In quantum information science, dissipation is commonly viewed as an adverse effect that destroys information through decoherence. But theoretical work shows that dissipation can be used to drive quantum systems to a desired state, and therefore might serve as a resource in quantum computations. The strongest adversary in quantum information science is decoherence, which arises owing to the coupling of a system with its environment1. The induced dissipation tends to destroy and wash out the interesting quantum effects that give rise to the power of quantum computation2, cryptography2 and simulation3. Whereas such a statement is true for many forms of dissipation, we show here that dissipation can also have exactly the opposite effect: it can be a fully fledged resource for universal quantum computation without any coherent dynamics needed to complement it. The coupling to the environment drives the system to a steady state where the outcome of the computation is encoded. In a similar vein, we show that dissipation can be used to engineer a large variety of strongly correlated states in steady state, including all stabilizer codes, matrix product states4, and their generalization to higher dimensions5.

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Quantum computation and quantum-state engineering driven by dissipation

Combinatorial Group Theory: COMBINATORIAL GROUP THEORY

1. (i) Suppose K is a conjugacy class of Sn contained in An; then K is called split if K is a union of two conjugacy classes of An. Show that the number of split conjugacy classes contained in An is equal to the number of characters χ ∈ Irr(Sn) such that χAn is not irreducible. (Hint. Consider the vector space of class functions on An which are invariant under conjugation by the transposition (12).)

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Character Theory of Finite Groups

For the list object, introduced in Chapter 5, it was shown that each data element contains at most one predecessor element and one successor element. Therefore, for any given data element or node in the list structure, we can talk in terms of a next element and a previous element.

Graphs and Digraphs

We study the computation power of the congested clique, a model of distributed computation where n players communicate with each other over a complete network in order to compute some function of their inputs. The number of bits that can be sent on any edge in a round is bounded by a parameter b We consider two versions of the model: in the first, the players communicate by unicast, allowing them to send a different message on each of their links in one round; in the second, the players communicate by broadcast, sending one message to all their neighbors.It is known that the unicast version of the model is quite powerful; to date, no lower bounds for this model are known. In this paper we provide a partial explanation by showing that the unicast congested clique can simulate powerful classes of bounded-depth circuits, implying that even slightly super-constant lower bounds for the congested clique would give new lower bounds in circuit complexity. Moreover, under a widely-believed conjecture on matrix multiplication, the triangle detection problem, studied in [8], can be solved in O(ne) time for any e > 0.The broadcast version of the congested clique is the well-known multi-party shared-blackboard model of communication complexity (with number-in-hand input). This version is more amenable to lower bounds, and in this paper we show that the subgraph detection problem studied in [8] requires polynomially many rounds for several classes of subgraphs. We also give upper bounds for the subgraph detection problem, and relate the hardness of triangle detection in the broadcast congested clique to the communication complexity of set disjointness in the 3-party number-on-forehead model.

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On the power of the congested clique model

Let G be a finite group. We define the noncommuting graph ∇(G) as follows: the vertex set of ∇(G) is G\Z(G) with two vertices x and y joined by an edge whenever the commutator of x and y is not the identity. We study some properties of ∇(G) and prove that, for many groups G, if H is a group with ∇(G) isomorphic to ∇(H) then |G| = |H|.

On the noncommuting graph associated with a finite group.

Let G be a group and τe(G) the set of numbers of elements of G of the same order. In this paper, by τe(G), we give a new characterization of A5, where A5 is the alternating group of degree 5. We get the theorem following: Theorem. Let G be a group, ${G\cong A_5}$ if and only if τe(G) = τe(A5) = {1, 15, 20, 24}.

A new characterization of a5

The power graph of a group G is a simple graph whose vertex-set is G and two vertices x and y in G are adjacent if and only if one of them is a power of the other. The subgraph of is obtained by deleting the vertex 1 (the identity element of G). In this paper, we first investigate some properties of the power graph and its subgraph . We next provide necessary and sufficient conditions for a power graph to be a strongly regular graph, a bipartite graph or a planar graph. Finally, we obtain some infinite families of finite groups G for which the power graph contains some cut-edges.

https://www.researchgate.net/profile/Alireza_Moghaddamfar/publication/257459603_Certain_properties_of_the_power_graph_associated_with_a_finite_group/links/5449223d0cf2f6388080dcf4.pdf

Certain properties of the power graph associated with a finite group

There are a variety of ways to associate directed or undirected graphs to a group. It may be interesting to investigate the relations between the structure of these graphs and characterizing certain properties of the group in terms of some properties of the associated graph. The power graph $\mathcal{P}(G)$ of a group $G$ is a simple graph whose vertex-set is $G$ and two vertices $x$ and $y$ in $G$ are adjacent if and only if $y=x^m$ or $x=y^m$ for some positive integer $m$. We also pay attention to the subgraph $\mathcal{P}^\ast(G)$ of $\mathcal{P}(G)$ which is obtained by deleting the vertex 1 (the identity element of $G$). In the present paper, we first investigate some properties of the power graph $\mathcal{P}(G)$ and the subgraph $\mathcal{P}^\ast(G)$. We next prove that many of finite groups such as finite simple groups, symmetric groups and the automorphism groups of sporadic simple groups can be uniquely determined by their power graphs among all finite groups. We have also determined up to isomorphism the structure of any finite group $G$ such that the graph $\mathcal{P}^\ast(G)$ is a strongly regular graph, a bipartite graph, a planar graph or an Eulerian graph. Finally, we obtained some infinite families of finite groups such that the graph $\mathcal{P}^\ast(G)$ containing some cut-edges.

Wujie Shi

Papers

On the noncommuting graph associated with a finite group.

A new characterization of a5

Certain properties of the power graph associated with a finite group

Certain properties of the power graph associated with a finite group

A new characterization of the sporadic simple groups