
[Show abstract] [Hide abstract]
ABSTRACT: .Spinpolarized density functional theory is used to study twohydrogen
defect complexes in silicon carbide. We find that the magnetism depends
on the distances of the two hydrogen atoms. Magnetism appears when the
two hydrogen defects are distant from each other, and magnetism cancels
out if they are close to each other. The critical distance between the two
hydrogen defects is determined. Physics Letters A 05/2014; · 1.63 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: In this paper, a semiempirical molecular dynamics model is developed.
The central collisions of C60 + C60 and
X@C60 + X@C60 (X = He, Ne, Ar) at various incident
energy are investigated within this model. The fullerene dimers like a
"dumbbell" can be formed by a selfassembly of C60 fullerene
and X@C60 (X = He, Ne) endohedral fullerenes, and the new
fullerene structure like "peanut" can be formed by a selfassembly of
Ar@C60. It is found that Ar atom plays a great role in the
collision of Ar@C60 + Ar@C60 because of its size
effect. The energy effect is found that various incident energies cannot
change the final structure at low energies if they are below a certain
energy. Modern Physics Letters B 12/2013; 27(30):50225. · 0.69 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: Helium defects in silicon carbide are studied using first principle
calculations. The magnetization of various defects, such as vacancies,
helium interstitials, and interstitial and vacancy complexes, are
investigated. There is no magnetic element in silicon carbide. However,
when a silicon atom is substituted by a helium atom, a ferromagnetic
ground state is found. The total magnetic moment is found to be
4.0μB. When the silicon atom is substituted by a helium
atom, the four nearest carbon atoms are separated, and the p orbitals of
the four carbon atoms are localized. This results in narrow bands within
the conduction and valence bands. The magnitude of the magnetic moment
is related to the CHe distance. Physics Letters A 10/2012; 376(45):33633367. · 1.63 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: Silicon carbide with various defects such as carbon or silicon vacancies, antisites, and helium or hydrogen interstitials are studied in detail by ab initio calculations. The energy minimized structures of vacancies and helium or hydrogen interstitials are investigated. The calculated electronic spectra explain well some of the important features of silicon carbide observed in experiments. The phonon spectra of silicon carbide with hydrogen interstitials between silicon and carbon bond are calculated, and the frequency of the hydrogen–carbon stretching mode is consistent with experiments. Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 10/2011; 269(19):20672074. · 1.19 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: The associated gamma radiation in the interaction of 14.9MeV neutrons and a natural silicon sample is investigated with the total gamma radiation measurement technique (TGRM). According to the systematic knowledge of 14.9MeV neutroninduced 28,29,30Si(n,xγ) reactions, 50 prompt gamma lines from (n,n′γ), (n,2nγ), (n,npγ), (n,dγ), (n,pγ), (n,αγ), and (n,nαγ) reactions of 28Si, 29Si, and 30Si and one delayed gamma line from 28Si(n,p)28Al(β−)28Si⁎(γ) (f1/2=2.24m) process, and nine final nuclei were determined, and 54 possible transitions are designated. Differential elemental production crosssections of 40 gamma lines at 40°, 55°, 90°, 125°, and 140° are determined. Using relative differential production crosssections, accurate integral isotopic crosssections of the 28Si(n,p)28Al reaction were determined, and partial integral isotopic crosssections of some reaction channels were also estimated. The present results are in good agreement with some recent experimental and evaluated results. Comparison between present experimental results and the model calculations shows that effect of isospin conservation is maybe important for associated gamma radiation in alpha and proton emission processes. Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 08/2011; 648(1):192209. · 1.32 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: The discrete γ radiation in the interaction of 14.9MeV neutrons and a natural silicon sample is investigated with a total γradiation measurement (TGRM) technique. Fifty prompt γ lines, one delayed γ line, and seven final nuclei are identified. Fortyone possible transitions are designated. Differential production cross sections of 40 γ lines at 40°, 55°, 90°, 125°, and 140° are determined. Using relative differential production cross sections, accurate integral isotopic cross sections of the 28Si(n,p)28Al reaction are determined, and partial integral isotopic cross sections of the 28Si(n,n′)28Si, 28Si(n,α)25Mg, 29Si(n,n′)29Si, and 30Si(n,n′)30Si reaction channels are also estimated. The present results are in good agreement with some recent experimental and evaluated results. Physical Review C 10/2010; 82(4). · 3.88 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We present an efficient and economic scheme for fiveparty quantum state sharing of an arbitrary mqubit state with $2m$ threeparticle GreenbergerHorneZeilinger (GHZ) states and threeparticle GHZstate measurements. It is more convenient than other schemes as it only resorts to threeparticle GHZ states and threeparticle joint measurement, not fiveparticle entanglements and fiveparticle joint measurements. Moreover, this symmetric scheme is in principle secure even though the number of the dishonest agents is more than one. Its total efficiency approaches the maximal value. Comment: 6 pages, 1 figure The European Physical Journal D 04/2010; · 1.40 Impact Factor

