JPS6142452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ternary logic circuit using a Josephson junction device.

A Josephson bonding device is already known, and this Josephson bonding device has the following advantages. The advantages of this are: (a) Low power consumption (several microwatts to several tens of microwatts)
w/gate) (b) Ultra-high switching speed (several tens of ps/gate) can be obtained, (c) Low power consumption reduces heat dissipation, and therefore allows for high-density integration, (d) Elements The structure is simple, conventional IC technology can be used for pattern formation, and (e) a variety of logical operations are possible with a simple circuit configuration.

On the other hand, almost all logic circuits used in current computers are based on binary logic. That is, logical operations are performed by associating electrical switches, on and off, with binary numbers "1" and "0". On the other hand, a ternary logic circuit has 3
It performs logical operations using two basic states, and compared to binary logic, (a) fewer digits are required to process the same information, enabling high-speed processing; (b) the same It has the following advantages: (c) high utilization efficiency for transmission media, and (c) high storage density.

However, despite the above advantages, 3
The reason why value logic circuits have hardly been put into practical use is that trying to perform three-value logic using a combination of transistors and diodes makes the circuit complicated, and the above (a)
This is because the advantages of (c) cannot be fully utilized.

The present invention is based on the above invention, and includes:
It is an object of the present invention to provide a ternary logic circuit using a Josephson junction device that can perform ternary logic with a simple circuit configuration while taking advantage of the advantages of the Josephson junction device. Therefore, the ternary logic circuit using the Josephson junction device according to the first aspect of the present invention has a plurality of input signal lines to which ternary input signals are supplied, an external magnetic field generating means, a Josephson junction, and a critical current. Three superconductor current branches A, B, C with Josephson junction devices with axis-asymmetric critical current-external magnetic field characteristics
and a first whose upper end is connected to the upper end of the superconductor current branch A via the superconductor current branch C and whose lower end is connected to the junction of the superconductor current branches A and B. a second constant current source whose upper end is connected to the junction of the superconductor current branches A and B and whose lower end is connected to the lower end of the superconductor current branch B; is connected to the upper end of the superconductor current branch A and the lower end is connected to the lower end of the superconductor current branch B, and the junction of the two resistors and the superconductor an output circuit installed between the junction of conductor current branches A and B, and a current branch having a resistor connected in parallel to said superconductor current branch C;
and a bias circuit for applying a bias magnetic field component to the Josephson junction of the Josephson junction device, and the external magnetic field generating means of the Josephson device provided in the superconductor current branch A is a current branch having the resistance. The external magnetic field generating means of the Josephson device provided in the superconductor current branch B adds an external magnetic field component that is a function of the value of the current flowing in the input signal line to the corresponding Josephson junction, and Adding the external magnetic field component, which is a function of the value, to the corresponding Josephson junction,
The external magnetic field generating means of the Josephson device provided in the superconductor current branch C is also configured to apply an external magnetic field component that is a function of the input signal current value flowing through the input signal line to the corresponding Josephson junction. It is characterized by the presence of Further, a ternary logic circuit using the second Josephson junction device of the present invention has a plurality of input signal lines to which ternary input signals are supplied, an external magnetic field generating means, a Josephson junction, and a critical current axis. Three superconductor current branches A, B, and C are provided with Josephson junction devices having critical current-external magnetic field characteristics asymmetrical to a first constant current source whose lower end is connected to the junction of the superconductor current branches A and B; and whose upper end is connected to the junction of the superconductor current branches A and B, and whose lower end is connected to the junction of the superconductor current branches A and B. a second constant current source connected to the lower end of the superconductor current branch B via the superconductor current branch C, and a second constant current source whose upper end is connected to the upper end of the superconductor current branch A and whose lower end is two resistors connected in series connected to the lower end of the superconductor current branch B;
The junction point of the two resistors and the superconductor current branch A
and B, a current branch having a resistor connected in parallel to the superconductor current branch C, and a current branch for applying a bias magnetic field component to the Josephson junction of the Josephson junction device. The external magnetic field generating means of the Josephson device, which includes a bias circuit and is provided in the superconductor current branch A, generates an external magnetic field component that is a function of the current value flowing through the input signal line to the corresponding Josephson junction. In addition, the external magnetic field generating means of the Josephson device provided in the superconductor current branch B applies an external magnetic field component that is a function of the value of the current flowing in the current branch having the resistance to the corresponding Josephson junction; The external magnetic field generating means of the Josephson device provided in the superconductor current branch C is also configured to apply an external magnetic field component that is a function of the input signal current value flowing through the input signal line to the corresponding Josephson junction. It is characterized by the presence of

