Reference-frame-independent (RFI) quantum key distribution (QKD) is a protocol which can share unconditional secret keys between two remote users without the alignment of slowly varying reference frames. We propose a passive decoy-state RFI-QKD protocol with heralded single-photon source (HSPS) and present its security analysis. Compared with RFI QKD using a weak coherent pulse source (WCPS), numerical simulations show that the passive decoy-state RFI QKD with HSPS performs better not only in secret key rate but also in secure transmission distance. Moreover, our protocol is robust against the relative motion of the reference frames as well as RFI QKD with the WCPS. In addition, we also exploit Hoeffding's inequality to investigate the finite-key effect on the security of the protocol.

Quantum pattern recognition algorithm for two-qubit systems has been implemented by quantum adiabatic evolution. We will estimate required running time for this algorithm by means of an analytical solution of time-dependent Hamiltonian since the time complexity of adiabatic quantum evolution is a limitation on the quantum computing. These results can be useful for experimental implementation.

Singular spectrum analysis and its multivariate or multichannel singular spectrum analysis (MSSA) variant are effective methods for time series representation, denoising and prediction, with broad application in many fields. However, a key element in MSSA is singular value decomposition of a high-dimensional matrix stack of component matrices, where the spatial (structural) information among multivariate time series is lost or distorted. This vector-space model also leads to difficulties including high dimensionality, small sample size, and numerical instability when applied to multi-dimensional time series. We present a generalized multivariate singular spectrum analysis (GMSSA) method to simultaneously decompose multivariate time series into constituent components, which can overcome the limitations of conventional multivariate singular spectrum analysis. In addition, we propose a SampEn-based method to determine the dominant components in GMSSA. We demonstrate the effectiveness and efficiency of GMSSA to simultaneously de-noise multivariate time series for attractor reconstruction, and to predict both simulated and real-world multivariate noisy time series.

We calculate the exclusive charmonium photo-production in the framework of color glass condensate. To obtain a good description of the vector meson production experimental data at HERA, we introduce a vector meson mass dependent skewness factor into the skewness effect. Then we extend the skewness improved model to the LHC energies. The numerical results of our model are in good agreement with the $J/\psi$ and $\psi(2S)$ data in ultra-peripheral proton–proton collisions at LHC, which show the significance of the vector meson mass-dependent skewness factor. A prediction of the exclusive charmonium photo-production in ultra-peripheral nucleus–nucleus collisions is performed since it can provide a good way to test the effectiveness of the color glass condensate.

Measurement of the neutron yield is performed at a primary energy of 400 MeV/u carbons for the Pb target. Water-bath activation-foil method is used in a moderation measurement with Au foils to detect the moderated neutrons. The neutron yield is determined to be $18.4{\pm}2.1$ per carbon by integrating the neutron flux over the entire water volume. The corresponding simulation values are performed by Geant4 code with three models to compare with the experimental results. The comparison shows that the calculated result with the INCL model is in good agreement with the experimental data.

We develop an isotropic empirical potential for molecular hydrogen (H$_{2}$) and deuterium (D$_{2}$) by fitting to solid-state data, which is appropriate for classical molecular dynamics (CMD) approach. Based on the prior isotropic intermolecular potential used in self-consistent phonon approximation, a zero-point energy term and an embedded energy term are introduced to describe the H$_{2}$–H$_{2}$ and D$_{2}$–D$_{2}$ interactions in CMD simulations. The structure, cohesive energy and elastic properties of solid H$_{2}$ (D$_{2})$ are used as the fitting database. The present method is tested by calculating the melting point of solid H$_{2}$, and the pressure and bulk elastic modulus as a function of volume. The developed potentials well reproduce many properties of solid H$_{2}$ and D$_{2}$.

We report the repetitively Q-switched laser operation of the Yb-doped calcium niobium gallium garnet disordered garnet crystal, achieved with an acousto-optic modulator in a compact plano-concave resonator that is end-pumped by a 935-nm diode laser. An average output power of 1.96 W is produced at pulse repetition rate of 50 kHz at emission wavelengths around 1035 nm, with a slope efficiency of 16%. The highest pulse energy of 269 $\mu$J is generated at pulse repetition rate of 1 kHz, with pulse width 12.1 ns and peak power 20.53 kW.

