Four Atom Quantum Entanglement: In quantum mechanics, distinct particles can be "entangled" into a multi-particle wave function with potential applications in quantum computation and improved atomic clocks. During this last year NIST demonstrated the entanglement of four trapped, laser-cooled ions using a method that in theory can be applied to any number of ions. The method uses a laser pulse to produce a specific entangled state "on demand," that is, no post-selection of the desired state from randomly occurring coincidences is required. The cover picture shows the lithographically fabricated microtrap in the background with a magnified image of the trapping region and the four ions in the foreground.