Mobile atom traps based on domain walls in magnetic nanowires

One of the most dramatic recent advances in physics has been the experimental realization of new states of matter as a consequence of using lasers to cool atoms to within a millionth of a degree of absolute zero. The development of laser-cooling techniques was the subject of the 1997 Nobel Prize in Physics, and the realization of a new state of matter, a Bose-Einstein Condensate, resulted in the 2001 Nobel Prize. The atoms to be cooled in this research project can be though of as tiny bar magnets (they are paramagnetic atoms), and at very low temperatures it is possible to trap them using relatively small magnetic fields.A quite separate recent development has been the advance of planar magnetic nanowire technologies. The extended geometry of these wires constrains magnetisation to lie along the wire length. When opposite magnetisation directions meet in a nanowire, they are separated by a transition region termed a 'domain wall'. These domain walls can be moved through nanowire circuits using externally applied magnetic fields but they are also themselves a source of magnetic field. We have recently shown how the magnetic field from a domain wall in a nanowire can be used to trap laser-cooled atoms.In this proposal, we aim to demonstrate experimentally and investigate atom trapping using domain walls in nanowires. The cold atoms trapped above a nanowire will be robustly confined and, crucially, mobile due to the precision with which the position of domain walls can be controlled. This is an excellent platform for further research in controlling interactions between neighbouring trapped atoms. In the burgeoning field of Quantum Information Processing (QIP) two atoms can be entangled by bringing them close and subsequently separating them. Furthermore, many identical copies of a fundamental nanowire circuit unit can be tessellated to create quantum-computing networks.This proposal also offers applications in other important research areas. The nanometre scale of the magnetic domain wall results in the trapped atoms being closer than a micrometre to the substrate. Varying the magnitude of external magnetic fields allows control of the exact atom-surface height, hence it is envisaged that domain-wall atom traps will be used to study atom-surface interactions. Developing a mobile nanomagnetic atom traps provides a precursor technology to more complicated quantum objects, and their application to new science, such as quantum collisions on surfaces, or new technologies, such as quantum information processing.