This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition optical lattices, strongly interacting gases one two dimensions, or lowest-Landau-level physics quasi-two-dimensional fast rotation. Strong correlations fermionic are discussed lattices near-Feshbach resonances BCS-BEC crossover.

Correlations of linear polarizations pairs photons have been measured with time-varying analyzers. The analyzer in each leg the apparatus is an acousto-optical switch followed by two polarizers. switches operate at incommensurate frequencies near 50 MHz. Each amounts to a polarizer which jumps between orientations time short compared photon transit time. results are good agreement quantum mechanical predictions but violate Bell's inequalities 5 standard deviations.

When a neutral atom moves in properly designed laser field, its center-of-mass motion may mimic the dynamics of charged particle magnetic with emergence Lorentz-like force. In this Colloquium we present physical principles at basis artificial (synthetic) magnetism and relate corresponding Aharonov-Bohm phase to Berry's that emerges when follows adiabatically one dressed states. We also discuss some manifestations for cold quantum gas, particular terms vortex nucleation. then generalise our...

A novel treatment of dissipation energy from a ``small'' quantum system to reservoir is presented. We replace the usual master equation for small-system density matrix by wave-function evolution including stochastic element. This approach provides new insight and it allows calculations on problems which would otherwise be exceedingly complicated. The applied here two- or three-level atom coupled laser field vacuum modes quantized electromagnetic field.

Using a focused laser beam we stir Bose-Einstein condensate of 87Rb confined in magnetic trap and observe the formation vortex for stirring frequency exceeding critical value. At larger rotation frequencies produce states which up to four vortices are simultaneously present. We have also measured lifetime single state after turning off beam.

We present two cooling mechanisms that lead to temperatures well below the Doppler limit. These are based on laser polarization gradients and work at low power when optical-pumping time between different ground-state sublevels becomes long. There is then a large lag internal atomic response motion, which leads force. In simple case of one-dimensional molasses, we identify types gradient occur counterpropagating waves have either orthogonal linear polarizations or circular polarizations....

We present a wave-function approach to the study of evolution small system when it is coupled large reservoir. Fluctuations and dissipation originate in this from quantum jumps that occur randomly during time system. This can be applied wide class relaxation operators Markovian regime, equivalent standard master-equation approach. For systems with number states N much larger than unity Monte Carlo less expensive terms calculation treatment. Indeed, wave function involves only components,...

Topological effects can result from a material's intrinsic properties, or be generated by external electromagnetic fields mechanical deformations. Researchers analyze how driven quantum systems lead to new topological states of matter.

There have been significant recent advances in realizing bandstructures with geometrical and topological features experiments on cold atomic gases. We provide an overview of these developments, beginning a summary the key concepts geometry topology for Bloch bands. describe different methods that used to generate novel atoms, as well physical observables allowed their characterization. focus principles underlie experimental approaches, providing conceptual framework within which view...

We show that the dressed-atom approach provides a quantitative understanding of main features radiative dipole forces (mean value, fluctuations, velocity dependence) in high-intensity limit where perturbative treatments are no longer valid. In an inhomogeneous laser beam, energies dressed states vary space, and this gives rise to dressed-state-dependent forces. Spontaneous transitions between lead multivalued instantaneous force fluctuating around mean value. The dependence is related...

We show that two independent Bose-Einstein condensates, each initially containing a well-defined number of atoms, will appear coherent in an experiment measures the beat note between these condensates. investigate role played by atomic interactions within condensate time evolution their relative phase.

We study the rotation of a 87Rb Bose-Einstein condensate confined in quadratic plus quartic potential. This trap configuration allows one to increase frequency gas above frequency. In such fast regime we observe dramatic change appearance quantum gas. The vortices which were easily detectable for slower become much less visible, and their surface density is well below value expected this domain. discuss some possible tracks account effect.

Il semble généralement admis qu'il existe, en théorie quantique du rayonnement, une indétermination dans la séparation des effets respectifs fluctuations vide et de réaction rayonnement.Nous montrons ici que cette est levée si l'on impose aux vitesses variation correspondantes d'être hermitiques (condition nécessaire pour qu'elles soient interprétables physiquement).Cette procédure généralisée au cas d'un petit système S interagissant avec un grand réservoir R, permet séparer deux types...

