Cesium atoms bouncing in a stable gravitational cavity

Coupled matter-wave solitons on oscillating reflectors under the effects of gravity

We consider coupled matter-waves solitons in Bose-Einstein condensates and study the dynamics under the combined effects of gravity and reflecting potential. The dynamics of matter-wave near a reflector oscillating periodically with time generates the dynamics of a special kind of localized structure called oscillon. We derive a mechanical model for the coupled oscillon dynamics. We pay special attention to the inter-component interaction and see that effective potential depends on the type (repulsive/attractive) and strength of interaction. We find that the inter-component interaction affects the frequency of oscillation and introduces an initial phase-shift between the reflector and the oscillon. This phase-shift, in addition to instantaneous phase change due to the oscillation of the reflector, results in interesting dynamics. The coupled oscillon is found to execute quasi-periodic and chaotic dynamics for both attractive and repulsive inter-component interactions. We analyze the maximum value of Lyapunov exponents and show that the dynamical response of the coupled oscillon depends on the ratio of the center of mass position and their separation.

Retroreflection and diffraction of a Bose-Einstein condensate by evanescent standing wave potential

The characteristic of the angular distributions of accelerated Bose-Einstein condensate (BEC) atoms incidence on the surface is designed using the mathematical modeling method. Here, we proposed the idea to study retroreflection and diffraction of a BEC from an evanescent standing wave potential (ESWP). The ESWP is formed by multiple reflections of the laser beam from the surface of the prism under the influence of gravity. After BEC's reflection and diffraction, the so-called BEC's density rainbow patterns develop due to the interference which depends on the surface structure which we model with the periodic decaying evanescent field. The interaction of accelerated bosonic atoms with a surface can help to demonstrate surface structures or to determine surface roughness, or to build future high spatial resolution and high sensitivity magnetic-field sensors in two-dimensional systems.

Dynamics of self-reinforcing matter-wave in gravito-optical surface trap

We consider matter-wave solitons/oscillons in the presence of gravito-optical surface traps within the framework of mean-field equations. We pay special attention to the dynamics of both solitons and oscillons against the reflecting platform, the position of which can either be varied periodically or quasiperiodically with time. It is seen that with the temporal variation of reflector's vertical position, the dynamics of the soliton can change from periodic to quasiperiodic while that of the oscillon can change from regular to chaotic. We find that the transition from regular to chaotic motion is prominent in Poincaré maps for different relevant recurrence times.

Demonstration of fold and cusp catastrophes in an atomic cloud reflected from an optical barrier in the presence of gravity

We experimentally demonstrate first-order (fold) and second-order (cusp) catastrophes in the density of an atomic cloud reflected from an optical barrier in the presence of gravity and show their corresponding universal asymptotic behavior. These catastrophes, arising from classical dynamics, enable robust, field-free refocusing of an expanding atomic cloud with a wide velocity distribution. Specifically, the density attained at the cusp point in our experiment reached 65% of the peak density of the atoms in the trap prior to their release. We thereby add caustics to the various phenomena with parallels in optics that can be harnessed for manipulation of cold atoms. The structural stability of catastrophes provides inherent robustness against variations in the system's dynamics and initial conditions, making them suitable for manipulation of atoms under imperfect conditions and limited controllability.

Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of (85)Rb and (87)Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum. To maintain excellent optical access to the region surrounding the surface, magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally, we demonstrate the loading of a hybrid optical-magnetic trap with (87)Rb and the creation of Bose-Einstein condensates via forced evaporative cooling close to the dielectric surface.

Experimental observation of a photon bouncing ball

An optical analogue of a quantum particle bouncing on a hard surface under the influence of gravity (a quantum bouncer) is experimentally demonstrated using a circularly curved optical waveguide. Spatially resolved tunneling optical microscopy measurements of multiple beam reflections at the waveguide edge clearly show the appearance of wave packet collapses and revivals (either integer and fractional), corresponding to the full quantum regime of the quantum bouncer.

