Li Bai-Wen

Deterministic secure communication without using entanglement

We show a deterministic secure direct communication protocol using single qubit in mixed state. The security of this protocol is based on the security proof of BB84 protocol. It can be realized with current technologies.We show a deterministic secure direct communication protocol using single qubit in a mixed state. The security of this protocol is based on the security proof of BB84 protocol. It can be realized by the current technologies.

Variational calculations for a hydrogen atom confined off-centre in an impenetrable spherical box using B-splines

We have calculated the energy levels of a hydrogen atom confined off-centre in an impenetrable spherical box using a linear variational method. Both the radial and angular wavefunctions are expanded in terms of B-splines. The validity of the approach has been examined for various off-centre distances. Comparison with other results given in the literature is made and consistent agreement is achieved. The change of the features of the energy levels in accord with the off-centre distance is revealed.

Energy spectra of the confined atoms obtained by using B-splines

We have calculated the energy spectra of one- and two-electron atoms (ions) centered in an impenetrable spherical box by variational method with B-splines as basis functions. Accurate results are obtained for both large and small radii of confinement. The critical box radius of confined hydrogen atom is also calculated to show the usefulness of our method. A partial energy degeneracy in confined hydrogen atom is found when the radius of spherical box is equal to the distance at which a node of single-node wavefunctions of free hydrogen atom is located.

Phase shift of the population oscillation and population trapping

Using our recently developed time-dependent multilevel approach, we have calculated the phase shift of the population oscillation of the excited potassium atom in frequency-modulated fields when the modulation amplitude is suddenly changed. The numerical results are in good agreement with the measurements. A new way of realizing population trapping is suggested.

Relativistic corrections to the Zeeman effect of helium atom

The high-order relativistic corrections to the Zeeman g-factors of the helium atom are calculated. All the relativistic correction terms and the term describing the motion of the mass centre are treated as perturbations. Most of our results are in good agreement with those of Yan and Drake [Phys. Rev. A 50 (1994) R1980], who used the wavefunctions constructed by Hylleraas coordinates. For the correction delta(gL) of the g-factor of the 3 (3)p State in He-4, our result, 2.91415 x 10(-7) a.u., should be more reasonable and accurate, although there are no experimental data available in the literature to compare.

Approximate good quantum numbers in Cs Stark states

Using Cs atom zero-field wavefunctions from a kind of atomic potential model, and the mean value of z-component of spin angular momentum (S-z) in each Stark state, we numerically investigate the approximate good quantum numbers in Cs Stark states. Our results quantitatively confirm the concept that m(l) and m(s) can be taken as the approximate good quantum numbers in two cases, except for some Stark states in a few special field points or ranges; however we also find that m(l) and m(s) cannot be treated as the approximate good quantum numbers for these special Stark states.

Large amplitude electromagnetic solitons in intense laser plasma interaction

This paper shows that the standing, backward- and forward-accelerated large amplitude relativistic electromagnetic solitons induced by intense laser pulse in long underdense collisionless homogeneous plasmas can be observed by particle simulations. In addition to the inhomogeneity of the plasma density, the acceleration of the solitons also depends upon not only the laser amplitude but also the plasma length. The electromagnetic frequency of the solitons is between about half and one of the unperturbed electron plasma frequency. The electrostatic field inside the soliton has a one-cycle structure in space, while the transverse electric and magnetic fields have half-cycle and one-cycle structure respectively. Analytical estimates for the existence of the solitons and their electromagnetic frequencies qualitatively coincide with our simulation results.

A new pseudospectral method for calculations of hydrogen atom in arbitrary external fields

A new pseudospectral method was introduced to calculate wavefunctions and energy levels of hydrogen atom in arbitrary potential. Some results of hydrogen atom in uniform magnetic fields were presented, high accuracy of results was obtained with simple calculations, and our calculations show very fast convergence. It suggests a new method for calculations of hydrogen atom in external fields.

Excitation energies of 1s2nd and 1s2nf states for the lithium isoelectronic sequence

The nonrelativistic energies of the 1s(2)nd and 1s(2)nf(n=6, 7, 8 and 9) states for the lithium isoelectronic sequence from Li I to Ne VIII are calculated by using a full core plus correlation method with multiconfiguration interaction wave function. Relativistic and mass-polarization effects on the energy are evaluated as the first-order perturbation theory. In most cases with nuclear charge, Z less than or equal to 7, the agreement between our predicted excitation energies and the experimental data is less than 1 cm(-1).

Energy of 1s2snp 4P States for the Lithium Isoelectronic Sequence

The nonrelativistic energies of the core-excited 1s2snp 4P (n = 2, 3, 4, 5) states for the lithium isoelectronic sequence from Be II to O VI are calculated with a full core plus correlation method using multiconfiguration interaction wavefunctions. The relativistic and mass-polarization effects on the energy are evaluated as the first order perturbation theory. Our predicted energies are lower than other theoretical results. They show that this full core plus correlation method is useful for the core-excited systems.