A Investigation of the Statistical Properties of Fluorescence from Single Atoms.

A.S. Shumovsky, Tran Quang

Božena Sobolewska, Roman Sobolewski

Martina Merz, Axel Schenzle

F. Ruschewitz, D. Bettermann, Jin-Long Peng +1 more

Single neutral atoms have been stored in a magneto-optical trap and imaged with the help of a CCD camera. The trapping of individual atoms is marked by steps in the fluorescence signal corresponding to the capture or loss of a single atom. The statistics of these capture and loss processes is explained by means of a birth-death model. The spatial distribution and the trap losses are investigated for the single-atom case and compared with the behaviour of a cloud of up to 2·10 5 atoms.

Jürgen Volz, M. Weber, R. Reicold +3 more

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.

HERBERT WALTHER

Modern methods of laser spectroscopy allow the study of single atoms or ions in an unperturbed environment. This has opened up interesting new experiments, an among them is the detailed study of radiation-atom coupling. This chapter reviews the following two experiments of this type: the single-atom maser and the study of the resonance fluorescence of a single stored ion. The simplest and most fundamental system for studying radiation-matter coupling is a single two-level atom interacting with a single mode of an electromagnetic field in a cavity. There is another aspect of the single-atom maser which is very interesting: the non-classical statistics of the photons in the cavity. The results obtained for the single-atom maser also give a new insight into the statistical properties of masers and lasers. A problem in radiation-matter interaction which has received a lot of interest is resonance fluorescence. The experiments to investigate antibunching in resonance fluorescence have been performed by means of laser-excited collimated atomic beams.