Suspension of atoms using optical pulses, and application to gravimetry

Atoms from a (87)Rb condensate are suspended against gravity using repeated reflections from a pulsed optical standing wave. Up to 100 reflections are observed, yielding suspension times of over 100 ms. The local gravitational acceleration can be determined from the pulse rate required to achieve suspension. Further, a gravitationally sensitive atom interferometer was implemented using the suspended atoms. This technique could potentially provide a precision measurement of gravity without requiring the atoms to fall a large distance.

Damped bounces of an isolated perfect quantum gas

The issue of the thermalization of an isolated quantum system is addressed by considering a perfect gas confined by gravity and initially trapped above a certain height. As we are interested in the behavior of truly isolated systems, we assume the gas is in a pure state of macroscopically well-defined energy. We show that, in general, for single-particle distributions, such a state is strictly equivalent to the microcanonical mixed state at the same energy. We derive an expression for the time-dependent gas density that depends on the initial gas state only via a few thermodynamic parameters. Though we consider noninteracting particles, the density relaxes into an asymptotic profile, but it is not the thermal equilibrium one determined by the gas energy and particle number.

Collisionless Boltzmann equation with an external periodic traveling force: analytical solution and application to molecular optics

We present an analytical solution to the collisionless Boltzmann equation for describing the distribution function of molecular ensembles subject to an external periodic traveling force of pulsed optical fields. We apply our solution to study a pulsed standing wave mirror for neutral molecules, recently proposed [P. Ryytty et al., Phys. Rev. Lett. 84, 5074 (2000)]. Using our analytical solution we study the effects of the anharmonicity of optical potential on the reflectivity of the molecular mirror and the corresponding optimal pulse duration. We demonstrate that the reflectivity of the molecular mirror can be significantly improved by optimizing the pulse duration of the external optical fields when taking into account the anharmonicity of molecular motion.

Optics with an atom laser beam

We report on the atom optical manipulation of an atom laser beam. Reflection, focusing, and its storage in a resonator are demonstrated. Precise and versatile mechanical control over an atom laser beam propagating in an inhomogeneous magnetic field is achieved by optically inducing spin flips between atomic ground states with different magnetic moment. The magnetic force acting on the atoms can thereby be effectively switched on and off. The surface of the atom optical element is determined by the resonance condition for the spin flip in the inhomogeneous magnetic field. More than 98% of the incident atom laser beam is reflected specularly.

Optical detection of cold atoms without spontaneous emission

We have demonstrated nondestructive detection of cold atoms with a probe laser by a frequency-modulation spectroscopy technique. We were able to tune the probe laser and its sidebands far from atomic resonance to reduce the spontaneous emission to less than 0.2 photon per atom during detection.

Quantum theoretical approach to a near-field optical system

The paper proposes a quantum theoretical formulation of an optical near-field system based on the projection-operator method. Special attention is paid to a nanometric probe tip-quantum mechanical sample system, whose interactions are essential for describing such phenomena as atom guidance and manipulation, or local excitation of a single quantum dot. The relationship to the virtual photon model--an intuitive model--is discussed, and the latter's empirical assumption of the Yukawa-type interaction between probe and sample is justified theoretically. Several applications of the theory are briefly outlined.

Optical trapping and manipulation of neutral particles using lasers

The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary role in areas of the physical and biological sciences. This paper reviews the early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology. Some further major achievements of these rapidly developing methods also are considered.

Specular versus diffuse reflection of atoms from an evanescent-wave mirror

We tested the specularity of the ref lection of slow atoms from an evanescent-wave mirror at normal incidence. In two of the three prisms that we tested the atoms were ref lected diffusely. This nonspecular ref lection appears to be correlated with the rms roughness of the surface supporting the evanescent wave. Only the highest quality surface (rms roughness of the order of 0.1 nm) leads to specular ref lection. This discovery imposes stringent limits on the use of these mirrors in atomic-optics experiments.