We propose a scheme for one-step generation of cluster states with atoms sent through a thermal cavity with strong classical driving field, based on the resonant atom--cavity interaction so that the operating time is sharply short, which is important in the view of decoherence.

The continuous variable quantum key distribution is expected to provide high secret key rate without single photon source and detector, while the lack of the effective key distillation method makes it unpractical under the high loss condition. Here we present a single-bit-reverse-reconciliation protocol against Gaussian classical Eve, which can distill the secret key through practical imperfect error correction with high efficiency. The simulation results show that this protocol can distill secret keys even when the transmission fibre is longer than 150 km, which may make the continuous variable scheme to outvie the single photon one.

We propose a protocol to directly implement the nonlocal phase gate of N λ-type three-level atoms trapped in distant cavities by using interference of polarized photons. The protocol uses the effects of quantum statistics of indistinguishable photons emitted by the atoms inside optical cavities.

We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result.

We present a kind of exact inflationary solution in the chaotic inflation scenario to non-minimal coupled scalar field, taking the Hubble parameter directly as a function of the scalar field φ, H(φ)=αφⁿ. Using the analysis of the WMAP3 data, we give the range of power index n.

The charged top-pions have been predicted by the topcolour-assisted technicolour (TC2) model and the observation of the charged top-pions can be regarded as the robust evidence of the model. We study the charged top-pion and gluon associated production at the LHC, i.e., pp→gII_t⁺. The cross section of this process can reach tens of pb, even hundreds of pb, and there will be enough gII_t⁺ events produced at the LHC. Because the gII_t⁺ production is a flavour-changing (FC) process, the SM background can be greatly depressed. Furthermore, there exists an FC decay mode c¯b for the charged top-pions, and such decay mode can provide us with the typical signals to detect the charged top-pions. Therefore, it is hopeful to find the charged top-pions via the gII_t⁺ production at the LHC.

Total fragmentation cross section for the reaction 158A Pb ions + Cu target is measured using the most sensitive track detector CR-39. Measured values are compared with calculations. Exposures of target-detector stack with 158A Pb projectiles are made at CERN-SPS beam facility. Results of calibration of CR-39 detector in a charge region (63≤Z≤83) are also reported, which can be used for high energy particle identification using CR-39 and in determination of partial charge changing cross sections. The charge resolution σ_Z achieved by this technique is about 0.2e. A systematic dependence of total fragmentation cross section on target properties is revealed and the corresponding results are presented.

Under the approximation of small birefringence, the properties of circularly polarized vortex beams tightly focused through a uniaxial birefringent crystal are studied. With the proper combination of the topological charge and the birefringence, the small focus, the small bottle beam and the inverse c-shaped intensity profile can be obtained. The effects of the focal shift and the Strehl ratio on the birefringence are analysed. A relation between angular momentum (included spin and orbital) and topological Pancharatnam charge is also presented.

Dicke-narrowing effect appears both in doubly dressed electromagnetically induced transparency and singly dressed four-wave-mixing lines due to the contribution of slow atoms resulting from de-excited effects of atom-wall collision and transient behaviour of atoms in a confined system. A robust recipe for high resolution spectroscopy of electromagnetically induced transparency dressed by two fields and four-wave-mixing lines comparable with the cold atoms is achievable in a thin vapour cell in experiments.

We numerically investigate the quality factors of two-dimensional (2D) photonic crystal (PC) microcavities using an auxiliary differential equations (ADE) technique in the context of finite-difference time-domain (FDTD) method. The microcavities are formed by point defects in the air hole lattice hexagonally patterned in ZnO (zinc oxide) matrix. The quality factors of these microcavities are limited primarily by the absorption of the background dielectric. We show that the ratio between the quality factors of microcavities in lossy and lossless background dielectric depends on the overlap between the field of cavity modes and the absorbing background dielectric in addition to the magnitude of absorption. These results will be helpful when designing and optimizing photonic crystal microcavities formed in lossy medium.

We study the formation mechanism and microstructure of nickel (Ni) atomic aggregates on the silicone oil surfaces by atomic force microscopy (AFM). Initially, the deposited atoms nucleate and form the compact clusters on the liquid surfaces. Then they perform Brownian motion and adhere upon impact. Finally the branched aggregates are formed. The Ni aggregates exhibit granular structure. The mean size of the granularities in the aggregates is of the order of 10 nm and it decreases with the nominal film thickness. The experiment shows that the Ni aggregates perform a directional diffusion towards the sample edge. The interpretation for this phenomenon is presented.

Undoped and Al-doped 3C-SiC films are deposited on Si(100) substrates by low-pressure chemical vapour deposition. Effects of aluminium incorporation on crystallinity, strain stress, surface morphology and growth rate of SiC films have been investigated. The x-ray diffraction patterns and rocking curves indicate that the crystallinity is improved with aluminium doping. Raman scatting patterns also demonstrate that the strain stress in SiC films is released due to the incorporation of Al ions and the increase of film thickness. Furthermore, due to the catalysis of surface reaction which is induced by trimethylaluminium, the growth rate is increased greatly and the growth process varies from three-dimensional island-growth mode to step-flow growth mode.

