JP3107034B2 - Superconducting flux quantum circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting circuit operating at a very low temperature, and more particularly to a tens of GHz to a few hundred GHz.
The present invention relates to a superconducting magnetic flux quantum circuit using a magnetic flux (for n magnetic flux quanta: n is a positive number) stored in a superconducting loop including a Josephson junction, which can be operated by the clock of FIG.

[0002]

2. Description of the Related Art In recent years, several tens of GHz to several hundreds of GHz have been developed.
Stored in a superconducting loop including a Josephson junction operable with a clock (in particular, a single flux quantum (SF
Various superconducting magnetic flux quantum circuits using n (single flux quantum Q: n is a positive number) have been proposed. A typical superconducting flux quantum circuit using SFQ is an RSFQ (Rapid Single Flux Quantum) circuit, for example, IEEE Trans on Applied Superconductiv.
ity, vol. 1, pp. 3-28, 1991 describes the detailed technology.

Here, among the circuits described in this document, a basic circuit called a T flip-flop which operates closest to the present invention will be described.

FIG. 8 is an equivalent circuit diagram showing a configuration of a conventional superconducting magnetic flux quantum circuit.

In FIG. 8, a conventional superconducting flux quantum circuit includes inductances L11 to L14 connected in series between two output terminals F0 and F1, and inductances L12 and L12.
A resistor R connected between the connection of L13 and the ground potential;
Josephson junction J11 connected between the connection between the inductances L11 and L12 and the ground potential, Josephson junction J12 connected between the connection between the inductances L11 and L12 and one end of the inductance L15, and connection between the inductances L13 and L14 Josephson junction J13 connected between the section and the ground potential, and inductances L13 and L13.
14 and a Josephson junction J14 connected between one end of the inductance L15. Note that the other end of the inductance L15 is connected to the terminal A, and a bias current Ib is supplied from a connection between the inductances L11 and L12.

The values of the inductances L12 and L13 constituting the superconducting loop and the superconducting critical current of the Josephson junctions J11 and J13 shown in FIG. Quantum (Φ ₀ ) 1
Each is set so as to be able to store the magnetic flux for each piece.

If the state where a current is flowing clockwise through the superconducting loop is "1" and the state where a current is flowing counterclockwise is "0", the superconducting loop in FIG. "Or" 0 ".

In such a configuration, for example, when the superconducting loop is initially in the "0" state, the terminals A to S
When the FQ pulse is input, the SFQ pulse is supplied to the Josephson junction J11 in the same direction as the current flowing in the superconducting loop, and the SFQ pulse is supplied to the Josephson junction J13 in the opposite direction to the current flowing. Is done.

At this time, since a current exceeding the superconducting critical current value flows through the Josephson junction J11, the current is switched from the superconducting state to the voltage state and the flowing current is cut off. Therefore, the SFQ pulse is generated at the output terminal F0 and the direction of the current flowing in the superconducting loop changes clockwise, so that the superconducting loop switches from "0" to "1".

In this state, when the SFQ pulse is input again from the terminal A, the current flowing through the superconducting loop is reversed in the Josephson junction J11 because the superconducting loop is in the "1" state. The SFQ pulse is supplied in the direction, and the SFQ pulse is supplied to the Josephson junction J13 in the same direction as the flowing current.

At this time, since a current exceeding the superconducting critical current value flows through the Josephson junction J13, the current is switched from the superconducting state to the voltage state and the flowing current is cut off. Therefore, the SFQ pulse is generated at the output terminal F1, and the direction of the current flowing in the superconducting loop changes counterclockwise, so that the superconducting loop switches from “1” to “0”.

As described above, in the conventional superconducting flux quantum circuit shown in FIG. 8, the state of the superconducting loop changes every time the SFQ pulse is input, and the pulse is alternately output from the two output terminals F0 and F1. Occur. At this time, if the period of the SFQ pulse input from the terminal A is fixed, the input SQ
Pulses having a period twice as long as the FQ pulse are generated from the output terminals F0 and F1.

[0013]

However, in the conventional superconducting flux quantum circuit as described above, the input SFQ
Only a pulse having a period twice as long as the pulse could be generated. In addition, since the pulse energy cannot be amplified, there is a problem that the application range of the circuit is small.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and can generate a pulse having an arbitrary multiple of the period of an input pulse. It is another object of the present invention to provide a superconducting magnetic flux quantum circuit having an amplifying function.