To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coaxial optical path is presented. The target image is obtained using double cameras with coaxial optical path. Since there is imaging optical path difference between the cameras, the images are different. In comparison of the image differences, the target range could be reversed. The principle of the ranging method and the ranging model are described. The relationship among parameters in the ranging process is analyzed quantitatively. Meanwhile, the system composition and technical realization scheme are also presented. Also, the principle of the method is verified by the equivalent experiment. The experimental results show that the design scheme is correct and feasible with good robustness. Generally, the ranging error is less than 10% with good convergence. The optical path is designed in a re-entrant mode to reduce the volume and weight of the system. Through the coaxial design, the visual passive range of the targets with any posture can be obtained in real time. The system can be widely used in electro-optical countermeasure and concealed photoelectric detection.

We propose a novel all fiber Mach–Zehnder interferometer (MZI) based on photonic crystal fiber (PCF) filled with liquid crystal (LC). The interference between the core mode and the cladding modes of a PCF is utilized. To excite the cladding modes, a region is formed using fiber fusion splicer. Due to the fact that varying effective index difference between the core region and the LC-filled cladding region can cause different transmission spectra, we mainly study the MZIs with different LC-filled structures and different lengths of LC filling. The measured results demonstrate that quite clear interference spectra can be obtained. Through analysis spatial frequency spectrum and temperature spectrum of two MZIs with different LC-filled structures, we can obtain that the MZI with adjacent two LC-filled holes has clearer interference spectrum and higher temperature sensitivity. Thus we choose this MZI to measure the temperature sensitivity with different lengths of LC filling. When the length of LC filling is 2 cm, the temperature sensitivities can be enlarged to 1.59 nm/$^{\circ}\!$C. The interferometer shows a good temperature tunability and sensitivity, which can be a good candidate for a highly tunable optical filtering and temperature sensing applications.

Propagation of coupled electrostatic drift and ion-acoustic waves (DIAWs) is presented. It is shown that nonlinear solitary vortical structures can be formed by low-frequency coupled electrostatic DIAWs. Primary waves of distinct (small, intermediate and large) scales are considered. Appropriate set of 3D equations consisting of the generalized Hasegawa–Mima equation for the electrostatic potential (involving both vector and scalar nonlinearities) and the equation of motion of ions parallel to magnetic field are obtained. According to experiments of laboratory plasma mainly focused to large scale DIAWs, the possibility of self-organization of DIAWs into the nonlinear solitary vortical structures is shown analytically. Peculiarities of scalar nonlinearities in the formation of solitary vortical structures are widely discussed.

The effects of three different typical resistivity models (Spitzer, Z&L and M&G) on the performance of pulsed inductive acceleration plasma are studied. Numerical results show that their influences decrease with the increase of the plasma temperature. The significant discriminations among them appear at the plasma temperature lower than 2.5 eV, and the maximum gap of the pulsed inductive plasma accelerated efficiency is approximately 2.5%. Moreover, the pulsed inductive plasma accelerated efficiency is absolutely related to the dynamic impedance parameters, such as voltage, inductance, capacitance and flow rate. However, the distribution of the efficiency as a function of plasma temperature with three resistivity models has nothing to do with the dynamic impedance parameter.

Tungsten has been chosen as one of the most promising candidates as the plasma-facing material in future fusion reactors. Although tungsten has numerous advantages compared with other materials, issues including dust are rather difficult to deal with. Dust is produced in fusion devices by energetic plasma-surface interaction. The re-deposition of dust particles could cause the retention of fuel atoms. In this work, tungsten is deposited with deuterium plasma by hollow cathode discharge to simulate the dust production in a tokamak. The morphology of the deposited tungsten can be described as a film with spherical particles on it. Thermal desorption spectra of the deposited tungsten show extremely high desorption of the peak positions. It is also found that there is a maximum retention of deuterium in the deposited tungsten samples due to the dynamic equilibrium of the deposition and sputtering process on the substrates.

