JP3911563B2 - Superconducting integrated circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a multiphase pulsating power supply regulator for driving a superconducting integrated circuit using a Josephson junction element and a combination structure with the superconducting integrated circuit.
[0002]
[Prior art]
One of the logic elements used in the Josephson integrated circuit is a latching type element using a Josephson junction element. The simplest circuit formed by the latching type element is the logic switch circuit shown in FIG. The latching type element has a property of holding the state once switched, and it is necessary to drive the logic switch circuit with an AC power source that turns off the power every clock in order to reset the latched state.
[0003]
The Josephson element has a non-linear current-voltage characteristic as shown in FIG. 1B, and a constant voltage source for supplying a constant voltage to the latching-type Josephson logic gate is constructed by applying this constant voltage (Vg) characteristic. it can. In general, an AC power supply is used as a power supply for resetting the switch state of the latching type Josephson logic gate.
[0004]
Since the clock for the switch operation is generated from the AC power supply, the frequency of the AC power supply increases corresponding to the high switching speed, and the polarity inversion time of the AC power supply decreases. Then, the probability of occurrence of punch through increases. Latching type circuits are expected to be applied to high-performance logic integrated circuits because they have the characteristics that the switch speed is less than picoseconds and the power consumption is extremely small (about 1/1000 of that of semiconductors). The present inventors reduced the probability of occurrence of a punch-through malfunction switch that occurs in a normal single-phase AC power supply by driving the Josephson logic circuit with a multiphase pulsating power supply (see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent No. 1602802 [0006]
FIG. 2 shows a waveform of a two-phase pulsating flow power source that has the smallest number of phases and can be operated easily among the multi-phase pulsating flow power sources. In FIG. 2, two DC-biased two-phase sine AC waves Pi1 and Pi2 having a phase difference of 180 degrees are generated from an AC power source. These DC-biased AC waves are clipped to obtain pulsating waves Po1 and Po2. As a clipping method, a DC biased two-phase sine AC wave is injected into a Josephson tunnel junction, and a constant voltage region appearing in the IV characteristics of the Josephson junction is used.
[0007]
In order to input the output of the logic cell driven by the one-phase pulsating power supply to the logic gate driven by the other-phase pulsating power supply, the two-phase pulsating power supply requires an overlapping period Tc. For this reason, the two-phase pulsating waveform has a duty ratio of 50% or more, and in order to obtain this, the clip level by the Josephson critical current must be 0.5 or less of the power supply Pi1, Pi2 (supply power supply peak current). is there.
[0008]
FIG. 3 shows a Josephson regulator circuit using a plurality of Josephson junctions J as a pulsating flow power source that outputs a pulsating flow waveform Po as shown in FIG. In the figure, R represents a connection terminal of a DC bias sine AC power supply of the regulator circuit. In this circuit, since the resistance is zero in the superconducting state, the DC biased AC power supply current Ip flows all into the n-stage (usually n = 2 to 4 stages) series Josephson junction element J. When the regulator current Ir exceeds the critical current of the Josephson junction device J, these devices are switched, and as a result, they are clipped by the transition to the constant voltage (Vg × n) region in the IV characteristics of the Josephson junction device. A pulsating voltage Po is generated, and a load current Il that is the sum of the gate currents Ig of the respective logic gates G is supplied through the power supply resistor Rp2.
[0009]
FIG. 4 is a diagram for explaining the output of the regulator circuit of FIG. 4A shows the IV characteristics of a Josephson junction element of one regulator circuit, FIG. 4B shows the pulsating power supply current output waveform Pi (Ip) and the regulator voltage waveform Po. The numbers in the figure are time. It is a number indicating the progress of. The regulator operating range starts from the time (1 in the figure) when the current Ip of the DC bias AC power supply exceeds the Josephson critical current value (IJc) of the Josephson junction element, and the regulator output voltage becomes voltage at the fall of the AC current. When Vg × n or less (4 in the figure), the process ends.
[0010]
[Problem to be Solved by the Invention]
The regulator circuit of FIG. 3 has the following problems. 1) Since the Josephson critical current value of the junction is not suppressed, it is difficult to increase the duty ratio of the pulsating power supply. 2) The Josephson current value of the Josephson junction element for the voltage regulator is made to correspond to the number of logic gates connected thereto (actually the consumption current of the connected gates because several gates are used). It is necessary and the number of gates can be determined at the time of design, which is a great limitation when designing an integrated circuit. 3) Since the power supply waveform supplied to the power supply line to which the logic gate is connected is not a sine wave, if the distance between the regulator and the gate becomes longer, reflection, voltage drop, etc. occur in the power supply line, and each logic gate Accurate power supply cannot be performed. 4) It is necessary to increase the power supply resistance Rp2 of each logic gate in order to reduce the crosstalk of the switch noise generated in each logic gate through the power supply line. As a result, the power supply voltage increases and the power consumption increases. There were issues such as inviting.
