arXiv subjects

Mohsen Bahramgiri

Publications and source records attributed to Mohsen Bahramgiri.

3 recordsLinked to original sources

arXiv2007

Enumerating the Classes of Local Equivalency in Graphs

There are local operators on (labeled) graphs $G$ with labels $(g_{ij})$ coming from a finite field. If the filed is binary, in other words, if the graph is ordinary, the operation is just the local complementation. That is, to choose a vertex and complement the subgraph induced by its neighbors. But, in the general case, there are two different types of operators. The first type is the following. Let $v$ be a vertex of the graph and $a\in \mathbf{F}_q$, the finite field of $q$ elements. The operator is to obtain a graph with labels $g'_{ij}=g_{ij}+ag_{vi}g_{vj}$. For the second type of operators, let $0\neq b\in \mathbf{F}_q$ and the resulted graph is a graph with labels $g''_{vi}=bg_{vi}$ and $g''_{ij}=g_{ij}$, for $i,j$ unequal to $v$. The local complementation operator (binary case) has appeared in combinatorial theory, and its properties have studied in the literature. Recently, a profound relation between local operators on graphs and quantum stabilizer codes has been found, and it has become a natural question to recognize equivalency classes under these operators. In the present article, we show that the number of graphs locally equivalent to a given graph is at most $q^{2n+1}$, and consequently, the number of classes of local equivalency is $q^{\frac{n^2}{2}-o(n)}$.

math.CO↗

arXiv2007

An Efficient Algorithm to Recognize Locally Equivalent Graphs in Non-Binary Case

Let $v$ be a vertex of a graph $G$. By the local complementation of $G$ at $v$ we mean to complement the subgraph induced by the neighbors of $v$. This operator can be generalized as follows. Assume that, each edge of $G$ has a label in the finite field $\mathbf{F}_q$. Let $(g_{ij})$ be set of labels ($g_{ij}$ is the label of edge $ij$). We define two types of operators. For the first one, let $v$ be a vertex of $G$ and $a\in \mathbf{F}_q$, and obtain the graph with labels $g'_{ij}=g_{ij}+ag_{vi}g_{vj}$. For the second, if $0\neq b\in \mathbf{F}_q$ the resulted graph is a graph with labels $g''_{vi}=bg_{vi}$ and $g''_{ij}=g_{ij}$, for $i,j$ unequal to $v$. It is clear that if the field is binary, the operators are just local complementations that we described. The problem of whether two graphs are equivalent under local complementations has been studied, \cite{bouchalg}. Here we consider the general case and assuming that $q$ is odd, present the first known efficient algorithm to verify whether two graphs are locally equivalent or not.

cs.DS↗

arXiv2007

Graph States Under the Action of Local Clifford Group in Non-Binary Case

Graph states are well-entangled quantum states that are defined based on a graph. Of course, if two graphs are isomorphic their associated states are the same. Also, we know local operations do not change the entanglement of quantum states. Therefore, graph states that are either isomorphic or equivalent under the local Clifford group have the same properties. In this paper, we first establish a bound on the number of graph states which are neither isomorphic nor equivalent under the action of local Clifford group. Also, we study graph states in non-binary case. We translate the action of local Clifford group, as well as measurement of Pauli operators, into transformations on their associated graphs. Finally, we present an efficient algorithm to verify whether two graph states, in non-binary case, are locally equivalent or not.

quant-ph↗