Adsorption and reaction of CO on two possible terminations of SrTiO₃ (100) surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory. The adsorption energy, Mulliken population analysis, density of states (DOS) and electronic density difference of CO on SrTiO₃ (100) surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy (0.449eV) is quite small. CO molecules adsorb weakly on the SrTiO₃ (100) surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.

We report the experiment results and data analyses based on a polaron exchange model for La_0.7Ca_0.3MnO₃ and Pr_0.7(Sr_1-xCa_x)_0.3MnO₃ epitaxial thin films. In the polaron exchange model with an energy balance condition, critical temperature of T_C for stable ferromagnetic (FM) ordering should depend on ∆ E as k_BT_C =E₀ exp(-ΔE/k_BT_C), where ∆ E denotes the potential barrier for the exchange polarons to overcome. Using the small polaron hopping model, the resistivity peak temperature T_P is a function of the hopping energy E_hop. The dependence of T_P on E_hop is similar to the dependence of T_C on ∆ E, which reveals that the polaron exchange relates to FM and insulator--metal transitions. The result indicates that the polaron exchange model is a simple way for describing the FM ordering, and is very helpful for understanding of complex doped manganites.

Influence of width of left well in Al_xGa_1-xN/GaN double quantum wells (DQWs) on absorption coefficients and wavelengths of the intersubband transitions (ISBTs) is investigated by solving the Schrödinger and Poisson equations self-consistently. When the width of left well is 1.79nm, three-energy-level DQWs are realized. The ISBT between the first odd and second odd order subbands (the 1_odd-2_odd ISBT) has a comparable absorption coefficient with the 1 _odd-2_even ISBT. Their wavelengths are located at 1.3 and 1.55μm, respectively. When the width of left well is 1.48nm, a four-energy-level DQWs is realized. The calculated results have a possible application to ultrafast two-colour optoelectronic devices operating within the optical communication wavelength range

Magnetic properties of Cu-doped LaMn_1-xCu_xO₃ (x=0.05--0.30) systems are carefully studied in the temperature range of 2--300K. A visible unexpected drop is observed in the ac susceptibility and the zero-field cooled dc magnetization curves for the dilute x≤0.10 near 100K, which depends on the measuring frequency and magnetic field. Measurements on frequency dependence of ac susceptibility, observation of magnetic relaxation, and the existence of critical field indicate that the anomaly can be attributed to the domain wall pinning effects. This is directly proven by the results of ball milled nano-sized powder counterparts compared with the bulk materials.

By introducing Arrhenius behaviour to the ferroparticles on the surface of the aggregated columnar structure in a diffusion model, equilibrium equations are set up. The solution of the equations shows that to keep the aggregated structures stable, a characteristic field is needed. The aggregation is enhanced by magnetic fields, yet suppressed as the temperature increases. Analysing the influence of the magnetic field on the interaction energy between the dipolar particles, we estimate the portion of the diffusing particles, and provide the agreeable ratio of the column radius over the centre-to-centre spacing between columns in a hexagonal columnar structure formed under a perpendicular magnetic field.

Ten thousands of unit-cell multilayer heterosturctures, [SrNb_0.05Ti_0.95O₃/La_0.9Sr_0.1MnO₃]₃ (SNTO/LSMO), have been epitaxial grown on SrTiO₃ (001) substrates by laser molecular beam epitaxy. The monitor of in-situ reflection high-energy electron diffraction demonstrates that the heterosturctures are layer-by-layer epitaxial growth. Atomic force microscope observation indicates that the surface of the heterosturcture is atomically smooth. The measurements of cross-sectional low magnification and high-resolution transmission electron microscopy as well as the corresponding selected area electron diffraction reveal that the interfaces are of perfect orientation, and the epitaxial crystalline structure shows the orientation relation of SNTO(001)//LSMO(001), and SNTO[100]//LSMO[100].

Y₂O₃ stabilized ZrO₂ (YSZ) thin films with different Y₂O₃ molar contents (0, 3, 7, and 12mol%) are deposited on BK7 substrates by electron-beam evaporation technique. The effects of different Y₂O₃ contents on residual stresses and structures of YSZ thin films are studied. Residual stresses are investigated by means of two different techniques: the curvature measurement and x-ray diffraction method. It is found that the evolution of residual stresses of YSZ thin films by the two different methods is consistent. Residual stresses of films transform from compressive stress into tensile stress and the tensile stress increases monotonically with the increase of Y₂O₃ content. At the same time, the structures of these films change from the mixture of amorphous and monoclinic phases into high temperature cubic phase. The variations of residual stress correspond to the evolution of structures induced by adding of Y₂O₃ content.

Europium-doped yttrium--silicon--oxide--nitride phosphors are synthesized by carbothermal reduction and nitridation method. The crystal structure of the phosphors changed gradually from oxide Y₂Si₂O₇ to nitride YSi₃N₅ state with increasing dosage of Si₃N₄ and carbon powder. The Y₂Si₂O₇:Eu phosphor shows a blue emission at 465nm with 300nm excitation and a characteristic red emission of Eu³⁺ at 612nm with 230nm excitation. The YSi₃N₅:Eu phosphor shows a broad emission band centred at 595nm with some sharp peaks of Eu³⁺ with 325nm excitation. The absorption of the studied phosphors increases from 450 to 700nm with an increment in nitrogen content. Blue-to-orange tunable luminescence is observed with 390nm excitation.