The ryotron—A variable inductance cryogenic device

Thin-film superconducting devices, called ryotrons, are capable of steering currents between paths by controlling the inductance in each branch. A number of different ryotron geometries are considered and analyzed. The ratio between the extreme inductance states of the ryotron is determined by the detailed configuration and by material properties. Inductance ratios as large as 146 have been observed. Using a favorable geometry, called the horseshoe ryotron, binary selection trees have been designed and operated. With a three-level, eight-output tree, the steady-state current division was achieved in 3.5×10^-9seconds.