JPH0334868B2 - - Google Patents

Description

[Detailed description of the invention] [Summary] Magnetic field coupling due to differences in the arrangement of magnetic field coupling lines in two or more types of magnetically coupled Josephson gate elements in which the dimensions of the Josephson junction are the same and the number of magnetic field coupling lines is different. In order to reduce the variation in magnetic field coupling, a magnetically coupled Josephson integrated circuit is proposed in which gate elements having different numbers of magnetic coupling lines have the same arrangement of magnetic coupling lines.

[Industrial application field]

The present invention relates to a magnetically coupled Josephson integrated circuit comprising two or more types of elements having the same Josephson junction dimensions and different numbers of magnetic coupling lines.

Conventionally, when fabricating logical products and majority gates in the same circuit in Josephson logic elements that have a large number of magnetic field coupling lines, the arrangement of the magnetic field coupling lines has not been particularly considered, so the magnetic field due to the difference in the arrangement of the magnetic field coupling lines There is a large variation in the degree of bonding, and countermeasures are desired.

[Conventional technology]

2 are plan views illustrating the arrangement of magnetic field coupling lines of a conventional 2/3 majority gate and a two-input AND gate, respectively.

In the figure, 11 and 21 are lower electrodes made of a superconducting material such as lead or niobium, 12 and 22 are upper electrodes made of the same superconducting material, 13 and 23 are Josephson junction regions, and 14, 15, 16, 1
7, and 24, 25, and 26 are magnetic field coupling lines.

The magnetic field coupling lines are concentrated at the center of the upper electrodes 13 and 23, and four 2/3 majority gates and three two-input AND gates are provided.

One of the magnetic field coupling lines for both gates is for providing a magnetic field offset.

Offset of the magnetic field is performed by applying a direct current to this magnetic field coupling line and biasing the magnetic field to an appropriate value.

In the arrangement of the magnetic field coupling lines in this example, the degree of magnetic field coupling is different between the 2/3 majority gate and the two-input AND gate, and furthermore, in the AND gate with the magnetic field coupling line in the center, the degree of magnetic field coupling of the central magnetic field coupling line is different. But the other 2
It has the disadvantage that the magnetic field coupling degree is larger than that of the main gate, and the variation in the degree of magnetic field coupling between the magnetic field coupling lines of the same gate becomes large.

In other words, the positions of the magnetic field coupling lines (also called magnetic field control lines or control lines) are different in Figure 2 1 and 2, and therefore the magnetic field sensitivity is different, and the circuits in Figure 2 1 and 2 are originally the same. Since the signal level is input, each circuit does not have the characteristic of responding at the same level, and the operating margin becomes small.

[Problem that the invention seeks to solve]

In conventional magnetically coupled Josephson integrated circuits, which are made up of two or more types of elements with the same junction dimensions and different numbers of magnetic coupling lines, variations (differences) in the degree of magnetic coupling are large and the circuit operating margin is small. .

[Means for solving problems]

The solution to the above problem is that in a magnetically coupled Josephson integrated circuit consisting of two or more types of elements with approximately the same junction dimensions and different numbers of magnetic coupling wires, the first number of magnetic coupling wires has the largest number. a certain first
and a second element having fewer magnetic field coupling lines than the first element.
of magnetic field coupling lines provided on the first element, and virtual magnetic field coupling lines whose number corresponds to the difference between the first number and the second number. This is achieved by a magnetic field coupling line Josephson integrated circuit having a second element having substantially the same arrangement as the magnetic field coupling line and a second element in which no magnetic field coupling line is disposed in the center of the electrode.

In particular, one magnetic field coupling line for magnetic field offset,
When forming a 2/3 majority gate element and a 2-input AND gate element by arranging 3 and 2 input signal magnetic field coupling lines on Josephson junctions having the same dimensions, the magnetic field coupling lines are In a magnetically coupled Josephson integrated circuit in which two Josephson junctions are arranged symmetrically with respect to the center of each Josephson junction, and one of them is removed,
The effects of invention are significant.

[Effect]

The present invention provides a magnetically coupled Josephson integrated circuit consisting of two or more types of elements with the same junction dimensions and different numbers of magnetic coupling lines, which improves magnetic field sensitivity by making the arrangement of the magnetic coupling lines the same for each element. It was experimentally confirmed that the difference could be reduced and applied to logic circuits.

In particular, the magnetic field coupling line has a high magnetic sensitivity at the center of the junction, so it was arranged to avoid the center.

〔Example〕

1 and 2 are plan views illustrating the arrangement of magnetic field coupling lines of a 2/3 majority gate and a two-input AND gate, respectively, according to the present invention.

In this embodiment as well, in contrast to the conventional example shown in FIG. 2, the above combination is adopted for the circuit configuration for simplicity.

