Thermal noise, intermittent failures, and yield in Josephson circuits

It is shown that a Josephson circuit is susceptible to thermal noise even though the operating temperature is 4.2K. The effect of thermal noise increases with bias and decreases with I/SUB m/, the maximum Josephson current. Each circuit on a Josephson chip will have a slightly different bias and I/SUB m/ due to processing spreads, and these variations can cause low yield or unacceptable thermal noise. Chip yield and thermal noise are calculated for a range of parameters, showing the tradeoff between them.