An electromagnetic trap can suspend 400 ions at a time, providing a useful system for studies of quantum information processing.
Ions can be pinned in place using oscillating and static electric fields, but trapping large numbers is challenging because experimenters must compensate for unavoidable background fields at each ion location. Daniel Stick at Sandia National Laboratories in Albuquerque, New Mexico, and his colleagues used 88 electrodes to measure and then suppress undesired electric fields at points around a ring-shaped trap. By compensating for background fields in just one direction, they succeeded in trapping 400 calcium ions at uniform intervals around the circle.
Most proposed quantum devices arrange ions in square lattices, but circular chains of ions could find uses in new designs as well as in quantum simulators, say the authors.