JPS60194378A - Superconductive quantum interference element circuit - Google Patents

Abstract

PURPOSE:To electrically adjust the critical current value of a superconductive element from the outside after said element is prepared, by using a superconductive three-terminal element having a control input terminal for controlling a critical current as the superconductive element. CONSTITUTION:One terminals of superconductive inductances 3, 4 are connected to a current supply terminal 5 while superconductive three-terminal elements having control input terminals 13, 14 for controlling a critical current are provided between the other terminals of the inductances 3, 4 and an earth. The max. critical current values at the zero voltage states of the superconductive three-terminal elements 11, 12 are flowed to control input terminals 13, 14 to make it possible to control the critical current values from the outside. Therefore, critical current values I0 of two superconductive three-terminal elements 11, 12 can be made equal to each other and, therefore, the manufacturing yield of the elements 11, 12 can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention relates to improving manufacturing yield in superconducting quantum interference device (SQUID) circuits.

(Prior art) Conventionally, this type of device was shown in FIG. 1. In FIG. 6, 3.4 is a superconducting inductance connected in series, and 5 is a constant point at the connection point of the superconducting inductances 3 and 4. Current supply terminals 1 and 2 for supplying current are Josephson elements connected between both ends of the superconducting inductance 3.4 and the ground, and the two superconducting inductances 3.4 and the two above A closed circuit is formed with the Josephson element 1.2.

Next, the operation will be explained.

FIG. 2 shows the current-voltage characteristics of the Josephson element 1.2, and as is clear from the figure, in the elements 1 and 2, in the zero voltage state, current flows up to a predetermined critical current value IO; When a current exceeding the current value 1o is applied, the Josephson element 1.2 changes to a finite voltage state.

Further, FIG. 3 shows the magnetic flux Φ in the closed circuit formed by the Josephson element 1.2 and the superconducting inductances 3 and 4 and the current supply terminal 5 when a constant current is supplied from the outside to the current supply terminal 5 of the above circuit. It shows the characteristics between the voltage and ■. Therefore, in the above circuit, the magnetic field can be detected using the characteristic curve shown in FIG. 3, and the period of the characteristic curve shown in FIG.
sWb) degree j If the value of s3 and 4 is L, it is determined by the value of the inductance and the critical current value ■0,
Also, the critical current value of the above two Josephson elements 1°2■
0 must be equal to each other.

The conventional superconducting quantum interference device circuit is configured as described above, and the Josephson device 1. It is difficult to set the critical current value Io to a desired value during the manufacture of the above-mentioned Josephson elements 1 and 2, and furthermore, it is impossible to change the critical current value 0 of the Josephson elements 1 and 2 after manufacture. However, there was a drawback that the yield during manufacturing was not good.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by using a superconducting three-terminal element having a control input terminal for controlling the critical current in place of the Josephson element, the manufacturing process can be improved. The purpose of this invention is to provide a superconducting quantum interference device circuit whose electrical characteristics can be adjusted from the outside later on, and whose manufacturing yield can be improved.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows a circuit diagram of a superconducting quantum interference device circuit according to an embodiment of the present invention. In FIG. 4, 11° and 12 are superconducting three-terminal elements, 3 and 4 are superconducting inductances, and 5 is a current supply. It is a terminal. Reference numerals 13 and 14 are control input terminals for the superconducting three-terminal elements 11.12, which are used to control the critical current value 1o of the superconducting three-terminal elements 11.12 to a desired value.

Next, the effects will be explained.

The superconducting three-terminal element 11.12 in this embodiment is different from the Josephson elements 1, 2 of the conventional circuit, except that it has a control input terminal 13.14 for controlling its critical current.
It has the same function as . Therefore, superconducting three-terminal device II
, 12 are the same as those shown in FIG. Furthermore, when a constant current is supplied from the outside to the current supply terminal 5 of the circuit of this embodiment shown in FIG. The characteristics of Φ and the voltage V of the current supply terminal 5 are the same as those shown in Fig. 3, and the magnetic field can be detected in the same manner as the conventional circuit by using the characteristic curve shown in Fig. 3. can.

However, in this embodiment circuit, the superconducting three-terminal element 11
．． The maximum critical current value 0 in the zero voltage state of 12 can be externally controlled by passing a current through the control input terminal 13.14, and therefore the critical current value io of the two superconducting three-terminal elements 11.12 can be mutually equal, so that the element 11
．． 12 manufacturing yield can be improved.

In the above embodiment, the superconducting quantum interference device is DC-3Q.
Although the case of a UID (direct current type superconducting quantum interference device) has been described, the same effects as in the above embodiment can be achieved also in an RF-3QU rD (alternating current type superconducting quantum interference device).

Furthermore, although the above embodiments have been described using a superconducting three-terminal element, this may also be a superconducting element using a heterojunction.

〔Effect of the invention〕

As described above, according to the superconducting quantum interference device circuit according to the present invention, the circuit can be adjusted without controlling the critical current value, and therefore the yield of the device can be improved.

[Brief explanation of drawings]

Claims (1)

[Claims] (1) Two superconducting inductances connected in series, a current supply terminal for supplying a constant current to the connection point of both superconducting inductances, and a connection between both ends of the two superconducting inductances and the ground. Two superconducting elements each connected to each other and having a predetermined critical current in a zero voltage state, magnetic flux generated by a closed circuit formed by the two superconducting inductances and the two superconducting elements, and the current supply terminal. In a superconducting quantum interference device circuit that detects a magnetic field by using the characteristics with respect to voltage, a superconducting three-terminal device having a control input terminal for controlling the critical current is used as each superconducting device. A superconducting quantum interference device circuit featuring: