Flux Mitigation in Wide Superconductive Striplines

The increasing complexity of modern superconductive circuits and single flux quantum (SFQ) circuits in particular have made the issue of flux trapping of growing importance. The use of wide superconductive striplines for signal routing has exacerbated this issue. Trapping residual magnetic fields in these striplines degrades performance while reducing margins, damaging the operability of superconductive circuits. In this chapter, an area-efficient topology for striplines is introduced to manage flux trapping in large-scale SFQ circuits. This topology is composed of narrow parallel lines in series with small resistors. The topology decreases the length of the striplines by exploiting the mutual inductance between the narrow parallel lines. The topology requires significantly less area while preventing flux trapping within wide superconductive striplines. The narrow parallel line topology also reduces coupling capacitance between striplines. The approach is compatible with automated routing of large-scale SFQ integrated circuits.