Abstract
We report on the simultaneous observation from four directions of the fluorescence of single 87Rb atoms trapped at the common focus of four high numerical aperture (NA=0.5) aspheric lenses. We use an interferometrically-guided pick-and-place technique to precisely and stably position the lenses along the four cardinal directions with their foci at a single central point. The geometry gives right angle access to a single quantum emitter, and will enable new trapping, excitation, and collection methods. The fluorescence signals indicate both sub-Poissonian atom number statistics and photon anti-bunching, showing suitability for cold atom quantum optics.
Highlights
Trapped neutral atoms are an important platform for quantum technologies and studies of fundamental quantum optics
Short-range dipoledipole interactions are predicted to dramatically modify the optical properties of matter in sub-wavelength arrays of single atoms [11]. These processes can be studied at the single-quantum level because high numerical aperture optics enable strong single-atom/single-photon interactions in free-space [12, 13], without optical cavities
After considering the commercially-available models, we selected one, Model 352240 from LightPath Technologies, NA = 0.5, that has already been used in similar experiments [30], and has proven to be diffraction limited over a wide spectral range and a relatively large field of view: ±25 μm in the transverse directions [31] and ±47 μm in the longitudinal direction
Summary
Trapped neutral atoms are an important platform for quantum technologies and studies of fundamental quantum optics. We use interferometric methods to precisely position and align the four lenses This approach achieves simultaneous, diffraction-limited performance at NA = 0.5 for wavelengths 780 nm, 795 nm and 852 nm, enabling strong interaction with the D1 and. We confirm the diffraction-limited performance with fluorescence measurements on a single atom trapped at the mutual focus of the four lenses. We place it in ultra-high vacuum (UHV) with a source of 87Rb and magnetic field controls, to produce a magneto-optical trap (MOT) around the focus of the four lenses. Observation of equal fluorescence signals from the two trap-axis lenses, and equal but weaker fluorescence signals from the two right-angle lenses, agrees with modeling of diffraction-limited collection from the prolate atomic probability distribution (long axis along the trap axis), that results from trapping in the single-beam FORT. Interference of light emitted in different directions can be achieved if the probability distribution is further compressed by a standing-wave [21] or crossed-beam [29] FORT
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