[0011]
Josephson integrated circuits are used in the field of processing data in a very low temperature environment such as electromagnetic waves in a wide energy range, or a very small signal output from a cryogenic detector for particle beams. As a result, the present invention provides a high-speed Josephson integrated circuit that uses superconductivity instead of a semiconductor integrated circuit that in principle deteriorates performance at extremely low temperatures or is restricted in use in extremely low temperature environments due to heat generation. Contributes to signal processing technology.
[0012]
[Means for Solving the Problems]
To achieve the above object, the present invention uses a multi-junction superconducting quantum interference device (SQUID) as a regulator of a multiphase pulsating current power source used in an integrated circuit using a Josephson junction device. The Josephson of the interference element by at least one of injecting an external magnetic field to be applied to the interference element by an AC power supply current itself connected to the multi-junction superconducting quantum interference element or asymmetrically injecting a current The critical current value is equivalently lowered. This makes it possible to provide a regulator that can increase the duty ratio of the power supply voltage and secure the signal transfer time between the logic gates of the multiphase power supply system even in the high-speed switch.
[0013]
Another invention provides a superconducting integrated circuit that incorporates a superconducting quantum interference device type regulator of a multiphase pulsating current power supply in each logic cell structure and supplies a constant voltage to the logic cell. Furthermore, another invention provides an integrated circuit that supplies a phase voltage of any one of multiphase pulsating current power supplies to a multi-junction superconducting quantum interference device having a logic cell structure incorporating a multi-junction superconducting quantum interference device type regulator. To do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 5 shows the basic configuration of the present invention. In the figure, Ip is a DC biased sinusoidal AC power supply current, Ir is a current flowing through the regulator, Rp1 is a power supply resistance, and SQUID is a multi-junction quantum interference device. The DC bias AC power supply current Ip is connected to the SQUID and the logic gate G through the power supply resistor rp1, and the voltage of the SQUID becomes the output of the regulator. In addition, since the structure which attached | subjected the same code | symbol in this specification and drawing is the same, description is abbreviate | omitted.
[0015]
The Josephson junction element in the SQUID functions in the same way as the Josephson element of the regulator of FIG. Here, the SQUID suppresses the Josephson critical current value (IJc) of the Josephson junction element that limits the duty ratio in the regulator operation, and causes the Josephson element to be in a constant voltage state with a low critical current value. However, since a single-junction quantum interference device does not generate a voltage between the devices, a multi-junction SQUID of two or more junctions is used.
[0016]
FIG. 6 is a regulator circuit example 1 according to the present invention, and FIG. 6A shows an equivalent circuit of the SQUID used. In the figure, J1 and J2 represent Josephson junction elements, and inductances L1 and L2 represent magnetic coupling of external magnetic field generation applied to the SQUID by Ir itself in an equivalent circuit. The inductance L1, the two Josephson junction elements J1 and J2, and the inductance L2 are connected by superconductivity to form a quantum interference loop. The current injection line is connected symmetrically to the quantum interference loop.
[0017]
The sine AC power supply current that is DC biased from the connection terminal R flows from the connection terminal R to the SQUID loop at the midpoint of the inductance L2. With this injected current, a magnetic field Φ is applied to the SQUID via the inductances L1 and L2.
[0018]
As is well known, when a magnetic field Φ is applied to the SQUID loop from the outside, the superconducting Josephson critical current value of the SQUID loop can be lowered. The threshold characteristic of this SQUID circuit is shown in FIG. In the drawing, the vertical axis represents Ir, and the horizontal axis represents the magnetic field Φ applied from the outside to the SQUID loop from L1. In the hatched area in the figure, the SQID loop cannot maintain the superconducting state, the Josephson junction elements J1 and J2 are both in the resistance state, and in the open area, both junction elements are in the superconducting state. means. FIG. 6B shows that the superconducting Josephson critical current decreases to IJc1 by applying an external magnetic field.
[0019]
FIG. 7 is a diagram for explaining the operation of the Josephson junction element of the SQUID circuit used in the regulator of the present invention. As described above, the Josephson critical current IJc is suppressed to IJc1, for example, as shown in FIG. As a result, the Josephson junction has a small current value (2 in FIGS. 7A and 7B), the voltage of the Josephson junction is transferred to the constant voltage region, and the duty ratio (T2) of the pulsating power supply voltage Po. ) Increases, and it becomes possible to increase the duty ratio of the multiphase pulsating flow power supply regulator to ensure an operation margin.
