14,217 research outputs found
Inhomogeneous substructures hidden in random networks
We study the structure of the load-based spanning tree (LST) that carries the
maximum weight of the Erdos-Renyi (ER) random network. The weight of an edge is
given by the edge-betweenness centrality, the effective number of shortest
paths through the edge. We find that the LSTs present very inhomogeneous
structures in contrast to the homogeneous structures of the original networks.
Moreover, it turns out that the structure of the LST changes dramatically as
the edge density of an ER network increases, from scale free with a cutoff,
scale free, to a starlike topology. These would not be possible if the weights
are randomly distributed, which implies that topology of the shortest path is
correlated in spite of the homogeneous topology of the random network.Comment: 4 pages, 4 figure
Topological Quantum Phase Transition in 5 Transition Metal Oxide NaIrO
We predict a quantum phase transition from normal to topological insulators
in the 5 transition metal oxide NaIrO, where the transition can be
driven by the change of the long-range hopping and trigonal crystal field
terms. From the first-principles-derived tight-binding Hamiltonian we determine
the phase boundary through the parity analysis. In addition, our
first-principles calculations for NaIrO model structures show that the
interlayer distance can be an important parameter for the existence of a
three-dimensional strong topological insulator phase. NaIrO is
suggested to be a candidate material which can have both a nontrivial topology
of bands and strong electron correlations
Bound on distributed entanglement
Using the convex-roof extended negativity and the negativity of assistance as
quantifications of bipartite entanglement, we consider the possible
remotely-distributed entanglement. For two pure states and
on bipartite systems and , we first show that the
possible amount of entanglement remotely distributed on the system by
joint measurement on the system is not less than the product of two
amounts of entanglement for the states and
in two-qubit and two-qutrit systems. We also provide some sufficient
conditions, for which the result can be generalized into higher-dimensional
quantum systems.Comment: 5 page
Generation of macroscopic superposition states with small nonlinearity
We suggest a scheme to generate a macroscopic superposition state
(Schrodinger cat state) of a free-propagating optical field using a beam
splitter, homodyne measurement and a very small Kerr nonlinear effect. Our
scheme makes it possible to considerably reduce the required nonlinear effect
to generate an optical cat state using simple and efficient optical elements.Comment: Significantly improved version, to be published in PRA as a Rapid
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