© M. Greiner.
Ultracold atoms move so slowly that they can be confined by the weak force of light. Here, rubidium atoms are confined in an optical lattice made of standing light waves. The lattice, which is not visible in the image, creates a rectangular array of potential energy "buckets" in which individual atoms can be trapped. The lattice sites are separated by 640 nanometers. The lattice is a few layers deep and its rectangular structure is clearly visible. This system provides a new tool for studying theories of phenomena ranging from superconductivity to black holes. It also has potential applications for studies of quantum entanglement, quantum communication, and possibly quantum computing. (Unit: 5)