Scientists from the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., have found a way to supply single chromium atoms on demand. Besides facilitating efforts to find a way to assemble nanostructures atom by atom, the work may open new avenues of research into quantum information architectures and isolated quantum systems.To initiate the capture process, Jabez J. McClelland, Shannon B. Hill and colleagues with NIST's Electron Physics Group inject a beam of the neutral atoms into a magneto-optic trap. A laser excites the atoms into various states, causing them to emit photons that indicate their presence and number. If just one atom enters the trap, it triggers a gate to halt the loading process.The next step is to develop a means to extract the single atoms from the trap -- for example, by using laser tweezers or gravity -- and to move them to a microscopic magnetic trap. McClelland said that further research also could include modifying the technique to work with other atomic species.