JPS5953639B2 - Three-value logic memory element using Josephson junction element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ternary logic storage element using a Josephson junction element that stores magnetic flux quantum states in correspondence with ternary logic using a superconducting current loop that includes the Josephson junction element. It is.

In current electronic computers, arithmetic processing and information storage are generally performed based on binary logic.

This kind of binary logic is based on making the on/off of a switch correspond to the binary numbers "l" and "o", so it is easy to construct arithmetic circuits and memory circuits using transistors, diodes, etc. In addition, binary logic information storage means using Josephson junction elements is already known, and has the advantage of being able to operate at high speed and easily achieving high density and extremely low power consumption. In a memory device using this Josephson junction element, the direction of persistent current flowing in a superconducting current loop including the Josephson junction element is generally made to correspond to binary logic. As a configuration, the magnetic flux quantum Φ.

A storage element has also been proposed in which a magnetic flux equivalent to (=-=2.07×10 −15 Weber) is introduced into and taken out of a superconducting current loop including a Josephson junction element.

Various information processing methods using ternary logic have also been proposed.
The use of value logic has the following advantages.

(1) The number of digits required to process the same amount of information is small, and high-speed processing is possible.

(2) High utilization efficiency for the same transmission medium.

(3) High storage density. However, if a circuit using transistors, diodes, etc. is used to perform processing based on three-value logic, the circuit configuration becomes extremely complicated, and the above-mentioned advantages cannot be fully exhibited.

The present invention uses three-valued logic ``01'', ``o'',
The object of the present invention is to provide a memory element that stores ``-1'' in correspondence with each other.

Examples will be described in detail below. J As shown in Fig. 1, when an external magnetic field He is applied to the superconducting current loop LP including two Josephson junction elements J1 and J2, the current reaches the limit where both Josephson junction elements J1 and J2 are in a voltage state. The critical current Ic is the value of the external magnetic field He
j changes as shown in Figure 2.

If we call the central curve in Figure 2 the ``o'' mode, then
When the device current I and the external magnetic fields He and 1 are given as in the "0" mode, the magnetic flux Φ that can enter the current loop LP is the magnetic flux quantum Φ.

Then, - 0.5 × Φ / Φo × 0.5 (
1).

The curves adjacent to this 6 game mode are 61″ mode and ″−
If we call the phi mode, ``0.5≦Φ/Φo≦'' when a current 1 within the curve of the 11th mode and an external magnetic field He are applied.
5 ......(2) Also, in 51'' mode, 1.5 Φ/Φo - 0.5... (
3).

The aforementioned 60'', 617, and '-1'' modes overlap in the shaded area, indicating that three types of modes can exist within this area.

Therefore, information is stored by associating three-value logic with these three types of modes. In order to store such three-value logic information, there are restrictions on the inductances Ll and L2 in the current loop LP, and if L1+L2=L,
In order for the three types of modes to overlap as shown in Figure 2, L
・EO O. 3l8? 1.465 (4) The relationship of Φ0 is required.

Note that IcO indicates the critical current of Josephson junction elements Jl and J2. For example, if IcO=1mA, equation (4) is 0.658[...]<3.03[...]...
・It becomes (5).

If the above-mentioned inductance L is smaller than the condition of equation (4), as shown in Figure 3, there is no region where the three types of modes overlap, so ternary logic information cannot be stored, and the inductance L becomes If the condition of equation (4) is greater than 3, then the fourth
As shown in the figure, an area where four or more types of modes overlap occurs and cannot be used for storing ternary logic information.

In addition, although the inductance L satisfies the condition of equation (4),
In the case of l8L2, for example, as shown in Figure 5, 4,
An asymmetrical overlap region is created, which allows storage of ternary logical information.

In the memory element shown in FIG. 1, the inductance Ll,
If L2 is selected to satisfy the condition of equation (4) and, for example, when writing 011 in the 601 state with no magnetic flux quantum, it will exceed the 0→1 threshold line, as shown in Figure 6. It would be a good idea to control it like this.

This can be done by simultaneously applying the element current 1 and the external magnetic field He, but it can also be done by setting the external magnetic field to He or more. That is, writing is possible using only the external magnetic field He. Also, when writing “-pi”,
It is sufficient to apply an external magnetic field in the negative direction of -He3 or more. Also, when writing "o" etc. from the state of tl" or 61", Heil He < He3 or -He3 He <-H
It is sufficient to apply an external magnetic field He of el. Further, the above-mentioned write magnetic fields He1 and He3 are as follows.

Furthermore, μ. is the magnetic permeability of vacuum 1.257X10-6 [H/m
], S is the area of the current loop LP. current loop LP
If the area S of is S=1001t, then 0kuHeku16
．． 46 [~pain] (0.207 [0e))...(8)1
．． 646 [Vm] × He3 × 32.91 [Vm] (0.
414[0e])...(9).

In the case of reading, it can be performed by applying an external magnetic field and an electric current, or either one of them, but this is destructive reading.

For example, when reading by applying only an external magnetic field, He
When applying an external magnetic field He such that He<He3, 6-1
If the stored content is ``, the state transitions to 60''. Again 1
1'' does not change, but -He,〈He
When an external magnetic field He of 〈-Hel is applied, the state transitions to "01."If the stored content is '-11 when the external magnetic field He is applied, there is no change.Also, in the case of the stored content of 101, HelkuHe<He3 or -He3<H
It does not change even if any external magnetic field He is applied. When a state transition occurs due to the application of an external magnetic field as described above, a voltage is instantaneously generated in the Josephson junction element.