[0015]

To achieve the above object, a superconducting flux quantum circuit according to the present invention comprises: a first Josephson junction having one end connected to a signal input end and the other end grounded;
A second Josephson junction having one end connected to the signal output end and the other end grounded, and an inductance connected between the signal input end and the signal output end;
Josephson junction is set to operate in an over-damping state with a Mackamba constant of about 1 , and the second
The Josephson junction is set so as to operate in an underdamping state having a Mackamba constant of about several tens .

At this time, the value of the superconducting critical current of the first Josephson junction, the value of the superconducting critical current of the second Josephson junction, and the value of the inductance are the same as those of the first Josephson junction, A second Josephson junction,
And a value that can store at least one magnetic flux quantum by the superconducting loop including the inductance.

A predetermined bias current may be supplied from the signal input terminal, and a predetermined bias current may be supplied from the signal input terminal and the signal output terminal.

Further, there is provided a control wiring disposed at a position magnetically coupled to the second Josephson junction and to which a control signal for changing a superconducting critical current value of the second Josephson junction is inputted. And a SQUID having a control wiring to which a control signal for changing a superconducting critical current value of the Josephson junction included therein is input, instead of the second Josephson junction. Is also good.

Another configuration of the superconducting magnetic flux quantum circuit according to the present invention includes a first Josephson junction having one end connected to a signal input end and the other end grounded, and one end connected to a first signal output end. A second Josephson junction, the other end of which is grounded;
A first inductance connected between the signal input end and the first signal output end, a third Josephson junction having one end connected to the second signal output end and the other end grounded; A second inductance connected between the signal input terminal and the second signal output terminal, wherein the first Josephson junction operates in an overdamping state with a Mackamba constant of about 1. The second Josephson junction is set so as to operate in an under-damping state having a Mackamba constant of about several tens, and the third Josephson junction is set in the third Josephson junction.
The Josephson junction is set so as to operate in an underdamping state having a Mackamba constant of about several tens .

At this time, the superconducting critical current value of the first Josephson junction, the superconducting critical current value of the second Josephson junction, the superconducting critical current value of the third Josephson junction, The value of the inductance of 1 and the value of the second inductance are at least fluxed by the first superconducting loop consisting of the first Josephson junction, the second Josephson junction, and the first inductance. Each of the first and second Josephson junctions, the third Josephson junction, and the second inductance formed by the second superconducting loop are each set to a value capable of storing a magnetic flux of one quantum. It may be set to a value that can store magnetic flux for one magnetic flux quantum.

Further, a predetermined bias current may be supplied from the signal input terminal, and a predetermined bias current is supplied from the signal input terminal, the first signal output terminal, and the second signal output terminal, respectively. It may be supplied.

Further, there is provided a control wiring arranged at a position magnetically coupled to the second Josephson junction and to which a control signal for changing a superconducting critical current value of the second Josephson junction is inputted. A control line, which is arranged at a position magnetically coupled to the third Josephson junction and to which a control signal for changing a superconducting critical current value of the third Josephson junction is inputted. You may have.

In addition, in place of the second Josephson junction, there may be provided an SQUID having a control wiring for inputting a control signal for changing a superconducting critical current value of the Josephson junction included therein. Alternatively, instead of the third Josephson junction, an SQUID including a control wiring to which a control signal for changing a superconducting critical current value of the Josephson junction included in the third Josephson junction may be input may be provided.

In the superconducting magnetic flux quantum circuit configured as described above, the first Josephson junction is set to operate in an overdamping state, and the second Josephson junction is operated in an underdamping state. Since it is set, each time a pulse is input from the signal input terminal, one magnetic flux quantum is stored in the superconducting loop.

Here, if the superconducting critical current value and the inductance value of the Josephson junction forming the superconducting loop are set to values that can store at least one magnetic flux quantum, When the magnetic flux can no longer be stored, a pulse having energy corresponding to the magnetic flux stored so far is output from the signal output terminal.

Also, by having a control wiring coupled to the second Josephson junction or an SQUID having a control wiring instead of the second Josephson junction, the superconducting loop of the Josephson junction constituting the superconducting loop is provided. Since the conduction critical current value can be changed by the control signal, the amount of magnetic flux (n flux quantum: n is a positive number) that can be stored by the superconducting loop can be changed by the control signal.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is an equivalent circuit diagram showing a configuration of a first embodiment of a superconducting magnetic flux quantum circuit according to the present invention.

