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We present an infinite sequence of finite graphs with trivial automorphism group and non-trivial quantum automorphism group. These are the first known examples of graphs with this property. Moreover, to the best of our knowledge, these are…

Quantum Algebra · Mathematics 2025-11-12 Josse van Dobben de Bruyn , David E. Roberson , Simon Schmidt

Over 50 years ago, Lov\'{a}sz proved that two graphs are isomorphic if and only if they admit the same number of homomorphisms from any graph [Acta Math. Hungar. 18 (1967), pp. 321--328]. In this work we prove that two graphs are quantum…

Quantum Physics · Physics 2019-10-22 Laura Mančinska , David E. Roberson

We formulate a notion of the quantum automorphism group of a $2$-graph. After some preliminary computations, we define quantum isomorphism between a pair of $2$-graphs. We produce a `non-trivial' example of a pair of $2$-graphs that are not…

Operator Algebras · Mathematics 2025-04-01 Soumalya Joardar , Atibur Rahaman , Jitender Sharma

We classify instances of quantum pseudo-telepathy in the graph isomorphism game, exploiting the recently discovered connection between quantum information and the theory of quantum automorphism groups. Specifically, we show that graphs…

Quantum Physics · Physics 2019-05-14 Benjamin Musto , David Reutter , Dominic Verdon

The symmetries of a finite graph are described by its automorphism group; in the setting of Woronowicz's quantum groups, a notion of a quantum automorphism group has been defined by Banica capturing the quantum symmetries of the graph. In…

Quantum Algebra · Mathematics 2019-07-01 Christian Eder , Viktor Levandovskyy , Julien Schanz , Simon Schmidt , Andreas Steenpass , Moritz Weber

We present a strong connection between quantum information and quantum permutation groups. Specifically, we define a notion of quantum isomorphisms of graphs based on quantum automorphisms from the theory of quantum groups, and then show…

Quantum Physics · Physics 2018-04-02 Martino Lupini , Laura Mančinska , David E. Roberson

The study of graph C*-algebras has a long history in operator algebras. Surprisingly, their quantum symmetries have never been computed so far. We close this gap by proving that the quantum automorphism group of a finite, directed graph…

Operator Algebras · Mathematics 2018-05-07 Simon Schmidt , Moritz Weber

We define a notion of quantum automorphism group of Graph C*-algebras for finite, connected graphs. Under the assumption that the underlying graph does not have any multiple edge or loop, the quantum automorphism group of underlying…

Operator Algebras · Mathematics 2018-10-11 Soumalya Joardar , Arnab Mandal

We initiate a systematic study of quantum properties of finite graphs, namely, quantum asymmetry, quantum symmetry, and quantum isomorphism. We define the Schmidt alternative for a class of graphs, which reveals to be a useful tool for…

Operator Algebras · Mathematics 2024-05-09 Paul Meunier

Recently, the work on quantum automorphism groups of graphs has seen renewed progress, which we expand in this paper. Quantum symmetry is a richer notion of symmetry than the classical symmetries of a graph. In general, it is non-trivial to…

Quantum Algebra · Mathematics 2024-04-24 Julien Schanz

Quantum graphs are defined by having a Laplacian defined on the edges of a metric graph with boundary conditions on each vertex such that the resulting operator, $\mathbf{L}$, is self-adjoint. We use Neumann boundary conditions although we…

Spectral Theory · Mathematics 2025-12-02 Mats-Erik Pistol

We undertake a study of the notion of a quantum graph over arbitrary finite-dimensional $C^*$-algebras $B$ equipped with arbitrary faithful states. Quantum graphs are realised principally as either certain operators on $L^2(B)$, the quantum…

Operator Algebras · Mathematics 2024-11-27 Matthew Daws

We introduce the notion of nonlocal symmetry of a graph $G$, defined as a winning quantum correlation for the $G$-automorphism game that cannot be produced classically. Recent connections between quantum group theory and quantum information…

Quantum Algebra · Mathematics 2021-02-11 David E. Roberson , Simon Schmidt

Motivated by the vast literature of quantum automorphism groups of graphs, we define and study quantum automorphism groups of matroids. A key feature of quantum groups is that there are many quantizations of a classical group, and this…

Quantum Algebra · Mathematics 2023-12-22 Daniel Corey , Michael Joswig , Julien Schanz , Marcel Wack , Moritz Weber

A homomorphism from a graph $X$ to a graph $Y$ is an adjacency preserving mapping $f:V(X) \rightarrow V(Y)$. We consider a nonlocal game in which Alice and Bob are trying to convince a verifier with certainty that a graph $X$ admits a…

Quantum Physics · Physics 2016-09-21 Laura Mančinska , David E. Roberson

The notion of the quantum automorphism group of a graph was introduced by J. Bichon in 2003 and T. Banica in 2005 respectively. This article explores primarily the quantum automorphism group of a graph $\Gamma$, denoted by…

Operator Algebras · Mathematics 2025-11-20 Rajibul Haque , Ujjal Karmakar , Arnab Mandal

We study Cayley graphs of abelian groups from the perspective of quantum symmetries. We develop a general strategy for determining the quantum automorphism groups of such graphs. Applying this procedure, we find the quantum symmetries of…

Quantum Algebra · Mathematics 2024-02-07 Daniel Gromada

Associated to a finite graph $X$ is its quantum automorphism group $G$. The main problem is to compute the Poincar\'e series of $G$, meaning the series $f(z)=1+c_1z+c_2z^2+...$ whose coefficients are multiplicities of 1 into tensor powers…

Quantum Algebra · Mathematics 2007-05-23 Teodor Banica

An asymmetric coloring of a graph is a coloring of its vertices that is not preserved by any non-identity automorphism of the graph. The motion of a graph is the minimal degree of its automorphism group, i.e., the minimum number of elements…

Group Theory · Mathematics 2021-11-16 Laszlo Babai

Let $G$ be a simple finite graph, and let $\mathcal U_G$ be the related quantum graph. We study the game algebra $C(\mathrm{Qut}(\mathcal U_G))$ of quantum automorphism of $\mathcal U_G$. Moreover, we prove that for any graph $G$ with…

Operator Algebras · Mathematics 2026-03-31 Olha Ostrovska , Vasyl Ostrovskyi , Lyudmila Turowska
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