No abstract

Bose-Einstein condensation has been achieved in a magnetic surface microtrap with 4 x 10(5) (87)Rb atoms. The strongly anisotropic trapping potential is generated by a microstructure which consists of microfabricated linear copper conductor of widths ranging from 3 to 30 microm. After loading a high number of atoms from a pulsed thermal source directly into a magneto-optical trap the magnetically stored atoms are transferred into the microtrap by adiabatic transformation of the trapping potential. In the microtrap the atoms are cooled to condensation using forced rf-evaporation. The complete in vacuo trap design is compatible with ultrahigh vacuum below 2 x 10(-11) mbar.

We have investigated Bose-Einstein condensates and ultra cold atoms in the vicinity of a surface of a magnetic microtrap. The atoms are prepared along copper conductors at distances to the surface between 300 µm and 20 µm. In this range, the lifetime decreases from 20 s to 0.7 s showing a linear dependence on the distance to the surface. The atoms manifest a weak thermal coupling to the surface, with measured heating rates remaining below 500 nK/s. In addition, we observe a periodic fragmentation of the condensate and thermal clouds when the surface is approached.PACS numbers: 03.75. Fi, 03.75.Be, 34.50.Dy, Micropotentials have proven to be a powerful tool to manipulate and structure the shape of a Bose-Einstein condensate [1] on a length scale shorter than the coherence length of the condensate. Besides the manipulation with light [2,3,4,5,6], current carrying microstructures [7] are particularly interesting since they can be tailored in an arbitrary way, providing a variety of potential geometries. In previous experiments with magnetic microtraps the work was mainly focused on the demonstration of different trapping geometries, loading schemes and guiding principles [8,9,10,11,12,13,14]. The recent realization of Bose-Einstein condensates in magnetic microtraps [15,16] however provides new possibilities to control coherent matter on the micrometer scale. Coherent beam splitters, on-chip interferometers or quantum dots may become feasible. In current experimental setups, the dimensions of the conductors vary from 1 µm to 100 µm and the distance between the trap minimum and the surface is typically of the same size. At such small distances the atoms are affected by the nearby surface. For experiments with coherent matter waves or even single atoms in microfabricated traps an understanding of the mutual influences of the atoms and the surface is highly desirable.In this letter, we describe three effects on ultra cold atoms which appear in the vicinity of the surface of a magnetic microtrap. We observe a decrease of the lifetime of the atomic cloud which scales roughly linearly with the distance to the surface. At 20 µm, the lifetime is reduced to less than 1 s, which has to be compared to the "far distance" value of 100 s. Simultaneously, an increased heating rate is observed which, however, does not exceed 500 nK/s. Furthermore, a periodic fragmentation of both, the thermal cloud and the condensate occurs when the surface is approached at distances of about 250 µm. This gives strong evidence for additional potentials arising from the nearby surface.In our experiment, the microtrap is generated by a microstructure which consists of seven parallel copper conductors with widths of 3 µm, 11 µm and 30 µm, a height of 2.5 µm and a length of 25 mm [17]. The conductors are electroplated on an Al 2 O 3 ceramic substrate.An additional copper wire with a circular diameter of 90 µm is mounted parallel to the microstructure, allowing for reference measurements. The free surface of the wire is in the plane of the fabricated c...

We investigate the many-body generalization of the orthogonality catastrophe by studying the generalized Loschmidt echo of Luttinger liquids (LLs) after a global change of interaction. It decays exponentially with system size and exhibits universal behaviour: the steady state exponent after quenching back and forth n-times between 2 LLs (bang-bang protocol) is 2n-times bigger than that of the adiabatic overlap, and depends only on the initial and final LL parameters. These are corroborated numerically by matrix-product state based methods of the XXZ Heisenberg model. An experimental setup consisting of a hybrid system containing cold atoms and a flux qubit coupled to a Feshbach resonance is proposed to measure the Loschmidt echo using rf spectroscopy or Ramsey interferometry. Introduction. The long coherence times and the possibility to control parameters very accurately in optical lattices allow to simulate exciting non-equilibrium effects in quantum many body systems. Particular attention has been devoted to the evolution of quantum stated after quenches [1] in which a parameter in the Hamiltonian is changed either suddenly or gradually. By measuring the Loschmidt echo (LE), it is possible to get insight into the dynamical properties of the quantum-many body state.The LE is defined as the overlap of two wave functions, |Ψ 0 (t) and |Ψ(t) , evolved from the same initial state, but with different Hamiltonians, H 0 and H,

The coherence of quantum systems is crucial to quantum information processing. Although superconducting qubits can process quantum information at microelectronics rates, it remains a challenge to preserve the coherence and therefore the quantum character of the information in these systems. An alternative is to share the tasks between different quantum platforms, for example, cold atoms storing the quantum information processed by superconducting circuits. Here we characterize the coherence of superposition states of 87 Rb atoms magnetically trapped on a superconducting atom chip. We load atoms into a persistent-current trap engineered next to a coplanar microwave resonator structure, and observe that the coherence of hyperfine ground states is preserved for several seconds. We show that large ensembles of a million of thermal atoms below 350 nK temperature and pure Bose-Einstein condensates with 3.5 Â 10 5 atoms can be prepared and manipulated at the superconducting interface. This opens the path towards the rich dynamics of strong collective coupling regimes.