Source Available from: Xihan Li
[Show abstract] [Hide abstract]
ABSTRACT: We propose an efficient faithful polarizationstate transmission scheme by utilizing frequency degree of freedom besides polarization and an additional qubit prepared in a fixed polarization. An arbitrary singlephoton polarization state is protected against the collective noise probabilistically. With the help of frequency beam splitter and frequency shifter, the success probability of our faithful qubit transmission scheme with frequency degree of freedom can be 1/2 in principle. Optics Communications 10/2009; · 1.54 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: The neutronrich fusion reactions are investigated systematically using the improved isospin dependent quantum molecular dynamics model. By studying the systematic dependence of fusion barrier on neuron excess, we find the enhancement of the fusion cross sections for neutronrich nuclear reactions that give the lowered static Coulomb barriers. The calculated fusion cross sections agree quantitatively with the experimental data. We further discuss the mechanism of the fusion enhancement of the cross sections for neutronrich nuclear reactions by analyzing the dynamical lowering of the Coulomb barrier that is attributed to the enhancement of the N/Z ratio at the neck region. Nuclear Physics A 10/2009; · 2.50 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We explore the connection between quantum brachistochrone (timeoptimal) evolution of a threequbit system and its residual entanglement called threetangle. The result shows that the entanglement between two qubits is not required for some brachistochrone evolutions of a threequbit system. However, the evolution between two distinct states cannot be implemented without its threetangle, except for the trivial cases in which less than three qubits attend evolution. Although both the probability density function of the timeaveraged threetangle and that of the timeaveraged squared concurrence between two subsystems become more and more uniform with the decrease in angles of separation between an initial state and a final state, the features of their most probable values exhibit a different trend. Comment: 6 pages, 3 figures Physical Review A 06/2009; · 2.99 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We present a singlephoton entanglement concentration protocol for longdistance quantum communication with quantum nondemolition detector. It is the first concentration protocol for singlephoton entangled states and it dose not require the two parties of quantum communication to know the accurate information about the coefficient $\alpha$ and $\beta$ of the less entangled states. Also, it does not resort to sophisticated singlephoton detectors, which makes this protocol more feasible in current experiments. Moreover, it can be iterated to get a higher efficiency and yield. All these advantages maybe make this protocol have more practical applications in longdistance quantum communication and quantum internet. Comment: 6 pages, 2 figures Quantum information & computation 06/2009; · 1.63 Impact Factor

Source Available from: Xihan Li
[Show abstract] [Hide abstract]
ABSTRACT: We present two robust quantum key distribution protocols against two kinds of collective noise, following some ideas in quantum dense coding. Threequbit entangled states are used as quantum information carriers, two of which forming the logical qubit which is invariant with a special type of collective noise. The information is encoded on logical qubits with four unitary operations, which can be read out faithfully with Bellstate analysis on two physical qubits and a singlephoton measurement on the other physical qubit, not threephoton joint measurements. Two bits of information are exchanged faithfully and securely by transmitting two physical qubits through a noisy channel. When the losses in the noisy channel is low, these protocols can be used to transmit a secret message directly in principle. Comment: 5 page, no figures International Journal of Quantum Information 03/2009; · 0.99 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We present a method for probabilistic quantum entanglement swapping between highdimensional pure entangled systems by introducing only one auxiliary twolevel particle. The probability of successful entanglement swapping is just the entanglement of the quantum channel. It can be used for practical longdistance quantum communication efficiently. We present a quantum secret sharing scheme based on quantum entanglement swapping with highdimensional pure entangled systems. It has the advantage of having high intrinsic qubit efficiency and high capacity. Moreover, it greatly reduces the classical information exchanged for creating the private key. Physica Scripta 03/2009; 79(3). · 1.03 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: A corresponding Comment, raised by Yang and Wen, claimed that (i) our scheme cannot complete the task of secret sharing well even if the agents obtain the information about their measuring bases; (ii) they give a feasible improvement of our protocol. In this Reply, we show that their first judgment is wrong and their improvement is insecure. Physics Letters A 01/2009; 373(3):399–400. · 1.63 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: This paper makes some qualitative and quantitative analyses about halo formation rules of some mirror nuclei with the relativistic meanfield (RMF) theory and the WoodsSaxon meanfield model. By analysing two opposite effects of Coulomb interaction on the proton halo formation, it finds that the energy level shift has a larger contribution than that of the Coulomb barrier when the mass number A is small, the hindrance of the Coulomb barrier becomes more obvious with the increase of the mass number A, and the overall effect of the Coulomb interaction almost disappears when A approx 39 as its two effects counteract with each other. Chinese Physics B 01/2009; 18(12):52675271. · 1.39 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We present an entanglement concentration protocol for electrons based on their spins and their charges. The combination of an electronic polarizing beam splitter and a charge detector functions as a parity check device for two electrons, with which the parties can reconstruct maximally entangled electron pairs from those in a lessentanglement state nonlocally. This protocol has a higher efficiency than those based on linear optics and it does not require the parties to know accurately the information about the lessentanglement state, which makes it more convenient in a practical application of solid quantum computation and communication. Comment: 4 pages, 2 figures Physics Letters A 10/2008; · 1.63 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: We present a scheme for multipartite entanglement purification of quantum systems in a GreenbergerHorneZeilinger state with quantum nondemolition detectors (QNDs). This scheme does not require the controllednot gates which cannot be implemented perfectly with linear optical elements at present, but QNDs based on crossKerr nonlinearities. It works with two steps, i.e., the bitflipping error correction and the phaseflipping error correction. These two steps can be iterated perfectly with parity checks and simple singlephoton measurements. This scheme does not require the parties to possess sophisticated single photon detectors. These features maybe make this scheme more efficient and feasible than others in practical applications. Comment: 8 pages, 5 figures The European Physical Journal D 10/2008; · 1.40 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: The halo structures in some light nuclei are investigated systemically with the nuclear asymptotic normalization coefficient (ANC) method and the relativistic meanfield (RMF) theory. Some important results about the halo structures in mirror nuclei are obtained, and some qualitative analyses are made to explore the role of Coulomb effects on the formation of proton halo nuclei. International Journal of Modern Physics E 10/2008; 17(09):17291738. · 0.84 Impact Factor

[Show abstract] [Hide abstract]
ABSTRACT: The fragment cross sections are calculated for reactions of Ne collisions with C, Al, Cu, Sn, Ta, and Pb targets at 600 Mev/nucleon using the the isospindependent BoltzmannLangevin equation. We found that the production cross sections for fragments Z = 2 to 9 are qualitatively reproduced by the present calculations except for C target. In order to understand the effects of heavy ion interaction with biomolecules well, we calculate the fragmentation cross sections for reactions of 12C + 2H, 12C, 14N, 16O at beam energies from 50 to 100 MeV/nucleon. It is found that fragment species increase approximately with increasing target mass. The obvious increment of the fragment cross sections for heavier targets at the beam energies from 50 to 80 MeV/nucleon are shown. International Journal of Modern Physics E 10/2008; 17(09):19271936. · 0.84 Impact Factor

Source Available from: Xihan Li
[Show abstract] [Hide abstract]
ABSTRACT: We present two efficient quantum key distribution schemes over two different collectivenoise channels. The accepted hypothesis of collective noise is that photons travel inside a time window small compared to the variation of noise. Noiseless subspaces are made up of two Bell states and the spatial degree of freedom is introduced to form two nonorthogonal bases. Although these protocols resort to entangled states for encoding the key bit, the receiver is only required to perform singleparticle product measurements and there is no basis mismatch. Moreover, the detection is passive as the receiver does not switch his measurements between two conjugate measurement bases to get the key. Comment: 6 pages, 1 figure; the revised version of the paper published in Phys. Rev. A 78, 022321 (2008). Some negligible errors on the error rates of eavesdropping check are corrected Physical Review A 07/2008; · 2.99 Impact Factor