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Josephson Memory Circuit Utilizing One Weak Link and One Tunnel Junction

IP.com Disclosure Number: IPCOM000083044D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Laibowitz, RB: AUTHOR

Abstract

A conventional Josephson memory loop consists of two tunnel junctions in a loop with a control (or bit) line and a sense line with a sense junction. Electrical access is provided into and out of the loop. The loop current can be changed in direction from clockwise to counterclockwise and back and the direction of the current is the information stored, i.e., clockwise --> 1 counterclockwise --> 0. In this description, a simpler loop is described which does not need a bit line and is shown in Fig. 1.

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Josephson Memory Circuit Utilizing One Weak Link and One Tunnel Junction

A conventional Josephson memory loop consists of two tunnel junctions in a loop with a control (or bit) line and a sense line with a sense junction. Electrical access is provided into and out of the loop. The loop current can be changed in direction from clockwise to counterclockwise and back and the direction of the current is the information stored, i.e., clockwise --> 1 counterclockwise --> 0. In this description, a simpler loop is described which does not need a bit line and is shown in Fig. 1.

Assume I(w) is The current necessary to drive either weak link, WL, or the tunnel junction, J1, into the voltage state. This is done for simplicity; in actual operation, the critical currents can be different for the two devices.

Applying now I/'/(w) where I/'/(w) ~ I(w), and then applying a microwave signal to device WL (which has an IW characteristic similar to that shown in Fig. 2*), WL switches from the zero voltage state to a finite voltage V where 2 eV = h upsilon, and upsilon is the frequency of the applied microwave signal.

Tunnel junction J1 is much less sensitive to microwave energy and stays in its zero voltage condition. This results in the current I/'/(w) flowing through device J1. When the current is removed, a clockwise circulating current equal in magnitude to I/'/(w) is set up. At this point, the microwave energy is removed. To reverse sense of the circulating current, I/'/(w) is...