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Quantum state transfer within a quantum computer can be achieved by using a network of qubits, and such a network can be modelled mathematically by a graph. Here, we focus on the corresponding Laplacian matrix, and those graphs for which…

Quantum Physics · Physics 2022-11-28 Nathaniel Johnston , Steve Kirkland , Sarah Plosker , Rebecca Storey , Xiaohong Zhang

Hadamard diagonalizable graphs are undirected graphs for which the corresponding Laplacian is diagonalizable by a Hadamard matrix. Such graphs have been studied in the context of quantum state transfer. Recently, the concept of a weak…

Combinatorics · Mathematics 2024-07-11 Darian McLaren , Hermie Monterde , Sarah Plosker

A graph is called "Laplacian integral" if the eigenvalues of its Laplacian matrix are all integers. We investigate the subset of these graphs whose Laplacian is furthermore diagonalized by a matrix with entries coming from a fixed set, in…

Combinatorics · Mathematics 2024-11-19 Nathaniel Johnston , Sarah Plosker

If the Laplacian matrix of a graph has a full set of orthogonal eigenvectors with entries $\pm1$, then the matrix formed by taking the columns as the eigenvectors is a Hadamard matrix and the graph is said to be Hadamard diagonalizable. In…

Recently normalized Laplacian matrices of graphs are studied as density matrices in quantum mechanics. Separability and entanglement of density matrices are important properties as they determine the nonclassical behavior in quantum…

Quantum Physics · Physics 2017-02-28 Chai Wah Wu

Recently, Macharete, Del-Vecchio, Teixeira and de Lima showed that a star and any threshold graph on the same number of vertices share the same eigenbasis relative to the Laplacian matrix. We use this fact to establish two main results in…

Combinatorics · Mathematics 2026-01-21 Leonardo de Lima , Renata Del-Vecchio , Hermie Monterde , Heber Teixeira

The intention of the paper is to move a step towards a classification of network topologies that exhibit periodic quantum dynamics. We show that the evolution of a quantum system, whose hamiltonian is identical to the adjacency matrix of a…

Quantum Physics · Physics 2007-05-23 Nitin Saxena , Simone Severini , Igor Shparlinski

Recently, Braunstein et al. [1] introduced normalized Laplacian matrices of graphs as density matrices in quantum mechanics and studied the relationships between quantum physical properties and graph theoretical properties of the underlying…

Quantum Physics · Physics 2011-11-15 Chai Wah Wu

Recently, Laplacian matrices of graphs are studied as density matrices in quantum mechanics. We continue this study and give conditions for separability of generalized Laplacian matrices of weighted graphs with unit trace. In particular, we…

Quantum Physics · Physics 2007-05-23 Chai Wah Wu

We study the continuous-time quantum walks on graphs in the adjacency algebra of the $n$-cube and its related distance regular graphs. For $k\geq 2$, we find graphs in the adjacency algebra of $(2^{k+2}-8)$-cube that admit instantaneous…

Combinatorics · Mathematics 2013-05-27 Ada Chan

Extending upon the observations of the emergence of quantum-like states from classical complex synchronized networks, this work adds mathematical rigor to the analysis of single Quantum-Like (QL) bits constructed by eigenvectors of the…

Quantum Physics · Physics 2026-01-28 Ethan Dickey , Abhijeet Vyas , Sabre Kais

Representing graphs as quantum states is becoming an increasingly important approach to study entanglement of mixed states, alternate to the standard linear algebraic density matrix-based approach of study. In this paper, we propose a…

Quantum Physics · Physics 2017-03-24 Bibhas Adhikari , Subhashish Banerjee , Satyabrata Adhikari , Atul Kumar

Normalized Laplacian matrices of graphs have recently been studied in the context of quantum mechanics as density matrices of quantum systems. Of particular interest is the relationship between quantum physical properties of the density…

Mathematical Physics · Physics 2011-11-15 Chai Wah Wu

We give a combinatorial characterization of graphs whose normalized Laplacian has three distinct eigenvalues. Strongly regular graphs and complete bipartite graphs are examples of such graphs, but we also construct more exotic families of…

Combinatorics · Mathematics 2012-02-15 Edwin R. van Dam , Gholamreza Omidi

The Laplacian matrix and its pseudo-inverse for a strongly connected directed graph is fundamental in computing many properties of a directed graph. Examples include random-walk centrality and betweenness measures, average hitting and…

Numerical Analysis · Mathematics 2020-09-16 Daniel Boley

As a fundamental metric for quantifying quantum advantage in non-local games, the quantum chromatic number reveals the power of entanglement in distributed tasks. In this paper, we investigate this parameter for $q$-ary Hamming graphs and a…

Combinatorics · Mathematics 2026-03-12 Xiwang Cao , Keqin Feng , Hexiang Huang , Yulin Yang , Zihao Zhang

Balancedly splittable Hadamard matrices are introduced and studied. A connection is made to the Hadamard diagonalizable strongly regular graphs, maximal equiangular lines set, and unbiased Hadamard matrices. Several construction methods are…

Combinatorics · Mathematics 2018-10-18 Hadi Kharaghani , Sho Suda

Density matrices of graphs are combinatorial laplacians normalized to have trace one (Braunstein \emph{et al.} \emph{Phys. Rev. A,} \textbf{73}:1, 012320 (2006)). If the vertices of a graph are arranged as an array, then its density matrix…

Computational Complexity · Computer Science 2008-07-03 Roland Hildebrand , Stefano Mancini , Simone Severini

Graph states are widely used in quantum information theory, including entanglement theory, quantum error correction, and one-way quantum computing. Graph states have a nice structure related to a certain graph, which is given by either a…

Quantum Physics · Physics 2015-11-20 Shawn X Cui , Nengkun Yu , Bei Zeng

Using graphs with clusters, we provide a unified approach for constructing graphs with pair state transfer-relative to the adjacency, Laplacian, and signless Laplacian matrix-between the same pair of states at the same time, despite being…

Combinatorics · Mathematics 2025-12-29 Hermie Monterde , Hiranmoy Pal
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