Showing papers by "Jörg Schmiedmayer published in 2004"

Atom chips: Fabrication and thermal properties

Abstract: Neutral atoms can be trapped and manipulated with surface mounted microscopic current carrying and charged structures. We present a lithographic fabrication process for such atom chips based on evaporated metal films. The size limit of this process is below 1 μm. At room temperature, thin wires can carry current densities of more than 107A∕cm2 and voltages of more than 500 V. Extensive test measurements for different substrates and metal thicknesses (up to 5 μm) are compared to models for the heating characteristics of the microscopic wires. Among the materials tested, we find that Si is the best suited substrate for atom chips.

Optimized magneto-optical trap for experiments with ultracold atoms near surfaces

Abstract: We present an integrated wire-based magneto-optical trap for the simplified trapping and cooling of large numbers of neutral atoms near material surfaces. With a modified $\mathrm{U}$-shaped current-carrying $\text{Cu}$ structure we collect more than $3\ifmmode\times\else\texttimes\fi{}{10}^{8}$ $^{87}\mathrm{Rb}$ atoms in a mirror magneto-optical trap without using quadrupole coils. These atoms are subsequently loaded to a $\mathrm{Z}$-wire trap where they are evaporatively cooled to a Bose-Einstein condensate close to the surface.

Atom Chips: Fabrication and Thermal Properties

Abstract: Neutral atoms can be trapped and manipulated with surface mounted microscopic current carrying and charged structures. We present a lithographic fabrication process for such atom chips based on evaporated metal films. The size limit of this process is below 1$\mu$m. At room temperature, thin wires can carry more than 10$^7$A/cm$^2$ current density and voltages of more than 500V. Extensive test measurements for different substrates and metal thicknesses (up to 5 $\mu$m) are compared to models for the heating characteristics of the microscopic wires. Among the materials tested, we find that Si is the best suited substrate for atom chips.

Atom fiber for omnidirectional guiding of cold neutral atoms.

Abstract: We present an omnidirectional matter waveguide on an atom chip. The guide is based on a combination of two current-carrying wires and a bias field pointing perpendicular to the chip surface. Thermal atoms are guided for more than two complete turns along a 25-mm-long spiral path (with curve radii as short as 200 µm) at various atom-surface distances (35–450 µm). An extension of the scheme for the guiding of Bose–Einstein condensates is outlined.

Rydberg atoms in magnetic quadrupole traps

Abstract: We investigate the electronic structure and properties of Rydberg atoms exposed to a magnetic quadrupole field It is shown that the spatial as well as generalized time-reversal symmetries lead to a two-fold degeneracy of the electronic states in the presence of the external field A delicate interplay between the Coulomb and magnetic interactions in the inhomogeneous field leads to an unusual weak field splitting of the energy levels as well as complex spatial patterns of the corresponding spin polarization density of individual Rydberg states Remarkably, the magnetic quadrupole field induces a permanent electric-dipole moment of the atom

Rydberg atoms in a magnetic guide

Abstract: We investigate electronically excited atoms in a magnetic guide. It turns out that the Hamiltonian describing this system possesses a wealth of both unitary as well as antiunitary symmetries that constitute an uncommon extensive symmetry group. One consequence is the twofold degeneracy of any energy level. The spectral properties are investigated for a wide range of field gradients and the spatial distributions of the spin polarization are analyzed. Wavelengths, oscillator strengths, and selection rules are provided for the corresponding electromagnetic transitions. The effects due to an additional homogeneous bias field constituting a Ioffe-Pritchard trap are explored equally.

Electronic structure of atoms in magnetic quadrupole traps

Abstract: We investigate the electronic structure and properties of atoms exposed to a magnetic quadrupole field. The spin spatial as well as generalized time-reversal symmetries are established and shown to lead to a twofold degeneracy of the electronic states in the presence of the field. Low lying as well as highly excited Rydberg states are computed and analyzed for a broad regime of field gradients. The delicate interplay between the Coulomb and various magnetic interactions leads to complex patterns of the spatial spin polarization of individual excited states. Electromagnetic transitions in the quadrupole field are studied in detail thereby providing the selection rules and, in particular, the transition wavelengths and corresponding dipole strengths. The peculiar property that the quadrupole magnetic field induces permanent electric dipole moments of the atoms is derived and discussed.

Microtraps and Atom Chips: Toolboxes for Cold Atom Physics

Abstract: Magnetic microtraps and Atom Chips are safe, small-scale, reliable and flexible tools to prepare ultra-cold and degenerate atom clouds as sources for various atom-optical experiments. We present an overview of the possibilities of the devices and indicate how a microtrap can be used to prepare and launch a Bose-Einstein condensate for use in an atom clock or an interferometer.

Failure of geometric electromagnetism in the adiabatic vector Kepler problem

Abstract: The magnetic moment of a particle orbiting a straight current-carrying wire may precess rapidly enough in the wire's magnetic field to justify an adiabatic approximation, eliminating the rapid time dependence of the magnetic moment and leaving only the particle position as a slow degree of freedom. To zeroth order in the adiabatic expansion, the orbits of the particle in the plane perpendicular to the wire are Keplerian ellipses. Higher-order postadiabatic corrections make the orbits precess, but recent analysis of this 'vector Kepler problem' has shown that the effective Hamiltonian incorporating a postadiabatic scalar potential ('geometric electromagnetism') fails to predict the precession correctly, while a heuristic alternative succeeds. In this paper we resolve the apparent failure of the postadiabatic approximation, by pointing out that the correct second-order analysis produces a third Hamiltonian, in which geometric electromagnetism is supplemented by a tensor potential. The heuristic Hamiltonian of Schmiedmayer and Scrinzi is then shown to be a canonical transformation of the correct adiabatic Hamiltonian, to second order. The transformation has the important advantage of removing a 1/r{sup 3} singularity which is an artifact of the adiabatic approximation.

Integration of light and atom optics on an atom chip

Abstract: The whole business of quantum computing with neutral atoms requires accurate preparation and control of their quantum states The envisioned procedure of preparing and operating an atom chip quantum processor involves two main tools at all its stages: quasi‐static electro‐magnetic fields to provide taylored potentials for trapping and guiding atomic qubits and light optical elements for initialisation, gate operation and read‐out Our vision is to implement microoptics directly on the atom chip A large scale quantum processor will probably involve microscale structures such as waveguides or photonic crystals As a final goal even the light sources themselves (diode lasers) might be integrated on the chip The miniaturisation of optical elements already is a rapidly growing field driven by the telecommunication boom We hope to adapt these techniques to develope an atom optical toolbox for Quantum Information Processing Our first experiments aim at the detection of few or even single atoms in miniaturize