9,766 research outputs found
Does three-tangle properly quantify the three-party entanglement for Greenberger-Horne-Zeilinger-type states?
Some mixed states composed of only GHZ states can be expressed in terms of
only W-states. This fact implies that such states have vanishing three-tangle.
One of such rank-3 states, , is explicitly presented in this paper.
These results are used to compute analytically the three-tangle of a rank-4
mixed state composed of four GHZ states. This analysis with
considering Bloch sphere of qudit system allows us to derive the
hyper-polyhedron. It is shown that the states in this hyper-polyhedron have
vanishing three-tangle. Computing the one-tangles for and ,
we prove the monogamy inequality explicitly. Making use of the fact that the
three-tangle of is zero, we try to explain why the W-class in the
whole mixed states is not of measure zero contrary to the case of pure states.Comment: 10 pages, no figure V2: new calculational results are included. 11
pages: V3 accepted in the Rapid Communication of PRA, 4 pages (two column
Mixed-State Entanglement and Quantum Teleportation through Noisy Channels
The quantum teleportation with noisy EPR state is discussed. Using an optimal
decomposition technique, we compute the concurrence, entanglement of formation
and Groverian measure for various noisy EPR resources. It is shown analytically
that all entanglement measures reduce to zero when , where
is an average fidelity between Alice and Bob. This fact indicates
that the entanglement is a genuine physical resource for the teleportation
process. This fact gives valuable clues on the optimal decomposition for
higher-qubit mixed states. As an example, the optimal decompositions for the
three-qubit mixed states are discussed by adopting a teleportation with W-stateComment: 18 pages, 4 figure
New Candidates for Topological Insulators : Pb-based chalcogenide series
Here, we theoretically predict that the series of Pb-based layered
chalcogenides, PbBiSe and PbSbTe, are possible
new candidates for topological insulators. As increases, the phase
transition from a topological insulator to a band insulator is found to occur
between and 3 for both series. Significantly, among the new topological
insulators, we found a bulk band gap of 0.40eV in PbBiSe which is one
of the largest gap topological insulators, and that PbSbTe is
located in the immediate vicinity of the topological phase boundary, making its
topological phase easily tunable by changing external parameters such as
lattice constants. Due to the three-dimensional Dirac cone at the phase
boundary, massless Dirac fermions also may be easily accessible in
PbSbTe
Prediction of Giant Spin Motive Force due to Rashba Spin-Orbit Coupling
Magnetization dynamics in a ferromagnet can induce a spin-dependent electric
field through spin motive force. Spin current generated by the spin-dependent
electric field can in turn modify the magnetization dynamics through
spin-transfer torque. While this feedback effect is usually weak and thus
ignored, we predict that in Rashba spin-orbit coupling systems with large
Rashba parameter , the coupling generates the spin-dependent
electric field [\pm(\alpha_{\rm R}m_e/e\hbar) (\vhat{z}\times \partial
\vec{m}/\partial t)], which can be large enough to modify the magnetization
dynamics significantly. This effect should be relevant for device applications
based on ultrathin magnetic layers with strong Rashba spin-orbit coupling.Comment: 4+ pages, 2 figure
Effects of the Internal and External Factors of Small and Mediumsized Corporations on Green Management Performances through the Establishment and Utilization of Information Systems and Building Relationships for Information and Knowledge
The current research was intended to examine the effects of internal and external factors of small and medium-sizedcorporations (SMC) on green management performances through the establishment and utilization of InformationTechnology (IT) and building external relations. The results of the study showed that of the corporate internal factors, theinterest levels of CEOs concerning the environment did not significantly affect the establishment and utilization ofinformation systems that required large expenses and investments in technological core competencies. Of the corporateexternal factors, the intensity of competition within the industry was shown to have a significant effect on buildingrelationships for information and knowledge, but not on the establishment and utilization of information systems. On theother hand, government regulations on the environment had significant effects both on the establishment and utilization ofinformation systems and on building relationships for information and knowledge. The establishment and utilization ofinformation systems had significant effects on building relationships for information and knowledge, but not on greenmanagement performances. However, building relationships for information and knowledge showed significant effects ongreen management performances, suggesting the importance of building relationships for information and knowledge withexternal parties
