In the last 30 days

• Open/close Dynamical control of soliton formation and propagation in a Y-type atomic system with dual ladder-type electromagnetically induced transparency

  Liu-Gang Si et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065403 Tag this article

  Article References Full text PDF (344 KB)

  We have investigated the nonlinear interaction between a weak-pulsed probe field and a four-level Y-type atomic system with dual ladder-type electromagnetically induced transparency. Two strong coupling fields induce a quantum destructive interference effect which depletes the population in the two nearly degenerate uppermost levels of the system and dramatically enhances the linear as well as nonlinear dispersion while simultaneously significantly suppressing the probe field absorption. We present the semiclassical quantum analysis of the system. The perturbation method of multiple scales is used to derive a differential envelope equation that describes the propagation of the probe field in the Y-type atomic system. It is then demonstrated that bright and dark optical solitons can be formed in this system.

• Open/close Cavity QED implementation of the multi-qubit refined Deutsch–Jozsa algorithm

  Wan Li Yang et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 055501 Tag this article

  Article References Full text PDF (1.18 MB)

  We theoretically study the realization of a multi-qubit refined Deutsch–Jozsa (DJ) algorithm using resonant interaction of many Rydberg atoms with a single-mode microwave cavity, in which the multi-qubit controlled phase gates could be accomplished efficiently. We show how to achieve a multi-qubit refined DJ algorithm in high fidelity, even in the case of a weak cavity decay and some imperfection. We argue that the required operations in our scheme are almost within the present experimental possibilities.

• Open/close Deterministic remote preparation of an arbitrary W-class state with multiparty

  Ming-Xing Luo et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065501 Tag this article

  Article References Full text PDF (206 KB)

  Our concern is to design some deterministic schemes for remotely preparing an arbitrary W-class state from one sender to one of a number of receivers. Compared with previous remote preparation schemes, the real receiver in our schemes is unknown to the sender. Firstly, by introducing a novel entanglement transformation the sender can deterministically prepare an arbitrary W-class state with complex spectra to one of two remote receivers via two four-particle GHZ states as the quantum channel. As for preparing a W-class state with real spectra, by constructing a general and useful measurement basis for the sender, another economical protocol can be designed with unit success probability. These schemes are extended to multiparties via two multi-particle GHZ states as the quantum channel. The classical communication costs of all the schemes are calculated to determine the classical resources required.

• Open/close Propagation of twin light pulses under magneto-optical switching operations in a four-level inverted-Y atomic medium

  Jiahua Li et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065502 Tag this article

  Article References Full text PDF (1.42 MB)

  Propagation dynamics of twin laser pulses through a cold four-level inverted-Y atomic medium is investigated theoretically via switching on and off an external magnetic field under the application of a strong driving field. By numerically solving the coupled Bloch–Maxwell equations for atom and field simultaneously on a spacetime grid, our spatio-temporal results clearly show that dynamic control of twin-pulse propagation and magneto-optic dual switching operation are possible in such an inverted-Y system. The proposed scheme may be used for the design of magneto-optic switching and magneto-optic storage devices.

• Open/close Two-electron–one-photon M1 and E2 transitions between the states of the 2p³ and 2s²2p odd configurations for B-like ions with 18 ≤ Z ≤ 92

  Jiguang Li et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 035005 Tag this article

  Article References Full text PDF (134 KB)

  Two-electron–one-photon (TEOP) M1 and E2 transition energies, line strengths and transition probabilities between the states of the 2p ³ and 2s ²2p odd configurations for B-like ions with 18 ≤ Z ≤ 92 have been calculated using the GRASP2K package based on the multiconfiguration Dirac–Hartree–Fock (MCDHF) method. Employing active-space techniques to expand the configuration list, we have systematically considered the valence, core–valence and core–core electron correlation effects. Breit interaction and quantum electrodynamical (QED) effects were also included to correct atomic state wavefunctions and the corresponding energies. Influences of electron correlation, Breit interaction and QED effects on transition energies and line strengths of the TEOP M1 and E2 transitions were analysed in detail. The present results were also compared with other theoretical and experimental values.

