The invention of laser cooling has enabled clouds of gaseous atoms to be slowed down to velocities of just a few cm/s. These so called ‘cold atoms’ can be studied far more easily when they are travelling at slower velocities and scientists are now investigating fundamental quantum phenomena in the research community’s bid towards quantum computing.

However, if quantum computing is to be realised, understanding the concept is not enough. Researchers must also be able to control and manipulate atoms. One way of achieving this would be to take advantage of the magnetic moment of atoms such as 87Rb and fabricating ferromagnetic structures which are capable of reflecting these paramagnetic atoms.

Most mirror designs produced so far consist of hard magnetic materials where the magnetic state is difficult to reconfigure. Now a new design has been developed in the form of an array of undulating planar nanowires of the soft magnetic material Ni80Fe20 in a joint effort from Sheffield, Durham, and Bath Universities in the UK. Tom Hayward of the University of Sheffield explains what the team observes each time a magnetic field is applied to the new mirror. “When we apply a magnetic field perpendicular to the nanowires length we populate the wires with domain walls, nanoscopic regions in which the magnetisation changes direction. These domain walls act as sources of magnetic field which reflect atoms. On the other hand, when we apply the field parallel to the length of the nanowires the domain walls are swept out, and hence the mirror is no longer reflecting.”

The mirror may yield information on the interactions between domain walls and cold atoms and might even be capable of trapping a single atom in potential wells created by the domain walls. Hayward explains why this is would be such a great achievement. “By reconfiguring the magnetisation of the nanowires we will be able to move the atom traps around nanowire circuits, much like electric charge can be moved around conventional microelectronics. Our ultimate aim is to use such technology for quantum computation.”