For example, a voltage of 0.1 m is generated for a period of about 10 PS.
Therefore, by detecting this voltage, the stored contents can be read out in relation to the external magnetic field. However, when reading by applying only an external magnetic field, the voltages generated in Josephson junction elements Jl and J2 in Figure 1 are in the opposite direction.5, so the voltage between the connection point of the current loop LP and the external circuit is Even if you try to detect them, they will cancel each other out and nothing will appear. Also, when reading by applying only current, 61
602 in the case of any memory contents of ``and! ding''
611, "-1", and 1 cannot be distinguished. Therefore, if a current and an external magnetic field are applied simultaneously, the stored contents of the ternary logic information can be read out.

That is, as shown in FIG. 7, the direction of the current 1 and the external magnetic field He
By selecting the direction and magnitude of , that is, the current in one square direction,
When a positive magnetic field is applied, there is no state transition in the state of 10゛ and T゛, but the state of Tl7 changes to 60゛, while when a negative direction current and a negative magnetic field are applied, the state changes to "-1", In the rainbow state, there is no state transition, but in the 61° state there is a transition to 10°2, so T'j and '-r can be read out separately. Note that in the case of the stored content of "0", no state transition occurs as in the case where only the external magnetic field and only the current are applied. Furthermore, by making the inductances Ll and L2 different, it is possible to read out ternary logic information by applying only a current. That is, inductance Ll, L2
By making the
If the memory content is 1゜゛, a transition to the “0” state will occur, but if the memory content is “1゛”, the transition will not occur to the “10” state.On the contrary, when the current is passed in the negative direction , 11'', the state transitions to 60''. When current flows in the positive direction and a state transition occurs, a positive voltage is generated between the connection point between the current loop and the external circuit, and when current flows in the negative direction and a state transition occurs, a negative voltage is generated. occurs. As mentioned above, the reading of ternary logic information is performed by two operations; if no voltage is detected under any of the driving conditions, it will be ``0'', and if voltage is detected under either driving condition, it will be 61. '', if the voltage is detected under the other driving condition, the read information will be '-1''.

FIG. 8 shows an embodiment of the present invention including a readout circuit.
A superconducting current loop LP including two Josephson junction elements Jl, J2 and inductances Ll, L2 (7) A load resistor R1 and a line C are connected between points A and B, and a wire C is connected in the vicinity of this line C. Then, the series circuit of load resistors R2 and R3 is connected in parallel with the series circuit of these Josephson junction elements J3 and J4, and the connection point of Josephson junction elements J3 and J4 is connected to the load resistance. R2,
An output line D is connected between the connection point of R3. When a reading current 1 and an external magnetic field He are applied in the positive direction, only when the memory content is '-1', line C shows a voltage due to the voltage between points A and B due to state transition in the direction of the arrow. Current flows. When a bias current 1R is allowed to flow, only Josephson junction element J3 (or J4) becomes a voltage state, and a current flows in the output line D in the direction of the arrow. Also, the read current I
and an external magnetic field He are applied in the negative direction, a current flows in the direction opposite to the arrow in the output line D only when the memory content is "T".If the memory content is "0", the output line D No current flows regardless of the direction of the current 1 and the external magnetic field He. Fig. 9 shows a schematic perspective view of the circuit configuration of Fig. 8, where the same reference numerals as in Fig. 8 indicate the same parts, and H indicates superposition. This is a line through which a current flows to apply an external magnetic field He to the conduction current loop LP.

The superconducting current loop LP is composed of upper and lower lines sandwiching Josephson junction elements Jl and J2 on both sides, and the inductance satisfies the condition of equation (4) by selecting the width, thickness, and length of the upper and lower lines. is configured to a value of A large number of such memory elements are formed on an insulating substrate to constitute a memory device, and since the memory element can have a minute area, it is easy to create a large-capacity memory device. Furthermore, since the power consumption can be reduced by two to three orders of magnitude compared to a general semiconductor integrated memory element, it becomes easy to increase the density. Furthermore, since it is a ternary logic storage element,
Large capacity information storage becomes possible. As explained above,
In the present invention, the magnetic flux quantum Φ is determined by determining the inductance L of the superconducting current loop LP including two Josephson junction elements Jl and J2 according to the condition of equation (4).

A memory element using a Josephson junction element, which can have one state in three types: forward direction, reverse direction, or none, and stores the three types of states in correspondence with three-valued logic information. It is possible to store ternary logical information.

Therefore, extremely low power consumption and high density storage can be easily achieved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an embodiment of the present invention, Figs. 2 to 5 are external magnetic field versus critical current characteristic curves due to inductance of a superconducting current loop, and Figs. 6 and 7 are writing and reading operations. FIG. 8 is a circuit diagram of an embodiment of the present invention including a detection circuit, and FIG. 91 is a schematic perspective view of a memory element having the circuit configuration of FIG. 8. J1 to J4 are Josephson junction elements, Ll, 2 are inductances, LP is a superconducting current loop, L1 to R3 are load resistances, and He is an external magnetic field.

Claims (1)

[Claims] 1 The inductance L of a superconducting current loop including two Josephson junction elements is 0.0, where the critical current of the Josephson junction element is Ic_0 and the magnetic flux quantum is Φ_0.
The value satisfies the condition of 318≦[L・Lc_0]/[Φ_0]≦1.465, and one magnetic flux quantum is stored in the superconducting current loop as three types of states: forward direction, reverse direction, or none, A ternary logic storage element using a Josephson junction element, characterized in that the three types of states correspond to ternary logic information.