We present a scheme that produces strong U(1)-like gauge field on cold atoms confined in two-dimensional square optical lattice. Our proposal relies two essential features, long-lived metastable excited state exists for alkaline-earth or ytterbium and an superlattice. As the by Jaksch Zoller (2003 New J. Phys. 5 56), laser-assisted tunneling between adjacent sites creates effective magnetic field. In tight-binding approximation, atomic motion is described Harper Hamiltonian, with flux across...

Phase transitions are ubiquitous in our three-dimensional world. By contrast, most conventional do not occur infinite uniform low-dimensional systems because of the increased role thermal fluctuations. The crossover between these situations constitutes an important issue, dramatically illustrated by Bose-Einstein condensation: a gas strongly confined along one direction space may condense this without exhibiting true long-range order perpendicular plane. Here we explore transverse...

This chapter presents an overview of the specific experimental tools developed in field ultra-cold gases to achieve and probe superfluidity vapours bosonic atoms. First, it describes main cooling techniques: magneto-optical trap, which brings atomic vapour from room temperature down sub-mK range, evaporative scheme, bridges gap superfluid regime. It then proceeds study interaction effects. shows that these play a central role understanding both static dynamic properties trapped Bose–Einstein...

We create supercurrents in annular two-dimensional Bose gases through a temperature quench of the normal-to-superfluid phase transition. detect amplitude and chirality these by measuring spiral patterns resulting from interference cloud with central reference disk. These measurements demonstrate stochastic nature supercurrents. further measure their distribution for different times compare it predictions based on Kibble-Zurek mechanism.

Mixtures of ultracold gases with long-range interactions are expected to open new avenues in the study quantum matter. Natural candidates for this research spin mixtures atomic species large magnetic moments. However, lifetime such assemblies can be strongly affected by dipolar relaxation that occurs spin-flip collisions. Here we present experimental results a mixture composed two lowest Zeeman states $^{162}$Dy atoms, act as dark respect light-induced quadratic effect. We show that, due an...

Using a focused laser beam we stir 87Rb Bose-Einstein condensate confined in magnetic trap. We observe that the steady states of correspond to an elliptic cloud, stationary rotating frame. These depend nonlinearly on stirring parameters (amplitude and frequency), various solutions can be reached experimentally depending path followed this parameter space. dynamically unstable such instabilities lead vortex nucleation condensate.

We study the quadrupole oscillation of a Bose-Einstein condensate 87Rb atoms confined in an axisymmetric magnetic trap, after it has been stirred by auxiliary laser beam. The stirring may lead to nucleation one or more vortices, whose presence is revealed unambiguously precession axes quadrupolar mode. For frequency Omega below single vortex threshold Omega(c), no measurable occurs. Just above angular momentum deduced from approximately Planck's over 2pi. frequencies Omega(c) smooth and...

We present an investigation of the cesium magneto-optical trap, with particular regard to best combination atomic density and temperature that can be produced. Conditions in trap depend on four independent parameters: detuning intensity light, gradient magnetic field, number atoms trapped. have varied all these parameters measured distribution trapped cloud. Both nonlinear variation position restoring force reabsorption photons scattered cloud limit maximum density, we empirical model takes...

The random sequence of pulses given by a photodetector recording the fluorescence light emitted single atom can exhibit periods darkness if two transitions, one weak and strong, are simultaneously driven (Dehmelt's electron shelving scheme). We introduce new statistical functions for characterizing these (average length, repetition rate) we show how to extract spectroscopic information from this type signals.

We measure the energy distribution of a slow Cesium atomic beam when it is chopped into short pulse and we find results which agree well with time-energy uncertainty principle. The chopper consists in an mirror formed by laser evanescent wave whose intensity pulsed. use temporally diffracted to design Young-slit-type interferometer, interfering paths consist trajectories bouncing at two different times on mirror. By changing intensity, can scan phase difference between arms.