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Programmable Josephson Current Injection Logic Device

IP.com Disclosure Number: IPCOM000047742D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Beha, H: AUTHOR [+2]

Abstract

Improvements are described to Josephson current injection interferometers which result in a larger discrimination ratio and a larger operating window for the signal currents. Programmable control currents, coupled into the interferometer loop, determine the logic function performed by the device. These currents, at the same time, affect the supply current, thereby optimizing the operating point for the programmed logic function. Fig. 1 shows the equivalent circuit of a current injection junction interferometer that can be used. It comprises 3 junctions with different maximum Josephson currents aI0, bI0 and cI0 . The input currents iA and iB as well as the split supply currents Ig1, Ig2 are injected at points A and B, respectively.

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Programmable Josephson Current Injection Logic Device

Improvements are described to Josephson current injection interferometers which result in a larger discrimination ratio and a larger operating window for the signal currents. Programmable control currents, coupled into the interferometer loop, determine the logic function performed by the device. These currents, at the same time, affect the supply current, thereby optimizing the operating point for the programmed logic function. Fig. 1 shows the equivalent circuit of a current injection junction interferometer that can be used. It comprises 3 junctions with different maximum Josephson currents aI0, bI0 and cI0 . The input currents iA and iB as well as the split supply currents Ig1, Ig2 are injected at points A and B, respectively. A control line current iC is coupled to the loop inductance L and, at the same time, effects the shunt device Jsh, a Josephson device providing a bypass for at least part of the supply current Ig when in the superconducting state. Figs. 2 and 3 schematically illustrate how the interferometer threshold characteristic is affected by programmable control currents iC . With no control current applied (iC = 0), part of the supply current Ig flows through device Jsh to ground, thereby reducing the current fed into the interferometer. With iC = 0, the device is suitable for an AND operation on applied input currents iA and iB, as demonstrated in Fig. 2. When applying a control current iC of...