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

Exploring the Association Between Rosacea and Parkinson Disease:A Danish Nationwide Cohort Study

Importance: The pathogenesis of rosacea is unclear, but increased matrix metalloproteinase target tissue activity appears to play an important role. Parkinson disease and other neurodegenerative disorders also display increased matrix metalloproteinase activity that contribute to neuronal loss.Objective: To investigate the risk of incident (new-onset) Parkinson disease in patients with rosacea.Design, Setting, and Participants: A nationwide cohort study of the Danish population was conducted using individual-level linkage of administrative registers. All Danish citizens 18 years or older from January 1, 1997, to December 31, 2011 (N = 5 472 745), were included. Data analysis was conducted from June 26 to July 27, 2015.Main Outcomes and Measures: The main outcome was a diagnosis of Parkinson disease. Incidence rates (IRs) per 10 000 person-years were calculated, and incidence rate ratios (IRRs) adjusted for age, sex, socioeconomic status, smoking, alcohol abuse, medication, and comorbidity were estimated by Poisson regression models.Results: A total of 5 404 692 individuals were included in the reference population; of these, 22 387 individuals (9812 [43.8%] women; mean [SD] age at diagnosis, 75.9 [10.2] years) received a diagnosis of Parkinson disease during the study period and 68 053 individuals (45 712 [67.2%] women; mean age, 42.2 [16.5] years) were registered as having rosacea. The IRs of Parkinson disease per 10 000 person-years were 3.54 (95% CI, 3.49-3.59) in the reference population and 7.62 (95% CI, 6.78-8.57) in patients with rosacea. The adjusted IRR of Parkinson disease was 1.71 (95%, CI 1.52-1.92) in patients with rosacea compared with the reference population. There was a 2-fold increased risk of Parkinson disease in patients classified as having ocular rosacea (adjusted IRR, 2.03 [95% CI, 1.67-2.48]), and tetracycline therapy appeared to reduce the risk of Parkinson disease (adjusted IRR, 0.98 [95% CI, 0.97-0.99]).Conclusions and Relevance: Rosacea constitutes an independent risk factor for Parkinson disease. This association could be due to shared pathogenic mechanisms involving elevated matrix metalloproteinase activity. The clinical consequences of this association require further study.</p

Diffraction grating characterisation for cold-atom experiments

We have studied the optical properties of gratings micro-fabricated into semiconductor wafers, which can be used for simplifying cold-atom experiments. The study entailed characterisation of diffraction efficiency as a function of coating, periodicity, duty cycle and geometry using over 100 distinct gratings. The critical parameters of experimental use, such as diffraction angle and wavelength are also discussed, with an outlook to achieving optimal ultracold experimental conditions

Laser frequency stabilization to a single ion

A fundamental limit to the stability of a single-ion optical frequency standard is set by quantum noise in the measurement of the internal state of the ion. We discuss how the interrogation sequence and the processing of the atomic resonance signal can be optimized in order to obtain the highest possible stability under realistic experimental conditions. A servo algorithm is presented that stabilizes a laser frequency to the single-ion signal and that eliminates errors due to laser frequency drift. Numerical simulations of the servo characteristics are compared to experimental data from a frequency comparison of two single-ion standards based on a transition at 688 THz in 171Yb+. Experimentally, an instability sigma_y(100 s)=9*10^{-16} is obtained in the frequency difference between both standards.Comment: 15 pages, 5 figures, submitted to J. Phys.

Utilising diffractive optics towards a compact, cold atom clock

Laser cooled atomic samples have resulted in profound advances in precision metrology [1], however the technology is typically complex and bulky. In recent publications we described a micro-fabricated optical element, that greatly facilitates miniaturisation of ultra-cold atom technology [2], [3], [4], [5]. Portable devices should be feasible with accuracy vastly exceeding that of equivalent room-temperature technology, with a minimal footprint. These laser cooled samples are ideal for atomic clocks. Here we will discuss the implementation of our micro-fabricated diffractive optics towards building a robust, compact cold atom clock

Comparative simulations of Fresnel holography methods for atomic waveguides

We have simulated the optical properties of micro-fabricated Fresnel zone plates (FZPs) as an alternative to spatial light modulators (SLMs) for producing non-trivial light potentials to trap atoms within a lensless Fresnel arrangement. We show that binary (1-bit) FZPs with wavelength (1μm) spatial resolution consistently outperform kinoforms of spatial and phase resolution comparable to commercial SLMs in root mean square error comparisons, with FZP kinoforms demonstrating increasing improvement for complex target intensity distributions. Moreover, as sub-wavelength resolution microfabrication is possible, FZPs provide an exciting possibility for the creation of static cold-atom trapping potentials useful to atomtronics, interferometry, and the study of fundamental physics

Experimental investigation of cut-off phenomena in non-linear photonic crystal fibers

The modal cut-off is investigated experimentally in a series of high quality non-linear photonic crystal fibers. We demonstrate a suitable measurement technique to determine the cut-off wavelength and verify it by inspecting the near field of the modes that may be excited below and above the cut-off. We observe a double peak structure in the cut-off spectra, which is attributed to a splitting of the higher order modes. The cut-off is measured for seven different fiber geometries with different pitches and relative hole size, and a very good agreement with recent theoretical work is found.Comment: 3 pages including 1 table and 4 figures. Accepted for Optics Letter