218,009 research outputs found
Link power coordination for energy conservation in complex communication networks
Communication networks consume huge, and rapidly growing, amount of energy.
However, a lot of the energy consumption is wasted due to the lack of global
link power coordination in these complex systems. This paper proposes several
link power coordination schemes to achieve energy-efficient routing by
progressively putting some links into energy saving mode and hence aggregating
traffic during periods of low traffic load. We show that the achievable energy
savings not only depend on the link power coordination schemes, but also on the
network topologies. In the random network, there is no scheme that can
significantly outperform others. In the scale-free network, when the largest
betweenness first (LBF) scheme is used, phase transition of the networks'
transmission capacities during the traffic cooling down phase is observed.
Motivated by this, a hybrid link power coordination scheme is proposed to
significantly reduce the energy consumption in the scale-free network. In a
real Internet Service Provider (ISP)'s router-level Internet topology, however,
the smallest betweenness first (SBF) scheme significantly outperforms other
schemes.Comment: 6 pages, 4 figure
One-step preparation of cluster states in quantum dot molecules
Cluster states, a special type of highly entangled states, are a universal
resource for measurement-based quantum computation. Here, we propose an
efficient one-step generation scheme for cluster states in semiconductor
quantum dot molecules, where qubits are encoded on singlet and triplet state of
two coupled quantum dots. By applying a collective electrical field or
simultaneously adjusting interdot bias voltages of all double-dot molecule, we
get a switchable Ising-like interaction between any two adjacent quantum
molecule qubits. The initialization, the single qubit measurement, and the
experimental parameters are discussed, which shows the large cluster state
preparation and one-way quantum computation implementable in semiconductor
quantum dots with the present techniques.Comment: 5 pages, 3 figure
Electronic Properties of Graphene Nanoribbon on Si(001) Substrate
We show by first-principles calculations that the electronic properties of
zigzag graphene nanoribbons (Z-GNRs) adsorbed on Si(001) substrate strongly
depend on ribbon width and adsorption orientation. Only narrow Z-GNRs with even
rows of zigzag chains across their width adsorbed perpendicularly to the Si
dimer rows possess an energy gap, while wider Z-GNRs are metallic due to
width-dependent interface hybridization. The Z-GNRs can be metastably adsorbed
parallel to the Si dimer rows, but show uniform metallic nature independent of
ribbon width due to adsorption induced dangling-bond states on the Si surface.Comment: 13 pages, 3 figure
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