Evaluation of Two Methods for Suppressing Ground Current in the Superconducting Integrated Circuits

Keisuke KUROIWA  Masataka MORIYA  Tadayuki KOBAYASHI  Yoshinao MIZUGAKI  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.3   pp.296-300
Publication Date: 2011/03/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.296
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Superconducting Signal Processing Technologies)
superconductor,  Meissner effect,  current distribution,  superconducting integrated circuits,  SQUID,  superconducting ground plane,  

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Although larger scale integration enhances the practicability of superconducting Josephson circuits, several technical problems begin to emerge during its progress. One of the problems is the increase of current through a ground plane (ground current). Excess ground current produces additional magnetic field and reduces operation margins of the circuits, because superconducting Josephson devices are very sensitive to magnetic field. In this paper, we evaluate current distribution in a superconducting ground plane by means of both experiments and numerical calculation. We also verify two methods for suppressing the ground current. One is a slot structure in the ground plane, and the other is alignment of the current-extraction point. Suppression of the ground current is quantitatively evaluated.