Hereinafter, the present invention will be explained with reference to the drawings. Prior to this, a brief explanation of the Josephson bonding device will be given. FIG. 1 shows a Josephson junction element, and FIG. 2 shows an example of a Josephson junction device having a line for generating an external magnetic field.
FIG. 3 shows the voltage-current characteristics of the Josephson junction device, and FIG. 4 shows the external magnetic field-critical current characteristics of the Josephson junction device of FIG. 2.

In FIG. 1, 1 and 2 are superconducting thin films, and 3 is an oxide film. As shown in Figure 3, when the device current I is increased, the voltage across the Josephson junction device is zero until it reaches the critical current value Ic, and the device current I exceeds the critical current value Ic. produces a voltage across the Josephson junction element. This voltage varies depending on the thin film material, but in the case of lead it is approximately 2.7 mV. As the device current I is decreased, the Josephson junction device remains in a voltage state until the minimum current I _MIN is reached, but I _MIN
When the voltage is below, it becomes a no-voltage state. In FIG. 3, points P ₁ and P ₂ indicate the intersection of the voltage-current characteristic curve of the Josephson junction element and the load straight line, and these points P ₁ and P ₂ are stable points. In order to shift the Josephson junction element from a no-voltage state to a voltage state, the critical current value Ic may be set to below the current at the stable point _P1 . In order to shift the Josephson junction element from a voltage state to a non-voltage state, the element current I may be set to be less than or equal to the minimum current value I _MIN .

In Fig. 2, 4 is a line for generating an external magnetic field, and 5 is a line for generating an external magnetic field.
6 is a substrate made of silicon or glass, 6 is a thin film of superconducting metal serving as a ground plane for the strip line, and 7 is an insulating layer made of SiO ₂ or the like. The insulating layer 7 functions as a dielectric for the strip line. The Josephson bonding device shown in FIG. 2 is of the so-called in-line gate type. FIG. 4 shows the external magnetic field-critical current characteristics of the Josephson junction device of FIG. 2. The external magnetic field H is a current I flowing through the external magnetic field generation line 4.
This is caused by _H. In the external magnetic field vs. critical current characteristic shown in Figure 4, the characteristic curve is asymmetrical with respect to the critical current value Ic axis, but in the so-called cross gate type Josephson junction device, the external magnetic field vs. critical current The characteristics are symmetrical about the critical current Ic axis. In the present invention, an in-line gate type Josephson junction device is used.

FIG. 5 shows a Josephson junction device operating as a basic gate. When an element current I flows through Josephson junction device J and it is in a no-voltage state, when a predetermined current flows through input signal lines 4', 4' (connected to external magnetic field generation lines 4, 4), Josephson junction device J is in a voltage state and current flows through load resistor _R1 . The above is a general description of the Josephson bonding apparatus.

FIG. 6 shows an example of a three-value logic circuit using a Josephson junction device, and FIG. 7 is an explanatory diagram of its operation. In the figure, 8 and 9 are current sources that flow constant current pulses, 10 is an input signal line, 11 is an output circuit, J ₁ and J ₂ are Josephson junction devices, Is is an input signal current, I _p is an output signal current, and A , B shows a current branch provided with a Josephson junction device. The input signal line 10 is integrated with the partial magnetic field generating line 4 of the Josephson junction devices J ₁ and J ₂ . Note that all wiring between elements is made of superconductor. The input signal current I _s takes one value of "-1", "0" or "1", and the output signal current I _p also takes a value of "-1", "0" or "1". It takes one value. In Josephson junction device J ₁ , the relationship between the direction of the element current and the direction of the input signal current I _s flowing through the external magnetic field generation line 4 is the input signal current I _s
The relationship is such that when the logic is "1", the above-mentioned two currents are in the same phase. In the Josephson joining machine J ₂ ,
When the input signal current _Is is logic "-1", the element current and the input signal current _Is are in phase.

