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<jats:p>We investigate the anisotropic spin–orbit coupled spin-2 Bose–Einstein condensates with Ioffe–Pritchard magnetic field. With nonzero magnetic field, anisotropic spin–orbit coupling will introduce several vortices and further generate a vortex chain. Inside the vortex chain, the vortices connect to each other, forming a line along the axis. The physical nature of the vortex chain can be explained by the particle current and the momentum distribution. The vortex number inside the vortex chain can be influenced via varying the magnetic field. Through adjusting the anisotropy of the spin–orbit coupling, the direction of the vortex chain is changed, and the vortex lattice can be triggered. Moreover, accompanied by the variation of the atomic interactions, the density and the momentum distribution of the vortex chain are affected. The realization and the detection of the vortex chain are compatible with current experimental techniques.</jats:p>

<jats:p>The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution (CVQKD) system. In traditional implementations for atmospheric channels, the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier. However, the underwater transmission of this pulses tends to suffer from severe attenuation, which inevitably deteriorates the security of the whole CVQKD system. In this paper, we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels. We estimate the parameters of the trans-media channels, involving atmosphere, sea surface and seawater and find that the short-wave infrared performs well in the above channels. The 450-nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere, sea surface and seawater channels. Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km. In addition, we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance, which contributes to the establishment of practical global quantum networks.</jats:p>

<jats:p>The conservation law for first-order coherence and mutual correlation of a bipartite qubit state was firstly proposed by Svozilík <jats:italic>et al.</jats:italic>, and their theories laid the foundation for the study of coherence migration under unitary transformations. In this paper, we generalize the framework of first-order coherence and mutual correlation to an arbitrary (<jats:italic>m</jats:italic> ⊗ <jats:italic>n</jats:italic>)-dimensional bipartite composite state by introducing an extended Bloch decomposition form of the state. We also generalize two kinds of unitary operators in high-dimensional systems, which can bring about coherence migration and help to obtain the maximum or minimum first-order coherence. Meanwhile, the coherence migration in open quantum systems is investigated. We take depolarizing channels as examples and establish that the reduced first-order coherence of the principal system over time is completely transformed into mutual correlation of the (2 ⊗ 4)-dimensional system-environment bipartite composite state. It is expected that our results may provide a valuable idea or method for controlling the quantum resource such as coherence and quantum correlations.</jats:p>

<jats:p>Fractional calculus is a 300 years topic, which has been introduced to real physics systems modeling and engineering applications. In the last few decades, fractional-order nonlinear chaotic systems have been widely investigated. Firstly, the most used methods to solve fractional-order chaotic systems are reviewed. Characteristics and memory effect in those method are summarized. Then we discuss the memory effect in the fractional-order chaotic systems through the fractional-order calculus and numerical solution algorithms. It shows that the integer-order derivative has full memory effect, while the fractional-order derivative has nonideal memory effect due to the kernel function. Memory loss and short memory are discussed. Finally, applications of the fractional-order chaotic systems regarding the memory effects are investigated. The work summarized in this manuscript provides reference value for the applied scientists and engineering community of fractional-order nonlinear chaotic systems.</jats:p>

<jats:p>Based on the mean-field theory, we investigate the thermodynamic properties of the two-dimensional (2D) charged spin-1/2 Fermi gas. Landé factor <jats:italic>g</jats:italic> is introduced to measure the strength of the paramagnetic effect. There is a competition between diamagnetism and paramagnetism in the system. The larger the Landé factor, the smaller the entropy and specific heat. Diamagnetism tends to increase the entropy, while paramagnetism leads to the decrease of the entropy. We find that there exists a critical value of Landé factor for the transition point due to the competition. The entropy of the system increases with the magnetic field when <jats:italic>g</jats:italic> &lt; 0.58. With the growth of paramagnetism, when <jats:italic>g</jats:italic> &gt; 0.58, the entropy first decreases with the magnetic field, then reaches a minimum value, and finally increases again. Both the entropy and specific heat increase with the temperature, and no phase transition occurs. The specific heat tends to a constant value at the high-temperature limit, and it approaches to zero at very low temperatures, which have been proved by the analytical calculation.</jats:p>

<jats:p>We study the dynamical quantum phase transitions (DQPTs) in the <jats:italic>XY</jats:italic> chains with the Dzyaloshinskii–Moriya interaction and the <jats:italic>XZY</jats:italic>–<jats:italic>YZX</jats:italic> type of three-site interaction after a sudden quench. Both the models can be mapped to the spinless free fermion models by the Jordan–Wigner and Bogoliubov transformations with the form <jats:inline-formula> <jats:tex-math> <?CDATA $H= \sum _{k}{\varepsilon }_{k}({\eta }_{k}^{\dagger }{\eta }_{k}-\displaystyle \frac{1}{2})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>H</mml:mi> <mml:mo>=</mml:mo> <mml:msub> <mml:mo>∑</mml:mo> <mml:mi>k</mml:mi> </mml:msub> <mml:mrow> <mml:msub> <mml:mi>ε</mml:mi> <mml:mi>k</mml:mi> </mml:msub> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msubsup> <mml:mi>η</mml:mi> <mml:mi>k</mml:mi> <mml:mo>†</mml:mo> </mml:msubsup> <mml:msub> <mml:mi>η</mml:mi> <mml:mi>k</mml:mi> </mml:msub> <mml:mo>−</mml:mo> <mml:mstyle displaystyle="true"> <mml:mfrac> <mml:mn>1</mml:mn> <mml:mn>2</mml:mn> </mml:mfrac> </mml:mstyle> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_6_060505_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, where the quasiparticle excitation spectra <jats:italic>ε<jats:sub>k</jats:sub> </jats:italic> may be smaller than 0 for some <jats:italic>k</jats:italic> and are asymmetrical (<jats:italic>ε<jats:sub>k</jats:sub> </jats:italic> ≠ <jats:italic>ε</jats:italic> <jats:sub>–<jats:italic>k</jats:italic> </jats:sub>). It is found that the factors of Loschmidt echo equal 1 for some <jats:italic>k</jats:italic> corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfying <jats:italic>ε<jats:sub>k</jats:sub> </jats:italic> ⋅ <jats:italic>ε</jats:italic> <jats:sub>–<jats:italic>k</jats:italic> </jats:sub> &lt; 0, when the quench is from the gapless phase. By considering the quench from different ground states, we obtain the conditions for the occurrence of DQPTs for the general <jats:italic>XY</jats:italic> chains with gapless phase, and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Moreover, we analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. The conclusion can also be extended to the general quantum spin chains.</jats:p>

