Bose-Einstein condensates in `giant' toroidal magnetic traps

The experimental realisation of gaseous Bose-Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here we report on progress towards the development of an 87Rb BEC experiment in a large (~10cm diameter) toroidal storage ring. A BEC will be formed at a localised region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are many-fold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.Comment: 5 pages, 3 figures (Figs. 1 and 2 now work

Spatial interference from well-separated condensates

We use magnetic levitation and a variable-separation dual optical plug to obtain clear spatial interference between two condensates axially separated by up to 0.25 mm -- the largest separation observed with this kind of interferometer. Clear planar fringes are observed using standard (i.e. non-tomographic) resonant absorption imaging. The effect of a weak inverted parabola potential on fringe separation is observed and agrees well with theory.Comment: 4 pages, 5 figures - modified to take into account referees' improvement

Demonstration of an inductively coupled ring trap for cold atoms

We report the first demonstration of an inductively coupled magnetic ring trap for cold atoms. A uniform, ac magnetic field is used to induce current in a copper ring, which creates an opposing magnetic field that is time-averaged to produce a smooth cylindrically symmetric ring trap of radius 5 mm. We use a laser-cooled atomic sample to characterize the loading efficiency and adiabaticity of the magnetic potential, achieving a vacuum-limited lifetime in the trap. This technique is suitable for creating scalable toroidal waveguides for applications in matter-wave interferometry, offering long interaction times and large enclosed areas

Extinction by Miscalculation:

Species at Risk Act, Sakinaw sockeye, Cultus sockeye, fisheries management, extinction.

Detecting sterile neutrinos with KATRIN like experiments

A sterile neutrino with mass in the eV range, mixing with the electron antineutrino, is allowed and possibly even preferred by cosmology and oscillation experiments. If such eV-mass neutrinos exist they provide a much better target for direct detection in beta decay experiments than the active neutrinos which are expected to have sub-eV masses. Their relatively high mass would allow for an easy separation from the primary decay signal in experiments such as KATRIN.Comment: 23 pages, 7 figures. References & Figures updated. Text reviewed and revised. Accepted for publication JCA

A large magnetic storage ring for Bose-Einstein condensates

Cold atomic clouds and Bose-Einstein condensates have been stored in a 10cm diameter vertically-oriented magnetic ring. An azimuthal magnetic field enables low-loss propagation of atomic clouds over a total distance of 2m, with a heating rate of less than 50nK/s. The vertical geometry was used to split an atomic cloud into two counter-rotating clouds which were recombined after one revolution. The system will be ideal for studying condensate collisions and ultimately Sagnac interferometry.Comment: 4 pages, 5 figure

Experimental Demonstration of Optimal Unambiguous State Discrimination

We present the first full demonstration of unambiguous state discrimination between non-orthogonal quantum states. Using a novel free space interferometer we have realised the optimum quantum measurement scheme for two non-orthogonal states of light, known as the Ivanovic-Dieks-Peres (IDP) measurement. We have for the first time gained access to all three possible outcomes of this measurement. All aspects of this generalised measurement scheme, including its superiority over a standard von Neumann measurement, have been demonstrated within 1.5% of the IDP predictions

Enhanced frequency up-conversion in Rb vapor

We demonstrate highly efficient generation of coherent 420nm light via up-conversion of near-infrared lasers in a hot rubidium vapor cell. By optimizing pump polarizations and frequencies we achieve a single-pass conversion efficiency of 260% per Watt, significantly higher than in previous experiments. A full exploration of the coherent light generation and fluorescence as a function of both pump frequencies reveals that coherent blue light is generated close to 85Rb two-photon resonances, as predicted by theory, but at high vapor pressure is suppressed in spectral regions that do not support phase matching or exhibit single-photon Kerr refraction. Favorable scaling of our current 1mW blue beam power with additional pump power is predicted.Comment: 6 pages, 4 figures. Modified to include referees' improvement