One-junction superconducting memory cell with column sense

Abstract

A superconducting memory cell consisting of one Josephson junction and one inductor and using a column-sense technique is demonstrated to make very dense memory possible. Information is stored in the inductor in the form of a single flux quantum by applying bipolar x and y selection signals. For readout, a voltage pulse generated from the cell propagates along the column using a structure equivalent to a Josephson transmission line. It is accomplished by inserting a dc-biased junction in the column for every group of four or eight cells. Dense memory arrays are possible because the cell is the simplest flux storage cell and contains no sense gate. An experimental memory array has been demonstrated with sense margin of /spl plusmn/22% and cell size of 54 squares. (A square is the normalized area to the minimum junction size.) This is a factor of two smaller than the miniaturized cells reported recently with 121, 98, and 80 squares.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>