We describe the fabrication and construction of a setup for creating lattices of magnetic microtraps for ultracold atoms on an atom chip. The lattice is defined by lithographic patterning of a permanent magnetic film. Patterned magnetic-film atom chips enable a large variety of trapping geometries over a wide range of length scales. We demonstrate an atom chip with a lattice constant of 10 μm, suitable for experiments in quantum information science employing the interaction between atoms in highly excited Rydberg energy levels. The active trapping region contains lattice regions with square and hexagonal symmetry, with the two regions joined at an interface. A structure of macroscopic wires, cutout of a silver foil, was mounted under the atom chip in order to load ultracold 87 Rb atoms into the microtraps. We demonstrate loading of atoms into the square and hexagonal lattice sections simultaneously and show resolved imaging of individual lattice sites. Magnetic-film lattices on atom chips provide a versatile platform for experiments with ultracold atoms, in particular for quantum information science and quantum simulation. © 2014 AIP Publishing LLC.

Trapping a Rydberg atom close to a surface is an important step towards the realisation of many proposals of quantum information or hybrid quantum systems. One of the challenges in these experiments is to overcome the electric field emanating from contaminations on the surface. Here we report on measurements of an electric field created by 87 Rb atoms absorbed on a 25 nm thick layer of SiO 2 , covering a 90 nm layer of Au. The electric field is measured using a two-photon transition to the 23D 5/2 and 25S 1/2 state. The electric field value that we measure is higher than typical values measured above metal surfaces, but is consistent with other measurements above SiO 2 surfaces. In addition, we measure the temporal behaviour of the field and observe that we can reduce it in a single experimental cycle, using UV light or by mildly heating the surface, whereas the buildup of the field takes thousands of cycles. We explain these results by a change in the ad-atoms distribution on the surface. These results indicate that the stray electric field can be reduced, opening new possibilities for experiments with trapped Rydberg atoms near surfaces. † Present address: CQ Center for Collective Quantum Phenomena and Their Applications,

We observe a density-dependent collective suppression of optical pumping between the hyperfine ground states in an array of submicrometer-sized clouds of dense and cold rubidium atoms. The suppressed Raman transition rate can be explained by strong resonant dipole-dipole interactions that are enhanced by increasing atom density, and are already significant at densities of 0.1k 3 , where k denotes the resonance wavenumber. The observations are consistent with stochastic electrodynamics simulations that incorporate the effects of population transfer via internal atomic levels embedded in a coupled-dipole model.

Experiments handling Rydberg atoms near surfaces must necessarily deal with the high sensitivity of Rydberg atoms to (stray) electric fields that typically emanate from adsorbates on the surface. We demonstrate a method to modify and reduce the stray electric field by changing the adsorbates distribution. We use one of the Rydberg excitation lasers to locally affect the adsorbed dipole distribution. By adjusting the averaged exposure time we change the strength (with the minimal value less than 0.2 V/cm at 78 µm from the chip) and even the sign of the perpendicular field component. This technique is a useful tool for experiments handling Ryberg atoms near surfaces, including atom chips. arXiv:1710.05301v1 [physics.atom-ph]

The kinetics of a key noncovalent, hydrogen bonding interaction was studied in situ using coherent anti-stokes Raman scattering (CARS) microspectroscopy in a microfluidic device. The association of model compounds, pyridine and hexafluoroisopropanol, was quantitatively monitored with submicrometer resolution. Lower limits for the very high formation and dissociation rate constants of the model 1:1 pyridine-hexafluoroisopropanol hydrogen bonded complex in dichloromethane-d2 were determined to be k1 > 10(5) M(-1)s(-1) and k-1 > 333.3 s(-1), respectively.