Spatially strongly confined atomic excitation via a two dimensional stimulated Raman adiabatic passage.

We consider a method of sub-wavelength superlocalization and patterning of atomic matter waves via a two dimensional stimulated Raman adiabatic passage (2D STIRAP) process. An atom initially prepared in its ground level interacts with a doughnut-shaped optical vortex pump beam and a traveling wave Stokes laser beam with a constant (top-hat) intensity profile in space. The beams are sent in a counter-intuitive temporal sequence, in which the Stokes pulse precedes the pump pulse.

Cold atoms meet lattice gauge theory.

The central idea of this review is to consider quantum field theory models relevant for particle physics and replace the fermionic matter in these models by a bosonic one. This is mostly motivated by the fact that bosons are more 'accessible' and easier to manipulate for experimentalists, but this 'substitution' also leads to new physics and novel phenomena. It allows us to gain new information about among other things confinement and the dynamics of the deconfinement transition.

Azimuthal modulation of electromagnetically induced grating using structured light.

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level [Formula: see text]-type atomic system interacting with a weak probe field and two simultaneous position-dependent coupling fields-a two dimensional standing wave and an optical vortex beam. Upon derivation of the Maxwell wave equation, describing the dynamic response of the probe light in the atomic medium, we perform numerical calculations of the amplitude, phase modulations and Fraunhofer diffraction pattern of the probe field under different system parameters. We show that due to the azimuthal modulation of the Laguerre-Gaussian field, a two-dimensional asymmetric grating is observed, giving an increase of the zeroth and high orders of diffraction, thus transferring the probe energy to the high orders of direction.

Ferris wheel patterning of Rydberg atoms using electromagnetically induced transparency with optical vortex fields.

We study the formation of spatially dependent electromagnetically induced transparency (EIT) patterns from pairs of Laguerre-Gauss (LG) modes in an ensemble of cold interacting Rydberg atoms. The EIT patterns can be generated when two-photon detuning does not compensate for the Rydberg level energy shift induced by van der Waals interaction. Depending on the topological numbers of each LG mode, we can pattern dark and bright Ferris-wheel-like structures in the absorption profile with tunable barriers between sites, providing confinement of Rydberg atoms in transverse direction while rendering them transparent to light at specific angular positions.

Ultraprecise Rydberg atomic localization using optical vortices.

We propose a robust localization of the highly-excited Rydberg atoms interacting with doughnut-shaped optical vortices. Compared with the earlier standing-wave (SW)-based localization methods, a vortex beam can provide an ultraprecise two-dimensional localization solely in the zero-intensity center, within a confined excitation region down to the nanometer scale. We show that the presence of the Rydberg-Rydberg interaction permits counter-intuitively much stronger confinement towards a high spatial resolution when it is partially compensated by a suitable detuning.

Strongly confined atomic localization by Rydberg coherent population trapping.

We investigate the possibility to attain strongly confined atomic localization using interacting Rydberg atoms in a coherent population trapping ladder configuration, where a standing-wave is used as a coupling field in the second leg of the ladder. Depending on the degree of compensation for the Rydberg level energy shift induced by the van der Waals interaction, by the coupling field detuning, we distinguish between two antiblockade regimes, i.e.

Localization Driven Superradiant Instability.

The prominent Dicke superradiant phase arises from coupling an ensemble of atoms to a cavity optical field when an external optical pumping exceeds a threshold strength. Here we report a prediction of the superradiant instability driven by Anderson localization, realized with a hybrid system of the Dicke and Aubry-André (DAA) model for bosons trapped in a one-dimensional (1D) quasiperiodic optical lattice and coupled to a cavity. Our central finding is that for bosons condensed in a localized phase given by the DAA model, the resonant superradiant scattering is induced, for which the critical optical pumping of the superradiant phase transition approaches zero, giving an instability driven by the Anderson localization.

How to Dress Radio-Frequency Photons with Tunable Momentum.

We demonstrate how the combination of oscillating magnetic forces and radio-frequency (rf) pulses endows rf photons with tunable momentum. We observe velocity-selective spin-flip transitions and the associated Doppler shift. Recoil-dressed photons are a promising tool for measurements and quantum simulations, including the realization of gauge potentials and spin-orbit coupling schemes which do not involve optical transitions.

Azimuthal modulation of electromagnetically induced transparency using structured light.

Recently a scheme has been proposed for detection of the structured light by measuring the transmission of a vortex beam through a cloud of cold rubidium atoms with energy levels of the Λ-type configuration [N. Radwell et al., Phys.

Topological lattice using multi-frequency radiation.

We describe anoveltechniqueforcreatinganartificialmagneticfieldforultracoldatomsusinga periodicallypulsedpairofcounterpropagatingRamanlasersthatdrivetransitionsbetween a pair of internal atomic spin states: a multi-frequency coupling term. In conjunction with a magnetic field gradient, this dynamically generates a rectangular lattice with a non-staggered magnetic flux. For a wide range of parameters, the resulting Bloch bands have non-trivial topology, reminiscent of Landau levels, as quantified by their Chern numbers.

Superfluidity enhanced by spin-flip tunnelling in the presence of a magnetic field.

It is well-known that when the magnetic field is stronger than a critical value, the spin imbalance can break the Cooper pairs of electrons and hence hinder the superconductivity in a spin-singlet channel. In a bilayer system of ultra-cold Fermi gases, however, we demonstrate that the critical value of the magnetic field at zero temperature can be significantly increased by including a spin-flip tunnelling, which opens a gap in the spin-triplet channel near the Fermi surface and hence reduces the influence of the effective magnetic field on the superfluidity. The phase transition also changes from first order to second order when the tunnelling exceeds a critical value.

Magnetically generated spin-orbit coupling for ultracold atoms.

We present a new technique for producing two- and three-dimensional Rashba-type spin-orbit couplings for ultracold atoms without involving light. The method relies on a sequence of pulsed inhomogeneous magnetic fields imprinting suitable phase gradients on the atoms. For sufficiently short pulse durations, the time-averaged Hamiltonian well approximates the Rashba Hamiltonian.

Synthetic 3D spin-orbit coupling.

We describe a method for creating a three-dimensional analogue to Rashba spin-orbit coupling in systems of ultracold atoms. This laser induced coupling uses Raman transitions to link four internal atomic states with a tetrahedral geometry, and gives rise to a Dirac point that is robust against environmental perturbations. We present an exact result showing that such a spin-orbit coupling in a fermionic system always gives rise to a molecular bound state.

Spin field effect transistors with ultracold atoms.

We propose a method of constructing cold atom analogs of the spintronic device known as the Datta-Das transistor (DDT), which, despite its seminal conceptual role in spintronics, has never been successfully realized with electrons. We propose two alternative schemes for an atomic DDT, both of which are based on the experimental setup for tripod stimulated Raman adiabatic passage. Both setups involve atomic beams incident on a series of laser fields mimicking the relativistic spin-orbit coupling for electrons that is the operating mechanism of the DDT.

Double and negative reflection of cold atoms in non-Abelian gauge potentials.

Atom reflection is studied in the presence of a non-Abelian vector potential proportional to a spin-1/2 operator. The potential is produced by a relatively simple laser configuration for atoms with a tripod level scheme. We show that the atomic motion is described by two different dispersion branches with positive or negative chirality.