Arrangement and method relating to digital information in superconducting circuits

• US 6,188,236 B1
• Filed: 12/19/1997
• Issued: 02/13/2001
• Est. Priority Date: 06/30/1995
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Wikborg, Erland
• Primary Examiner(s): Santamauro, Jon
• Assistant Examiner(s): LE, DON P
• Application Number:
  US08/994,442
• Time in Patent Office: 1,152 Days
• Field of Search: 326/3, 326/4, 326/6, 326/99, 505/190, 505/858, 505/859, 505/861, 327/527, 327/528, 327/366, 327/367, 327/186, 331/107.S
• US Class Current: 326/3
• CPC Class Codes: H03K 19/1954 with injection of the control current

Abstract

A logic circuit arrangement includes signal input and signal output devices and a number of SFQ circuits having Josephson junctions in which carrier devices are used for carrying digital information. The SFQ circuits are sampled at the input/output for producing DC voltages and a train having at least two single flux quanta is used as a carrier device for information and phase locking between at least two Josephson junctions is used to provide at least two different dynamic states of which at least one provides an output signal.

Claims

1. A logic circuit arrangement comprising signal input means, signal output means, and a number of single flux quantum circuits comprising Josephson junctions, wherein the single flux quantum circuits are sampled at at least one of the signal input and output means for producing DC voltages, digital information is carried by a train comprising at least two single flux quanta, and at least two different dynamic states are available via phase locking between at least two of the Josephson junctions, of which dynamic states at least one provides an output signal wherein at least one Josephson junction is connected to each of the signal input and output means, between which an active circuit comprising a number of Josephson junctions is arranged.

2. The arrangement of claim 1, wherein the Josephson junctions of the single flux quantum circuits are so arranged that at least two dynamic states are available and an output signal is determined by the phase locking between the Josephson junctions of the different single flux quantum circuits.

3. The arrangement of claim 1, wherein input digital information is stored as a voltage.

4. The arrangement of claim 1, wherein at least some of the Josephson junctions are directly connected.

5. The arrangement of claim 1, further comprising voltage supplying means connected to the active circuit, wherein a further Josephson junction is connected to the voltage supplying means.

6. The arrangement of claim 1, wherein at least one of the signal input and signal output means comprises a superconductor.

7. The arrangement of claim 6, wherein the superconductor is a High Temperature Superconductor (HAS).

8. The arrangement of claim 6, wherein at least one of the signal input and signal output means comprises a Josephson Transmission Line (JCL).

9. The arrangement of claim 5, wherein the voltage supplying means comprises conventional superconducting wiring.

10. The arrangement of claim 6, wherein at least one of the signal input and signal output means and the voltage supplying means comprises a microstrip line.

11. The arrangement of claim 1, wherein the arrangement comprises at least one OR element.

12. The arrangement of claim 1, wherein the arrangement comprises an AND element.

13. The arrangement of claim 1, wherein the arrangement comprises an element which can be used as an AND element or an OR element, and requirements for producing an output signal determine whether the arrangement operates as an AND element or an OR element.

14. The arrangement of claim 1, wherein the arrangement comprises at least first and second signal input means.

15. The arrangement of claim 14, wherein to provide an output voltage over the output means, a voltage, input on only one of the signal input means which is represented by a train of single flux quanta which are able to switch a Josephson junction of the active circuit, is required to provide an output voltage signal, and the arrangement operates as an OR element.

16. The arrangement of claim 14, wherein to provide an output signal, input signals on both signal input means are required and the arrangement operates as an AND element.

17. The arrangement of claim 11, further comprising at least one voltage supplying means connected to a further Josephson junction and to at least a number of logic elements comprised by the circuit.

18. The arrangement of claim 17, wherein a voltage applied via at least one of a first input means and a second input locks a quantum mechanical phase difference across the further Josephson junction of the output means.

19. The arrangement of claim 1, wherein a Josephson junction is connected to the signal input and output means, between which an active circuit means comprising at least one Josephson junction is arranged and to which a voltage supplying means is connected over a resistor and to which at least one Josephson junction is connected and the arrangement comprises a NOT element.

20. The arrangement of claim 19, wherein the active circuit means comprises a highly non-linear circuit means, and in an absence of any input signal representing a first dynamical state, an output signal is provided, whereas through the highly non-linear circuit means all single flux quanta are eliminated when an input voltage signal is present, thus representing a second dynamical state.

21. The arrangement of claim 20, wherein the active circuit means comprises an interferometer comprising two Josephson junctions and an inductor.

22. The arrangement of claim 21, wherein via the resistor between the voltage supplying means and the active circuit means and a set standard voltage on the signal output means, mutual phase locking between the Josephson junction connected to the voltage supplying means and the Josephson junctions of the active circuit means is provided.

23. The arrangement of claim 22, wherein the active circuit means comprises an inductor for preventing penetration of single flux quanta from the signal output means to the signal input means.

24. The arrangement of claim 22, wherein an input voltage through a first resistor and an inductor of the interferometer produces a phase shift of the interferometer and switches it to a zero voltage state giving a logical zero output signal.

25. The arrangement of claim 1, wherein at least one of the Josephson junctions is shunted.

26. An arrangement for processing digital information, comprising a number of logic elements, each comprising input and output means, wherein the input and output means comprise superconductors, and a superconducting voltage supplying means is connected to each logic element for supplying the respective logic element with substantially the same voltage as is supplied to other logic elements, and each logic element further comprises a number of Josephson junctions arranged such that phase locking of single flux quanta between the Josephson junctions determines output signals of the logic elements.

27. The arrangement of claim 26, wherein phase locking between different Josephson junctions provides different dynamic states.

28. The arrangement of claim 26, wherein digital information is carried by a train of fluxons.

29. The arrangement of claim 26, wherein digital information is represented as voltage levels, and a difference between voltage levels is given by an I_cR_n-product of the involved Josephson junctions.

30. A method for stabilizing a digital logic circuit having a number of logic elements each including a number of Josephson junctions, comprising the steps of connecting each logic element to superconducting voltage supply means, supplying to each logic element substantially the same voltage, and using phase locking between Josephson junctions of each respective element to provide an output signal of the respective logic element.

31. The method of claim 30, wherein digital information is represented as voltage levels and an input voltage is converted into a train of single flux quanta comprising at least two single flux quanta by a Josephson junction.

32. A method according to claim 30, wherein the digital logic circuit includes signal input means and signal output means, and further comprising the step of connecting at least one Josephson junction to each of the signal input means and signal output means, between which an active circuit comprising a number of Josephson junctions is arranged.