Superconducting circuit for generating pulse signal
A superconducting circuit includes a first transformer to produce a first alternating-current output at a secondary-side inductor, a second transformer to produce a second alternating-current output at a secondary-side inductor, a first pulse generating circuit to produce a single flux quantum pulse responsive to the first alternating-current output, a second pulse generating circuit to produce a single flux quantum pulse responsive to the second alternating-current output, and a confluence buffer circuit to merge the single flux quantum pulses from the pulse generating circuits, wherein each of the pulse generating circuits includes a superconducting loop including the secondary-side inductor, a first Josephson junction situated in the superconducting loop to generate the single flux quantum pulse, and a second Josephson junction situated in the superconducting loop, a threshold value of the second Josephson junction for an electric current flowing through the secondary-side inductor being different from that of the first Josephson junction.
1. A superconducting circuit, comprising:
a first transformer to receive an alternating-current input at a primary-side inductor and to produce a first alternating-current output at a secondary-side inductor;
a second transformer to receive the alternating-current input at a primary-side inductor and to produce a second alternating-current output at a secondary-side inductor;
a first pulse generating circuit coupled to the secondary-side inductor of the first transformer to produce at an output node a single flux quantum pulse responsive to the first alternating-current output;
a second pulse generating circuit coupled to the secondary-side inductor of the second transformer to produce at an output node a single flux quantum pulse responsive to the second alternating-current output; and
a confluence buffer circuit coupled to the output node of the first pulse generating circuit and the output node of the second pulse generating circuit to produce a pulse signal made by merging the single flux quantum pulse from the first pulse generating circuit and the single flux quantum pulse from the second pulse generating circuit,
wherein each of the first pulse generating circuit and the second pulse generating circuit includes:
a superconducting loop including the secondary-side inductor;
a first Josephson junction situated in the superconducting loop to generate the single flux quantum pulse; and
a second Josephson junction situated in the superconducting loop, a threshold value of the second Josephson junction for an electric current flowing through the secondary-side inductor being different from that of the first Josephson junction.
2. The superconducting circuit as claimed in claim 1 , wherein at least one of a critical junction current and an applied bias current are different between the first Josephson junction and the second Josephson junction.
3. The superconducting circuit as claimed in claim 2 , wherein a path for supplying the bias current to the first pulse generating circuit is provided independently of a path for supplying the bias current to the second pulse generating circuit.
4. The superconducting circuit as claimed in claim 1 , wherein one of the threshold value of the first Josephson junction and the threshold value of the second Josephson junction has an absolute value larger than an amplitude of the alternating-current output generated by the secondary-side inductor.
5. The superconducting circuit as claimed in claim 1 , wherein one of the first pulse generating circuit and the second pulse generating circuit is used alone to generate a pulse signal.