JPS62211713A - Josephson regulator - Google Patents

Abstract

PURPOSE:To stably operate a Josephson digital circuit by taking out the current in a SQUID with a superconductive load inductor and supplying it to a Josephson gate through a dropping inductor. CONSTITUTION:The circuit consists of the loop of an input inductor 9 in which input current I flows, a superconductive quantum interferometer (SQYUID) loop 7 and a load loop 8. The loop of the SQUID loop 7 is made up of the first superconductive inductor 10 connected magnetically with the input inductor 9, a Josephson junction 6 (shunt resistance Ro 14) and the second superconductive inductor 11. The load loop 8 is constituted of a superconductive load inductor 12 connected magnetically with the second superconductive inductor 11 of the loop 7 and plural series circuits of one Josephson gate 3 and one dropping inductor 2 connected in parallel and inserted between two terminals of the superconductive inductor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a Josephson regulator, and more particularly to a bias current regulator for a digital circuit.

[Prior art] In a Josephson digital circuit that requires a bias current having a trapezoidal waveform,
Niivy Conference Proceedings x
(AIP Conference Proceedings
GS), Vol. 44, 1978, p. 8470, a dill Cefson regulator that utilizes the nonlinear I-V characteristic of quasiparticle tunneling in a dichroic tunnel junction is used. . As shown in FIG. 3, this conventional Gil Cefson regiator is constructed by inserting Josephson junctions connected in m@t rows between a power supply bus and a ground terminal.

Summary 3 In the figure, 1 is a regierator junction consisting of m Josephson junctions connected in series, 2 is a dropping resistor with a resistance value R, 3 is a Josephson digital gate, 4 is a load resistance of Josephson digital gate 3, and 5 is a power supply It's a bus. As can be seen from Figure 3, the dropping resistance 2,
n digital gates 3 and load resistors 4 are each connected to a power supply bus 5. The operation of this regulator will be explained with reference to Fig. 4 (a), (blk). 10 is the critical current of regierator junction 1, 3° is the maximum input current,
The gap voltage is 7g. Figure 4 (bl is a characteristic diagram showing temporal changes in the input current and output current to the regierator junction 1. The vertical axis is the current I, and the horizontal axis is the time t. For the sinusoidal force lightning current shown in
Current step due to quasiparticle tunneling in the IV characteristic of the regierator junction in Figure 4 (a) (Figure 4 (d in al)
, e) is clamped to a rainbow voltage mVg, and the output current shown in () of Figure 4 flows on the power supply bus 5. This flat portion of the output current (between ded and d in FIG. 4G) is the operating period for supplying bias current to the digital circuit. - The ratio of operating periods in a cycle is called duty, and the larger the duty, the better the efficiency of the Digimel circuit.

Some of the problems with conventional Joseph non-regulators are discussed below.

(1) The fluctuation of the current value during the operation period depends on the sharp current rise at the gap voltage due to quasiparticle tunneling in the regulator junction. Figure 4 (The larger the slope between al and de, the smaller the fluctuation in the output current value. Fluctuation τ of the output current value and the average value of the output current. ut) Ratio Δl/"ou
t is approximately 7% in commonly used Pb-based junctions. Such large bias current value fluctuations are caused by
This greatly limits the operating margin of each Josephson digital gate.

(2) Approximately half of the sinusoidal waveform power input to the electric power regiator is consumed in the electric power regiator and generates heat. The higher the deity, the more significant this heating effect becomes. This heat causes deterioration of the IV characteristic of the regulator junction, further increasing the aforementioned bias condition value variation ΔI. This more heat-generating effect is produced by IDM Technical Digest (IDM).
EDM Technical Digests) No. 34
Vol., No. 2, 1979, p. 489, etc., the current value fluctuation ΔI/Iout of a data tier 0-chi Joseph nonregiator made with Pb-based junctions is as high as 12 chi. And, it is very easy to cause Josephson digital gate malfunction.

(3) Average value of the output current of the Gikosen 7 non-regulator If the bias current required for the digital gate is Ig, the current to be output to the power supply bus 5 is n1g = nαIc
In this case, Ic is the critical current value of each Josephson digital gate, and α is a constant determined at the time of circuit design, which is usually 0.
．． 5〈α×1◇. α2m is constant,
Although 7g is a physical constant, the above is not satisfied because the dropping resistance R and the gate critical current Ic are variables that vary independently from the designed values depending on process conditions and the like. In other words, if R, IC, etc. deviate from the design value,
The designed optimum bias condition of g=αlc is not maintained, leading to margin deterioration or malfunction.

[Problem that the invention seeks to solve]

The above-mentioned conventional Josephson regiator mainly has a simple configuration in which multiple junction junctions are connected in series, so stability of the output current, temperature changes, and manufacturing variations are affected. big.

