Superconductive shift register utilizing Josephson tunnelling devices

Abstract

A .[.two-phase.]. superconductive shift register using Josephson tunnelling devices is provided wherein a plurality of shift register stages each includes a first and second branch in parallel to which a DC current is supplied. A Josephson tunnelling device is located in each branch which operates in its no voltage state when the DC current is applied thereto. A first and second input means is provided for switching one of the Josephson tunnelling devices in accordance with an input to cause the input current to flow through the other branch. A first and second .[.coupling.]. .Iadd.control .Iaddend.means are located between the stages of the shift register, the first .[.coupling.]. .Iadd.control .Iaddend.means coupling the first branch circuits of successive stages and the second .[.coupling.]. .Iadd.control .Iaddend.means coupling second branch circuits of successive stages. The .[.coupling.]. .Iadd.control .Iaddend.means are .[.energized.]. .Iadd.effective .Iaddend.in response to phase time pulses and current flow in the preceding stage causing the Josephson device in the next stage to switch to its finite voltage stage thereby causing the current to flow in the opposite branch in the next stage.

What is claimed is: 
     
       1. A two-phase shift register using Josephson tunnelling devices comprising: a plurality of shift register stages;   a current source for providing DC current to each of said shift register stages;   a first and second branch circuit in parallel in each of said shift register states;   a first and second Josephson tunnelling device located in said first and second branch circuits, respectively, said devices operating in their no-voltage state;   a first and second input means for setting the associated Josephson junction to its finite voltage state causing the input current to flow in the opposite branch;   a first and second coupling means located between the first and second branches, respectively, of the stages of said shift register;   a source of phase time pulses, said first and second coupling means between successive stages being energized alternately by a current pulse at the opposite phase times; and   said first and second coupling means responding simultaneously to said phase time pulse and to the branch circuit in which the current flows in the preceding stage thereby causing the current to flow in the opposite branch in the succeeding state.   
     
     
       2. A two phase shift using Josephson tunnelling devices according to claim 1, wherein said first and second coupling means each consists of a Josephson device having a bypass circuit connected thereacross through which a current pulse passes when the Josephson device is switched to its finite voltage state. 
     
     
       3. A two phase shift register using Josephson tunnelling devices according to claim 1, wherein said current is applied in series to the successive stages and in parallel to the branches within each stage, said current in the successive stages passing through the branch having a Josephson device in the no-voltage state. 
     
     
       4. A two phase shift register using Josephson tunnelling devices according to claim 1, wherein said first and second branch circuits in parallel constitute superconductive circuits. 
     
     
       5. A two phase shift register using Josephson tunnelling devices according to claim 1, wherein said first and second Josephson tunnelling devices in said first and second branch circuits, respectively, comprise two stripline conductors separated by an insulator barrier so that tunnelling takes place through said barrier to give a zero voltage current up to a critical current value beyond which the device switches into a finite voltage state. 
     
     
       6. A two phase shift register using Josephson tunnelling devices according to claim 2, wherein said first and second coupling means each further include a bypass circuit connected across said Josephson tunneling device and having a terminating resistance therein, said bypass circuit forming the input to the Josephson device of said branch circuit associated therewith in the next stage. 
     
     
       7. A two phase shift register using Josephson tunnelling devices according to claim 6, wherein the first and second coupling means bypass circuit produces a magnetic field when the current flows therethrough which lowers the critical current value of the associated Josephson tunnelling device in the next stage causing it to switch to its finite voltage state thereby causing the current to switch to the other branch of said next stage. .Iadd. 8. A shift register using Josephson tunnelling devices comprising: a plurality of shift register stages;   a current source for providing DC current to each of said shift register stages;   a first and second branch circuit in parallel in each of said shift register stages;   a first and second Josephson tunnelling device located in said first and second branch circuits, respectively;   control means associated with each of said first and second Josephson devices in each stage for selectively setting one of said devices to its finite voltage state causing said DC current to flow through the non-selected Josephson device in the other branch of said stage;   at least one phasing means coupled to each of said first and second Josephson tunnelling devices in each stage for sequentially timing the applications of said control means to successive shift register stages for shifting information stored in one stage of said shift register to a succeeding stage. .Iaddend..Iadd. 9. A shift register using Josephson tunnelling devices according to claim 8, wherein said control means associated with each of said first and second Josephson devices in each stage subsequent to the first stage includes a section of said first and second branch circuit of the previous stage as control inputs, respectively. .Iaddend. .Iadd. 10. A shift register using Josephson tunnelling devices according to claim 9, wherein said phasing means includes a timing control input which when energized by a phase timing pulse from a phase timing source simultaneously with the current flowing in said associated control input causes the controlled Josephson device to switch to its finite voltage state, thereby causing transfer of the gating current to the other branch of said stage. .Iaddend..Iadd. 11. A shift register using Josephson tunnelling devices according to claim 9, wherein said section of said branch circuit of each stage serves as the control input to the opposite branch of the next stage so that the same gating current flow condition is transferred from stage to stage. .Iaddend.