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Three-Junction SQUID With Sharp Threshold

IP.com Disclosure Number: IPCOM000043585D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Kaplan, SB: AUTHOR

Abstract

A three-junction SQUID may be coupled so that a screening junction partially shields the flux applied to a second junction until a flux transition is sustained in the screening junction, whereupon the screening junction aids in switching the second junction to the voltage state. This allows arbitrary coupling (Fig. 1) and yet has sharp threshold characteristics. Background A coupled SQUID system, described in [*], has a screening SQUID which partially shields the flux applied to a second SQUID until a flux transition is sustained in the screening SQUID. The screening SQUID then aids in switching the second SQUID to the voltage state. Fig.

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Three-Junction SQUID With Sharp Threshold

A three-junction SQUID may be coupled so that a screening junction partially shields the flux applied to a second junction until a flux transition is sustained in the screening junction, whereupon the screening junction aids in switching the second junction to the voltage state. This allows arbitrary coupling (Fig.
1) and yet has sharp threshold characteristics. Background A coupled SQUID system, described in [*], has a screening SQUID which partially shields the flux applied to a second SQUID until a flux transition is sustained in the screening SQUID. The screening SQUID then aids in switching the second SQUID to the voltage state. Fig. 2 shows a schematic of this device, which has a threshold with a sharp drop at

(Image Omitted)

The coupling constant

(Image Omitted)

is one of the parameters that controls the shape of the resultant threshold curve. In particular, one would like a to approach unity to: 1) provide almost complete screening of the applied flux to keep the top of the threshold curve flat, and

2) to be able to provide the largest "anti-screening"

currents after the flux transition has taken place in

the shielding SQUID. This results in the lowest

threshold floor, and thus the widest operating window. Unfortunately, when a groundplane is employed to limit inductances and when transmission lines are needed, the coupling factor is usually N 0.5. This is a consequence of the heights of the film above the groundp...