Superconducting devices based on coherent operation of Josephson junction arrays above 77K

Arrays of Josephson junctions operating coherently at 77K seem to be the ideal candidates for re-shaping the future of the electronics industry. Their advantages over their semiconducting counterparts (higher operating speed, lower power consumption/electronic noise) can be exploited in practice because of their practicality: cooling down to 77K is both cheap and easy to handle. These developments naturally fit into the increasing interest of some semiconductor technologies in lower operation temperatures. Therefore, it looks attractive to link semiconductor and 77K superconductor technologies to improve system level performance. Currently, however, in the vast majority of applications 4.2K superconducting technology is used as it provides significantly superior performances relative to devices build in the 77K technology. Recent significant improvements in the performance of superconducting devices operating as 77K, as well as, in their fabrication technologies may change all that. Several such examples will be considered here. Firstly, when coherency is achieved in large series SQUID-arrays magnetic flux sensors or voltage amplifiers can be build having record values for their output voltage and flux noise sensitivities outperforming even single SQUID-based devices operating at 4.2 K. Secondly, when coherency is achieved in parallel SQUID-arrays placed in a uniform magnetic field B, B-field tuned microwave generators can be build. Large parallel SQUID arrays were also implemented to achieve record values for current amplification at 77K, highly efficient ratchets with unidirectional magnetic vortices motion and integrated nano-magnetic sensors.