Referring to FIG. 1, a superconducting magnetic flux quantum circuit according to the present embodiment includes a DC / SFQ converter 1 that outputs a SFQ pulse having a constant cycle corresponding to an input voltage (DC), and a DC / SQ converter.
An inductance L1 connected in series between the output terminal of the FQ converter 1 and the ground potential, and a damping resistor Rd2
And a Josephson junction J1 connected in parallel between the output terminal of the DC / SFQ converter 1 and the ground potential, and a damping resistor Rd1, and a bias feed connected between the output terminal of the DC / SFQ converter 1 and the DC power supply DC. Resistance Rb
1 and a Josephson junction J2 connected between the connection between the inductance L1 and the damping resistor Rd2 and the ground potential.
And is constituted by.

Here, the Josephson junction J1 is set so as to operate in an over-damping state with a Mackamba constant β of about 1 depending on the value of the damping resistor Rd1 connected in parallel. Also, Josephson junction J2
Is set so as to operate in an under-damping state with a Mackamba constant β of about several tens depending on the value of the damping resistor Rd2 connected in parallel.

Further, the value of the inductance L1 constituting the superconducting loop and the superconducting critical current value of the Josephson junctions J1 and J2 are n flux quantum (Φ ₀ ) (n is a positive number).
Is set to be able to store the magnetic flux. The current flowing in the superconducting loop increases as the stored magnetic flux (the number of magnetic flux quantum (Φ ₀ )) increases. Therefore, the number of magnetic flux quanta (Φ ₀ ) that can be stored in the superconducting loop is determined by a preset Josephson junction J1,
It is determined by the superconducting critical current value of J2.

Here, the bias current supplied to the Josephson junction J1 is set to 50% of the superconducting critical current value by, for example, the values of the DC power supply DC and the bias feed resistor Rb1.

Next, the operation of the superconducting magnetic flux quantum circuit shown in FIG. 1 will be described with reference to FIG.

FIG. 2 is a waveform chart showing the operation of the superconducting magnetic flux quantum circuit shown in FIG. The operation waveforms shown in FIG. 2 show simulation results.
2A shows an output waveform of the DC / SFQ converter 1 (input of the superconducting magnetic flux quantum circuit), and FIG. 2B shows a current waveform (loop current) flowing through the inductance L1 of the superconducting loop. c) shows a current waveform (output of the superconducting magnetic flux quantum circuit) flowing through the damping resistor Rd2.

It is to be noted that the following description will be made so that the magnetic flux for four magnetic flux quanta (Φ ₀ ) can be stored in the superconducting loop (n
= 4), the value of the inductance L1, and the superconducting critical current value of the Josephson junctions J1 and J2 are respectively set.

As shown in FIG. 2A, when the SFQ pulse is output from the DC / SFQ converter 1 at a constant period and supplied to the Josephson junction J1, the Josephson junction J1 has a McCumber constant β of about 1 Since the superconducting loop is set so as to operate in the over-damping state, the superconducting loop generates a magnetic flux quantum (Φ ₀ ) 1 every time the SFQ pulse is input.
The magnetic flux for each piece is stored.

At this time, as shown in FIG. 2 (b), the current flowing through the superconducting loop is the stored magnetic flux (magnetic flux quantum (Φ
₀ ), and when the value exceeds the superconducting critical current value of the Josephson junction J2, that is, the number of stored magnetic flux quanta (Φ ₀ ) becomes L of the superconducting loop.
When the I product is exceeded, Josephson junction J2 switches to a voltage state.

Here, the Josephson junction J2 is set so as to operate in an under-damping state with a Mackamba constant β of about several tens, so that the Josephson junction J2
Switches to the voltage state, the magnetic flux stored in the superconducting loop is discharged at a time, and a pulse current is generated in the damping resistor Rd2 as shown in FIG. 2 (c).

As described above, since the LI product of the superconducting loop is set to 4Φ ₀ in this embodiment, when the magnetic flux equivalent to five flux quanta (Φ ₀ ) is applied to the superconducting loop, Josephson Junction J2 switches to the voltage state. Therefore, a pulse having a period five times the period of the SFQ pulse input to the superconducting flux quantum circuit is output. Also,
Because it has an energy of pulses 4Fai ₀ output at this time, it inputted SFQ pulse of energy (1.phi
It is possible to obtain a pulse having an energy which is four times as large as that of ₀ ).

Therefore, according to the superconducting magnetic flux quantum circuit of this embodiment, it is possible to obtain a pulse having a period five times as long as the period of the input pulse and having a four-fold increase in energy. Thus, a 1/5 frequency divider having an amplifying function can be easily realized.

