Nanoscale Atomic Density Microscopy

Abstract

Quantum simulations with ultracold atoms typically create atomic wave functions with structures at optical length scales, where direct imaging suffers from the diffraction limit. In analogy to advances in optical microscopy for biological applications, we use a nonlinear atomic response to surpass the diffraction limit. Exploiting quantum interference, we demonstrate imaging with superresolution ofλ/50and excellent temporal resolution of 500 ns. We characterize our microscope’s performance by measuring the ensemble-averaged probability density of atoms within the unit cells of an optical lattice and observe the dynamics of atoms excited into motion. This approach can be readily applied to image any atomic or molecular system, as long as it hosts a three-level system.

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Plain Language Summary

The wavelike nature of light limits the resolution of conventional imaging devices such as microscopes. To get around this limitation, researchers have developed a variety of techniques known as superresolution imaging to visualize such things as a single atom on a surface or the dynamics of individual molecules within a living cell. Here, we bring superresolution imaging to an ensemble of ultracold atoms, which allows us to “see” individual atoms with an unprecedented resolution of about 11 nm—50 times the resolution of conventional lenses—and observe changes in the atomic wave functions.

Our target is a 1D chain of ytterbium atoms trapped in an optical lattice. Two lasers work to change the spin state of the atoms via a common excited state, which generates interference between the excitation pathways. By varying the strength of each of the two lasers, we can change the spin mixture from all up to all down, for example. We then count the atoms by shining another laser on them. Since only one spin state absorbs the laser light, we can effectively choose which atoms to count. This lets us map the atomic wave function with a subwavelength spatial resolution and a temporal resolution of about 500 ns.

By bringing superresolution imaging to cold atomic systems, we add a new technique to the atomic physics toolbox. This will enable new direct probes of the atomic wave function in a variety of many-body systems.