The drawback is that the operating margin is small and malfunctions are likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a closed circuit regulator having improved constant current characteristics.

Means for Solving Problem c] The Joseph non-regulator of the present invention includes a superconducting quantum interferometer in which a Josephson junction, an IEl, and a second superconducting inductor are connected in a ring shape, and the first superconducting inductor. an input inductor magnetically coupled to the second superconducting inductor, a superconducting load inductor coupled to the second superconducting inductor and the magnetic field, and one or more superconducting load inductors connected in parallel between both terminals of the superconducting load inductor #. A unit circuit including a series circuit of a Josephson gate (-) and a dropping inductor (-) is inserted.

[Effect]

The present invention extracts a nonlinear circulating current flowing through a superconducting angiointerferometer (SQUID) using a superconducting load inductor and supplies it to a Josephson gate via a dropping inductor.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

This embodiment uses Josephson junction I6 (shunt resistance R
o), W-1, second superconducting inductor 10°11(
The superconducting quantum interferometer 7 connected in a ring-like manner and the input inductor 9 magnetically coupled to the first superconducting inductor 10 (inductance Lp
) and a superconducting load inductor 9#12 (inductance L7!) magnetically coupled to the second superconducting inductor 11.
, ), and a plurality of − Josephson gates 3 connected in parallel and inserted between both terminals of the superconducting load inductor 12.

Next, before explaining the operation of this embodiment, a single junction 5QU
The circulating current of ID will be explained.

I! Figure 2 (al) is a characteristic diagram showing the relationship between external magnetic flux and circulating current in a single-junction 5QUID during quasi-static operation.

In Figure 2 Cal, the horizontal axis is the external magnetic flux Φex' applied to the external flux 5QUID, and the vertical axis is Io circulating through the 8QUID circuit.
is the critical current of the Josephson junction, L is SQUID
This is the inductance of the loop. The solid line in Fig. 2 (a) shows the stable point of the circulating current, and the arrow indicates the direction of change of the stable point when the external magnetic flux Φe) (increases from Φex = o. (As you can see from ω, as Φex changes, Is reaches its maximum value 1o, and then rapidly changes by Δk, creating a waveform like a saw blade. Every time the current changes ΔI, 8QUID quanta The state is =0.1.
It changes as 2.3... Figure 2 (Tade 14 I
The modulus of s, ΔI, is shown in Figure 2 (β at −).
is about 1-2.

Φe of sine waveform on 5QUID with β = 100 in ) of Fig. 2
The temporal change in Is when xk is applied is shown.

In Figure 2 G), the horizontal axis shows time t1, the vertical axis shows Is, the dotted line shows Is when the Josephson junction is removed from the 5QUID loop, and the solid line shows the actual Is. Figure 2Φ
] is the current waveform of the conventional example (Fig. 4 Φ)) During the operation period shown in Fig. 2 (b), there are countless sawtooth-shaped quantum states as shown in Fig. 2 (al). The time interval Δt between adjacent quantum states is expressed as follows as a function ω of de2π nity D, the period of the clock, and β.

However, the time for the quantum state of 5QtJID to transition from k to +1 is physically limited, and
hand Development), Volume 24, I
E143, 1980, it is simply a compliant shunt resistance, and in a microbridge type junction, it is a dynamic resistance R, d (V~0) in a region where the voltage is almost zero, and a tunnel type junction. In the case of a junction, it is RozF (C is the junction capacity fk). Both bridge type junctions and tunnel type junctions are expressed by a relational expression called normal resistance RNN. T is temperature and Tc is critical temperature. Ro
=ξRNN. Transition of the quantum state of S QLI I D depending on the relationship between the magnitudes of Δt and τ 1! :
It is shown in FIG. 2(C). Is on the vertical axis in Figure 2 (C),
The horizontal axis is time. As seen from Fig. 2(c), Δt
It becomes a modulator of IS when ~. Therefore Δ
1τ is the ideal condition, and from the equations α] and 2O), we get the following. As can be seen from equation 6), the clock frequencies ν and β
2 is inversely proportional. In other words, the faster the 5QtJLD circuit is driven with AC external magnetic flux, the less clearly the transition between each quantum state of the 5QUID appears in the circulating current. Clock 1ns (bipolar, y=Q, 5GHz)
, duty 80% r = 3 mV, assuming that ξ = 1, β is approximately 17, and if a bridge type junction with small capacitance is used, this is an example.

The circulating current of the single-junction 5QUID has been explained above.

This circulating current is taken out using a superconducting load inductor 12 magnetically coupled to the second superconducting inductor 11 and supplied to a load including the Josephson digital gate via a dropping inductor.

Next, the operation of the embodiment will be explained.