In the superconducting magnetic flux quantum circuit of the present embodiment, a damping resistor Rd1 is connected in parallel so that the Josephson junction J1 operates in an overdamping state with a Mackamba constant β of about 1, and the Josephson junction J2 is connected. The damping resistor Rd2 is connected in parallel so as to operate in an underdamping state of about several tens of Mackamba constants β. For example, as in a Josephson junction made of a high-temperature superconductor, the Mackamba constant is determined by the characteristics of the junction itself. Can be set as described above, the same effect can be obtained without connecting a damping resistor.

Further, superconducting flux quantum circuit of this embodiment is set to LI product of the superconductive loop 4Fai _0,
The LI product may be set to an arbitrary value (nΦ ₀ ). By doing so, a 1 / (n + 1) frequency dividing circuit can be easily realized.

(Second Embodiment) Next, a second embodiment of the superconducting magnetic flux quantum circuit of the present invention will be described with reference to the drawings.

FIG. 3 shows a second embodiment of the superconducting flux quantum circuit according to the present invention.
FIG. 3 is an equivalent circuit diagram illustrating a configuration of an example.

In FIG. 3, the superconducting magnetic flux quantum circuit of the present embodiment has a configuration obtained by adding a bias feed resistor Rb2 to the configuration of the superconducting magnetic flux quantum circuit of the first embodiment. That is, one end of the bias feed resistor Rb2 is connected to the connection between the inductance L1 and the damping resistor Rd2, and the other end of the bias feed resistor Rb2 is connected to the second DC power supply DC.
2 are connected. Also, the bias feed resistance Rb
The other end of 1 is connected to a first DC power supply DC1.
The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

As in the first embodiment, the Josephson junction J1 is set so as to operate in an over-damping state with a Mackamba constant β of about 1 by the value of the damping resistor Rd1 connected in parallel. The Josephson junction J2 is set so as to operate in an under-damping state with a Mackamba constant β = about several tens depending on the value of the damping resistor Rd2 connected in parallel. The bias current supplied to the Josephson junctions J1 and J2 depends on the values of the first DC power supply DC1 and the bias feed resistance Rb1, and the second DC current DC2 and the bias feed resistance Rb1, for example. Each is set to 50% of the superconducting critical current value.

Next, the operation of the superconducting magnetic flux quantum circuit shown in FIG. 3 will be described with reference to FIG.

FIG. 4 is a waveform diagram showing the operation of the superconducting magnetic flux quantum circuit shown in FIG. The operation waveforms shown in FIG. 4 show simulation results.
4A shows an output waveform of the DC / SFQ converter (input of the superconducting flux quantum circuit), and FIG. 4B shows a current waveform (loop current) flowing through the inductance L1 of the superconducting loop.
FIG. 4C shows the waveform of the current flowing through the damping resistor Rd2 (the output of the superconducting magnetic flux quantum circuit).

In the following, similarly to the first embodiment, the value of the inductance L1 and the value of the inductance L1 are set so that the magnetic flux for four flux quanta (Φ ₀ ) can be stored in the superconducting loop (n = 4). The case where the superconducting critical current values of the Josephson junctions J1 and J2 are respectively set will be described.

As shown in FIG. 4A, when a SF / Q pulse is output from the DC / SFQ converter at a constant period and supplied to the Josephson junction J1, the Josephson junction J1 is connected to the MacKamba as in the first embodiment. Since the superconducting loop is set to operate in an overdamping state with a constant β = 1, the superconducting loop stores a magnetic flux for one magnetic flux quantum (Φ ₀ ) every time an SFQ pulse is input.

At this time, as shown in FIG. 4B, the current flowing through the superconducting loop is the stored magnetic flux (magnetic flux quantum (Φ
₀ ), the number increases stepwise. Since a direct current bias current is supplied to the Josephson junction J2 via the bias feed resistor Rb2, a current obtained by adding a stepwise increasing current to this bias current becomes a superconducting critical current value of the Josephson junction J2. , That is, when the number of stored flux quanta (Φ ₀ ) exceeds the LI product of the superconducting loop, the Josephson junction J2 switches to a voltage state.

Since the Josephson junction J2 is set so as to operate in an under-damping state with a Mackamba constant β = several tens as in the first embodiment, when the Josephson junction J2 is switched to a voltage state, the superconductivity is reduced. The magnetic flux stored in the loop is discharged at a time, and FIG.
As shown in the figure, a pulse current is generated in the damping resistor Rd2. At the same time, a magnetic flux in the opposite direction is stored in the superconducting loop, and the current flowing in the superconducting loop is reversed as shown in FIG. The magnitude of the reverse magnetic flux stored in the superconducting loop is determined by the Josephson junction J
2 and the value of the damping resistor Rd2.