WN$_{x}$films are deposited by reactive chemical vapor deposition at different amounts of nitrogen in gas mixtures. Experimental data demonstrate that nitrogen amount has a strong effect on microstructure, phase formation, texture morphology, mechanical and optical properties of the WN$_{x}$ films. With increasing nitrogen a phase transition from a single WN phase with low crystallinity structure to a well-mixed crystallized hexagonal WN and face-centered-cubic W$_{2}$N phases appears. Relatively smooth morphology at lower N$_{2}$ concentration changes to a really smooth morphology and then granular with coarse surface at higher N$_{2}$ concentration. The SEM observation clearly shows a columnar structure at lower N$_{2}$ concentration and a dense nanoplates one for higher nitrogen content. The hardness of WN thin films mainly depends on the film microstructure. The absorbance peak position shifts to shorter wavelength continuously with increasing nitrogen amount and decreasing particle size.

Tantalum phosphide (TaP) is predicted to be a kind of topological semimetal. Several defects of TaP induced by H irradiation are studied by the density functional theory. Electronic dispersion curves and density of states of these defects are reported. Various defects have different impacts on the topological properties. Weyl point positions are not affected by most defects. The H atom can tune the Fermi level as an interstitial. The defect of substitutional H on P site does not affect the topological properties. P and Ta vacancies of concentration 1/64 as well as the defect of substitutional H on Ta site destruct part of the Weyl points.

Bi$_{2}$Te$_{3}$ thin films and GeTe/B$_{2}$Te$_{3}$ superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric (TE) measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi$_{2}$Te$_{3}$ thin films and GeTe/B$_{2}$Te$_{3}$ superlattices, respectively. High TE performances with figure-of-merit ($ZT$) values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi$_{2}$Te$_{3}$ thin films, respectively. These $ZT$ values are higher than those of p-type Bi$_{2}$Te$_{3}$ alloys as reported. Relatively high $ZT$ of the GeTe/B$_{2}$Te$_{3}$ superlattices at 300–380 K were 0.62–0.76. The achieved high $ZT$ value may be attributed to the unique nano- and micro-structures of the films, which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi$_{2}$Te$_{3}$-based thin films can serve as high-performance materials for applications in TE devices.

We investigate the anisotropic magnetic transports in topological semimetal TaSb$_2$. The compound shows the large magnetoresistance (MR) without saturation and the metal-insulator-like transition no matter whether the magnetic field is parallel to $c$-axis or $a$-axis, except that the MR for ${\boldsymbol B}\|c$ is almost twice as large as that of ${\boldsymbol B}\|a$ at low temperatures. The adopted Kohler's rule can be obeyed by the MR at distinct temperatures for ${\boldsymbol B}\|c$, but it is slightly violated as ${\boldsymbol B}\|a$. The angle-dependent MR measurements exhibit the two-fold rotational symmetry below 70 K, consistent with the monoclinic crystal structure of TaSb$_2$. The dumbbell-like picture of angle-dependent MR in TaSb$_2$ suggests a strongly anisotropic Fermi surface at low temperatures. However, it finally loses the two-fold symmetry over 70 K, implying a possible topological phase transition at around the temperature where $T_{\rm m}$ is related to a metal-insulator-like transition under magnetic fields.

Superior characteristics of AlGaN-channel metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs) at high temperatures are demonstrated in detail. The temperature coefficient of the maximum saturation drain current for the AlGaN-channel MIS HEMT can be reduced by 50% compared with the GaN-channel HEMT. Moreover, benefiting from the better suppression of gate current and reduced leakage current in the buffer layer, the AlGaN-channel MIS HEMT demonstrates an average breakdown electric field of 1.83 MV/cm at 25$^{\circ}\!$C and 1.06 MV/cm at 300$^{\circ}\!$C, which is almost 2 times and 3 times respectively larger than that of the reference GaN-channel HEMT. Pulsed mode analyses suggest that the proposed device suffers from smaller current collapse when the temperature reaches as high as 300$^{\circ}\!$C.

The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space, and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise. A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth–Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.

The aspect of formation and evolution of the recycled pulsar (PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram ($B$–$P$ diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate (or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.

Supernova 1987A is a core collapse supernova in the Large Magellanic Cloud, inside which the product is most likely a neutron star. Despite the most sensitive available detection instruments from radio to $\gamma$-ray wavebands being exploited in the pass thirty years, there have not yet been any pulse signals detected. By considering the density of the medium plasma in the remnant of 1987A, we find that the plasma cut-off frequency is approximately 7 GHz, a value higher than the conventional observational waveband of radio pulsars. As derived, with the expansion of the supernova remnant, the radio signal will be detected in 2073 A.D. at 3 GHz.