Abstract
We demonstrate single-shot imaging and narrow-line cooling of individual alkaline-earth atoms in optical tweezers; specifically, strontium trapped in light. Our approach enables high-fidelity detection of single atoms by imaging photons from the broad singlet transition while cooling on the narrow intercombination line, and we extend this technique to highly uniform two-dimensional tweezer arrays with 121 sites. 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 to near the motional ground state of a tweezer, which is tuned to a magic-trapping configuration achieved by elliptical polarization. Finally, we present calculations, in agreement with our experimental results, that predict a linear-polarization and polarization-independent magic crossing at 520(2) nm and 500.65(50) nm, respectively. 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.
2 More- Received 17 October 2018
- Revised 6 December 2018
DOI:https://doi.org/10.1103/PhysRevX.8.041055
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
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Alkaline Atoms Held with Optical Tweezers
Published 28 December 2018
Three separate groups demonstrate the trapping of two-electron atoms in arrays of optical tweezers, opening up new opportunities for quantum simulation and many-body studies.
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Popular Summary
Cold atoms trapped in optical tweezers have become a powerful tool for quantum science. However, well-developed trapping techniques have so far been restricted to alkali atoms, which have just a single valence electron. Applying tweezer techniques to the two-valence-electron alkaline-earth atoms, which are used in the most precise atomic clocks, would enable many new experiments in precision metrology and quantum science that have been proposed over the past decade. Here, we lay the groundwork for such future experiments by demonstrating robust imaging and cooling of individual alkaline-earth atoms in optical tweezers.
We detect and cool individual strontium atoms in optical tweezer arrays with up to 121 sites. By exciting the atoms via semiforbidden transitions between singlet and triplet states, we demonstrate two cooling mechanisms: sideband cooling, in which an atom gradually settles state-by-state to close to the ground state; and Sisyphus cooling (named after the Greek myth of Sisyphus indefinitely pushing a boulder up a hill), where a precisely tuned laser beam repeatedly knocks gradually warming atoms back down a potential hill. Using both cooling schemes, we achieve single-shot, single-atom-resolved imaging by detecting photons from the broad singlet transition.
Our results pave the way for an entire spectrum of experiments with individually controlled alkaline-earth atoms in the context of quantum computing, quantum simulation, and precision metrology. These experiments include coherent control of the optical clock transition, entanglement operations using Rydberg-mediated interactions, deterministic assembly of molecules, and optical trapping of alkaline-earth ions.