Superconducting RSFQ logic: Towards 100GHz digital electronics

The Rapid Single-Flux-Quantum logic (RSFQ) presents an efficient way to achieve ultra fast digital operations. This logic uses the macroscopic effects which can be found in nano-structured superconductor devices such as the Josephson AC and DC effects, and the magnetic flux quantization. As the typical time of the Josephson junction quantized phase leap 2π is in the order of picoseconds, the RSFQ circuits can operate with clock frequencies in the order of hundreds of GHz. This invited paper focuses on basic principles of superconducting RSFQ logic as well as on typical applications, such as the signal conversion or petaflops computing systems. In addition we point out the benefits of the semi-metallic NbN-Ta_xN-NbN Josephson junction technology, which has been developed at CEA-INAC in Grenoble.