Modern Physics Letters B

We analyze correlations between two parties sharing a general mixed two-qubit state ρ_SM in order to predict measurement outcomes. It is an interesting question as to what can be predicted about the results of two complementary projective measurements on one qubit from the measurement results on the other qubit. To quantify these predictions the complementary knowledge excessesΔK(Π_M→Π_S) and ΔK(Π′_M→Π′_S) are used, where Π_S, Π′_S resp. Π_M, Π′_M represent projective measurements on the qubit S resp. M. We derive an inequality ΔK²(Π_M→Π_S) + ΔK²(Π′_M→Π′_S)≤(B_max/2)², where B_max is the maximum violation of Bell inequalities. This inequality restricts our capability to enhance the complementary predictions for any state ρ_SM and for arbitrary Π_S, Π′_S and Π_M, Π′_M. This result is experimentally verified on two-photon Werner states prepared by means of spontaneous parametric down-conversion.

A variational approach is used to study the intermediate-coupling polaron in bulk III-V nitride semiconductors with wurtzite crystal structure within the macroscopic dielectric continuum model and the uniaxial model. The polaronic self-trapping energy and effective mass are theoretically derived for the LO and TO polarizations mixing due to the anisotropy effect. The numerical computation has been performed for the polaronic self-trapping energy and effective mass for wurtzite nitrides GaN, AlN and InN. The results show that the self-trapping energies of the wurtzite nitrides are bigger than the zinc-blende structures above calculated materials. It is also found that the structure anisotropy increases the electron–phonon interaction in wurtizte nitride semiconductors. It indicates that the LO-like phonon influence on the polaronic effective mass and self-trapping energy are dominant and anisotropy effect is obvious.

In this paper, by using simple technique we introduce an efficient method of determining superconducting transition temperatures in experiment, we have also figured out the main influencing factors on the accuracy of T_c measurement. We present a useful relationship and the calculating formulae. This method is suited to determine superconducting transition temperatures in superconductors at temperatures of liquid He as well.

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of ~20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with ~30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.

A series of relative errors ε of the pressure broadening coefficient γ_fit with respect to the real one γ₀ from fitting overlapped spectrum which are composed of two lines with the Voigt profile, are deduced and analyzed in detail for different pressure ranges. ε is found to be related with the value of γ₀ and the spectral center distance δυ₀ of the two component spectral lines which are not resolved. The influence of δυ₀, pressures P and γ₀ on ε is discussed. This work can be taken as a useful reference for the analysis of the observed spectrum which is overlapped by two lines to achieve more precise results of γ_fit.

We derive the general shape equations in terms of Euler angles for an elastic model of uniform ribbon with noncircular cross section and vanishing spontaneous curvatures. We show that it has in general not a planar solution for a closed ribbon free of external force and torque. We study the conditions to form a helix with the axis along the direction of the applied force for a ribbon under external force and twisting. We find that if the bending rigidity is greater than the twisting rigidity, then no such helical rod can exist. Our stability analysis shows that a helical ribbon is in general stable or at least metastable under arbitrary force and torque. We find that the extension of the ribbon may undergo a discontinuous transition from a twisted straight rod to a helical ribbon. The intrinsic asymmetric elasticity of a helical ribbon under external torque is also studied.