A Sub-ns Clock Cryogenic System For Josephson Computers

Josephson gates have speed and low power dissipation, as demonstrated in a 6300-gate 8b digital signal processor and a 4kb SRAM.1 2 3 Josephson LSI chips operate up to 1GHz but their gate count and memory capacity are not sufficient to permit fabrication of computing systems using only these chips. The solution is to combine them with semiconductor chips. But, in this case, the propagation delay caused by VO cables, typically 1.3m, is a serious problem because Josephson chips must be kept at low temperature, typically 4.2K.