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Continuous atom laser with Bose–Einstein condensates involving three-body interactions

Journal of Physics B: Atomic, Molecular and Optical Physics, 2010

We demonstrate, through numerical simulations, the emission of a coherent continuous matter wave of constant amplitude from a Bose-Einstein Condensate in a shallow optical dipole trap. The process is achieved by spatial control of the variations of the scattering length along the trapping axis, including elastic three body interactions due to dipole interactions. In our approach, the outcoupling mechanism are atomic interactions and thus, the trap remains unaltered. We calculate analytically the parameters for the experimental implementation of this CW atom laser.

Loading of a Bose-Einstein condensate in the boson accumulation regime

Europhysics Letters (EPL), 2001

We study the optical loading of a trapped Bose-Einstein condensate by spontaneous emission of atoms in excited electronic state in the Boson-Accumulation Regime. We generalize the previous simplified analysis of ref. [Phys. Rev. A 53, 2466 (1996)], to a 3D case in which more than one trap level of the excited state trap is considered. By solving the corresponding quantum many-body master equation, we demonstrate that also for this general situation the photon reabsorption can help to increase the condensate fraction. Such effect could be employed to realize a continuous atom laser, and to overcome condensate losses.

Bose-Einstein Condensation in Atomic Gases

Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326), 1998

This paper presents fundamental principles, characteristics and limitations of various experimental methods of cooling and trapping of neutral atoms by laser light and magnetic fields. In addition to surveying the experimental techniques, basic properties of quantum degenerate gases are discussed with particular emphasis on the Bose-Einstein condensate. We also present main parameters and expected characteristics of the first Polish BEC apparatus build in the National Laboratory of Atomic, Molecular and Optical Physics.

Amplification of Light and Atoms in a Bose-Einstein Condensate

Physical Review Letters, 2000

A Bose-Einstein condensate illuminated by a single off-resonant laser beam ("dressed condensate") shows a high gain for matter waves and light. We have characterized the optical and atom-optical properties of the dressed condensate by injecting light or atoms, illuminating the key role of longlived matter wave gratings produced by the condensate at rest and recoiling atoms. The narrow bandwidth for optical gain gave rise to an extremely slow group velocity of an amplified light pulse (∼ 1 m/s).

Dynamics of a Bose-Einstein condensate at finite temperature in an atom-optical coherence filter

Physical Review A, 2002

The macroscopic coherent tunneling through the barriers of a periodic potential is used as an atomoptical filter to separate the condensate and the thermal components of a 87 Rb mixed cloud. We condense in the combined potential of a laser standing-wave superimposed on the axis of a cigar-shape magnetic trap and induce condensate dipole oscillation in the presence of a static thermal component. The oscillation is damped due to interaction with the thermal fraction and we investigate the role played by the periodic potential in the damping process.

Continuous optical loading of a Bose-Einstein condensate in the Thomas-Fermi regime

Europhysics Letters (EPL), 2003

We discuss the optical loading of a Bose-Einstein condensate in the Thomas-Fermi regime. The condensate is loaded via spontaneous emission from a reservoir of excited-state atoms. By means of a master equation formalism, we discuss the modification of the condensate temperature during the loading. We identify the threshold temperature, T th , above (below) which the loading process leads to cooling (heating), respectively. The consequences of our analysis for the continuous loading of an atom laser are discussed.

Pumping two dilute-gas Bose-Einstein condensates with Raman light scattering

Physical Review A, 1998

We propose an optical method for increasing the number of atoms in a pair of dilute gas Bose-Einstein condensates. The method uses laser-driven Raman transitions which scatter atoms between the condensate and non-condensate atom fractions. For a range of condensate phase differences there is destructive quantum interference of the amplitudes for scattering atoms out of the condensates. Because the total atom scattering rate into the condensates is unaffected the condensates grow. This mechanism is analogous to that responsible for optical lasing without inversion. Growth using macroscopic quantum interference may find application as a pump for an atom laser. 03.75.Fi,42.50.Vk,05.30.Jp,32.80.Pj In the recent experiments demonstrating Bose-Einstein condensation of alkali vapors the first stages of cooling are optical [1]. The final stage utilises evaporation of the hottest atoms out of the trap . Despite the great success of evaporation it has the disadvantage of removing atoms from the system. Consequently alternative final stage cooling methods are being investigated. Velocity selective coherent population trapping (VSCPT) is one optical method potentially capable of cooling to the Bose-Einstein transition point .

The physics of trapped dilute-gas Bose–Einstein condensates

Physics Reports, 1998

Contents 1. Introduction 4 1.1. The experiments 4 1.2. The theory 7 1.3. Outline 7 2. Ground state properties of dilute-gas Bose-Einstein condensates in traps 8 2.1. Hamiltonian: binary collision model 8 2.2. Mean-field theory 9 2.3. Ground state properties of a condensate with repulsive interactions 10 2.4. Ground state properties of a condensate with attractive interactions 14 2.5. Vortex states 16 2.6. Condensate lifetime 18 2.7. Binary mixtures of Bose-Einstein condensates 19 2.8. Beyond mean-field theory: quantum properties of trapped condensates 20 3. Elementary excitations of a trapped Bose-Einstein condensate 29 3.1. Collective excitations of a trapped Bose-Einstein condensate (at ¹"0) 30 3.2. Propagation of sound in a Bose-Einstein condensate 34 3.3. Decay of collective excitations 35 3.4. Collective excitations of trapped double condensates 36 3.5. Finite temperature excitations 37 4. Light scattering from a Bose-Einstein condensate 40 4.1. Coherent light scattering 40 4.2. Incoherent light scattering 42 4.3. Manipulation of the scattering length via light scattering 47 4.4. Nonlinear atom optics 47 4.5. Interaction with quantised cavity radiation fields 48 5. Broken gauge symmetry in pairs of condensates 48 5.1. Interference of two Bose-Einstein condensates and measurement-induced phase 48 5.2. Collapses and revivals of the interference pattern visibility 54 5.3. Pumping of twin-trap condensates 55 5.4. Detection of broken gauge symmetry via light scattering 56 5.5. Pumping of double condensates via light scattering 58 5.6. Establishment of relative phase via light scattering 59 6. Quantum dynamics of a Bose-Einstein condensate in a double-well potential 60 6.1. Coherent quantum tunnelling 60 6.2. Quantum phase between tunnelling Bose-Einstein condensates 62 7. The atom laser 63 7.1. What is an ''atom laser"? 6 3 7.2. Proposed models 64 7.3. An atom laser based on evaporative cooling 65 7.4. An atom laser based on optical cooling 68 7.5. Output couplers for Bose-Einstein condensates 70 7.6. Higher-order coherence of Bose-Einstein condensates 71 8. Conclusions 72 Appendix A. Bose-Einstein condensation in a weakly interacting gas: Bogoliubov theory 73 A.1. Elimination of the condensate mode 74 A.2. Bogoliubov transformation 74 References 76

Optical Devices for Cold Atoms and Bose-Einstein Condensates

2007

The manipulation of cold atoms with optical fields is a very promising technique for a variety of applications ranging from laser cooling and trapping to coherent atom transport and matter wave interferometry. Optical fields have also been proposed as interesting tools for quantum information processing with cold atoms. In this paper, we present a theoretical study of the dynamics of a cold 87Rb atomic cloud falling in the gravity field in the presence of two crossing dipole guides. The cloud is either deflected or split between the two branches of this guide. We explore the possibilities of optimization of this device and present preliminary results obtained in the case of zero-temperature dilute Bose-Einstein condensates.