Skyrmion Lattice in Two-Dimensional Chiral Magnet
We develop a theory of the magnetic field-induced formation of Skyrmion
crystal state in chiral magnets in two spatial dimensions, motivated by the
recent discovery of the Skyrmionic phase of magnetization in thin film of
FeCoSi and in the A-phase of MnSi. Ginzburg-Landau functional
of the chiral magnet re-written in the CP representation is shown to be a
convenient framework for the analysis of the Skyrmion states. Phase diagram of
the model at zero temperature gives a sequence of ground states, helical spin
Skyrme crystal ferromagnet, as the external field
increases, in good accord with the thin-film experiment. In close analogy
with Abrikosov's derivation of the vortex lattice solution in type-II
superconductor, the CP mean-field equation is solved and shown to reproduce
the Skyrmion crystal state.Comment: 10 pages, 7 figure
Microscopic Theory of Rashba Interaction in Magnetic Metal
Theory of Rashba spin-orbit coupling in magnetic metals is worked out from
microscopic Hamiltonian describing d-orbitals. When structural inversion
symmetry is broken, electron hopping between -orbitals generates chiral
ordering of orbital angular momentum, which combines with atomic spin-orbit
coupling to result in the Rashba interaction. Rashba parameter characterizing
the interaction is band-specific, even reversing its sign from band to band.
Large enhancement of the Rashba parameter found in recent experiments is
attributed to the orbital mixing of 3d magnetic atoms with non-magnetic heavy
elements as we demonstrate by first-principles and tight-binding calculations.Comment: 5 pages, 2 figure
Plasmonic colloidal nanoparticles with open eccentric cavities via acid-induced chemical transformation
Surface-enhanced Raman spectroscopy (SERS) has been considered a promising technique for the detection of trace molecules in biomedicine and environmental monitoring. The ideal metal nanoparticles for SERS must not only fulfill important requirements such as high near-field enhancement and a tunable far-field response but also overcome the diffusion limitation at extremely lower concentrations of a target material. Here, we introduce a novel method to produce gold nanoparticles with open eccentric cavities by selectively adapting the structure of non-plasmonic nanoparticles via acid-mediated surface replacement. Copper oxide nanoparticles with open eccentric cavities are first prepared using a microwave-irradiation-assisted surfactant-free hydrothermal reaction and are then transformed into gold nanoparticles by an acidic gold precursor while maintaining their original structure. Because of the strong near-field enhancement occurring at the mouth of the open cavities and the very rough surfaces resulting from the uniformly covered hyperbranched sharp multi-tips and the free access of SERS molecules inside of the nanoparticles without diffusion limitation, adenine, one of the four bases in DNA, in an extremely diluted aqueous solution (1.0 pM) was successfully detected with excellent reproducibility upon laser excitation with a 785-nm wavelength. The gold nanoparticles with open eccentric cavities provide a powerful platform for the detection of ultra-trace analytes in an aqueous solution within near-infrared wavelengths, which is essential for highly sensitive, reliable and direct in vivo analysis.None1132sciescopu
Theory of magnetic field-induced metaelectric critical end point in BiMnO
A recent experiment on the multiferroic BiMnO compound under a strong
applied magnetic field revealed a rich phase diagram driven by the coupling of
magnetic and charge (dipolar) degrees of freedom. Based on the
exchange-striction mechanism, we propose here a theoretical model with the
intent to capture the interplay of the spin and dipolar moments in the presence
of a magnetic field in BiMnO. Experimentally observed behavior of the
dielectric constants, magnetic susceptibility, and the polarization is, for the
most part, reproduced by our model. The critical behavior observed near the
polarization reversal point in the phase diagram is interpreted as
arising from the proximity to the critical end point.Comment: Theory; relevant experiment uploaded as arXiv:0810.190
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