of conductors with different disorder configurations.

This kind of persistent current was first predicted to be experimentally observable in micrometer-scale rings in 1983 by Markus Büttiker, Yoseph Imry, and Rolf Landauer. Because the effect requires the phase coherence of electrons around the entire ring, the current can not be observed when the ring is interrupted by an ammeter and thus the current must by measured indirectly