JPH01125104A - Superconducting oscillation circuit - Google Patents

Abstract

PURPOSE:To attain high speed operation with simple constitution without any AC power supply by passing an optional part of a line tying two Josephson elements, a respective inductance and a load resistor through the vicinity of other Josephson element. CONSTITUTION:The title circuit is constituted such that a line connecting two Josephson elements 2, 7, inductances 4, 8 and resistors 5, 9 passes in the vicinity of other Josephson elements 7, 2 at optional parts 10, 11. Thus, suppose that a 1st Josephson element 2 is in the superconducting state depending on the voltage state, a current flows to the line arranged in the vicinity of a 2nd Josephson element 7 by a magnetic field due to the current after a prescribed time constant, the 2nd Josephson element 7 is brought into the voltage state by the magnetic field due to the current and then the 1st Josephson element is changed into the voltage state from the superconductng state after a prescribed time constant. Outputs of the Josephson element 2 act like those from an astable multivibrator by repeating the operation above.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a superconducting oscillation circuit using a Josephson element.

BACKGROUND OF THE INVENTION A Josephson element having a Josephson tunnel effect usually has hysteresis in its current-voltage characteristics as shown in FIG. In other words, when the voltage (V) is zero, the current (I)
There is a superconducting state where current flows, and a voltage state where there is a finite voltage and current flows. A voltage state rather than a superconducting state can be easily achieved by passing a current larger than the critical current (I m ) through the Josephson element, or by applying a magnetic field greater than its critical magnetic field Hm to the Josephson element.

However, in order to change from a voltage state to a superconducting state, it is necessary not only to reduce the magnetic field applied to the Josephson element, but also to sufficiently reduce the current flowing through the Josephson element.

For this reason, in the past, when using a Josephson element, it was necessary to use an AC power supply (for details, see IBM Journal Op Research and Development: IBM Journal
f Research and Development
It is stated in Vol. 124, No. 2 (1980). ).

Problems to be Solved by the Invention However, the configuration of the above-mentioned conventional example requires an AC power supply drive circuit, making the configuration complicated.

The present invention solves the above-mentioned problems of the prior art, and aims to provide a superconducting oscillator circuit that does not require an AC power source, has a simple configuration, and can operate at high speed. That is.

Means for Solving the Problems In order to achieve the above object, the present invention includes a constant current source whose one terminal is grounded, a first Josephson element connected to the other terminal of the constant current source, A first resistor whose one terminal is connected to the other terminal of the first Josephson element and whose other terminal is grounded; and a first resistor whose other terminal is connected to the other terminal of the first Josephson element. inductance and
a second resistor having one terminal connected to the other terminal of the first inductance and the other terminal being grounded; a third resistor connected to the other terminal of the constant current source; a second Josephson element connected between the resistor No. 3 and ground; a second inductance connected to the connection point of the third resistor and the second Josephson element; One terminal is connected to the other terminal,
a fourth resistor whose other terminal is grounded, the first Josephson element, the first inductance and the second
Any part of the line connecting the 40th resistor passes near the second Josephson element, and any part of the line connecting the second Josephson element, the second inductance, and the 40th resistor passes near the 40th resistor. It is configured to pass near the No. 1 Josephson element.

action The present invention has the following effects due to the above configuration.

That is, if the first Josephson element becomes superconducting due to the voltage state, a current flows through a wire placed near the second Josephson element after a certain time constant, and the magnetic field caused by this current causes the second Josephson element to become superconducting. The Josephson element enters the electrical state regardless of its previous state. When the second Josephson element enters the voltage state, after a certain time constant,
A current flows through a wire placed near the first Josephson element, and the resulting magnetic field changes the first Josephson element from a superconducting state to a voltage state. When the first Josephson element enters a voltage state, no current flows through the line passing near the second Josephson element after a certain time constant, and only a current below the critical current flows through the second Josephson element. Since no current is flowing, the second Josephson element changes from a voltage state to a superconducting state. When the second Josephson element becomes superconducting, no current flows in the wires near the first Josephson element after a certain time constant, and only a current below the critical current flows through the first Josephson element. Therefore, the first Josephson element changes from a voltage state to a superconducting state. By repeating this, the output of the first or second Josephson element can function similar to an astable multi-vibrator well known in digital circuits.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a superconducting oscillation circuit in one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a DC constant current source that supplies power to the circuit, one terminal of which is grounded. 2 is a first Josephson element connected to the other terminal of DC constant current source 1;
3 is a first resistor whose one terminal is connected to the other terminal of the first Josephson element 2 and whose other terminal is grounded;
is a first inductance connected to the other terminal of the first Josephson element 2, and 6 is a second resistor whose one terminal is connected to the other terminal of the first inductance and whose other terminal is grounded. , 6 is a third resistor connected to the other terminal of the DC constant current source 1, 7 is a second Josephson element connected between the third resistor 6 and ground, and 8 is a third resistor 6. and a second inductance connected to the connection point of the second Josephson element 7, and 9 a fourth resistor whose one terminal is connected to the other terminal of the second inductance 8 and whose other terminal is grounded. It is. A wire 1o connecting the first inductance 4 and the second resistor 6 passes near the second Josephson element 7, and the magnetic flux generated by the current flowing therein is transferred to the second Josephson element 7.
A wire 11 that interlinks with the Josephson element 7 and connects the second inductance 8 and the fourth resistor 9 passes near the first Josephson element 2, and the magnetic flux generated by the current flowing through it passes through the first It is designed to be interlinked with the Josephson element 2 of.

Next, the operation of the above embodiment will be explained.