In the figure, 11 and 21 are lower electrodes made of a superconducting material such as lead or niobium, 12 and 22 are upper electrodes made of the same superconducting material, 13 and 23 are Josephson junction regions, and 14, 15, 16, 1
7, and 24A, 25A, and 26A are magnetic field coupling lines.

1. The 2/3 majority gate in FIG. 1 is the same as the conventional example in FIG. 1, but the arrangement of the magnetic field coupling lines of the AND gate in FIG. It is made the same as three of the lines.

Further, in FIG. 1 and 2, the lowermost magnetic field coupling line is removed, but any other line may be removed.

By making this arrangement, the arrangement of the magnetic field coupling lines of the two types of gates becomes the same, and
It is possible to avoid arranging the magnetic field coupling line in the center of the upper electrode, which has particularly high magnetic field sensitivity, and it is possible to reduce variations in the degree of magnetic field coupling and increase the operating margin of the circuit.

Figure 3 is A explaining the structure of Josephson device.
-A sectional view.

In the figure, reference numeral 1 denotes a tunnel junction made of a thin alumina layer or the like, which is formed between a lower electrode 21 and an upper electrode 22 each made of a superconducting material to form a Josephson junction.

2 is a thick insulating layer defining a region 23 of the Josephson element.

The magnetic field coupling lines 24A, 25A, and 26A are formed on the upper electrode 22 with the insulating layer 3 interposed therebetween.

Next, a full adder will be described as an example of a circuit configured with the different types of gates explained in the above example.

FIGS. 4 1 and 2 are circuit diagrams of a full adder using a current flip-flop based on Josephson elements.

FIG. 41 shows a sum signal generation circuit, and FIG. 42 shows a carry signal generation circuit.

As an example of configuring a full adder with a current flip-flop consisting of a superconducting loop, the sum signal S _o ,
The carry signal C _o can be realized using the following logic.

S _o = A _o (B _{o o-1} + _o (C _o-1 ) + _o (B _o C _o-1 + _{o o-1} ), _o = _o (B _{o o-1} + _o C _o-1 ) +A _o (B _o C _o-1 + _{o o-1} ), C _o = A _o B _o +C _o-1 (A _o +B _o ), _o = _{o o} + _o-1 ( _o + _o ).Here Here, A _o and B _o are input signals, and C _o-1 is a carry signal from the previous stage.

The sum signal S _o can be constructed from a logical sum and an AND gate according to the above logic.

The carry signal C _o can be realized according to the above logic, but in order to reduce the number of circuit stages, it can be realized with one stage of 2/3 majority gate.

That is, the 2/3 majority gate receives the input signal A _o ,
If two or more of the three inputs of B _o and the carry signal Co _-1 from the previous stage are "1", the carry signal _Co becomes "1".

In the figure, each loop is a current flip-flop with Josephson junctions in its respective branches.

The x mark represents a Josephson junction (represented by JJ), and the arrow and U-shaped symbol represent a magnetic field coupling line, to which the above input signal is applied.

In this case, the 2-input AND gate and the 2/3 majority gate are used to determine the threshold value of all magnetic coupling lines [the limit value of the control current (current flowing through the magnetic coupling lines) that allows superconducting current to flow through the Josephson junction. ] is desired to be the same, so the first method according to the present invention
The structure shown in the figure was adopted.

〔Effect of the invention〕

As explained in detail above, according to the present invention, in a magnetically coupled Josephson integrated circuit comprising two or more types of elements with the same Josephson junction dimensions and different numbers of magnetic coupling lines, variations in the degree of magnetic coupling are small. , the circuit has a large operating margin.

[Brief explanation of the drawing]

1 and 2 are plan views illustrating the arrangement of magnetic field coupling lines of a 2/3 majority gate and a two-input AND gate according to the present invention, respectively, and FIGS. 2 1 and 2 are 2/3 majority gates according to the conventional example, respectively. 3 is a cross-sectional view taken along the line A-A in FIG. 1 to explain the structure of the Josephson device, and FIG. 4 1 and 2 are the currents generated by the Josephson device. FIG. 2 is a circuit diagram of a full adder using flip-flops. In the figure, 11 and 21 are lower electrodes, 12 and 2
2 is the upper electrode, 13 and 23 are Josephson junction regions, 14, 15, 16, 17, 24A, 25A,
26A is a magnetic field coupling line.

Claims (1)

[Scope of Claims] 1. In a magnetically coupled Josephson integrated circuit comprising two or more types of elements with substantially the same junction dimensions and different numbers of magnetic coupling lines, the first number of magnetic coupling lines is the largest. a certain first
and a second element having fewer magnetic field coupling lines than the first element.
of magnetic field coupling lines provided on the first element, and virtual magnetic field coupling lines whose number corresponds to the difference between the first number and the second number. A second element having substantially the same arrangement as the magnetic field coupling line and a second element having no magnetic field coupling line disposed in the center of the electrode.