Cryotron

Cryotron, miniature switch used in computers, consisting of a short wire around which is wound a fine control coil, kept at the temperature of liquid helium so that the wire and coil are superconducting. A signal in the coil produces a magnetic field that causes the wire to lose its superconductivity and become resistant to electric current. This action stores or produces a “bit” of information. Cryotron computers may contain 100 billion components to the cubic inch, and can obtain a required bit of information from a store of 300,000 in less than a 10-millionth of a second.

See also: Superconductivity.