Digital logic gates using hot-phonon controlled superconducting nanotransistors

We describe the fabrication and digital switching operation of a NOR logic gate that uses a single, dual-input superconducting nanotransistor. The nanotransistor is a weak-link device that has integrated hot-phonon injectors to control its critical current. The fabrication process utilizes a self-aligned method, where the two heaters act as a mask for reactive ion etching to define the device pattern. This device is much simpler to fabricate than previously reported superconducting transistors and the principle of operation makes it possible to use a single nanotransistor, with multiple input heaters, as a NOR logic gate, allowing lower power consumption and improved levels of integration.