As described above, in this embodiment, since the LI product of the superconducting loop is set to 4Φ ₀ , the time when three magnetic fluxes (Φ ₀ ) are initially stored in the superconducting loop is determined. And the Josephson junction J2 switches to the voltage state,
A pulse current is generated in the damping resistor Rd2. However, at the same time, two magnetic flux quanta (Φ ₀ ) in the opposite direction are stored in the superconducting loop, so that in order to switch the Josephson junction J2 to the voltage state, five magnetic flux quanta (Φ ₀ ) are required. It is necessary to store the minute magnetic flux in a superconducting loop. Therefore, thereafter, as in the first embodiment, a pulse having a cycle five times as long as the cycle of the input pulse is output.

Therefore, the superconducting magnetic flux quantum circuit of the present embodiment can easily realize a 1/5 frequency-dividing circuit as in the first embodiment. Further, by storing the magnetic flux in both the positive and negative directions in the superconducting loop as in the present embodiment, the operation margin with respect to the variation of the circuit constant becomes wider than in the first embodiment.

In the structure of the present embodiment, if the value of the Mackamba constant can be set as described above by the characteristics of the junction itself as in the first embodiment, the same effect can be obtained without connecting a damping resistor. Can be obtained. Furthermore, if the LI product of the superconducting loop is set to an arbitrary value (nΦ ₀ ), a 1 / (n + 1) frequency dividing circuit can be easily realized.

Third Embodiment Next, a third embodiment of the superconducting magnetic flux quantum circuit according to the present invention will be described with reference to the drawings.

FIG. 5 shows a third embodiment of the superconducting flux quantum circuit according to the present invention.
FIG. 3 is an equivalent circuit diagram illustrating a configuration of an example.

In FIG. 5, the superconducting magnetic flux quantum circuit according to the present embodiment is different from the superconducting magnetic flux quantum circuit according to the second embodiment in that the second superconducting flux quantum circuit comprises an inductance L1, an inductance L3, and a Josephson junction J3. This is a configuration in which a loop is added. That is, the inductance L2 and the damping resistor Rd3 are connected in series between the output terminal of the DC / SFQ converter and the ground potential, and the Josephson junction J3 is connected between the connection point of the inductance L2 and the damping resistor Rd3 and the ground potential. I have. One end of a bias feed resistor Rb3 is connected to a connection between the inductance L2 and the damping resistor Rd3, and the other end of the bias feed resistor Rb3 is connected to a third DC power supply DC3. The other configuration is the same as that of the second embodiment, and the description is omitted.

It should be noted that the Josephson junction J1 is set to operate in an over-damping state with a Mackamba constant β of about 1 depending on the value of the damping resistor Rd1 connected in parallel. Josephson junction J2 is
According to the value of the damping resistor Rd2 connected in parallel, it is set so as to operate in an under-damping state where the Mackamba constant β = about several tens. Similarly, the Josephson junction J3 is connected to a damping resistor Rd3 connected in parallel.
Is set so as to operate in an under-damping state with a Mackamba constant β = about several tens.

Further, the value of the inductance L1 constituting the first superconducting loop, and the Josephson junctions J1, J2
Is set so that magnetic flux of n magnetic flux quanta (Φ ₀ ) (n is a positive number) can be stored. Similarly, the value of the inductance L2 constituting the second superconducting loop and the superconducting critical current value of the Josephson junctions J1 and J3 are equivalent to n flux quantum (Φ ₀ ) (n is a positive number).
Is set to be able to store the magnetic flux.

Further, Josephson junctions J1, J2 and J
The bias current supplied to the first DC power supply DC1 and the bias feed resistance Rb1, the second DC current DC2 and the bias feed resistance Rb1, and the third DC power supply DC
3 and the value of the bias feed resistance Rb3, respectively, are set to 50% of the superconducting critical current value of the Josephson junction.

Next, the operation of the superconducting magnetic flux quantum circuit shown in FIG. 5 will be described with reference to FIG.

FIG. 6 is a waveform chart showing the operation of the superconducting magnetic flux quantum circuit shown in FIG. The operation waveform shown in FIG. 6 shows a simulation result.
(A) shows an output waveform of the DC / SFQ converter (input of the superconducting flux quantum circuit), and FIG. 6 (b) shows a current waveform (loop current 1) flowing through the inductance L1 of the first superconducting loop. FIG. 6C shows a current waveform (output 1 of the superconducting magnetic flux quantum circuit) flowing through the damping resistor Rd2, which is the output of the first superconducting loop. FIG. 6D shows a current waveform (loop current 2) flowing through the inductance L2 of the second superconducting loop, and FIG. 6E shows a damping resistor Rd3 which is the output of the second superconducting loop.
Of the current flowing through the superconducting flux quantum circuit (output 2).

In the following, the value of the inductance L1 and the value of the Josephson junction J1, J2, J3, and J4 are set so that two magnetic flux quanta (Φ ₀ ) can be stored in the first superconducting loop (n = 2). The superconducting critical current value of J2 is set, and the value of the inductance L2 and the value of Joseph are set so that the magnetic flux for four flux quanta (Φ ₀ ) can be stored in the second superconducting loop (n = 4). The case where the superconducting critical current values of the son junctions J1 and J3 are set respectively will be described.

As shown in FIG. 6A, the DC / SFQ
An SFQ pulse is output from the inverter at regular intervals,
When supplied to the Sefson junction J1, the Josephson junction J
1 is an over-damping state with Mackamba constant β = 1
The first superconductivity because it is set to operate in
The loop generates a flux quantum every time an SFQ pulse is input.
(Φ ₀) Store one magnetic flux.

At this time, as shown in FIG.
The current flowing in the superconducting loop increases stepwise according to the stored magnetic flux (the number of magnetic flux quanta (Φ ₀ )).
A bias feed resistor Rb2 is connected to the Josephson junction J2.
, A current obtained by adding a stepwise increasing current to the bias current exceeds the superconducting critical current value of the Josephson junction J2, that is, the accumulated magnetic flux. When the number of quanta (Φ ₀ ) exceeds the LI product of the first superconducting loop, Josephson junction J2 switches to a voltage state.

The Josephson junction J2 has a Mackamba constant β
When the Josephson junction J2 is switched to the voltage state, the magnetic flux stored in the first superconducting loop is discharged at a time when the Josephson junction J2 is switched to the voltage state. As shown in (c), a pulse current is generated in the damping resistor Rd2. Also,
At the same time, the first superconducting loop stores a magnetic flux in a direction opposite to that of the first superconducting loop, and the current flowing in the first superconducting loop is inverted as shown in FIG. The magnitude of the reverse magnetic flux stored in the first superconducting loop depends on the bias current value of the Josephson junction J2 and the damping resistance Rd2.
Depends on the value of

On the other hand, as shown in FIG. 6D, when the SFQ pulse was supplied to the Josephson junction J1, the current flowing in the second superconducting loop was stored similarly to the first superconducting loop. It increases stepwise according to the magnetic flux (the number of magnetic flux quanta (Φ ₀ )). Since a direct current bias current is supplied to the Josephson junction J3 via the bias feed resistor Rb3, a current obtained by adding a stepwise increasing current to the bias current becomes a superconducting critical current value of the Josephson junction J3. , Ie, when the number of stored flux quanta (Φ ₀ ) exceeds the LI product of the second superconducting loop, the Josephson junction J3 switches to a voltage state.

The Josephson junction J3 has a Mackamba constant β
When the Josephson junction J3 is switched to the voltage state, the magnetic flux stored in the second superconducting loop is discharged at a time when the Josephson junction J3 is switched to the voltage state. As shown in (e), a pulse current is generated in the damping resistor Rd3. Also,
At the same time, a magnetic flux in the opposite direction is stored in the second superconducting loop, and the current flowing in the superconducting loop is reversed as shown in FIG. The magnitude of the reverse magnetic flux stored in the second superconducting loop is determined by the Josephson junction J
3 and the value of the damping resistor Rd3.

[0070] As described above, in this embodiment LI product of the first superconducting loop is set to 2 [phi _0, since the LI product of the second superconducting loop is set to 4Fai _0, the second embodiment As in the example, the first superconducting loop outputs a pulse having a cycle three times the cycle of the input pulse, and the second superconducting loop outputs a pulse having a cycle five times the cycle of the input pulse. Is done.

Therefore, according to the superconducting magnetic flux quantum circuit of this embodiment, two pulses having different periods can be simultaneously obtained from one circuit.

In this embodiment, the configuration in which two superconducting loops are connected in parallel is shown, but a configuration in which more superconducting loops are connected in parallel may be adopted. in this case,
Pulses with more different periods can be obtained simultaneously.

(Fourth Embodiment) FIG. 7 is an equivalent circuit diagram showing a configuration of a fourth embodiment of the superconducting magnetic flux quantum circuit of the present invention.

