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A continuous quantum walk on a graph $X$ with adjacency matrix $A$ is specified by the 1-parameter family of unitary matrices $U(t)=\exp(itA)$. These matrices act on the state space of a quantum system, the states of which we may represent…

Combinatorics · Mathematics 2017-10-12 Chris Godsil

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

We consider quantum state transfer on finite graphs which are attached to infinite paths. The finite graph represents an operational quantum system for performing useful quantum information tasks. In contrast, the infinite paths represent…

Quantum Physics · Physics 2022-11-30 Pierre-Antoine Bernard , Christino Tamon , Luc Vinet , Weichen Xie

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

We study a transport phenomenon in certain coined quantum walks where a subspace of states localized at a vertex gets transferred to another vertex. We first develop characterizations for perfect and pretty good subspace state transfer…

Combinatorics · Mathematics 2025-12-01 Yichi Xu , Hanmeng Zhan

We study perfect state transfer on quantum networks represented by weighted graphs. Our focus is on graphs constructed from the join and related graph operators. Some specific results we prove include: (1) The join of a weighted two-vertex…

Quantum Physics · Physics 2010-01-09 R. J. Angeles-Canul , R. Norton , M. Opperman , C. Paribello , M. Russell , C. Tamon

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

Let $G$ be a graph with adjacency matrix $A$. The transition matrix corresponding to $G$ is defined by $H(t):=\exp{\left(itA\right)}$, $t\in\Rl$. The graph $G$ is said to have perfect state transfer (PST) from a vertex $u$ to another vertex…

Combinatorics · Mathematics 2019-01-08 Hiranmoy Pal , Bikash Bhattacharjya

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

Quantum walks, an important tool in quantum computing, have been very successfully investigated using techniques in algebraic graph theory. We are motivated by the study of state transfer in continuous-time quantum walks, which is…

Combinatorics · Mathematics 2017-10-09 Chris Godsil , Krystal Guo , Mark Kempton , Gabor Lippner

Let $G$ be a graph with adjacency matrix $A$. The transition matrix of $G$ relative to $A$ is defined by $H(t):=\exp{\left(-itA\right)},\;t\in\Rl$. The graph $G$ is said to admit pretty good state transfer between a pair of vertices $u$ and…

Combinatorics · Mathematics 2019-01-08 Hiranmoy Pal , Bikash Bhattacharjya

We propose new families of graphs which exhibit quantum perfect state transfer. Our constructions are based on the join operator on graphs, its circulant generalizations, and the Cartesian product of graphs. We build upon the results of…

Quantum Physics · Physics 2010-01-09 R. J. Angeles-Canul , R. Norton , M. Opperman , C. Paribello , M. Russell , C. Tamon

We construct infinite families of graphs in which pretty good state transfer can be induced by adding a potential to the nodes of the graph (i.e. adding a number to a diagonal entry of the adjacency matrix). Indeed, we show that given any…

Combinatorics · Mathematics 2018-04-06 Or Eisenberg , Mark Kempton , Gabor Lippner

We consider a system of qubits coupled via nearest-neighbour interaction governed by the Heisenberg Hamiltonian. We further suppose that all coupling constants are equal to $1$. We are interested in determining which graphs allow for a…

Combinatorics · Mathematics 2018-05-23 Gabriel Coutinho , Henry Liu

Quantum walks generated by the adjacency matrix or the Laplacian are known to exhibit low transfer fidelity on general graphs. In this paper, we study continuous-time quantum walks governed by the generalized Laplacian operator L_k = A+kD,…

Quantum Physics · Physics 2025-10-13 Yujia Shi

A weighted graph $G$ with countable vertex set is bounded if there is an upper bound on the maximum of the sum of absolute values of all edge weights incident to a vertex in $G$. In this paper, we prove a fundamental result on equitable…

Combinatorics · Mathematics 2025-10-08 Chris Godsil , Steve Kirkland , Sarojini Mohapatra , Hermie Monterde , Hiranmoy Pal

This paper focuses on periodicity and perfect state transfer of Grover walks on two well-known families of Cayley graphs, namely, the unitary Cayley graphs and the quadratic unitary Cayley graphs. Let $R$ be a finite commutative ring. The…

Combinatorics · Mathematics 2026-04-07 Koushik Bhakta , Bikash Bhattacharjya

We study pretty good quantum state transfer (i.e., state transfer that becomes arbitrarily close to perfect) between vertices of graphs with an involution in the presence of an energy potential. In particular, we show that if a graph has an…

Combinatorics · Mathematics 2017-02-24 Mark Kempton , Gabor Lippner , Shing-Tung Yau

Let $G$ be a graph with adjacency matrix $A$. The transition matrix of $G$ is denoted by $H(t)$ and it is defined by $H(t):=\exp{\left(itA\right)},\;t\in\mathbb{R}.$ The graph $G$ has perfect state transfer (PST) from a vertex $u$ to…

Combinatorics · Mathematics 2019-01-08 Hiranmoy Pal , Bikash Bhattacharjya

This paper is a sequel to the work of Bhattacharjya et al.\ (J. Phys. A-Math. 57.33: 335303, https://doi.org/10.1088/1751-8121/ad6653) on quantum state transfer on blow-up graphs, where instead of the adjacency matrix, we take the Laplacian…

Combinatorics · Mathematics 2025-04-17 Hermie Monterde , Hiranmoy Pal , Steve Kirkland