Superconductive computer circuits are an old dream of the computer business. Josephson Junctions can be tremendously fast: an 1100 MHz processor was built in 1988. But superconductivity required cooling to liquid helium temperatures, among other drawbacks.
The recent 'high temperature' devices have revived hope for the idea. The latest circuit fashion is to build quantum transfer devices, which send a 'one' by sending one single quantum of electromagnetic flux.