Abstract
We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about . We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.
- Received 20 September 2012
DOI:https://doi.org/10.1103/PhysRevX.2.041014
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Published by the American Physical Society
Synopsis
Cooling Neutral Atoms in Optical Tweezers
Published 29 November 2012
Individual neutral atoms trapped in optical tweezers have been cooled to their quantum ground state, raising hopes that they can be used to process quantum information.
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Popular Summary
A single atom is so tiny that its interaction with our everyday environment will cause it to zip around at many meters per second. Even when it is confined in a tiny trap in space and isolated from its environment—a feat that physicists have managed—it will typically be left jiggling around, or “vibrating,” considerably in the trap. On the other hand, precise control of the quantum state of a single atom, with potential usefulness in atom-based quantum logic devices, requires the basic step of bringing the atom down to its vibrational ground state. So far, this step has remained elusive for single neutral atoms, although it has been achieved for single atomic ions and gases of neutral atoms. In this experimental paper, we report the successful cooling of an isolated, single neutral atom to its three-dimensional, vibrational ground state by bringing the technique of optical tweezers into the area of atomic ground-state cooling.
The lack of charge of a single neutral atom is desirable in principle in the context of quantum processing, because it reduces the coupling of the atom with any uncontrolled environmental effects. But at the same time it poses a technical challenge to the effort of cooling the atom’s vibrational motion, because a nonzero charge would allow for the use of large electromagnetic forces, and, in turn, the efficient use of a now-well-established technique called Raman sideband cooling. To isolate a single atom and enable the use of large trapping forces to cool a single neutral atom, we have turned to optical tweezers. An optical tweezer is created simply by a tightly focused beam of light. It yields a strong, three-dimensional trap with a very small volume. The trapping force is sufficiently strong to allow the technique of Raman sideband cooling to be extended to the domain of single neutral atoms. We have successfully cooled the vibrations of single rubidium atoms () in all three directions.
Our experiment generates a new source of ground-state neutral atoms for quantum information processing and quantum simulations. It also opens up new opportunities for full atomic cooling in a variety of novel traps. For example, one may imagine transporting localized atoms by taking advantage of the easy mobility of optical tweezers. Making arrays or rings of tweezers, if combined with high-fidelity ground-state preparation, would also offer a new, bottom-up approach to quantum simulation.