181 research outputs found
Cold atoms near superconductors: Atomic spin coherence beyond the Johnson noise limit
We report on the measurement of atomic spin coherence near the surface of a
superconducting niobium wire. As compared to normal conducting metal surfaces,
the atomic spin coherence is maintained for time periods beyond the Johnson
noise limit. The result provides experimental evidence that magnetic near field
noise near the superconductor is strongly suppressed. Such long atomic spin
coherence times near superconductors open the way towards the development of
coherently coupled cold atom / solid state hybrid quantum systems with
potential applications in quantum information processing and precision force
sensing.Comment: Major revisions of the text for submission to New Journal of Physics
8 pages, 4 figure
Bovine Sperm Sexing Alters Sperm Morphokinetics and Subsequent Early Embryonic Development
In artificial insemination the use of sex-sorted bovine sperm results in reduced conception, the causes of which are only partly understood. Therefore, we set out to investigate the effects of sexing on bovine sperm function and early embryonic development. Computer-assisted semen analysis (CASA) of sperm of the same bulls (n = 5), before and after sexing, demonstrated significantly reduced fast (A) and slow (B) progressively motile sperm (p [less than] 0.05) after sexing. Sexed-sperm also revealed significantly less hyperactivated sperm (p [less than] 0.05). As shown by time-lapse videomicroscopy of in vitro produced embryos (n = 360), embryos derived from sexed-sperm displayed significantly increased incidences of arrest at the 4-cell stage (p [less than] 0.05). The relative risk for shrinkage/fusion of blastomeres with subsequent lysis was 1.71 times higher in the embryos derived from sexed-sperm as compared to conventional embryos (p [less than] 0.05) resulting in significantly reduced blastocyst rates (p [less than] 0.001). The relative risk for cleavage was 2.36 times lower in the embryos derived from sex-sorted sperm (p [less than] 0.001). Additionally, sexed-sperm-derived embryos showed reduced survival times (hazard ratio HR = 1.54, p [less than] 0.001) which were bull dependent (p [less than] 0.001). However, the percentage of apoptotic cells was similar to conventional embryos. Furthermore, embryos derived from sexed-sperm were found to reach developmental stages at similar timings as conventional embryos. Our results suggest that reduced conception rates after sexing are due to altered sperm morphokinetics, decreasing the chance of sperm to reach and fertilise the oocyte, and aberrant early embryonic development
GHz Rabi flopping to Rydberg states in hot atomic vapor cells
We report on the observation of Rabi oscillations to a Rydberg state on a
timescale below one nanosecond in thermal rubidium vapor. We use a
bandwidth-limited pulsed excitation and observe up to 6 full Rabi cycles within
a pulse duration of ~ 4 ns. We find good agreement between the experiment and
numerical simulations based on a surprisingly simple model. This result shows
that fully coherent dynamics with Rydberg states can be achieved even in
thermal atomic vapor thus suggesting small vapor cells as a platform for room
temperature quantum devices. Furthermore the result implies that previous
coherent dynamics in single atom Rydberg gates can be accelerated by three
orders of magnitude.Comment: 4 pages, 3 figure
Direct neutron capture of 48Ca at kT = 52 keV
The neutron capture cross section of 48Ca was measured relative to the known
gold cross section at kT = 52 keV using the fast cyclic activation technique.
The experiment was performed at the Van-de-Graaff accelerator, Universitaet
Tuebingen. The new experimental result is in good agreement with a calculation
using the direct capture model. The 1/v behaviour of the capture cross section
at thermonuclear energies is confirmed, and the adopted reaction rate which is
based on several previous experimental investigations remains unchanged.Comment: 9 pages (uses Revtex), 2 postscript figures, accepted for publication
as Brief Report in Phys. Rev.
Trapping of ultra-cold atoms with the magnetic field of vortices in a thin film superconducting micro-structure
We store and control ultra-cold atoms in a new type of trap using magnetic
fields of vortices in a high temperature superconducting micro-structure. This
is the first time ultra-cold atoms have been trapped in the field of magnetic
flux quanta. We generate the attractive trapping potential for the atoms by
combining the magnetic field of a superconductor in the remanent state with
external homogeneous magnetic fields. We show the control of crucial atom trap
characteristics such as an efficient intrinsic loading mechanism, spatial
positioning of the trapped atoms and the vortex density in the superconductor.
The measured trap characteristics are in good agreement with our numerical
simulations.Comment: 4pages, comments are welcom
Partial versus general compulsory solidarity: an experimental analysis
We focus on ways and means of solidarity and their more or less voluntary and involuntary character. Alternative ways of redistribution are modeled by combining redistribution as emergent from a non-discriminatory voluntary contribution mechanism, VCM, with an outside option for a “super-rich”, R, participant to donate to VCM participants. The outsider may discriminate between participants of the VCM on the basis of information accessible at a cost to her. Inclusion in and exclusion from the VCM are involuntary while contributions in it are voluntary. How involuntary inclusion of R in VCM affects her discriminatory voluntary donations and contribution behavior is explored experimentally
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