Imaging strontium superfluids atom by atom

Ultracold atoms cooled to nanoKelvin temperatures can be trapped in crystals of light to engineer artificial materials and investigate their properties. Such optical lattice systems have a lattice spacing of several hundreds of nanometers, accessible to optical microscopes. Quantum-gas microscopes exploit this fact to take fluorescence images of the system resolving every single lattice site and every single atom in a single shot. They are an invaluable tool to explore the many-body properties of artificial materials, which often cannot be predicted using classical computing methods, in a quantum simulation approach.Quantum-gas microscopy has been realized for some atomic species. Different elements can however provide exciting new tools for quantum simulation. In our work, we realized a quantum-gas microscope with atomic strontium, and imaged strontium lattice superfluids at the single-atom level for the first time. Strontium is an alkaline-earth element, which hence has two valence electrons. Its more complex optical spectrum includes an ultranarrow optical transition that is used to operate the world's most precise atomic clocks. Our experiments therefore pave the way towards combining quantum-gas microscopy and quantum metrology tools for engineering the next-generation quantum simulators.