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We have developed and characterized an atom-guiding technique that loads $3times10^6$ cold rubidium atoms into hollow-core optical fibre, an order-of-magnitude larger than previously reported results. This result was possible because it was guided by a physically realistic simulation that could provide the specifications for loading efficiencies of 3% and a peak optical depth of 600. The simulation further showed that the demonstrated loading efficiency is limited solely by the geometric overlap of the atom cloud and the optical guide beam, and is thus open to further improvement with experimental modification. The experimental arrangement allows observation of the real-time effects of light-assisted cold atom collisions and background gas collisions by tracking the dynamics of the cold atom cloud as it falls into the fibre. The combination of these observations, and physical understanding from the simulation, allows estimation of the limits to loading cold atoms into hollow-core fibres.
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We demonstrate the production of micron-sized high density atom clouds of interest for meso- scopic quantum information processing. We evaporate atoms from 60 microK, 3x10^14 atoms/cm^3 samples contained in a highly anisotropic optical lattice formed by interfering di racted beams from a holographic phase plate. After evaporating to 1 microK by lowering the con ning potential, in less than a second the atom density reduces to 8x10^13 cm^- 3 at a phase space density approaching unity. Adiabatic recompression of the atoms then increases the density to levels in excess of 1x10^15 cm^-3. The resulting clouds are typically 8 microns in the longest dimension. Such samples are small enough to enable mesoscopic quantum manipulation using Rydberg blockade and have the high densities required to investigate new collision phenomena.
We demonstrate the production of high density cold atom samples (2e14 atoms/cc) in a simple optical lattice formed with YAG light that is diffracted from a holographic phase plate. A loading protocol is described that results in 10,000 atoms per lattice site. Rapid free evaporation leads to phase space densities of 1/150 within 50 msec. The resulting small, high density atomic clouds are very attractive for a number of experiments, including ultracold Rydberg atom physics.
In this article we describe the design, construction and implementation of our ion-atom hybrid system incorporating a high resolution time of flight mass spectrometer (TOFMS). Potassium atoms ($^{39}$K) in a Magneto Optical Trap (MOT) and laser cooled calcium ions ($^{40}$Ca$^+$) in a linear Paul trap are spatially overlapped and the combined trap is integrated with a TOFMS for radial extraction and detection of reaction products. We also present some experimental results showing interactions between $^{39}$K$^+$ and $^{39}$K, $^{40}$Ca$^+$ and $^{39}$K$^+$ as well as $^{40}$Ca$^+$ and $^{39}$K pairs. Finally, we discuss prospects for cooling CaH$^+$ molecular ions in the hybrid ion-atom system.
The research on cold-atom interferometers gathers a large community of about 50 groups worldwide both in the academic and now in the industrial sectors. The interest in this sub-field of quantum sensing and metrology lies in the large panel of possible applications of cold-atom sensors for measuring inertial and gravitational signals with a high level of stability and accuracy. This review presents the evolution of the field over the last 30 years and focuses on the acceleration of the research effort in the last 10 years. The article describes the physics principle of cold-atom gravito-inertial sensors as well as the main parts of hardware and the expertise required when starting the design of such sensors. It then reviews the progress in the development of instruments measuring gravitational and inertial signals, with a highlight on the limitations to the performances of the sensors, on their applications, and on the latest directions of research.
We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped atomic nitrogen and NH molecules at a temperature of $sim 600$~mK. We measure a small N+NH trap loss rate coefficient of $k^{(mathrm{N+NH})}_mathrm{loss} = 8(4) times 10^{-13}$~cm$^{3}$s$^{-1}$. Accurate quantum scattering calculations based on {it ab initio} interaction potentials are in agreement with experiment and indicate the magnetic dipole interaction to be the dominant loss mechanism. Our theory further indicates the ratio of N+NH elastic to inelastic collisions remains large ($>100$) into the mK regime.
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