Trapping atoms inside of a submicron volume for applications such as quantum computing and nanoscale optics poses a host of experimental difficulties. One idea for doing this takes advantage of the strong electric field that can be excited on the surface of metal nanoparticles.
Ultracold atoms in an optical lattice share a lot of physics with electrons in a crystalline solid and it is a system that is often much easier to control. By forcing an optical lattice to vary with time, it is possible to engineer the energy of cold atoms and essentially bring them to a halt.
When an atom is bombarded with just enough energy to fully ionize it, how do the electrons and nucleus break apart from each other? Experimentalists are now able to study such a four-body breakup by bombarding a helium atom with an electron.