Quantum Fisher Information of W States in Decoherence Channels

We study the quantum Fisher information (QFI) of W states analytically with respect to SU(2) rotations in the basic decoherence channels i.e. depolarizing (DPC), amplitude damping (ADC) and phase damping (PDC), and present the interesting behavior of QFI of W states, especially when compared to that of GHZ states [Ma et al., Phys. Rev. A, 84, 022302 (2011)]. We find that when initially pure W states are under decoherence, i) DPC: as decoherence starts and increases, QFI smoothly decays; ii) ADC: just as decoherence starts, QFI exhibits a sudden drop to the shot noise level and as decoherence increases, QFI continues to decrease to zero and then increases back to the shot noise level; iii) PDC: just as decoherence starts, a sudden death of QFI occurs and QFI remains zero for any rate of decoherence, therefore W states in phase damping channel do not provide phase sensitivity. We also find that, on the contrary to GHZ states, pure or decohered W states are not sensitive with respect to rotations in z direction and the sensitivities with respect to rotations in x and y directions are equal to each other, implying no sudden change points of QFI due to competition between directions.Comment: 3 pages, 1 (eps) figure. Comments are welcom

Analyzing competitiveness of automotive industry through cumulative belief degrees

Copyright @ 2012 The European Mathematical SocietyThis study aims to analyze the automotive industry from competitiveness perspective using a novel cumulative belief degrees (CBD) approach. For this purpose, a mathematical model based on CBD is proposed to quantify the relations among the variables in a system. This model is used to analyze the Turkish Automotive Industry through scenario analysis.This research is supported by SEDEFED (Federation of Industrial Associations), REF (TÜSİAD Sabanci University Competitiveness Forum), and OSD (Automotive Manufacturers Association

Constructing Quantum Logic Gates Using q-Deformed Harmonic Oscillator Algebras

We study two-level q-deformed angular momentum states and us- ing q-deformed harmonic oscillators, we provide a framework for con- structing qubits and quantum gates. We also present the construction of some basic quantum gates including CNOT, SWAP, Toffoli and Fredkin.Comment: Slightly modified version of the accepted manuscrip

Generating multi-atom entangled W states via light-matter interface based fusion mechanism

W state is a key resource in quantum communication. Fusion technology has been proven to be a good candidate for preparing a large-size W state from two or more small-size W states in linear optical system. It is of great importance to study how to fuse W states via light-matter interface. Here we show that it is possible to prepare large-size W-state networks using a fusion mechanism in cavity QED system. The detuned interaction between three atoms and a vacuum cavity mode constitute the main fusion mechanism, based on which two or three small-size atomic W states can be fused into a larger-size W state. If no excitation is detected from those three atoms, the remaining atoms are still in the product of two or three new W states, which can be re-fused. The complicated Fredkin gate used in the previous fusion schemes is avoided here. W states of size 2 can be fused as well. The feasibility analysis shows that our fusion processes maybe implementable with the current technology. Our results demonstrate how the light-matter interaction based fusion mechanism can be realized, and may become the starting point for the fusion of multipartite entanglement in cavity QED system.Comment: 9 pages, 2 figure

Numerical Analyses of Soil Deformations Around Deep Excavations

In this study, the deep excavation of Cincin Station located along the Bağcılar - Otogar metro line which is currently under construction in Istanbul is modeled numerically. The excavation (depth 32.5 m) of the station is carried out with a surrounding slurry trench diaphragm wall and top-down construction method. The six slabs of the station building and the foundation mat are used as support elements. Lateral soil displacements are measured with inclinometers placed in the wall and nearby soil layers. The results of numerical analysis using soil profile and geotechnical parameters obtained from conventional field and laboratory tests and measured lateral displacements are compared. Then using the same soil model, soil displacements expected to occur if some other alternative excavation support systems were used is investigated. As alternative support systems use of steel pipes as internal bracing and a piled wall with pre-stressed tie-backs are considered. The calculated soil displacements for different support systems are compared with each other and the measured values. The effects of certain design parameters such as the rigidity of internal bracing elements, the pile diameters and the pre-stressing level of tie-backs are investigated through numerical analysis