First, if the first Josephson element 2 changes from a voltage state to a superconducting state, current begins to flow through the first Josephson element 2, but the wire 1o has a first inductance 4 and a second resistor 6. The current flows with a delay of a time constant determined by . Therefore, at the moment the first Josephson element 2 becomes superconducting, all the current flowing through the first Josephson element 2 flows through the first resistor 3 to ground. Next, after a time period corresponding to a time constant determined by the inductance value of the first inductance 4 and the resistance value of the second resistor 6, current begins to flow through the wire 10. When a current flows through the wire 10, the magnetic field created by this current interlinks with the second Josephson element 7, so that the second Josephson element 7 becomes a voltage state regardless of its previous state. When the second Josephson element 7 is in a voltage state, the line 11 has the inductance value of the second inductance 8 and the fourth inductance value.
After a time constant determined by the resistance value of the resistor 9, a current flows, and the first Josephson element 2, which is interlinked with the magnetic field created by this current, changes from a superconducting state to a voltage state.

As a result, the internal resistance R2 of the first Josephson element 2 increases, and almost all of the current from the constant current source 1 flows through the third resistor 6, second inductance 8, and fourth resistor 9. First Josephson element2. The voltage at the connection point between and the first resistor 3 becomes almost 0, and after a time constant determined by the inductance value of the first inductance 4 and the resistance values of the first and second resistors 3 and 6, In the wire 10, almost no current flows through the wire 10, and the first
The magnetic field interlinking with the Josephson element 2 becomes less than the critical magnetic field. At this time, the resistance value of the second Josephson element 7 in the voltage state is Rv? and the resistance value of the fourth resistor 9 is R9
If Rv7<<Rg, the current flowing through the second Josephson element 7 is less than the critical current, so the second Josephson element 7 becomes a superconducting state rather than a voltage state. When the second Josephson element 7 becomes superconducting,
After a time constant determined by the inductance value of the second inductance 8 and the resistance value of the fourth resistor 9, the current flowing through the wire 11 becomes zero, and the magnetic field interlinking with the first Josephson element 2 becomes less than the critical magnetic field. Become. On the other hand, if the voltage state resistance of the first Josephson element 2 is Rv2 and the resistance value of the third resistor 6 is R6, then the second Josephson element 7 is in a superconducting state and its internal resistance is zero. Therefore, the first Josephson element 2 has R6·io/(R6+RV2)
A current flows (where io is the current of the constant current source 1). Here, if RV2>>R6 is set and the current flowing through the first Josephson element 2 is set to be less than the critical current, the first Josephson element 2 becomes a superconducting state again, and it becomes -normal. , the third resistor 6 and the second Josephson element 7, or the first Josephson element 2
An oscillation signal can be obtained from the connection between the first inductance 4 and the first inductance 4. That is, it is possible to perform an operation equivalent to that of an astable multivibrator, which is well known in digital circuits. Moreover, by using the Josephson element 2.7, the state changes quickly! /), high-speed operation can be performed. Note that the oscillation frequency is determined by resistance 3.6.6.9.
It is clear from the above description that it is determined by the respective resistance values of and the inductance value of 4.8.

As described above, according to this embodiment, the line 1 connecting the first Josephson element 2, the first inductance 4, and the second resistor 6
0 passes near the second Josephson element 7, and the second
Josephson element 7, second inductance 8 and fourth
By making the line 11 connecting the resistors 9 pass near the first Josephson element 2, an oscillation circuit that operates at high speed with a simple configuration can be realized without converting the power source to AC.

Note that in the above explanation, the case where the line 1o passing near the second Josephson element was connected between the first inductance 4 and the second resistor 60 was explained. The location passing near the element 7 may be between the first Josephson element 2 and the first inductance 4, or between the second resistor 5 and the ground, or between the first inductance 4 and the second resistor 6. may be replaced. Similarly, the point where the line 11 passes near the first Josephson element 2 may be between the second Josephson element 7 and the second inductance 80, or between the fourth resistor 9 and the ground. Further, the second inductance 8 and the fourth resistor 9 may be replaced.

Effects of the Invention As described above, according to the present invention, any part of the line connecting two Josephson elements and their respective inductances and load resistances passes near the other Josephson element, thereby reducing power supply. It can be operated at high speed with a simple configuration without converting to AC.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a superconducting oscillation circuit in one embodiment of the present invention, and FIG. 2 is an explanatory diagram of voltage-current characteristics of a Josephson element. DESCRIPTION OF SYMBOLS 1... DC constant current source, 2... First Josephson element, 3°... First resistance, 4°... First inductance, 5... Second resistor, 6...・Third resistance, 7...
- Second Josephson element, 8... second inductance, 9... fourth resistor.

Claims (1)

[Claims] A constant current source with one terminal grounded, a first Josephson element connected to the other terminal of the constant current source, and one terminal connected to the other terminal of the first Josephson element. , a first resistor whose other terminal is grounded, and a first resistor whose other terminal is connected to the other terminal of the first Josephson element.
an inductance, a second resistor having one terminal connected to the other terminal of the first inductance and the other terminal grounded, and a third resistor connected to the other terminal of the constant current source. , a second Josephson element connected between this third resistor and ground, a second inductance connected to the connection point of the third resistor and second Josephson element, and this third a fourth resistor, one terminal of which is connected to the other terminal of the second inductance, and the other terminal of which is grounded, and the first Josephson element, the first inductance, and the second resistor are connected. An arbitrary point of the line passing through the vicinity of the second Josephson element,
A superconducting oscillator circuit, characterized in that a line connecting the Josephson element, the second inductance, and the fourth resistor is configured such that any part thereof passes near the first Josephson element.