Atoms can be trapped and guided using nanofabricated wires on surfaces, achieving the scales required by quantum information proposals. These atom chips form the basis for robust and widespread applications of cold atoms ranging from atom optics to fundamental questions in mesoscopic physics, and possibly quantum information systems.

We have designed and experimentally studied a simple beam splitter for atoms guided on an Atom Chip, using a current carrying Y-shaped wire and a bias magnetic field. This beam splitter and other similar designs can be used to build atom optical elements on the mesoscopic scale, and integrate them in matterwave quantum circuits.

We demonstrate guiding of cold neutral atoms along a current carrying wire. Atoms either move in Kepler-like orbits around the wire or are guided in a potential tube on the side of the wire which is created by applying an additional homogeneous bias field. These atom guides are very versatile and promising for applications in atom optics. PACS number(s): 03.75. Be, 39.10.+j, 32.80.Pj, In atom optics [1] it is usually desirable to separate atoms as far as possible from material objects in order to obtain pure and isolated quantum systems. With cooling and trapping techniques [2] being well established, there is now an interest in bringing the atoms close to material macroscopic objects. The proximity of the atoms to the object allows the design of tailored and easily controllable potentials which can be used to build novel atom optical elements.In this letter we demonstrate two simple and versatile atom guides that are based on magnetic trapping potentials created by a thin current carrying wire: The 'Kepler guide' and the 'side guide'. In our experiments we study the transport of cold lithium atoms from a magneticoptical trap in these guiding potentials. We were able to measure scaling properties and extract characteristic atomic velocity distributions for each guide. The 'side guide' is especially interesting because it can easily be miniaturized and combined with other guides to form mesoscopic atom optical networks.We start with discussing the interaction of a neutral atom and a current carrying wire and then describe our guiding experiments.Kepler guide: The magnetic field of a rectilinear current I is given by:whereê ϕ is the circular unit vector in cylindrical coordinates. An atom with total spin S and magnetic moment µ = g S µ B S experiences the interaction potentialwhere S is the projection of S on B. In general the vector coupling µ · B results in a very complicated motion for the atom. However, in our experiments the Larmor precession (ω L ) of the magnetic moment is much faster than the apparent change of direction of the magnetic field in the rest frame of the atom (ω B ) and an adiabatic approximation can be applied. S is then constant and the atom can be described as moving in a scalar 1/r potential. For µ "parallel" to B, ( µ · B > 0), the atom is in its high field seeking state, and the interaction between the atom and the wire is attractive (see Fig. 1). The atoms in this state can be trapped and move in Kepler-like orbits around the wire [3][4][5][6]. b)

We experimentally and numerically investigate the quantum accelerator mode dynamics of an atom optical realization of the quantum delta-kicked accelerator, whose classical dynamics are chaotic. Using a Ramsey-type experiment, we observe interference, demonstrating that quantum accelerator modes are formed coherently. We construct a link between the behavior of the evolution's fidelity and the phase space structure of a recently proposed pseudoclassical map, and thus account for the observed interference visibilities.

We present detailed observations of the quantum delta-kicked rotor in the vicinity of a quantum resonance. Our experiment consists of an ensemble of cold cesium atoms subject to a pulsed off-resonant standing wave of light. We measure the mean energy and show clearly that at the quantum resonance it is a local maximum. We also examine the effect of noise on the system and find that the greatest sensitivity to this occurs at the resonances. This makes these regions ideal for examining quantum-classical correspondence. A picture based on diffraction is developed which allows the experiments to be readily understood.