First-principles calculations based on density functional theory are performed for zinc-blende B_xGa_1-xAs alloy with a special quasirandom structure (SQS) approach in a 64-atom supercell. Structural,electronic and optical properties of B_xGa_1-xAs alloy are comprehensively investigated under optimized geometry structures. It was found that calculated lattice constant slightly deviated from Vegard's law and significant bond length relaxation is shown. Calculated bowing parameters of energy gap are small (2.57 eV-5.01 eV) and are weakly composition-dependent. Finally,effects of boron composition on optical parameters including dielectric function, reflectivity,refractive index,absorption coefficient and energy loss function are analyzed in detail.

Quantum key generation rate of decoy state quantum key distribution(QKD) with a heralded single-photon source(HSPS) is deduced.Relationship between quantum key generation rate and detection efficiency of sender is discussed.Optimal intensities and key generation rate of decoy state QKD with a weak coherent pulse(WCP) and an HSPS are analyzed.It shows that key generation rate increases with increase of detection efficiency of sender and its security distance is the same as with a perfect single photon source.Decoy state QKD increases security distance and key rate of QKD.Due to less dark counts QKD with HSPS works longer distance than WCP.

The fiber fine structure in solar radio bursts carries small-scale magnetic field information in the initial phase of the burst.We deal with fiber structures to analyze the frequency drift rate.The background is obtained by a wavelet transformation.With a subtraction of the background and a threshold processing,the fiber structures are seperated.We select continuous segments in each channel.The cubic spline interpolation is used to fit the intensity-time relation with which the moments of intensity maxima are determined.Finally,the drift rate is calculated with linear regression.The algorithm is used to calculate frequency drift rate of the radio fiber event on 21-April-2002.The mean frequency drift rate obtained is beween -0.041 0~-0.013 8 GHz·s^-1.

The BEM is introduced and applied to solar magnetic force-free field problems. So that the magnetic structure above the sun can be analyzed directly from the observational data. The agreement between calculation and observation shows that the BEM is a useful tool to the solar physics.