<jats:p>A new design of surface plasmon resonance (SPR) sensor employing circular-lattice holey fiber to achieve high-sensitivity detection is proposed. The sensing performance of the proposed sensor is numerically investigated and the results indicate that our proposed SPR sensor can be applied to the near-mid infrared detection. Moreover, the maximum wavelength sensitivity of our proposed sensor can reach as high as 1.76×10<jats:sup>4</jats:sup> nm/refractive index unit (RIU) and the maximum wavelength interrogation resolution can be up to 5.68×10<jats:sup>−6</jats:sup> RIU when the refractive index (RI) of analyte lies in (1.31, 1.36). Thanks to its excellent sensing performance, our proposed SPR sensor will have great potential applications for biological analytes detection, food safety control, bio-molecules detection and so on.</jats:p>

<jats:p>Here, simultaneous <jats:italic>in-situ</jats:italic> calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press (LVP) up to 15 GPa and 1400 K by an acoustic travel-time approach. Based on the recently reported <jats:italic>P</jats:italic>–<jats:italic>t</jats:italic> <jats:sub>S</jats:sub> and <jats:italic>P</jats:italic>–<jats:italic>T</jats:italic>–<jats:italic>t</jats:italic> <jats:sub>P</jats:sub>–<jats:italic>t</jats:italic> <jats:sub>S</jats:sub> equations for Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> buffer rod, the cell pressures and temperatures in the chamber of LVP were <jats:italic>in-situ</jats:italic> determined, in comparison with those by conventional off-line (or fixed-points) pressure calibration method and direct thermocouple measurement, respectively. It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures, owing to the stress relaxation as accumulate in the LVP chamber. This acoustic travel-time method is verified to be a good way for precise determination of thermal (cell) pressures at high temperature conditions, and is of great importance and necessity to conduct <jats:italic>in-situ</jats:italic> physical property measurements under extreme high <jats:italic>P</jats:italic>–<jats:italic>T</jats:italic> conditions, especially when the precious synchrotron x-ray/neutron diffraction beams are not available.</jats:p>

<jats:p>By combing the time-dependent density functional calculations for electrons with molecular dynamics simulations for ions (TDDFT-MD) nonadiabatically in real time, we investigate the microscopic mechanism of collisions between cytosine and low-energy protons with incident energy ranging from 150 eV to 1000 eV. To explore the effects of the collision site and the proton incident energy on irradiation processes of cytosine, two collision sites are specially considered, which are N and O both acting as the proton receptors when forming hydrogen bonds with guanine. Not only the energy loss and the scattering angle of the projectile but also the electronic and ionic degrees of freedom of the target are identified. It is found that the energy loss of proton increases linearly with the increase of the incident energy in both situations, which are 14.2% and 21.1% of the incident energy respectively. However, the scattering angles show different behaviors in these two situations when the incident kinetic energy increases. When proton collides with O, the scattering angle of proton is larger and the energy lost is more, while proton captures less electrons from O. The calculated fragment mass distribution shows the high counts of the fragment mass of 1, implying the production of H<jats:sup>+</jats:sup> fragment ion from cytosine even for proton with the incident energy lower than keV. Furthermore, the calculated results show that N on cytosine is easier to be combined with low-energy protons to form NH bonds than O.</jats:p>

<jats:p>It is known that ion-focused regime (IFR) can effectively suppress expansion of a relativistic electron beam (REB). Using the particle-in-cell Monte Carlo collision (PIC-MCC) method, we numerically investigate the propagation of an REB in neutral gas. The results demonstrate that the beam body is charge neutralization and a stable IFR can be established. As a result, the beam transverse dimensions and longitudinal velocities keep close to the initial parameters. We also calculate the charge and current neutralization factors of the REB. Combined with envelope equations, we obtain the variations of beam envelopes, which agree well with the PIC simulations. However, both the energy loss and instabilities of the REB may lead to a low transport efficiency during long-range propagation. It is proved that decreasing the initial pulse length of the REB can avoid the influence of electron avalanche. Using parts of REB pulses to build a long-distance IFR in advance can improve the beam quality of subsequent pulses. Further, a long-distance IFR may contribute to the implementation of long-range propagation of the REB in space environment.</jats:p>