Single atom dipole trap

Abstract

In the experiment, single Rubidium-87 atoms are loaded out of a molasses of Doppler-cooled atoms into the focus of a Gaussian laser beam created by a single mode laser diode with a wavelength of 856 nm. A confocal microscope outside our vacuum chamber is used to focus the trapping beam to a minimal waist of 3.5 /spl mu/m (thus creating a trap depth of 1-2 mK) and to collect the fluorescence light from the center of the dipole trap. The collected fluorescence light is coupled into a single-mode optical fiber for spatial filtering, and the photons are detected with an avalanche photodiode. With this setup the overall detection efficiency of photons emitted from the trap region is about 0.2%. First experimental results show sub-Poissonian occupation statistics of the dipole trap: only single atoms are observed inside our trap, never two ore more. The measured 1/e lifetime of atoms inside the dipole trap in the presence of cooling light is about 1-2 seconds. To prove that we really observe single atoms inside the trap, a Hanbury-Brown-Twiss measurement of the fluorescence light from the trap will be shown. The trapping of single atoms inside our dipole trap marks the first step towards the investigation of the properties of an entangled atom photon state. Progress in preparing and analyzing single atoms in well defined hyperfine ground states will be reported.