As nanostructures continue to become increasingly small in size, they approach a limit at which their behavior may become atomic in character, and study of the nanostructure then falls into the arena of basic atomic, molecular, and optical (AMO) physics. Until recently, research in AMO physics centered on the interpretation of the internal structure and dynamics of atoms and molecules through application of the fundamentals of quantum mechanics. However, the past few years have witnessed a major change in this emphasis, brought about by experiments made possible by technological breakthroughs in laser and atomic trapping technology. In this new generation of experiment, the translational motion of the free atom is determined by quantum mechanical, not classical, considerations. Out of this new regime have grown the tools and concepts of quantum control and atom manipulation. Application of these principles has led to advances in both the understanding of basic atomic and molecular physics and the underlying principles of quantum mechanics, and to an increasing number of potential applications.
In the optical fields generated by ultrastable, ultrahigh-resolution laser systems, individual atoms can be cooled, captured, and positioned with incredible precision. Examples of the impact of these control techniques increase in number regularly. Nanowires ten times smaller than the smallest feature on a computer chip are constructed by dropping cold atoms onto a laser field at the surface of a crystal. Atoms are guided through an optically generated waveguide and deposited at predetermined locations on a surface. Interferometers based on atomic matter waves are the new tools for testing fundamental quantum measurement principles appropriate to the quantum behavior of extremely small structures. Laser beams are used as tweezers to stretch and position polymers. Coherent matter waves emerging from atom lasers probe the limits of quantum statistics and offer possibilities for new sources for atom manipulators fashioned from laser beams. And trapped ions are one scheme that points the way to a possible realization of the quantum computer. About $2 million is invested in activities related to these topics in PHY/MPS, roughly 10% of the total AMO physics budget.