Logic and memory application is one of the most attractive application fields for Josephson devices. Recent studies on this field are outlined and future prospects are discussed.
A variety of high-sensitivity Josephson switching devices have been progressively investigated for implementing a highspeed, low-power integrated logic circuit. Attention is paid to a nonlinear current in jection interferometer logic scheme, in which logical delay as fast as 13ps has been experimentally obtained with speed-power product less than 30aJ. In memory application, high-density integration has been predominantly investigated. A 16K bit RAM model circuit as well as a 64bit fully-decoded high speed RAM is successfully fabricated. Access time as fast as 2ns for 64bit RAM and 7ns for 16K bit RAM is obtained experimentally with extremely low power dissipation. Also, fabrication technology has been dramatically advanced, especially for Pb-alloy Josephson devices. Essential problems on reproducibility, production yield, and reliability for large scale integration are almost solved today.
Hereafter, large scale integration, high-density packaging, high-efficiency cryo-cooling etc. for ultrafast Josephson computer assembly will be studied and developed. Functional logic device scheme and material research beside Pb-alloy are also interesting in the future. Much work in this respect will be expecsed.
