Some theoretical considerations regarding the maximum speed of active devices, with special reference to Josephson junctions

Several factors affecting the theoretical performance limits of active logic devices are discussed, including the theory of relativity and the negentropy principle of information. The foregoing are employed to analyze a hypothetical optimal switching element, and a relationship between maximum operating speed and device temperature is determined assuming a simple model for heat transfer. The results indicate that there are two critical points on the curve: one at which device temperature becomes greater than ambient, and heat transfer by conduction is dominant, and a second where heat transfer by radiation becomes dominant. For the model assumed, these occur at about 10¹³and 10¹⁴ops/sec, respectively. At the second, the device temperature is approximately 10⁴degrees K. The foregoing results are then applied to Josephson Junction devices, and a maximum speed for such devices is estimated.