Motion of a single superconducting vortex

Procedures have been developed to trap a single quantized vortex in a superconducting thin film and systematically move it around under the influence of an applied Lorentz force. The location of the vortex is determined from the diffraction pattern of a Josephson junction formed by superconducting cross strips and a normal-metal barrier; the force is applied by a current in the superconducting film. Vortices move across the junction in a reproducible series of discrete steps, typically a few micrometers long. The elementary pinning force is found to be approximately 10^-6 N/m in a Pb-Bi film and to vary as (1-t)3/2, where t is the reduced temperature. By controlling the pinning sites along a symmetry axis of the junction, one can perform rather simple read and write operations for logic elements.