When the input signal current I _s is logic "0", the operating point of Josephson junction device J ₁ is at point e, and the operating point of Josephson junction device J ₂ is at point f. When a constant current pulse I is supplied to Josephson junction devices J ₁ and J ₂ , the critical current Ic is larger than the element current I at points e and f, so the Josephson junction devices
J ₁ and J ₂ remain voltage-free. Devices J ₁ and J ₂
Since no voltage develops across the superconductor current branches A and B, no voltage develops across the output circuit 11.
No current flows through. That is, a logic "0" output signal current flows through the output circuit 11.

Assuming that the input signal current I _s is (+i), ie, logic "1", an external magnetic field H is applied to Josephson junction devices J ₁ and J ₂ by this current i. As a result, the operating point of device J ₁ shifts to point a, and the operating point of device J ₂ shifts to point b. Josephson joining equipment
When a constant current pulse I is supplied to J ₁ and J ₂ , the device J ₁
Since the critical current Ic is smaller than the element current I, the device _J1 is in a voltage state. Device J ₂ does not come into voltage state and remains voltage-free. When Josephson junction device J ₁ enters a voltage state, a voltage is generated across current branch A, and current iR flows in output circuit 11 in the direction of the arrow. If this state corresponds to logic "1", an output signal of logic "1" is generated in the output circuit 11. Note that the input signal current I _s is a pulse current, which is synchronized with the constant current pulse I flowing from the current sources 8 and 9.

When the input signal current is (-i), that is, the logic is "-1", the operating point of Josephson junction device J ₁ shifts to point C, and the operating point of Josephson junction device J ₂ shifts to point d. When a constant current pulse I flows through Josephson junction devices J ₁ and J ₂ , only device J ₂ is in a voltage state. As a result, a voltage is generated only across the current branch B, and a current (-iR) flows through the output circuit 11. In other words, an output signal of logic "-1" is generated.

To summarize the above operation, in the circuit shown in FIG. 6, for input signal current I _s (-i, 0, i), output signal current I _p (-iR,
0, iR) flows, and the above circuit becomes a ternary logic circuit that obtains the same output signal as the input signal. In the circuit of FIG. 6, by simply flowing the input signal current I _s in the opposite direction, the output signal current I _p will be equal to the input signal current I _s .
(iR, 0, -iR) is obtained. That is, by changing the direction of the input signal current, this circuit
It becomes a negative circuit.

FIG. 8 is a diagram showing another example of a ternary logic circuit using Josephson junction device, and FIG.
Figure 0 is an explanatory diagram of its operation. The circuit of FIG. 8 operates as a cycling gate or double cycling gate. A cycling gate obtains an output signal of (0, 1, -1) for an input signal of (-1, 0, 1). In other words, the cycling gate is “-
For input signals of "1" and "0", the output signal is "1" added, and for the input signal of "1", the output signal is "2".
The output signal obtained by subtracting . A double cycling gate is an input signal (-1, 0,
This is a gate that obtains an output signal (1, -1, 0) for 1).

The circuit in FIG. 8 can basically be the same as the circuit in FIG. 6, with the only difference being the bias circuits 12 and 1.
3 are provided with bias currents I _B1 and I
This is the point where _B2 was played. By passing the bias current I _B1 , a bias magnetic field H _B1 is applied to the Josephson junction element J ₁ , and by passing the bias current I _B2 , a bias magnetic field H _B2 is applied to the Josephson junction element J ₂ . Bias circuit 12,1
It goes without saying that the external magnetic field generating line 4 is formed in a part of the magnetic field 3.

When the input signal current I _s flowing through the input signal 10 is logic "0", as shown in FIG. 9, the operating point of the Josephson junction device J ₁ is at point a, and the operating point of the Josephson junction device J ₂ is at point b. At the point. Therefore, a voltage is generated only across the superconductor current branch A, which causes an output signal current I _p to flow in the output circuit 11 in the direction of the arrow.

When the input signal current I _s flowing through the input signal line 10 is logic "1", the operating point of Josephson junction device J ₁ is point c, and the operating point of Josephson junction device J ₂ is point d. Therefore, a voltage is generated only across the superconductor current branch B, which causes an output signal current I _p to flow in the output line 11 in the direction opposite to the arrow.

When the input signal current I _s flowing through the input signal line 10 is logic "-1", the operating point of the Josephson junction device J ₁ is point e, and the operating point of the Josephson junction device J ₂ is point f. Therefore, a voltage also occurs across superconductor current branch A, and a voltage also occurs across superconductor current branch B, which causes output circuit 1
No current flows through 1. As can be seen from the above explanation, when the bias magnetic fields H _B1 and H _B2 are set as shown in FIG. 9, the circuit of FIG.
It becomes a gate.

The circuit of FIG. 8 becomes a double cycling gate when bias magnetic fields H _B1 and H _B2 are applied as shown in FIG. 10. Since the operating principle is the same as the cycling gate, the explanation of the double cycling gate will be omitted. The above description has been made of a three-value logic circuit with one type of input signal, that is, one variable, but a three-value logic circuit with multiple variables will be described below.

FIG. 12 shows an example of a multi-variable binary logic circuit. The circuit shown in FIG. 12 functions as a ternary logic circuit. n ternary logical variables
The logical sum of A ₁ , A ₂ ,...A _o is A ₁ +A ₂ +...A _o ≡MAX (A ₁ , A ₂ ,...A _o ). That is, the value of the logical sum of the ternary logical variables A ₁ , A ₂ , . . . _{A o is} the maximum value among the values of A ₁ , A ₂ , . Figure 11 shows 3 when there are two variables.
This shows a value OR (logical sum) operation truth table. As can be seen from this table, when the value of the logical function is "1", variable A ₁ is "1" or variable A ₂ is "1", and when the value of the logical function is "0", variable A Either one of ₁ and A ₂ is "0" and the other is "-1", or both variables A ₁ and A ₂ are "0",
When the value of the logical function is "-1", both variables A ₁ and A ₂ are "-1".

In FIG. 12, 14 and 15 are bias circuits, and 16 and 17 are input signal lines. The bias current I _B1 flowing through the bias circuit 14 applies a bias magnetic field to the Josephson joining devices J ₁ and J ₂ , and the bias current I _B2 flowing through the bias circuit 15 applies a bias magnetic field to the Josephson joining device J ₃ . Input signal current I _A1 flowing through input signal line 16
corresponds to the three-value logic variable A ₁ and the input signal line 17
The input signal current I _A2 flowing through corresponds to the three-value logic variable A ₂ .

Bias current I _B1 causes Josephson junction device J 1 to enter voltage state only when input signal current I _A1 is logic “ ₁ ” and Josephson junction device J ₂ enters voltage state only when input signal current I _A2 is logic “1”. adjusted to suit the condition. Bias current I _B2 is adjusted such that Josephson junction J ₃ is in a voltage state only when input signal currents I _A1 and I _A2 are both logic "-1".

In the circuit of FIG. 12, the bias current I _B1 ,
It is clear that if I _B2 is set as above, this circuit will operate as an OR circuit, so
Further explanation will be omitted.

13 is a diagram showing an embodiment of the first invention of the present invention. The circuit in FIG. 13 also shows a ternary OR circuit for two variables. The OR circuit shown in FIG. 12 has the following problems. In FIG. 12, when either one of the input signal currents I _A1 , I _A2 is logic "1" and the input signal currents I _A1 , I
When _A2 are both logic "1", the output signal current I _p becomes logic "1", but in the former case, device J ₁ or
Either one of J ₂ will be in a voltage state, and in the latter case both devices J ₁ and J ₂ will be in a voltage state. That is, in the former case, a voltage of approximately 2.7 mV is generated across the current branch A, and a current corresponding to this voltage flows to the output circuit 11, and in the latter case, a voltage of approximately 5.4 mV is generated across the current branch A.
voltage is generated, and a current corresponding to this is generated in output circuit 1.
Flows to 1. As described above, even if the output signal is logic "1", the current value differs depending on the case. The circuit shown in FIG. 13 is an improvement on this point. In the circuit of FIG. 13, four Josephson junction devices J ₁ , J ₂ , J ₃ , J ₄ are used, current branch A is provided with Josephson junction device J ₄ and current branch B is provided with Josephson junction device J ₃ . is provided, and Josephson junction devices J ₁ and J ₂ are provided in the current branch C. 13th
Although the bias circuit is not shown in the diagram, each device
A bias magnetic field is applied to J ₁ , J ₂ , J ₃ , and J ₄ . The bias magnetic field for Josephson junction device J ₁ is such that the input signal current I _A1 is logic “1”.
The device J ₁ is regulated so that it is in a voltage state only when . The bias magnetic field for Josephson junction device J ₂ is adjusted such that device J ₂ is in a voltage state only when input signal current I _A2 is a logic "1". The bias magnetic field for Josephson junction device J ₃ is such that the input signal currents I _A1 and I _A2 are both logic "-".
1'' so that device _J3 is in voltage state only. The bias magnetic field for Josephson junction device J ₄ is adjusted such that device J ₄ is in a voltage state only when a predetermined amount of current flows in current branch 18 . Note that the bias magnetic field for Josephson bonding device _J4 may be omitted in some cases.

When the input signal current I _A1 or I _A2 is a logic "1", Josephson junction device J ₁ or J ₂ is in a voltage state and a voltage is developed across current branch C. This causes a predetermined current to flow in the current branch 18, which brings Josephson junction device _J4 into a voltage state. When the device J ₄ enters the voltage state, a voltage is present across the current branch A, causing an output signal current to flow in the output circuit 11 in the direction of the arrow.

When operating other gates using the OR circuit shown in FIG. 12 or the OR circuit shown in FIG. If used, the circuits of FIGS. 12 and 13 operate as NOR circuits.

FIG. 15 shows a second embodiment of the present invention, and this circuit operates as a binary AND circuit of two variables. The logical product of n ternary logical variables A ₁ , A ₂ , . . . A _o is A ₁ ·A ₂ , . . . A _o ≡MIN (A ₁ , A _{2 ,} . That is, the value of the logical product of the ternary logical variables A ₁ , A ₂ , . . . _{A o is} the minimum value among the values of A ₁ , A ₁ , . Figure 14 shows the three-value AND of two variables A ₁ and A ₂
(logical product) This shows the operational truth table.

Although the bias circuit is omitted in FIG. 15, a bias magnetic field is applied to each Josephson joining device J ₁ , J ₂ , J ₃ , and J ₄ . The bias magnetic field for Josephson junction device J ₁ is adjusted such that device J ₁ is in a voltage state only when input signal currents I _A1 and I _A2 are both logic "1". The bias magnetic field for Josephson junction device J ₂ is such that the input signal current I _A1 is
The bias field for Josephson junction device J ₃ is adjusted such that device J ₂ is in the voltage state only when the input signal current I _A2 is at logic “−”.
1'', the device _J3 is regulated to be in voltage state. The bias magnetic field for Josephson junction device J ₄ is adjusted such that device J ₄ is in a voltage state only when a predetermined range of current flows in current branch 18 . Either one of the input signal currents I _A1 and I _A2 is logic "-1" or both are logic "-1"
When , a voltage is generated across the current branch C, and a predetermined current flows through the current branch 18. This places Josephson junction device J ₄ in a voltage state;
Output signal current I in the direction opposite to the arrow in the output circuit 11
_p flows. Since further explanation of the operation is considered unnecessary, further explanation will be omitted.
If the output signal is used in the opposite direction in Fig. 15,
This circuit becomes a NAND circuit.

As is clear from the above description, according to the present invention, a desired three-valued logic circuit can be constructed with a significantly reduced number of circuit elements. For example, if a three-value AND circuit is constructed using transistors, 10 to 20 transistors are required, but according to the present invention, a three-value AND circuit is constructed using only four Josephson junction devices. can. Further, according to the present invention, the actual current value corresponding to the logical value of the output can be made constant.

[Brief explanation of the drawing]

Figure 1 is a perspective view of Josephson junction element, Figure 2
Figure 3 is a perspective view of the Josephson junction device, Figure 3 is a voltage-current characteristic diagram of the Josephson junction element shown in Figure 1, Figure 4 is a critical current-external magnetic field characteristic diagram of the Josephson junction device shown in Figure 2, and Figure 5 is a circuit diagram of a basic gate using a Josephson junction device, and Figure 6 is a circuit diagram of a ternary logic circuit using a Josephson junction device.
A circuit diagram showing an example, FIG. 7 is an explanatory diagram of the operation of the circuit in FIG.
A circuit diagram showing another example of a value logic circuit, Figures 9 and 10 are diagrams explaining the operation of the circuit in Figure 8, Figure 11 is a diagram showing the truth value of 3-value OR operation, and Figure 12 is a multivariable FIG. 13 is a circuit diagram showing an example of a ternary logic circuit of the present invention, and FIG.
FIG. 4 is a diagram showing a three-value AND truth value, and FIG. 15 is a circuit diagram of a second embodiment of the present invention. 1 and 2... superconducting thin film, 3... oxide film, 4...
External magnetic field generation line, 5... board, 6... ground plane, 7... insulating layer, 8 and 9... power supply,
10...Input signal line, 11...Output circuit, 12
and 13...bias circuit, 14 and 15...bias circuit, 16 and 17...input signal line, 18...
Current branches, J and J ₁ to J ₄ ... Josephson junction device, A to C ... superconductor current branches, R _L ... load resistance.

Claims (1)

[Claims] 1. A Josephson device that has a plurality of input signal lines to which three-value input signals are supplied, an external magnetic field generating means, a Josephson junction, and has critical current-external magnetic field characteristics that are asymmetrical with respect to the critical current axis. Three superconductor current branches A, B, and C are provided with bonding devices, and their upper ends are connected to the upper end of the superconductor current branch A via the superconductor current branch C, and their lower ends are connected to the upper end of the superconductor current branch A. a first connected to the junction of superconductor current branches A and B;
a second constant current source whose upper end is connected to the junction of the superconductor current branches A and B and whose lower end is connected to the lower end of the superconductor current branch B; is connected to the upper end of the superconductor current branch A and the lower end is connected to the lower end of the superconductor current branch B, and the junction of the two resistors and the superconductor A bias magnetic field is applied to an output circuit installed between the junction of conductor current branches A and B, a current branch having a resistor connected in parallel to the superconducting current branch C, and a Josephson junction of a Josephson junction device. and a bias circuit for adding a component, and the means for generating an external magnetic field of the Josephson device provided in the superconductor current branch A has an external magnetic field that is a function of the value of the current flowing in the current branch having the resistance. In addition to applying a magnetic field component to the corresponding Josephson junction, external magnetic field generating means of the Josephson device provided in the superconductor current branch B generate an external magnetic field component that is a function of the input signal current value flowing in the input signal line. In addition to the corresponding Josephson junction, the external magnetic field generating means of the Josephson device provided in the superconductor current branch C also generates an external magnetic field component that is a function of the input signal current value flowing through the input signal line using a corresponding Josephson junction. A ternary logic circuit using a Josephson junction device, characterized in that the circuit is configured to add to a Josephson junction device. 2. A Josephson junction device is provided which has a plurality of input signal lines to which three-value input signals are supplied, an external magnetic field generating means, a Josephson junction, and has critical current-external magnetic field characteristics asymmetrical with respect to the critical current axis. Three superconductor current branches A, B, C,
a first constant current source whose upper end is connected to the upper end of the superconductor current branch A and whose lower end is connected to the junction of the superconductor current branches A and B; a second constant current source connected to the junction of branches A and B, the lower end of which is connected to the lower end of the superconductor current branch B via the superconductor current branch C; two resistors connected in series, the upper end of which is connected to the upper end of the superconductor current branch A, and the lower end of which is connected to the lower end of the superconductor current branch B; the junction of the two resistors and the superconductor; An output circuit installed between the junction of current branches A and B, a current branch having a resistor connected in parallel to the superconductor current branch C, and a bias magnetic field component at the Josephson junction of the Josephson junction device. Equipped with a bias circuit for adding
and the external magnetic field generating means of the Josephson device provided in the superconductor current branch A applies an external magnetic field component, which is a function of the current value flowing through the input signal line, to the corresponding Josephson junction; The external magnetic field generating means of the Josephson device provided in the current branch B applies an external magnetic field component that is a function of the current value flowing in the current branch having the resistance to the corresponding Josephson junction, and The external magnetic field generating means of the Josephson device provided in path C is also configured to apply an external magnetic field component that is a function of the value of the input signal current flowing through the input signal line to the corresponding Josephson junction. Three-value logic circuit using Josephson junction device.