3 research outputs found
Quantum walks as a probe of structural anomalies in graphs
We study how quantum walks can be used to find structural anomalies in graphs
via several examples. Two of our examples are based on star graphs, graphs with
a single central vertex to which the other vertices, which we call external
vertices, are connected by edges. In the basic star graph, these are the only
edges. If we now connect a subset of the external vertices to form a complete
subgraph, a quantum walk can be used to find these vertices with a quantum
speedup. Thus, under some circumstances, a quantum walk can be used to locate
where the connectivity of a network changes. We also look at the case of two
stars connected at one of their external vertices. A quantum walk can find the
vertex shared by both graphs, again with a quantum speedup. This provides an
example of using a quantum walk in order to find where two networks are
connected. Finally, we use a quantum walk on a complete bipartite graph to find
an extra edge that destroys the bipartite nature of the graph.Comment: 10 pages, 2 figure
Realization of the Optimal Universal Quantum Entangler
We present the first experimental demonstration of the ''optimal'' and
''universal'' quantum entangling process involving qubits encoded in the
polarization of single photons. The structure of the ''quantum entangling
machine'' consists of the quantum injected optical parametric amplifier by
which the contextual realization of the 1->2 universal quantum cloning and of
the universal NOT (U-NOT) gate has also been achieved.Comment: 10 pages, 3 figures, to appear in Physical Review