291 research outputs found
Multiple teleportation via the partially entangled states
We investigate the multiple teleportation with some nonmaximally entangled
channels. The efficiencies of two multiple teleportation protocols, the
separate multiple teleportation protocol (SMTP) and the global multiple
teleportation protocol (GMTP), are calculated. We show that GMTP is more
efficient than SMTP.Comment: 4 pages, 2 figure
Generation of four-photon polarization entangled state based on EPR entanglers
We show how to prepare four-photon polarization entangled states based on
some Einstein-Podolsky-Rosen (EPR) entanglers. An EPR entangler consists of two
single photons, linear optics elements, quantum non-demolition measurement
using a weak cross-Kerr nonlinearity, and classical feed forward. This
entangler which acts as the most primary part in the construction of our scheme
allows us to make two separable polarization qubits entangled near
deterministically. Therefore, the efficiency of the present device completely
depends on that of EPR entanglers, and it has a high success probability.Comment: 5 pages, 3 figure
Multifunctional nanocomposite co-containing diamondlike carbon thin films
Metal-containing, hydrogenated carbon films (Me-a-C:H) is a special class of nanocomposite films of particular interest since they can be multifunctional through the synergistic interaction of their individual components. Thus, nanocomposite thin films possess high potential in a wide field of engineering applications, especially in small scale devices. A series of multifunctional nanocomposite Co-a-C:H thin films have been synthesized by a hybrid chemical vapor deposition (CVD) and physical vapor deposition (PVD) process to uncover the relationship between synthesis, microstructure and properties. The effects of deposition parameters on the microstructural evolution and properties have been systematically studied. The results showed that the microstructure can be controlled through proper adjustment of the processing parameters, to produce Co in the shape of: nano particles, elongated particles, wormlike columns, self-assembled multilayers, self-assembled nano columns embedded in an amorphous a-C:H matrix. Self-assembly of Co nano columns in a-C:H is discovered. As-deposited Co-a-C:H thin films are composed of defect rich ε-Co encapsulated in a-C:H matrix. Regarding the properties, raising C content (reducing Co content) in the films improves their hardness and corrosion resistance and decreases friction and wear rate. All the Co-a-C:H films exhibit a low surface roughness. Nano columnar Co-a-C:H films show size-dependent magnetic behavior, such as superparamagnetic and perpendicular magnetism. Annealing studies reveal that the phase transitions of Co in Co-a-C:H film follow the sequence of Co-a-C:H film → (300 °C) ε-Co + δ ′–Co2C → (343 °C) hcp-Co + δ ′–Co2C → (407 °C) hcp-Co + graphite → (459 °C) fcc-Co + graphite. A mechanism and a zone diagram are presented to describe the microstructural evolution of Co-a-C:H films. Knowledge gained from this research allows the design and synthesis of nanocomposite Co-a-C:H films and other multifunctional systems of interest for new applications in the field of nanotechnology
Understanding Mobile Traffic Patterns of Large Scale Cellular Towers in Urban Environment
Understanding mobile traffic patterns of large scale cellular towers in urban
environment is extremely valuable for Internet service providers, mobile users,
and government managers of modern metropolis. This paper aims at extracting and
modeling the traffic patterns of large scale towers deployed in a metropolitan
city. To achieve this goal, we need to address several challenges, including
lack of appropriate tools for processing large scale traffic measurement data,
unknown traffic patterns, as well as handling complicated factors of urban
ecology and human behaviors that affect traffic patterns. Our core contribution
is a powerful model which combines three dimensional information (time,
locations of towers, and traffic frequency spectrum) to extract and model the
traffic patterns of thousands of cellular towers. Our empirical analysis
reveals the following important observations. First, only five basic
time-domain traffic patterns exist among the 9,600 cellular towers. Second,
each of the extracted traffic pattern maps to one type of geographical
locations related to urban ecology, including residential area, business
district, transport, entertainment, and comprehensive area. Third, our
frequency-domain traffic spectrum analysis suggests that the traffic of any
tower among the 9,600 can be constructed using a linear combination of four
primary components corresponding to human activity behaviors. We believe that
the proposed traffic patterns extraction and modeling methodology, combined
with the empirical analysis on the mobile traffic, pave the way toward a deep
understanding of the traffic patterns of large scale cellular towers in modern
metropolis.Comment: To appear at IMC 201
On coherence of quantum operations by using Choi-Jamio{\l}kowski isomorphism
In quantum information, most information processing processes involve quantum
channels. One manifestation of a quantum channel is quantum operation acting on
quantum states. The coherence of quantum operations can be considered as a
quantum resource, which can be exploited to perform certain quantum tasks. From
the viewpoint of Choi-Jamio{\l}kowski isomorphism, we study the coherence of
quantum operations in the framework of resource theory. We define the phase-out
superoperation and give the operation which transforms the Choi-Jamio{\l}kowski
state of a quantum operation to the Choi-Jamio{\l}kowski state of the another
quantum operation obtained by using the phase-out superoperation to act on the
quantum operation. The set of maximally incoherent superoperations, the set of
nonactivating coherent superoperations and the set of de-phase incoherent
superoperations are defined and we prove that these sets are closed to compound
operation and convex combination of quantum superoperations. Further, we
introduce the fidelity coherence measure of quantum operations and obtain the
exact form of the fidelity coherence measure of the unitary operations on the
single qubit.Comment: 10 pages, no figur
Life-cycle energy and GHG emissions of forest biomass harvest and transport for biofuel production in Michigan
High dependence on imported oil has increased U.S. strategic vulnerability and prompted more research in the area of renewable energy production. Ethanol production from renewable woody biomass, which could be a substitute for gasoline, has seen increased interest. This study analysed energy use and greenhouse gas emission impacts on the forest biomass supply chain activities within the State of Michigan. A life-cycle assessment of harvesting and transportation stages was completed utilizing peer-reviewed literature. Results for forest-delivered ethanol were compared with those for petroleum gasoline using data specific to the U.S. The analysis from a woody biomass feedstock supply perspective uncovered that ethanol production is more environmentally friendly (about 62% less greenhouse gas emissions) compared with petroleum based fossil fuel production. Sensitivity analysis was conducted with key inputs associated with harvesting and transportation operations. The results showed that research focused on improving biomass recovery efficiency and truck fuel economy further reduced GHG emissions and energy consumption
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