Atom In Tweezer Research Articles

Narrow-line imaging of single strontium atoms in shallow optical tweezers

Single strontium atoms held in optical tweezers have so far only been imaged using the broad ${}^{1}{S}_{0}{\text{\ensuremath{-}}}^{1}{P}_{1}\phantom{\rule{0.16em}{0ex}}$transition. For Yb, use of the narrow (183-kHz wide) ${}^{1}{S}_{0}{\text{\ensuremath{-}}}^{3}{P}_{1}\phantom{\rule{0.16em}{0ex}}$transition for simultaneous imaging and cooling has been demonstrated in tweezers with a magic wavelength for the imaging transition. We demonstrate high-fidelity imaging of single Sr atoms using its even narrower (7.4-kHz wide) ${}^{1}{S}_{0}{\text{\ensuremath{-}}}^{3}{P}_{1}\phantom{\rule{0.16em}{0ex}}$transition. The atoms are trapped in nonmagic-wavelength tweezers. We detect the photons scattered during Sisyphus cooling, thus keeping the atoms near the motional ground state of the tweezer throughout imaging. The fidelity of detection is 0.9991(4) with a survival probability of 0.97(2). An atom in a tweezer can be held under imaging conditions for 79(3) seconds allowing for hundreds of images to be taken, limited mainly by background gas collisions. The use of a fully closed (cycling) transition for imaging will provide a useful tool for state specific detection. We detect atoms in an array of 36 tweezers with 813.4-nm light and trap depths of 135(20) $\ensuremath{\mu}$K. This trap depth is three times shallower than typically used for imaging on the broad ${}^{1}{S}_{0}{\text{\ensuremath{-}}}^{1}{P}_{1}\phantom{\rule{0.16em}{0ex}}$transition. Narrow-line imaging opens the possibility to even further reduce this trap depth, as long as all trap frequencies are kept larger than the imaging transition linewidth. Imaging using a narrow-linewidth transition in a nonmagic-wavelength tweezer also allows for selective imaging of a given tweezer. As a demonstration, we selectively image (hide) a single tweezer from the array. This provides a useful tool for quantum error correction protocols.

2000-Times Repeated Imaging of Strontium Atoms in Clock-Magic Tweezer Arrays.

We demonstrate single-atom resolved imaging with a survival probability of 0.99932(8) and a fidelity of 0.99991(1), enabling us to perform repeated high-fidelity imaging of single atoms in tweezers thousands of times. We further observe lifetimes under laser cooling of more than seven minutes, an order of magnitude longer than in previous tweezer studies. Experiments are performed with strontium atoms in 813.4nm tweezer arrays, which is at a magic wavelength for the clock transition. Tuning to this wavelength is enabled by off-magic Sisyphus cooling on the intercombination line, which lets us choose the tweezer wavelength almost arbitrarily. We find that a single not retroreflected cooling beam in the radial direction is sufficient for mitigating recoil heating during imaging. Moreover, this cooling technique yields temperatures below 5 μK, as measured by release and recapture. Finally, we demonstrate clock-state resolved detection with average survival probability of 0.996(1) and average state detection fidelity of 0.981(1). Our work paves the way for atom-by-atom assembly of large defect-free arrays of alkaline-earth atoms, in which repeated interrogation of the clock transition is an imminent possibility.

Alkaline-Earth Atoms in Optical Tweezers

We demonstrate single-shot imaging and narrow-line cooling of individual alkaline earth atoms in optical tweezers; specifically, strontium-88 atoms trapped in $515.2~\text{nm}$ light. We achieve high-fidelity single-atom-resolved imaging by detecting photons from the broad singlet transition while cooling on the narrow intercombination line, and extend this technique to highly uniform two-dimensional arrays of $121$ tweezers. Cooling during imaging is based on a previously unobserved narrow-line Sisyphus mechanism, which we predict to be applicable in a wide variety of experimental situations. Further, we demonstrate optically resolved sideband cooling of a single atom close to the motional ground state of a tweezer. Precise determination of losses during imaging indicate that the branching ratio from $^1$P$_1$ to $^1$D$_2$ is more than a factor of two larger than commonly quoted, a discrepancy also predicted by our ab initio calculations. We also measure the differential polarizability of the intercombination line in a $515.2~\text{nm}$ tweezer and achieve a magic-trapping configuration by tuning the tweezer polarization from linear to elliptical. We present calculations, in agreement with our results, which predict a magic crossing for linear polarization at $520(2)~\text{nm}$ and a crossing independent of polarization at 500.65(50)nm. Our results pave the way for a wide range of novel experimental avenues based on individually controlled alkaline earth atoms in tweezers -- from fundamental experiments in atomic physics to quantum computing, simulation, and metrology implementations.