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We prove new results on perfect state transfer of quantum walks on quotient graphs. Since a graph $G$ has perfect state transfer if and only if its quotient $G/\pi$, under any equitable partition $\pi$, has perfect state transfer, we…

Quantum Physics · Physics 2012-11-05 R. Bachman , E. Fredette , J. Fuller , M. Landry , M. Opperman , C. Tamon , A. Tollefson

We study the existence of state transfer with respect to the $q$-Laplacian matrix of a graph equipped with a non-trivial involution. We show that the occurrence of perfect state transfer between certain pair (or plus) states in such a graph…

Combinatorics · Mathematics 2025-09-26 Swornalata Ojha , Hiranmoy Pal

We consider the representation of a continuous-time quantum walk in a graph $X$ by the matrix $\exp(itA(X))$. We provide necessary and sufficient criteria for distance-regular graphs and, more generally, for graphs in association schemes to…

Combinatorics · Mathematics 2018-05-23 Gabriel Coutinho , Chris Godsil , Krystal Guo , Frédéric Vanhove

Twin vertices in simple unweighted graphs are vertices that have the same neighbours and, in the case of weighted graphs with possible loops, the corresponding incident edges have equal weights. In this paper, we explore the role of twin…

Combinatorics · Mathematics 2023-12-29 Stephen Kirkland , Hermie Monterde , Sarah Plosker

Perfect quantum state transfer is achievable in different settings, including linear qubit chains, bi-dimensional arrays, ladders, etc. The most studied case contemplates transferring arbitrary one-qubit pure states in systems with…

Quantum Physics · Physics 2026-04-06 Pablo Serra , Alejandro Ferrón , Omar Osenda

Let $L$ denote the Laplacian matrix of a graph $G$. We study continuous quantum walks on $G$ defined by the transition matrix $U(t)=\exp\left(itL\right)$. The initial state is of the pair state form, $e_a-e_b$ with $a,b$ being any two…

Combinatorics · Mathematics 2020-09-07 Qiuting Chen , Chris Godsil

A continuous-time quantum walk on a graph evolves according to the unitary operator $e^{-iAt}$, where $A$ is the adjacency matrix of the graph. Perfect state transfer (PST) in a quantum walk is the transfer of a quantum state from one node…

Quantum Physics · Physics 2021-11-02 Jaideep Mulherkar , Rishikant Rajdeepak , V. Sunitha

Pretty good state transfer in networks of qubits occurs when a continuous-time quantum walk allows the transmission of a qubit state from one node of the network to another, with fidelity arbitrarily close to 1. We prove that in a…

Quantum Physics · Physics 2018-06-22 Leonardo Banchi , Gabriel Coutinho , Chris Godsil , Simone Severini

We introduce the concept of group state transfer on graphs, summarize its relationship to other concepts in the theory of quantum walks, set up a basic theory, and discuss examples. Let $X$ be a graph with adjacency matrix $A$ and consider…

Quantum Physics · Physics 2021-03-17 Luke C. Brown , William J. Martin , Duncan Wright

Perfect state transfer (PST) has great significance due to its applications in quantum information processing and quantum computation. In this paper we present a characterization on connected simple Cayley graph $\Gamma={\rm Cay}(G,S)$…

Quantum Physics · Physics 2017-12-27 Yingying Tan , Keqin Feng , Xiwang Cao

This paper investigates perfect state transfer in Grover walks, a model of discrete-time quantum walks. We establish a necessary and sufficient condition for the occurrence of perfect state transfer on graphs belonging to an association…

Combinatorics · Mathematics 2025-06-23 Koushik Bhakta , Bikash Bhattacharjya

We introduce and study peak state transfer, a notion of high state transfer in qubit networks modeled by continuous-time quantum walks. Unlike perfect or pretty good state transfer, peak state transfer does not require fidelity arbitrarily…

Quantum Physics · Physics 2025-10-02 Gabriel Coutinho , Krystal Guo , Vincent Schmeits

The ability to accurately transfer quantum information through networks is an important primitive in distributed quantum systems. While perfect quantum state transfer (PST) can be effected by a single particle undergoing continuous-time…

Quantum Physics · Physics 2015-04-01 Steven J. Large , Michael S. Underwood , David L. Feder

We study perfect state transfer in Grover walks on two important classes of graphs: strongly regular graphs and strongly walk-regular graphs. The latter class is a generalization of the former. We first give a complete classification of…

Combinatorics · Mathematics 2026-02-04 Sho Kubota , Hiroto Sekido , Harunobu Yata , Kiyoto Yoshino

An oriented circulant graph is called integral if all eigenvalues of its Hermitian adjacency matrix are integers. The main purpose of this paper is to investigate the existence of perfect state transfer ($\PST$ for short) and multiple state…

Combinatorics · Mathematics 2022-10-06 Xing-Kun Song

In this paper, we first give a necessary and sufficient condition for a graph to have Laplacian pretty good pair state transfer. As an application of such result, we give a complete characterization of Laplacian pretty good edge state…

Combinatorics · Mathematics 2022-09-13 Wei Wang , Xiaogang Liu , Jing Wang

We study the existence of quantum state transfer in $\mathcal{Q}$-graphs in this paper. The $\mathcal{Q}$-graph of a graph $G$, denoted by $\mathcal{Q}(G)$, is the graph derived from $G$ by plugging a new vertex to each edge of $G$ and…

Combinatorics · Mathematics 2021-08-18 Xiao-Qin Zhang , Shu-Yu Cui , Gui-Xian Tian

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

A continuous-time quantum walk on a graph is a matrix-valued function $\exp(-\mathtt{i} At)$ over the reals, where $A$ is the adjacency matrix of the graph. Such a quantum walk has universal perfect state transfer if for all vertices $u,v$,…

Quantum Physics · Physics 2017-01-20 Erin Connelly , Nathaniel Grammel , Michael Kraut , Luis Serazo , Christino Tamon

Perfect state transfer between two marked vertices of a graph by means of discrete-time quantum walk is analyzed. We consider the quantum walk search algorithm with two marked vertices, sender and receiver. It is shown by explicit…

Quantum Physics · Physics 2016-08-02 Martin Stefanak , Stanislav Skoupy