High performance Nb Josephson devices for petaflops computing

The Hybrid Technology Multi-Threaded (HTMT) approach to petaflops computing includes large numbers of ultra-high performance Nb Rapid Single Flux Quan tum IRSFQ) processor and memory chips, making it by far the largest active superconducting electronics project in the United States. In order to achie ve petaflops, RSFQ circuits with 10(5) to 10(6) junctions per chip will be required to operate at clock speeds of 50 to 100 GHz, far beyond the curren t state of the art. In this paper, we review the state of the art of Nh cir cuit fabrication and discuss the requirements for significantly improving c ircuit density and speed.