Modern Physics Letters B

Quantum entanglement and nonlocality will suffer inevitable harm from decoherence environment. Based on GHZ state, we study the harm of the generalized amplitude damping (GAD) operation and the protection by the single local filtering (SLF) operation in this paper. We verify that the SLF functions to depress the loss of entanglement and nonlocality from GAD. This conclusion will guide us to select the best method to protect the GHZ state from GAD decoherence.

The influence of a high hydrostatic pressure on the basal-plane electrical resistance along the twin boundaries in underdoped HoBa₂Cu₃O${}_{7-\delta }$ single crystals is investigated. An enhancement of the phase segregation caused by the high-pressure-induced redistribution of the labile oxygen has been revealed. The temperature dependences of the electrical resistance above $T_c$ can be approximated well within the framework of the model of $s-d$ electron–phonon scattering.

Metallic Cu nanowires have been synthesized by thermal reduction of CuO nanowires in low concentration hydrogen environment. The Cu nanowires can be formed after removing oxide group from the metal oxide nanowires within temperature range from 200${}^{\circ }$C to 500${}^{\circ }$C. These nanowires have twisted structure with 100–200 nm and average lengths of 10 $\mu$m can be obtained in optimum temperature range 300–400${}^{\circ }$C reduced for 30 min. The X-ray diffraction (XRD) pattern shows Cu peaks recognized at (111), (200) and (220). Scanning electron microscopy (SEM) images reveal the reduction temperatures strongly affect the nanowires formation. Transmission electron microscopy (TEM) images confirmed that Cu nanowires have single crystalline structures with 0.21 nm fringe spacing which correspond to (111) growth direction. The results indicate that thermal reduction of copper oxide nanowires in low concentration hydrogen environment can produce high purity and single crystalline Cu nanowires.

In this work, we investigate a completely integrable seventh-order member of the KdV6 hierarchy. We develop two extensions of (2+1) dimensions for this equation. We show that the dispersion relations are distinct that will reflect on the structures of the obtained solutions. We use the simplified Hirota’s method to determine multiple soliton solutions for these three equations. The integrability of the extended equations is tested by using the Painlevé analysis.

The frontal instability of lock-exchange density currents is numerically investigated using dissipative particle dynamics (DPD) at the mesoscopic particle level. For modeling two-phase flow, the “color” repulsion model is adopted to describe binary fluids according to Rothman–Keller method. The present DPD simulation can reproduce the flow phenomena of lock-exchange density currents, including the lobe-and-cleft instability that appears at the head, as well as the formation of coherent billow structures at the interface behind the head due to the growth of Kelvin–Helmholtz instability. Furthermore, through the DPD simulation, some small-scale characteristics can be observed, which are difficult to be captured in macroscopic simulation and experiment.

The effect of anisotropic surface tension and anisotropic interface kinetics on deep cellular crystal growth is studied. An asymptotic solution of deep cellular crystal growth in directional solidification is obtained by using the matched asymptotic expansion method and the multiple variable expansion method. The results show that as the anisotropic parameters increase, the total length of deep cellular crystal increases and the root depth increases, whereas the curvature of the interface near the root increases or the curvature radius decreases.

In this work, dependence of energy confinement time on plasma internal inductance has been studied by using the solution of Grad–Shafranov equation (GSE) for circular cross-section HT-7 tokamak. For this, the Shafranov parameter (asymmetry factor) and poloidal beta were obtained from solution of GSE. Then we can find the dependence of energy confinement time, on plasma internal inductance. It is observed that the maximum energy confinement time is related to the low values of internal inductance $(0.7<l_i<0.9)$.

The surface of high density polyethylene (HDPE) substrate was bombarded by the CH${}_x$ group ion beam, which was generated by the mixture of CH₄/H₂. Varying the CH₄/H₂ ratio, HDPE surfaces with different chemical bond structures and properties were obtained. Raman and XPS results show that $s{p}^2$ and $s{p}^3$ bond structures are formed at HDPE surface bombarded by CH${}_x$ group ions. The $s{p}^3$ bond fraction at bombarded HDPE surface depends on the H₂ ratio in CH₄/H₂ mixture, because the H ion/atom/molecule can improve the growth of $s{p}^3$ bond structure. For HDPE surface bombarded by CH₄/H₂ = 50/50, $s{p}^3$ bond fraction reaches the maximum of 30.5%, the surface roughness decreases to 17.04 nm, and the static contact angle of polar H₂O molecule increased to 140.2${}^{\circ }$.

Density functional theory is used to resolve the adatom-step and adatom–adatom interactions on vicinal Cu(111) surface. We demonstrated that the interactions between 3d adatoms appreciably depend on the distance from a surface step. Our calculations show that the magnitude of the repulsive barrier related to the surface step is larger for 3d adatoms located at the upper surface terrace than for adatoms located at the lower surface terrace.

In this work, we extend the discussion that began in Ref. 16 [A. L. de Paula, Jr., J. G. G. de Oliveira, Jr., J. G. P. de Faria, D. S. Freitas and M. C. Nemes, Phys. Rev. A 89 (2014) 022303] to deal with the dynamics of the concurrence of a many-body system. In that previous paper, the discussion was focused on the residual entanglement between the partitions of the system. The purpose of the present contribution is to shed some light on the dynamical properties of entanglement among the environment oscillators. We consider a system consisting of a harmonic oscillator linearly coupled to N others and solve the corresponding dynamical problem analytically. We divide the environment into two arbitrary partitions and the entanglement dynamics between any of these partitions is quantified and it shows that in the case when excitations in each partition are equal, the concurrence reaches the value 1 and the two partitions of the environment are maximally entangled. For long times, the excitations of the main oscillator are completely transferred to environment and the environment oscillators are found entangled.

Harmonic generation spectra from H${}_2^{+}$ molecule ion driven by the chirped pulse combined with a terahertz (THz) pulse have been theoretically investigated by numerically solving the non-Born–Oppenheimer time-dependent Schrödinger equation (NBO-TDSE). The results show that with the introduction of the chirp, the harmonic cutoff is extended, resulting in a smooth supercontinuum. Further, when the initial vibrational state is prepared as $v=3$, and by properly adding a THz controlling pulse, the harmonic yield is enhanced by almost six orders of magnitude compared with the single chirped pulse case. Quantum analyses are shown to explain the harmonic extension and enhancement. Furthermore, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Finally, by properly superposing the harmonics, a series of intense 35 as XUV pulses can be obtained, which are almost six orders of magnitude improvement in comparison with the single chirped pulse case.

A Y-branch electro-optic (EO) polymer modulator has been designed and fabricated. High performance side-chain polyurethane-imide (PUI) with a high EO coefficient of larger than 50 pm/V and a moderate glass-transition temperature $(T_g)$ of 206${}^{\circ }$C is used as EO polymer core layer of the modulator. The fabricated phase modulator exhibits a low half-wave voltage of 1.94 V at 1550 nm in single arm modulation with 1 cm EO interaction length and 2 cm total length. The results show that the modulator fabricated by side-chain PUI EO materials possesses potential applications in low driving voltage and low cost optical systems.