The superconducting magnetic flux quantum circuit of the present embodiment is obtained by connecting the Josephson junction J2 of the superconducting magnetic flux quantum circuit of the first embodiment to
SQUID (Superconducting Quantum) with control line
Interference Device). The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

As shown in FIG. 7, SQUID2 includes inductances L3 and L4 connected in series, and a damping resistor Rd connected in parallel with inductances L3 and L4.
And Josephson junctions J4 and J5, one ends of which are connected to both ends of a damping resistor Rd4 and the other end is grounded.
And is constituted by. Inductors L5 and L6 connected in series are arranged at positions magnetically coupled to the inductances L3 and L4 of the SQUID2. The terminals of the inductance L5 not connected to the inductance L6 are connected to the ground potential,
The terminal of the inductance L6 that is not connected to 5 is connected to the control power supply (DC4) via the bias feed resistance Rd4.

In the SQUID 2 shown in FIG. 7, by changing the value of the control current supplied to the control wiring having the inductances L5 and L6, the current flowing through the inductances L3 and L4 changes and the superconductivity of the Josephson junctions J4 and J5 changes. The critical current value can be changed.

Therefore, the inductance L1 and jose
Superconducting loop consisting of Fuson junction J1 and SQUID2
LI product is changed by the control current of SQUID2
Can be stored in a superconducting loop
The magnitude of the magnetic flux (flux quantum (Φ ₀Can change the number))
It is possible to arbitrarily change the period of the output pulse
Can be.

For example, if the number of pulses output from the superconducting magnetic flux quantum circuit of this embodiment is read by a counter,
A digital value corresponding to the analog voltage input as the control voltage can be obtained. That is, if the superconducting magnetic flux quantum circuit of this embodiment is used, an A / D (analog / digital) conversion circuit can be configured.

In this embodiment, the Josephson junction J2 shown in the first embodiment is replaced by a SQUID capable of efficiently changing the superconducting critical current value of the Josephson junction.
However, the control wiring may be magnetically coupled to the Josephson junction J2 to change the superconducting critical current value.

Further, not only the circuit shown in the first embodiment but also the Josephson junction J2 shown in the second embodiment
The same effect as that of the present embodiment can be obtained by replacing the Josephson junctions J2 and J3 shown in the third embodiment with SQUIDs.

[0081]

Since the present invention is configured as described above, the following effects can be obtained.

When the first Josephson junction is set to operate in the over-damping state and the second Josephson junction is set to operate in the under-damping state, a pulse is input from the signal input terminal. Each time the magnetic flux of one flux quantum is stored in the superconducting loop, the number of input pulses can be stored according to the magnitude of the magnetic flux stored in the superconducting loop.

By setting the superconducting critical current value and the inductance value of the Josephson junction forming the superconducting loop to values that can store at least one magnetic flux quantum, When the magnetic flux can no longer be stored, a pulse having energy corresponding to the magnetic flux stored up to that point is output from the signal output terminal. It is possible to obtain a pulse having the energy and the amplified energy. Therefore, a frequency dividing circuit having an amplifying function can be easily realized.

Further, by supplying a predetermined bias current from the signal input terminal and the signal output terminal, respectively, the operation margin with respect to the variation of the circuit constant is widened as compared with the case where the predetermined bias current is supplied only from the signal input terminal. .

Further, the superconducting critical current value of the second Josephson junction or the third Josephson junction is arranged at a position magnetically coupled to the second Josephson junction or the third Josephson junction. Having a control wiring to which a control signal for changing
Since the I product can be changed by the control signal, the magnitude of the magnetic flux that can be stored in the superconducting loop can be changed, and the period of the output pulse can be arbitrarily changed.

In particular, an SQ having control wiring instead of the second Josephson junction or the third Josephson junction
By having the UID, the LI product of the superconducting loop can be changed efficiently.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram showing a configuration of a first embodiment of a superconducting magnetic flux quantum circuit of the present invention.

FIG. 2 is a waveform chart showing an operation state of the superconducting magnetic flux quantum circuit shown in FIG.

FIG. 3 is an equivalent circuit diagram showing a configuration of a second embodiment of the superconducting magnetic flux quantum circuit of the present invention.

FIG. 4 is a waveform chart showing an operation state of the superconducting magnetic flux quantum circuit shown in FIG.

FIG. 5 is an equivalent circuit diagram showing a configuration of a third embodiment of the superconducting magnetic flux quantum circuit of the present invention.

6 is a waveform chart showing an operation state of the superconducting magnetic flux quantum circuit shown in FIG.

FIG. 7 is an equivalent circuit diagram showing a configuration of a fourth embodiment of the superconducting magnetic flux quantum circuit of the present invention.

FIG. 8 is an equivalent circuit diagram showing a configuration of a conventional superconducting magnetic flux quantum circuit.

