Implementation of superconductive passive phase shifters in high-speed integrated RSFQdigital circuits

Abstract

The reduction of the critical current density in rapid single-flux quantum (RSFQ) circuitsenables new application fields, like quantum computing and photonic detector readout. Thelow current density fabrication process creates new design challenges, such aslower stability against thermal fluctuations, violation of the lumped elementscondition for microstrip inductances and increased sensitivity to the technologicalspread. To overcome these issues, we suggest a passive phase shifter as a promisingalternative technique for superconductive phase dropping in the RSFQ electronics.Here, we study experimentally their applicability in high-speed RSFQ digital circuits.Conclusions are drawn about the impact of the passive phase shifters on the complexity,the speed and the bit error rate of the investigated RSFQ circuits. We demonstrate thesuccessful operation of different circuits with implemented passive phase shifters at low andhigh speeds.