Superconducting latch driver circuit generating sufficient output voltage and pulse-width

1. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L, and

wherein said resistance R and said inductance L are connected in series to provide a coupling between the output of said latch circuit and a ground potential, inductance Lload of said load inductance, resistance Rload of said load resistance, a gap voltage Vg of said Josephson junction, and a critical current Ic of said Josephson junction are related as:

R<Vg/Ic,

R<<Rload,

L>>Lload, and

L/R>>L load/ R load.

2. The circuit as claimed in claim 1 , further comprising a SQUID (superconducting quantum interference device), said SQUID configured to be driven by said inductance L in the reset circuit.

3. A feedback driver circuit for a superconducting double-loop sigma-delta modulator, comprising the claimed circuit of claim 2 .

4. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L, and

wherein said latch circuit includes a capacitor connected in parallel with the Josephson junction, said Josephson junction lacking the hysteresis characteristic.

5. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L, and

wherein said latch circuit includes two circuits connected in parallel with each other, each of said two circuits including multiple stages of Josephson junctions.

6. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit;

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit; and

a SQUID (superconducting quantum interference device), said SQUID configured to be driven by said load inductance,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L.

7. A feedback driver circuit for a superconducting double-loop sigma-delta modulator, comprising the claimed circuit of claim 6 .

8. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L, and

wherein said circuit serves as a superconducting interface circuit connected to a room temperature semiconductor circuit.

9. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L, and

wherein said latch circuit receives the single flux quantum from a single flex quantum logic circuit via at least one of a resistor and a Josephson junction.

10. A circuit comprising:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit;

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit; and

a series connection of a resistor and an inductor, wherein said latch circuit receives the single flux quantum from a single flux quantum logic circuit, said series connection providing a coupling between a ground potential and a node situated between said latch circuit and said single flux quantum logic circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L.

11. A multi-chip-type logic circuit, comprising a plurality of logic circuits connected in series, each said logic circuit including:

a latch circuit including a Josephson junction and configured to perform a latch operation based on a hysteresis characteristic in response to a single flux quantum;

a load circuit including load inductance and load resistance and coupled to an output of said latch circuit; and

a reset circuit provided between the output of said latch circuit and said load circuit and configured to reset said latch circuit a predetermined time after the latch operation by said latch circuit,

wherein said Josephson junction is driven by a direct current and the reset circuit includes a resistance R and an inductance L such that the predetermined time is responsive to a time constant determined by the resistance R and the inductance L.

12. A circuit for producing a voltage equal to a multiple of a gap voltage of a Josephson junction in response to a single flux quantum, comprising:

a high-voltage Josephson gate driven by an AC and including two series connections connected in parallel with each other, each of said two series connections including a plurality of Josephson junctions connected in series;

a buffer gate;

an inductance coupling between said high-voltage Josephson gate and said buffer gate and having such size as to store a single flux quantum, wherein said inductance and one of the Josephson junctions of said high-voltage Josephson gate constitute a superconducting loop.

13. The circuit as claimed in claim 12 , wherein said inductance is larger than a value of flux quantum divided by a critical current of said one of the Josephson junctions.

14. The circuit as claimed in claim 12 , further comprising:

a first ground plate constituting a ground of said high-voltage Josephson gate;

a second ground plate separate from said first ground plate and constituting a ground of a circuit inclusive of said buffer gate;

a superconductor coupling between said first ground plane and said second ground plane, said superconductor forming part of the inductance of said superconducting loop.

15. The circuit as claimed in claim 14 , wherein said superconductor coupling between said first ground plane and said second ground plane has a length and a width, a ratio of said length and said width being more than about 1.

16. The circuit as claimed in claim 12 , further comprising a Josephson junction, for isolating an output from an input, connected to said inductance in series.

17. The circuit as claimed in claim 12 , further comprising at least one of a Josephson transmission line and a buffer gate between said inductance and said buffer gate.

18. The circuit as claimed in claim 12 , further comprising a dumping resistor connected in parallel to said inductance, said dumping resistor serving to suppress resonance caused by said inductance and a parasitic capacitance.

19. The circuit as claimed in claim 12 , further comprising a dumping network including a resistor and an inductance connected in series, said dumping network being connected in parallel with said one of the Josephson junctions and serving to prevent a high-frequency voltage oscillation from propagating to a preceding circuit.

20. An A/D converter comprising a circuit of claim 12 .

21. A superconducting single flux quantum logic circuit comprising the circuit of claim 12 .

22. An A/D converter, comprising:

a superconducting sigma-delta digital modulator configured to convert an input analog signal into a digital signal comprised of single flux quantum pulses;

a demultiplexer circuit configured to demultiplex the digital signal supplied from said superconducting sigma-delta modulator into a plurality of sequences of single flux quantum pulses; and

a plurality of output interface circuits configured to produce voltages equal to a multiple of a gap voltage of a Josephson junction in response to the respective sequences of signal flux quantum pulses,

wherein each of said output interface circuits includes:

a high-voltage Josephson gate driven by an AC and including two series connections connected in parallel with each other, each of said two series connections including a plurality of Josephson junctions connected in series;

a buffer gate;

an inductance coupling between said high-voltage Josephson gate and said buffer gate and having such size as to store a single flux quantum,

wherein said inductance and one of the Josephson junctions of said high-voltage Josephson gate constitute a superconducting loop.