High-Tcsuperconducting integrated circuit: A dc SQUID with input coil

We have fabricated a high transition temperature superconducting integrated circuit consisting of a dc SQUID and an input coupling coil. The purpose is to ascertain the generic problems associated with constructing a high-Tccircuit as well as to fabricate a high performance dc SQUID. The superconductor used for both the SQUID and the input coil is Nb3Sn which must be deposited at 800°C. Importantly, the insulator separating SQUID and input coil maintains its integrity at this elevated temperature. A hole in the insulator permits contact to the innermost winding of the coil. This contact has been achieved without significant degradation of the superconductivity. Consequently, the device operates over a wide temperature range, from below 4.2 K to near Tc.