Wilbert Rooijakkers

Ferromagnetic atom guide with in situ loading

Magneto-optic and magnetostatic trapping is realized near a surface using current carrying coils wrapped around magnetizable cores, with up to 10{sup 9} cesium atoms. Ramping up the current while maintaining optical dissipation leads to tightly confined atom clouds with an aspect ratio of 1:1000. We study the three-dimensional character of the magnetic potential and characterize the atom number and density as functions of the applied current. The field gradient in the transverse dimension has been varied from 1 kG/cm.

Ferromagnets for integrated atom optics

A ferromagnetic atom chip for trapping neutral atoms above a substrate is fabricated and characterized. The chip is capable of generating an anisotropic quadrupole trap with gradients in excess of 15 kG/cm at a distance of more than 100 μm from the surface. This is a promising route to the study of ultracold low dimensional systems, interferometry, and atom optics which require tight confinement, while alleviating the problems of fragmentation seen in wire-based chips.

Mapping a cloud of ultra-cold atoms onto a miniature storage ring

We describe how to realize magnetic and magneto-optical confinement of ultra-cold atoms in a torus with adjustable diameter and how an elliptical cloud of ultra-cold atoms can be adiabatically transformed to have a toroidal shape. An experiment with cold 87Rb atoms demonstrates the feasibility of shape transformations. These techniques can be used for atom interferometry and quantum computation.

A tube-MOT of cesium atoms for loading microstructures

Summary form only given. The magneto-optical trap (MOT) has become the workhorse for many, if not most atom-optics experiments. The traditional MOT uses a pair of coils in anti-Helmholtz configuration to generate a quadrupole field with a typical gradient in the order of 10 Gauss/cm and a typical MOT diameter of 1 mm. In this paper we describe the formation of a surface MOT in a skewed magnetic field, produced by a magnetic laminate.We have imaged the fluorescence of the trapped cloud onto a CCD camera, and made cross sections of the trapped atom cloud.

Tightly confining waveguide for cold atom interferometry

Summary form only given. The integration of atom optics components on a small surface may lead to many new experiments exploring the boundaries of quantum mechanics. Coherent transport of atoms is a key ingredient, and for this reason many groups are developing magnetic waveguides for cold atoms. So far the confinement in these guides is rather poor, resulting in the population of many transverse modes. Typically 10 Gauss over 100 /spl mu/m gives a mode spacing of 40 kHz for Cs atoms. We have developed a new magnetic waveguide, based on ferromagnetic material. At saturation the surface-field is 1 Tesla, which can be applied over a 10 /spl mu/m distance corresponding to a mode spacing of 18 MHz. We use a sandwich of mu-metal and copper sheets to generate a magnetic field. An electrical current of up to 5 A is running through the copper, encircling the mu-metal sheet. This induces an upward or downward field in the mu-metal, similar to a solenoid with a ferromagnetic core. Thin kapton sheets are used to provide electrical isolation.