The Current Crowding Cryotron

An active three-terminal superconducting device having an intersection region at which a hot spot may be controllably formed is described. The intersection region may exhibit current crowding in response to imbalances in current densities applied to channels connected to intersection region. The current crowding may form a hot spot, in which the superconducting device may exhibit a measurable resistance. In some cases, a three-terminal superconducting device may be configured to sense an amount of superconducting current flowing in a channel or loop without having to perturb the superconducting state or amount of current flowing in the channel. A three-terminal superconducting device may be used to read out a number of fluxons stored in a superconducting memory element.