When a sine wave current Ip is passed through the input inductor 9, 5QUI
The current Is induced in the D loop 7 has a trapezoidal waveform as shown in FIG. 2(b). At that time, the amount of current change T'' during the Δ construction operation period is expressed by equation (4).The duty D is the maximum value of Ip, the magnetic coupling coefficient of Lp and Ll, and the maximum Joseph 7 of the Joseph non-junction 6.
It is determined by the current Io. A trapezoidal waveform current as shown in FIG. 2(b) is induced in the load loop 8. 5
Since the QUID loop 7 and the load loop 8 are coupled to each other, the inductance of the 5QUID loose (L1+
L2) and the coupling coefficient between the inductance Ll of the load louver 12 and the inductance L2 of the second superconducting inductor 11, Ld is the inductance of the Dron-Ping inductor 2, and N is the turns ratio of the second superconducting inductor 11.

β in equation (4)2 and equation (5) is therefore (Ll + L
l)'Io/Φ0. The relationship between Is and It is as follows: When each of the Josephson digital gates in the Iigami loop 8 switches from the superconducting state to the voltage state, the bias current flows through the gate load resistor 4 and decays exponentially. Therefore, if the period is sufficiently longer than the operation period 1, no problem will occur in the operation of Vl&111. ltx=”D
Then, this condition is ω Lω)2πDr ・・・・・・・・・・・・・・・
(8) If the gate bias of each Josephson digital gate connected in a column is Ig, the maximum value of Iz is Iz (max) = n 1 g, so the following equation is obtained. Therefore, the value of β of the fi8QUID loop is determined by equation (5), and the inductance values Ld, Lt, Ll, and L2 are limited by equations [F]) and (9). The analysis is as follows using actual numbers. ν=F=0.5
GH2゜D80%, r = 3mV, ξ
If = 1, then ru. Therefore L=10nH, n=10
0. N=50°k=0. In g LL << L2 , L2
=Lz, from equation 0), L2=Lt~0.3nH. With the above element parameters, l! When the circuit shown in FIG. 1 is configured, a trapezoidal waveform current similar to the second rotation flows through each Josephson digital gate.

The Cefson regulator of the present invention is capable of supplying a trapezoidal waveform current to each Josephson digital gate, and provides the following improvements over conventional Cefson regulators.

(1) A smaller W flow value fluctuation during the operating period is obtained than in the conventional Ji-Sefson regierator.

(2) The Josephson junction in the SQUID loop only instantaneously transitions to a resistive state, so the amount of heat generated is small, and unlike the conventional Josephson regiator, it does not utilize the quasi-particle tunneling L-V characteristic. Therefore, the current value fluctuation during the operation period does not deteriorate due to heat generation.

3) Since the output of the conventional digital gate is Ig = direct current, if the design value of the critical current Ic of the digital gate deviates from the design value, the optimum bias condition of 1g = αIc cannot be maintained. do not have.

The output of the Gisefson regierator of the present invention is 8 QU
It is proportional to the maximum Josephson current value IO of the Josephson junction in the ID loop. Therefore, if the Josephson digital gate and the Josephson junction in the 8QUID loop are fabricated under the same process conditions, they will deviate from the design value at a similar rate, so that the optimal bias condition will always be maintained.

〔Effect of the invention〕

As explained above, the present invention takes out the nonlinear circulation of 5QUID using a superconducting load inductor and supplies it to the Josephson gate via a dropping inductor, thereby allowing extremely stable operation of the Sefson digital circuit. It has the effect of being able to operate.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 () is a characteristic diagram showing the relationship between the circulating current of a single junction 5QUID and an external magnetic field, Characteristic diagram showing the relationship between circulating lj flow and time when driven, IEZ
Figure (C) is a partially enlarged view of Figures 2 to 3), Figure 3 is a circuit diagram for a conventional regierator, and Figure 4 (a) is a conventional circuit diagram for a conventional regierator. Characteristics, Figure 4(b)
is a power supply waveform diagram of the input and output of a conventional non-regiator. 1... Regierator junction, 2... Dropping inductor, 3... Josephson digital gate, 4... Gate load resistance, 5...
...Power bus, 6...Josephson junction,
7...5 QUID loop, 8...load loop, 9...input inductor, 10...
...First superconducting inductor, 11... Second superconducting inductor, 12... Superconducting load inductor, 13... Mutual inductance, 14...
...Shunt resistance. 2nd ■ (C) Spear 3 Figure

Claims (1)

[Claims] A superconducting quantum interferometer in which a Josephson junction, first and second superconducting inductors are connected in a ring shape, an input inductor magnetically coupled to the first superconducting inductor, and the second superconducting inductor. a superconducting load inductor magnetically coupled to the superconducting load inductor, and one or more series circuits of one Josephson gate and one dropping inductor inserted in parallel connection between both terminals of the superconducting load inductor. A Josephson regulator characterized by having a unit circuit.