• Open/close Phase sensitivity of high harmonic transient grating spectroscopy

  Y Mairesse et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065401 Tag this article

  Article References Full text PDF (619 KB)

  We study the spatial profile of high order harmonics generated by a transient grating of rotational excitation. We show that the phase modulation of the harmonic emission as a function of molecular alignment is encoded in the diffraction pattern. In molecular nitrogen, the phase difference between aligned and isotropic molecules decreases from 1.6 rad for harmonic 19 to less than 0.3 rad for harmonic 27. In CO ₂ we observe a strong phase jump for the highest harmonics. The position of this phase jump in the harmonic spectrum depends on the laser intensity, reflecting the contribution from multiple molecular orbitals to the harmonic emission.

• Open/close Intense-field many-body S-matrix theory

  A Becker and F H M Faisal  2005 J. Phys. B: At. Mol. Opt. Phys. 38 R1 Tag this article

  Article References Full text PDF (1.51 MB)

  Intense-field many-body S-matrix theory (IM ST) provides a systematic ab initio approach to investigate the dynamics of atoms and molecules interacting with intense laser radiation. We review the derivation of IM ST as well as its diagrammatic representation and point out its advantage over the conventional 'prior' and 'post' expansions which are shown to be special cases of IM ST. The practicality and usefulness of the theory is illustrated by its application to a number of current problems of atomic and molecular ionization in intense fields. We also present a consistent S-matrix formulation of the quantum amplitude for high harmonic generation (HHG) and point out some of the most general properties of HHG radiation emitted by a single atom as well as its relation to coherent emission from many atoms. Experimental results for single and double (multiple) ionization of atoms and the observed distributions of coincidence measurements are analysed and the dominant mechanisms behind them are discussed. Ionization of more complex systems such as diatomic and polyatomic molecules in intense laser fields is analysed as well using IM ST and the results are discussed with special attention to the role of molecular orbital symmetry and molecular orientation in space. The review ends with a summary and a brief outlook.

• Open/close The carrier-envelope phase dependence of above threshold dissociation for HD⁺ driven by the modulated laser field

  Zheng-Tang Liu et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 055601 Tag this article

  Article References Full text PDF (986 KB)

  The dependence of above threshold dissociation (ATD) dynamics of HD ⁺ on the carrier-envelope phase (CEP) of the modulated laser pulse is studied theoretically by numerically solving the time-dependent Schrödinger equation including the molecular vibrational and rotational degrees of freedom. The energy-dependent spectra of dissociated fragments, resulting from the ATD, are calculated by using an asymptotic-flow expression in the momentum space. We find that the ATD spectra are dependent on the CEP , indicating that the ATD dynamics can be efficiently controlled by varying the CEP . Moreover, we examine the ATD dynamics for different intensities and CEPs of the modulated laser pulse. The ATD dynamics process is interpreted in terms of the light-dressed potential.

• Open/close Above threshold ionization of atomic hydrogen in ns states with up to four excess photons

  E Karule and A Gailitis  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065601 Tag this article

  Article References Full text PDF (322 KB)

  In a high-intensity laser field an atom can absorb more photons than the minimum necessary for ionization. It is known as above threshold ionization (ATI). Theoretically it is the most difficult case to handle as we have to consider transitions in continuum. To study ATI we use the perturbation theory and Green's function formalism. We have derived the modified two-term Coulomb Green's function (CGF) Sturmian expansion. In each term explicit summation over all intermediate states is carried out. The transition amplitude may be obtained in a closed form. The generalized cross sections are evaluated for the photoionization of atomic hydrogen in ns states with up to four excess photons. Calculations are performed in a wide range of wavelengths for linear and circular polarization. In the cases for which data are available, our results agree very well with the previous ones.

• Open/close Protocol and quantum circuit for implementing the N-bit discrete quantum Fourier transform in cavity QED

  Hong-Fu Wang et al  2010 J. Phys. B: At. Mol. Opt. Phys. 43 065503 Tag this article

  Article References Full text PDF (273 KB)

  We present a simple protocol and quantum circuit for efficient implementation of the N-bit discrete quantum Fourier transform by using two-qubit controlled-NOT gate and SWCZ gate that is a combination of -SWAP and controlled- Z gates in cavity quantum electrodynamics. In this protocol long-lived electronic states in circular Rydberg atoms are used as quantum bits and the one-bit and two-bit quantum gate operations required for implementing the discrete quantum Fourier transform in the quantum circuit can be easily achieved with atom–microwave resonant interaction and atom–cavity interaction occurring only between two nearest-neighbour atoms. We present the detailed experimental procedure and analyse the experimental feasibility.