[Explanation of symbols]

 1 DC / SFQ converter 2 SQUID L1 to L6 Inductance J1 to J5 Josephson junction Rb1 to Rb4 Bias feed resistance Rd1 to Rd4 Damping resistance

Claims (14)

(57) [Claims] A first Josephson junction having one end connected to a signal input end and the other end grounded; a second Josephson junction connected to one end to a signal output end and the other end grounded; And an inductance connected between the signal input terminal and the signal output terminal, wherein the first Josephson junction has a Mackamba constant of about 1.
It is set to operate in the over damping state, the second Josephson junction number Makkanba constant 10
A superconducting flux quantum circuit set to operate in a degree of underdamping. 2. The superconducting junction of the first Josephson junction.
Field current value, superconducting critical voltage of the second Josephson junction
The flow value and the inductance value are equal to the first Josephson junction and the second Josephson junction;
Junction and superconducting loop consisting of the inductance
Therefore, storing magnetic flux for at least one magnetic flux quantum
The superconducting magnetic flux quantum circuit according to claim 1, wherein the superconducting magnetic flux quantum circuits are set to values that can be obtained . 3. A predetermined bias current from the signal input terminal.
3. The superconducting flux quantum circuit according to claim 1, wherein 4. The signal input terminal and the signal output terminal
Claims wherein a predetermined bias current is respectively supplied or
3. The superconducting magnetic flux quantum circuit according to 2. 5. The method according to claim 5, wherein said second Josephson junction is magnetically coupled to said second Josephson junction.
A second Josephson junction disposed at a coupling position;
Control signal to change the superconducting critical current value of
The control wiring according to claim 1, further comprising:
A superconducting flux quantum circuit. 6. A superconducting critical current value of a Josephson junction included therein is changed in place of the second Josephson junction.
SQ provided with a control wiring to which a control signal for receiving
The superconducting magnetic flux quantum circuit according to any one of claims 1 to 5, having a UID . 7. A first Josephson junction having one end connected to the signal input end and the other end grounded, and a second Josephson connected at one end to the first signal output end and the other end grounded. A third junction, one end of which is connected to the second signal output terminal and the other end of which is grounded; and a first junction connected between the signal input terminal and the first signal output terminal. And a second inductance connected between the signal input end and the second signal output end, wherein the first Josephson junction has a Mackamba constant of about 1
It is set to operate in the over damping state, the second Josephson junction number Makkanba constant 10
Is set to operate in underdamped condition degree, the third Josephson junction number Makkanba constant 10
A superconducting flux quantum circuit set to operate in a degree of underdamping. 8. The superconducting junction of the first Josephson junction.
Field current value, superconducting critical voltage of the second Josephson junction
Current value, superconducting critical current of the third Josephson junction
Value, the value of the first inductance, and the value of the second inductance.
The value of the conductance is the first Josephson junction, the second Josephson junction,
A first superjunction comprising a junction and the first inductance
The magnetic flux of at least one flux quantum by the conduction loop
Are set to values capable of storing the first Josephson junction and the third Josephson junction, respectively.
A second superjunction comprising a junction and the second inductance
The magnetic flux of at least one flux quantum by the conduction loop
8. A value which is set to a value that can store
A superconducting flux quantum circuit as described . 9. A predetermined bias current from the signal input terminal.
9. The superconducting magnetic flux quantum circuit according to claim 7, wherein: 10. The signal input terminal and the first signal output.
From the second signal output terminal.
9. The superconducting magnetic flux quantum circuit according to claim 7, wherein an assembling current is supplied . 11. The second Josephson junction and a magnetic field
And the second Josephson contact
Control signal to change the superconducting critical current
The control wiring according to any one of claims 7 to 10, further comprising:
A superconducting flux quantum circuit as described . 12. The third Josephson junction and magnetically
The third Josephson connection
Control signal to change the superconducting critical current
The control wiring according to any one of claims 7 to 11, comprising:
A superconducting flux quantum circuit as described . 13. The method according to claim 12, wherein said second Josephson junction is replaced with said second Josephson junction.
Te, varying the superconducting critical current value of the Josephson junction having its own
SQ provided with a control wiring to which a control signal for receiving
The superconducting magnetic flux quantum circuit according to any one of claims 7 to 12, having a UID . 14. The method according to claim 1, wherein said third Josephson junction is replaced with said third Josephson junction.
Te, varying the superconducting critical current value of the Josephson junction having its own
SQ provided with a control wiring to which a control signal for receiving
14. The superconducting magnetic flux quantum circuit according to claim 7, having a UID .