JPS6143826A - Self-reset superconduction loop circuit using josephson junction - Google Patents

Abstract

PURPOSE:To constitute a self-reset superconduction loop circuit not requiring an external reset signal by using a superconduction loop circuit comprising two gates using Josephson junction and a superconduction strip line having an inductance. CONSTITUTION:When an input current Is is inputted at a time t2 after a gate current Ig flows at a time t1, a gate 20 starts switching and a currrent IL appears on an input line 25 of a superconduction loop circuit 23 and a gate 24 at a time t3 with a time tau1 being the sum of the switch time of the gate 20 and the current transfer time from the time t2. On the other hand, a current IA flowing to the gates 20, 24 appears at a time t1 when the gate current Ig is inputted and is zero at the time t3 when the gate current Ig flows to the superconduction loop circuit 23. When the gate 20 is reset to the superconduction state by the decrease in the IA, since the voltage across the inductance of the superconduction loop circuit 23 is zero, the currnt IL is preserved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-resetting superconducting loop circuit constructed using a Josephson junction and a superconducting strip line.

Conventionally used in digital memory circuits, etc.

A superconducting loop circuit consisting of a Sefson junction and a superconducting stripline has the configuration shown in FIG. The superconducting loop circuit in the figure operates as follows.

When an input current Is is caused to flow through the input line 11 while a gate current 1 g is flowing from the gate current path 12, the gate 10 is switched to a voltage state. When the gate IO switches to the voltage state, the gate current Ig flows through the superconducting loop circuit 13. Gate 10 is reset to a zero voltage state as the bias current decreases. The -1 superconducting loop circuit 13 has inductance and the resistance component is zero, so the following equation holds true.

L-=V d electric current L: inductance, ■=voltage across the inductance: current flowing through the inductance, t=time Gate current Ig flows toward the superconducting loop circuit, gate 10
When reset to the zero voltage state, the gate current Igri continues to flow in the superconducting route 13 direction. When the gate current Ig becomes zero from this state, the current flowing in the superconducting strip line with the above-mentioned inductance is conserved when the voltage across the superconducting strip line is zero, so the superconducting loop circuit 13 A circulating current continues to flow through the circuit formed by the gate 10 and the gate 10.

Therefore, even if the gate current becomes zero, this superconducting loop circuit 13 is not reset to its original state. Conventionally, in order to reset the circuit, the reset gate 14 is connected in series with the superconducting loop circuit 13, a reset signal is applied from the outside using a reset input line 15 ft, and the reset 14 is switched to a voltage state. The circulating current flowing through the closed circuit was reset to zero by generating a voltage across the inductance.However, the reset method using the reset gate 14 shown in Figure 1 requires an external circuit that generates a reset signal. become. The circuit that generates this reset signal must be driven at a time when the gate current Ig that drove the gate 10 is zero, and a current that has a time dependence different from the current that drove the gate 10 must be used. Furthermore, a timing control circuit for determining the time at which the reset signal is applied is also required, which has the disadvantage of complicating the circuit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a self-resetting superconducting loop circuit using a Josephson junction that eliminates the above drawbacks and eliminates the need for an external reset signal.

According to the present invention, one or more switches using a Josephson junction are connected in series, and the switch is magnetically coupled to a first gate that switches or switches depending on the current applied to the input line. a second gate using a Josephson junction having an input line, a superconducting loop circuit consisting of a superconducting strip line having an inductance, and a gate current supplying gate current to the first gate and the superconducting loop circuit. a first current path in which the first gate and the second gate are connected in series, and a second current path in which the superconducting loop circuit and the input line of the second gate are connected in series. A self-resetting superconducting loop circuit is obtained using a Josephson junction characterized in that the conductors are coupled in parallel.

The present invention will be described in detail below with reference to the drawings. FIG. 2 is a diagram showing a first embodiment of the present invention, in which reference numerals 20 and 24 indicate magnetically coupled quantum interferometer gates. 22
is a gate current path through which a gate current Ig flows. 21ri is magnetically coupled to gate 20 by a gate 200 input line. 25 is a gate 24 coupled in series to gate 20;
This is a 0 input line.

23 is a superconducting loop circuit consisting of a superconducting strip line having an inductance L, and is connected in series with the gate 240 and the input line 25. Further, a second current path in which the gate 20 and the gate 24 are connected in series, and a second current path in which the superconducting loop circuit 23 and the input line 240 are connected in series are connected in parallel. .

The circuit κ shown in FIG. 2, the gate current Ig, and the input current Is are caused to flow in the time relationship shown in FIG. 3, respectively. Gate current Ig
When the input current Is is inputted at time i after flowing at time t, the gate 20 closes the switch and the current Is is input at time i.
, then G}20, the superconducting loop circuit 2 is delayed by 1 by the sum of the switching time and the current transfer time, and at time t, the superconducting loop circuit 2
A current IL appears on the input line 25 of 3 and gate 24. −1 The current flowing through the gates 20 and 24 is I
A, then IA is the time t when the gate current Ig is input.
1, and becomes zero at time t, when the gate current Ig flows toward the superconducting loop circuit 23. When IA decreases, K
Therefore, when the gate 20 is reset to the superconducting state, the voltage across the inductance of the superconducting loop circuit 23 becomes zero, so that the current IL is conserved. Input current I at time 14
Even if s becomes zero, the current IL+IA is not affected. When the gate current ig becomes zero at time 18J1, the current flowing through the superconducting loop circuit 23 is conserved, so that a circulating current flows through the closed circuit in which the superconducting loop circuit 23 and gates 2Q and 24 are connected in series. This circulating current causes 11. and IA ke Ik=-IL.

