose compatibility structure changes as external parameters modify the underlying commutation relations. For magnetic translation operators, the magnetic flux through the elementary translation cell induces a flux-controlled colour-switching transition between commuting and non-commuting compatibility sectors, accompanied by changes in the graph automorphism group. The proposed framework establishes a direct connection between operator theory, symmetry, graph theory, and extremal combinatorics, providing a new structural perspective on quantum systems.
We study the class of edge-coloured graphs arising from the graph-theoretic representation of quantum photonic experiments that generate multipartite W-states. Abstracting away physical amplitudes and phases, we introduce W-state graphs: matching-covered graphs equipped with a half-edge 2-colouring such that every perfect matching contains exactly one bichromatic edge and every vertex is incident with a red half-edge. Our main contribution is a complete structural characterization of W-state graphs. We show that a graph is a W-state graph if and only if each of its 3-connected components is a W-cone, a simple and rigid building block defined by a universal vertex and a factor-critical base. This characterization implies that no W-state graph is simple and yields a recognition algorithm running as fast as verifying whether a graph is matching-covered. We also show that the natural generalization to Dicke states encounters a complexity barrier: verifying one of the two Dicke state conditions is itself coNP-complete, resolving an open problem of Vardi and Zhang [IJCAI 2023]. Our results place W-state graphs firmly within classical matching theory and precisely delineate the combinatorial structures capable of realizing idealized W-states in the experiment-graph framework.