We report the generation of a new type of laser transverse mode that is analogous to a SU(2) elliptical wave packet of a quantum harmonic oscillator. Experimental results show that using a doughnut pump profile to excite an isotropic microchip laser in a spherical cavity can generate the elliptical transverse modes. The formation of elliptical transverse modes is found to be a spontaneous locking process of Hermite-Gaussian modes within the same family. The chaotic relaxation oscillation caused by the interaction of two nearly degenerate elliptical modes is also observed.

In the system with ions confined both in a linear trap and in a high-$Q$ single-mode optical cavity, a quantum computing scheme is proposed by using lasers and quantized cavity field, via Raman transition. A controlled-NOT gate with reduced operations can be performed on two non-neighboring ions without the involvement of both motional states of ions and cavity mode. Experimental feasibility of achieving our scheme is discussed.

Analytical and numerical schemes to solve the coupled-channel T-matrix equations at zero and negative energies are presented and the methodology is applied to the Ps-H system. Using a recent approach of potential simulation technique inside the T-Matrix method, improved predictions on the scattering length ${(3.89a}_0)$ has been made by reproducing the binding energy (1.067 eV) from direct solutions of the T-matrix equations at zero and negative energies, respectively.

In a previous paper [Phys. Rev. A 65, 032721 (2002)] we reexamined a model describing the structure of the low-energy Ps-H resonances as being due to quasibound states of the positron in the perturbed Coulomb potential of the ${\mathrm{H}}^{-}$ ion appearing in the closed, rearranged channel. In particular, we wished to understand why the lowest p-state resonance was so far away from the lowest quasibound $\mathrm{}\left(2p\right)\mathrm{}$ state. We found that the lowest resonance actually corresponds to the first-excited $\left[3p\right]$ state, while the lowest state is not recognizable as a resonance. In the present work we repeat our analysis, but this time for the lowest d state. We find that the lowest $\left[3d\right]$ state does correspond to a resonance shifted moderately.

We study the beating of a probe field with a time-varying susceptibility in a coherently prepared Raman medium. We consider the general case of an arbitrary variation of the susceptibility, which corresponds to a superposition of an arbitrary number of excited Raman transitions. We derive a general analytical solution and conservation relations for this process. We show that the interference between Raman polarizations may substantially affect frequency modulation and pulse compression for the probe field.

We calculate near-threshold photodetachment cross sections for ${\mathrm{Rb}}^{-},$ ${\mathrm{Cs}}^{-},$ and ${\mathrm{Fr}}^{-}$ using the Pauli equation method with a model potential describing the effective electron-atom interaction. Parameters of the model potential are fitted to reproduce ab initio scattering phase shifts obtained from Dirac R-matrix calculations. Special care is taken to formulate the boundary conditions near the atomic nucleus for solving the Pauli equation, based on the analytic solution of the Dirac equation for a Coulomb potential. We find a ${}^3{P}_1^o$ resonance contribution to the photodetachment cross section of ${\mathrm{Rb}}^{-},$ ${\mathrm{Cs}}^{-},$ and ${\mathrm{Fr}}^{-}$ ions. Our calculated total photodetachment cross sections for Cs agree with experiments after tuning the resonance position by 2.4 meV. For ${\mathrm{Rb}}^{-}$ and ${\mathrm{Fr}}^{-}$ the resonance contribution is much smaller than for Cs. We therefore also provide angle-differential cross sections and asymmetry parameters which are much more sensitive to the resonant contribution than total cross sections.

We study the average charge and the electronic energy loss of the swift (but not relativistic) clusters in a solid. A self-consistent average-charge theory for clusters in foils is presented on the basis of the fluid-mechanical model. Here the electron stripping rate is evaluated not only for an isolated ion, but also for cluster ions under the same background by taking into account the binding effect of the surrounding ions. This theory can elucidate very well not only the reduction of the cluster average charge per ion, but also its cluster-size and foil-thickness dependences of the recent data for the MeV/atom carbon clusters $\left({\mathrm{C}}_n\right)$ in carbon foils. The structure dependence is also proposed theoretically. In spite of the average-charge reduction, we can reconcile the enhancement of the energy losses of the corresponding clusters. The cluster energy losses with the inclusion of the Coulomb explosion by the wave-packet model is in much better agreement with the data at energies of 1–5.65 MeV/atom. Consistent agreement both in the diminution of average charge and in the enhancement of energy loss supports that the charge-state bulk effect is dominant in the cluster average charge.

A strong enhancement of the power emitted in laser assisted radiative recombination is reported. Also, strong modification and enhancement of the spectrum of the radiation emitted during radiative recombination in a plasma are reported. The reported results take place when the electron average translation velocity and the thermal velocity are comparable to or smaller than the amplitude of the quiver velocity.

We calculate the spectra and angular distributions of electrons from ionization of two-center molecules in linearly polarized strong laser pulses. A fully numerical quantum-mechanical method is compared to a simple semiclassical model designed to describe the diffraction of electrons when they recollide with the two-center core. Within both approaches, clear signatures of diffraction are found in the angular distributions. We discuss the dependence of electron diffraction on the internuclear distance and on the molecular orientation.

The arrival time probability distribution is defined by analogy with classical mechanics. The difficulty of requiring knowledge of the values of noncommuting operators is circumvented using the concept of weak measurements. The proposed procedure is suitable for free particles as well as for those subjected to an external potential. It is shown that such an approach imposes an inherent limitation on the accuracy of the arrival time determination.

By combining telecloning and the programmable quantum gate array presented by Nielsen and Chuang [Phys. Rev. Lett. 79, 321 (1997)], we propose a programmable quantum processor which can be programmed to implement a restricted set of operations with several identical data outputs. The outputs are approximately transformed versions of input data. The processor successes with certain probability.

We provide a quantum gambling protocol using three (symmetric) nonorthogonal states. The bias of the proposed protocol is less than that of previous ones, making it more practical. We show that the proposed scheme is secure against nonentanglement attacks. The security of the proposed scheme against entanglement attacks is shown heuristically.

We propose a method to refine entanglement via swapping from a pair of squeezed vacuum states by performing the Bell measurement of number sum and phase difference. The resultant states are maximally entangled by adjusting the two squeezing parameters to the same value. We then describe the teleportation of number states by using the entangled states prepared in this way.

Using a thallium atomic beam apparatus and a stabilized, frequency-doubled diode laser system, we have measured the scalar Stark shift in the ${6P}_{1/2}-{7S}_{1/2}$ transition of thallium. We determine the Stark shift to be $\Delta {\nu }_S=-103.23\left(39\right)\mathrm{}\mathrm{kHz}/(\mathrm{kV}/\mathrm{cm}{)}^2,$ providing more than an order of magnitude improvement in precision over earlier measurements of this quantity. This measurement serves as a stringent test of recently published thallium parity nonconservation calculations.

On the basis of the complex-scaled Floquet formalism, metastable states in intense laser fields are investigated by tracing the motion of resonance poles on the complex-energy Riemann surface. We analyzed a model system, in which an electron trapped in a one-dimensional potential well is exposed to an intense laser field. The formation of light-induced states (LIS) is found to be ubiquitous for a wide range of laser frequency. The mathematical origin of LIS, however, depends on the laser frequency. When the laser frequency is tuned to or lower than the one-photon ionization threshold, the LIS originates from a shadow pole of the original bound state. In such a case, the LIS’s are predicted to be experimentally detectable as intense peaks in photoelectron spectrum.

The dynamic stabilization of atomic hydrogen against ionization in high-frequency single- and two-color, circularly polarized laser pulses is observed by numerically solving the three-dimensional, time-dependent Schrödinger equation. The single-color case is revisited and numerically determined ionization rates are compared with both, the exact and the approximate high-frequency Floquet rates. The positions of the peaks in the photoelectron spectra can be explained with the help of dressed initial states. In two-color laser fields of opposite circular polarization, the stabilized probability density may be shaped in various ways. For laser frequencies ${\omega }_1$ and ${\omega }_2=n{\omega }_1,$ $n=2,3,\dots ,$ and sufficiently large excursion amplitudes, $\mathrm{}(n+1\mathrm{})\mathrm{}$ distinct probability density peaks are observed. This may be viewed as the generalization of the well-known “dichotomy” in linearly polarized laser fields, i.e, as “trichotomy,” “quatrochotomy,” “pentachotomy” etc. All those observed structures and their “hula-hoop”-like dynamics can be understood with the help of high-frequency Floquet theory and the two-color Kramers-Henneberger transformation. The shaping of the probability density in the stabilization regime can be realized without additional loss in the survival probability, as compared to the corresponding single-color results.

Quantum projection synthesis can be used for phase-probability-distribution measurement and optical-state truncation and preparation. The method relies on interfering optical light beams, which is a major challenge in experiments performed by pulsed light sources. In the pulsed regime, the time frequency overlap of the interfering light beams has a major impact on the efficiency of the method. In this paper, the pulse-mode projection-synthesis approach is developed, the mode structures of interfering light beams are characterized, and the effect of this overlap on the fidelity of optical-state truncation and preparation is investigated. By introducing the positive-operator-valued measure for the detection events in the scheme, the effect of mode mismatch between the photon-counting detectors and the incident light beams is also presented.

The theoretical framework behind a recent experiment by Nogueira et al. [Phys. Rev. Lett. 86, 4009 (2001)] of spatial antibunching in a two-photon state generated by collinear type-II parametric down-conversion and a birefringent double slit is presented. The fourth-order quantum correlation function is evaluated and shown to violate the classical Schwarz-type inequality, ensuring that the field does not have a classical analog. We expect these results to be useful in the rapidly growing fields of quantum imaging and quantum information.

A very efficient, wave-function independent method is presented for calculating Regge-pole positions and residues, as required in the analysis of heavy-particle collisions. The generation of high-precision residues is generally regarded as a very difficult problem; however, the present approach easily solves this. Our formalism exploits the existence of a linear moments equation representation for ${\Psi }^2,$ after analytic continuation into the complex r plane. Indeed, for rational fraction, singular (non-Fuchsian) scattering potentials, a moments’ representation proves indispensable in this regard. We illustrate our methodology using the polarization potential, $V\left(r\right)={\alpha }^2{/r}^a+\beta {/r}^b,a=4,\beta =0.\mathrm{}$