As a result, the gate current and the input line are connected to the gate 24. Here, the time is determined from the switching time of the gate 24 and the circuit constant of the closed circuit. Gate 24 is that gate! Since lcR becomes zero, the superconducting state is set.

FIG. 4 shows the threshold characteristics of the gate 24, with the current IA plotted on the vertical axis and the stain current IL plotted on the horizontal axis. Gate current Igs in FIG. 3 in the circuit shown in FIG. 2 above Input current Is
The operation based on the time relationship shown by the IC will be explained using FIG. The operating point, which was initially at point 40 at time 1°, changes to point 40 at time t when the gate current Iy is input.
1, and time tsVc moves to point 42 by the switch of gate 20. As the gate current Ig becomes zero, the operating point moves to point 43 at time IB, and the gate 24 switches. When the gate 24 switches, the currents IA and IL both become zero, so the operating point is Boi/)4
0 = go back.

Figure 5 shows a second embodiment of the present invention. The gate 50 is a quantum interferometer gate using an electric flt injection method, 52 is a superconducting loop circuit consisting of a gate current (g), a gate current strip line power (50), and 54 is a superconducting loop circuit (ICM) connected to the gate 50 in series. 55 is the input line of the gate 54, which is a superconducting loop circuit 5.
It is connected to columns 3 and 16. Resistor 56 transfers current to superconducting loose circuit 53 by switch of gate 50 and switch of gate 54! This damping resistor is connected in parallel to 5Q and 54 to ensure a reliable reset. The difference between the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. superconducting loop circuit 23,
The current IL flowing through the input line 25 of the gate 24 is J. The operating point at tlo is at time 0 in Figure 6 and point 61 is at time 1 in Figure 3. Point 63 of the operating point in Di/Toro 2 time type 3 Time 1.
is the operating point at . Furthermore, a gate 24 having asymmetric threshold characteristics as shown in FIG. 6 can also be used in the gate 24 for the purpose of widening the operating margin. −
(A third embodiment of the present invention is shown in FIG. 7.
Similarly to 20 to 25 in FIG. 2, 70 to 75 are the input lines of the 71st gate, the first gate, and the gate voltage, respectively.

Superconducting loop circuit consisting of flow path and inductance
j second gate, at the first input line of the second gate
The operating margin can be widened by constantly passing a constant input current from the first terminal. This T5 method is particularly effective when the second gate 74 is a gate with asymmetric threshold characteristics.

As is clear from the explanation above, the first gate, a two-junction or three-junction magnetically coupled quantum gate, a current injection quantum interference needle gate, a gate consisting of a single) Wsen junction, etc. It is also possible to use a gate using a Joseph non-junction, which has no resistance. In addition, the second gate is a two-junction, three-junction magnetically coupled quantum interferometer gate, a gate consisting of a simple Joseph non-junction, and a di-seven son junction with a magnetically coupled input line that creates no resistance. As explained in the trial, the self-resetting superconducting loop circuit using the Josephson gate according to the present invention can drive the circuit that generates the external reset signal and the set signal generation path compared to the east side. This eliminates the need for a timing circuit that provides timing for generating a power supply reset signal, and has advantages such as miniaturization of the circuit, ease of design, increased operating margin, and shortened operating time since no timing circuit is required.

Figure 3 shows the gate current 1gs and input current Is in the example.
It shows the time dependence of the current IA flowing through the first gate of the current generator L1 flowing through the superconducting loop. Figure 4 is the first
The figure shows the threshold characteristics of the gate used as the second gate in the embodiment, in which the vertical axis is the current IA flowing through the first gate, and the horizontal axis is the current N flowing through the superconducting loop. FIG. 5 shows a second embodiment of the invention. Figure 6 shows the threshold characteristics of a gate with asymmetric threshold characteristics, where the horizontal axis is the current i L flowing in the superconducting loop.
The vertical axis represents the current flowing through the first gate. FIG. 7d shows a third embodiment of the present invention.

In the figure, 10...ji, a gate using a Cefnon junction, 11...
- Input line, 12... Gate current path, 13... Superconducting loop circuit, 14... Reset gate, 15...
Reset-force line, 20...first gate, 21...
- First gate input line, 22...gate current path, 2
3... Superconducting loop circuit, 24... Second gate, 2
5... 1st operation point, 42... Operating point at time 13 in Figure 3, 43 - 3... Operating point at time t in Figure 3, 50... Operating point at time t in Figure 3. 1 gate, 51...first gate input line, 52
...Gate current path, 53...Superconducting loop circuit, 5
4... Second gate, 55... Input line of the second gate, 56... Damping resistor, 60... Operating point at time 1°K in Fig. 3, 61... Third Time t in the diagram,
62...Operating point at time t in FIG. 3, 63...Operating point at time t in FIG.
70... First gate, 71... Input line of first gate, 72... Gate current path, 73... Superconducting loop circuit, 74... Second gate, 75... - the first input line of the second gate, 76...W, the second input line of the gate of 2;

Patent applicant: Hiroa Yoda, Director of the Agency of Industrial Science and Technology.

Claims (1)

[Claims] A Josephson junction comprising one or more switches connected in series using a Josephson junction and having a first gate that switches with a current applied to the input line and an input line that is magnetically coupled. a superconducting loop circuit consisting of a superconducting strip line having an inductance; A first current path in which the first gate and the second gate are connected in series, and a second current path in which the superconducting loop circuit and the input line of the second gate are connected in series are connected in parallel. A self-resetting superconducting loop circuit using a Josephson junction characterized by: