Search

We discuss the experimental feasibility of quantum simulation with trapped ion crystals, using magnetic field gradients. We describe a micro structured planar ion trap, which contains a central wire loop generating a strong magnetic gradient of about 20 T/m in an ion crystal held about 160 μm above the surface. On the theoretical side, we extend a proposal about spin-spin interactions via magnetic gradient induced coupling (MAGIC) [J. Phys. B At. Mol. Opt. Phys. 42, 154009 (2009)]. We describe aspects where planar ion traps promise novel physics: spin-spin coupling strengths of transversal eigenmodes exhibit significant advantages over the coupling schemes in longitudinal direction that have been previously investigated. With a chip device and a magnetic field coil with small inductance, a resonant enhancement of magnetic spin forces through the application of alternating magnetic field gradients is proposed. Such resonantly enhanced spin-spin coupling may be used, for instance, to create Schrödinger cat states. Finally we investigate magnetic gradient interactions in two-dimensional ion crystals, and discuss frustration effects in such two-dimensional arrangements. [ABSTRACT FROM AUTHOR]

Superconductors are considered in view of applications to atom chip devices. The main features of magnetic traps based on superconducting wires in the Meissner and mixed states are discussed. The former state may mainly be interesting for improved atom optics, while in the latter, cold atoms may provide a probe of superconductor phenomena. The properties of a magnetic side guide based on a single superconducting strip wire placed in an external magnetic field are calculated analytically and numerically. In the mixed state of type II superconductors, inhomogeneous trapped magnetic flux, relaxation processes and noise caused by vortex motion are posing specific challenges for atom trapping. [ABSTRACT FROM AUTHOR]

We present experimental results demonstrating enhanced current modulation of an antireflection-coated edge-emitting laser diode placed in an external cavity. By eliminating the internal cavity of the laser diode and matching the external cavity free spectral range to the modulation frequency we have increased the modulation response up to nearly complete carrier suppression. We demonstrate the tunability of this enhanced modulation over a range of more than 3 GHz. The power of the modulated beam has been measured to be 10 mW. We have recorded a beat note between the first two optical sidebands of width 1 Hz at 6.834 GHz (corresponding to the hyperfine splitting of the 87Rb ground state). This technique enables the generation of two high-power phase-locked beams for coherent manipulation of atomic states. [ABSTRACT FROM AUTHOR]

We analyze atom-surface magnetic interactions on atom chips where the magnetic trapping potentials are produced by current carrying wires made of electrically anisotropic materials. We discuss a theory for time dependent fluctuations of the magnetic potential, arising from thermal noise originating from the surface. It is shown that using materials with a large electrical anisotropy results in a considerable reduction of heating and decoherence rates of ultra-cold atoms trapped near the surface, of up to several orders of magnitude. The trap loss rate due to spin flips is expected to be significantly reduced upon cooling the surface to low temperatures. In addition, the electrical anisotropy significantly suppresses the amplitude of static spatial potential corrugations due to current scattering within imperfect wires. Also the shape of the corrugation pattern depends on the electrical anisotropy: the preferred angle of the scattered current wave fronts can be varied over a wide range. Materials, fabrication, and experimental issues are discussed, and specific candidate materials are suggested. [ABSTRACT FROM AUTHOR]

We discuss the influence of the material type in metal wires to the electromagnetic fluctuations in magnetic microtraps close to the surface of an atom chip. We show that significant reduction of the magnetic noise can be achieved by replacing the pure noble metal wires with their dilute alloys. The alloy composition provides an additional degree of freedom which enables a controlled reduction of both magnetic noise and resistivity if the atom chip is cooled. In addition, we provide a careful re-analysis of the magnetically induced trap loss observed by Yu-Ju Lin et al. [Phys. Rev. Lett. 92, 050404 (2004)] and find good agreement with an improved theory. [ABSTRACT FROM AUTHOR]

The limitations for the coherent manipulation of neutral atoms with fabricated solid-state devices, so-called ‘atom chips’, are addressed. Specifically, we examine the dominant decoherence mechanism, which is due to the magnetic noise originating from the surface of the atom chip. It is shown that the contribution of fluctuations in the chip wires at the shot-noise level is not negligible. We estimate the coherence times and discuss ways to increase them. Our main conclusion is that future advances should allow for coherence times as long as 1 s, a few μm away from the surface. [ABSTRACT FROM AUTHOR]

Following almost a century of debate on possible “independent of measurement" elements of reality, or “induced" elements of reality - originally invoked as an ad-hoc collapse postulate, we propose a novel line of interference experiments which may be able to examine the regime of induced elements of reality. At the basis of the proposed experiment, lies the hypothesis that models of “induced" elements of reality should exhibit symmetry breaking within quantum evolution. The described symmetry experiment is thus aimed at being able to detect and resolve spatial symmetry breaking signatures. The proposed experiment stands at the edge of present day technological abilities and will be, so we believe, realizable in the near future. [ABSTRACT FROM AUTHOR]

Abstract. A large variety of trapping and guiding potentials can be designed by bringing cold atoms close to charged or current carrying material objects. We describe the basic principles of constructing microscopic traps and guides and how to load atoms into them. The simplicity and versatility of these methods will allow for miniaturization and integration of atom optical elements into matter-wave quantum circuits on Atom Chips. These could form the basis for robust and widespread applications in atom optics, ranging from fundamental studies in mesoscopic physics to possibly quantum information systems. [ABSTRACT FROM AUTHOR]

The teratogenicity of bromocryptine (CB-154, Sandoz, Basel) was studied in three groups of pregnant rats which received 0.625 mg/kg/day, 1.25 mg/kg/day, and 2.5 mg/kg/day bromocryptine, respectively, i.m. and in a control group of pregnant rats which received the solvent only. There was no significant difference in the birth rate, fetal resorption rate, male/female ratio and malformation rate between the four groups. There was a significant elevation of the average fetal and placental weights between the experimental and the control fetuses. Bromocryptine does cross the placental barrier and in our study might act as growth promoting factor. [ABSTRACT FROM AUTHOR]

The in vitro synthesis of RNA in the human placental tissue, incubated in organ culture, was investigated. We followed the synthesis of the poly A(-) and poly A(+) RNA fractions, and investigated the distribution of the newly synthesized RNA among the subcellular fractions isolated from first and third trimester placentas. The poly A(-) RNA was the major fraction of the RNA synthesized in vitro. The incorporation of [H]uridine into the poly A(+) RNA fraction was very low. As protein synthesis occurred during the entire incubation period, we suggest the presence of a pool of mRNA molecules in the form of mRNP particles. [ABSTRACT FROM AUTHOR]

Placental tissue slices from first trimester placentas synthesize and secrete proteins labeled by radioactive glucosamine are preferentially secreted as compared to proteins in general. One of the proteins synthesized and secreted is hCG. Processing and secretion of proteins, including hCG, by the tissue slices need a two-hour period. Both secretion and glycosylation of the protein can take place independently of protein synthesis. A method was developed for the specific determination of newly synthesized radioactive hCG in placental tissue. [ABSTRACT FROM AUTHOR]