[0020]
FIG. 8 shows a regulator circuit example 2 of the present invention. FIG. 8A shows an equivalent circuit of the SQUID to be used. In the regulator circuit example 2, in addition to the application of an external magnetic field, the current is injected between the Josephson junction element J1 and the inductance L2 in that the current is injected between the junction element and the inductance of the SQUID circuit. This is different from the regulator circuit example 1.
[0021]
The inflowing regulator current Ir is supplied to the SQUID loop from the connection point between the Josephson junction element J1 of the SQUID loop and the inductance L2, and therefore when the Josephson junction elements J1 and J2 are in the superconductive state, A larger current flows than the junction element J2. This current asymmetric injection equivalently lowers the Josephson critical current of the interference element.
[0022]
The threshold characteristic of this SQUID circuit is shown in FIG. (B) shows that the region of the superconducting state that changes periodically is inclined, and when the external magnetic field Φ is 0, the SQUID loop injection current is smaller than the maximum value because current injection into the SQUID loop is shown in FIG. This is because the Josephson junction elements J1 and J2 are asymmetrical as shown in the circuit of FIG. In the SQUID circuit of FIG. 8 (a), this asymmetric effect and the effect of external magnetic field application are superimposed. Therefore, in order to follow the operation line indicated by Ir and the arrow in FIG. 8 (b), the Josephson critical current can be further lowered. it can. As a result, the duty ratio of the multiphase pulsating flow power supply regulator can be increased to ensure an operation margin.
[0023]
FIG. 9A is a regulator circuit example 3 showing a three-junction SQUID circuit that suppresses the Josephson critical current by applying an external magnetic field generated by the injection current Ir and asymmetric injection of the injection current Ir. (B) is a regulator circuit example 4 showing a 4-junction SQUID circuit that suppresses the Josephson critical current by asymmetric injection of current. In any circuit, the Josephson critical current value in the response characteristic to the DC bias AC power supply current Ip is smaller than the sum of the Josephson critical current values of the branches connected in parallel in the Josephson junction.
The 1-junction SQUID circuit cannot be used in the regulator of the present invention because a voltage cannot be generated between the Josephson junction elements.
[0024]
FIG. 10 shows a circuit configuration example using the effectiveness of the present invention. A regulator circuit (SQUID) using a 2-junction SQUID, power supply resistors Rp1 and Rp2, and a logic gate are formed in one logic cell, and a pulsating voltage is obtained for each logic gate. At this time, the logic gate G shown in the figure has a logic function such as a logical OR, a logical AND, and a logical negation constituted by a plurality of Josephson junction elements. By providing each logic cell with the power supply resistors Rp1 and Rp2 and the regulator circuit of the multi-junction SQUID, each logic cell can be individualized, and has effects such as voltage drop to the logic gate and suppression of noise crosstalk.
[0025]
FIG. 11 shows a power supply bus for connecting the logic cell as shown in FIG. 10 to the two-phase DC bias AC power supplies Pi1 and Pi2 of P1 and P2 and the power supply circuit of each logic cell, and input / output signals of each logic gate. An example of a two-phase pulsating power supply system integrated circuit in which lines are sequentially connected to logic gates in logic cells driven by different phase power supplies is shown. In the figure, C1 (p1) represents a logic cell C1 connected to a P1 phase DC bias AC power supply, and C2 (p2) represents a logic cell C2 connected to a P2 phase DC bias AC power supply. With this configuration, power supply voltage drop and noise crosstalk are eliminated, so that the logic circuit can be additionally designed as appropriate. FIG. 11 shows an integrated circuit using a two-phase pulsating power supply system, but it is also possible to design this with a multiphase power supply system.
[0026]
【The invention's effect】
In the present invention, the regulator conditions based on the Josephson gate and the SQUID can be individually designed, and the number of gates when the regulator and the logic gate are integrated circuits can be excluded from the parameters. Design becomes easy. In addition, since the power supply line is supplied with a DC-biased AC sinusoidal current, the frequency characteristics of the power supply line do not include harmonics, which not only facilitates design but also enables stability and speedup. Become.
[0027]
Further, when the regulator and the logic gate are integrated, the regulator operation is individualized for each gate by the power supply resistor Rp1, so that the crosstalk accompanying the switch of the logic gate through the power supply line is caused by the multi-junction SQUID regulator. Be blocked. As a result, the pulsating power supply voltage supplied to the logic gate can be reduced. Conventionally, in this type of power supply, a power supply voltage of 11.2 mV and an operating voltage of about 1 mV are used. However, in the present invention, an operating voltage of about 1 mV is obtained with a power supply voltage of 2.8 mV.
[Brief description of the drawings]
1A is a basic configuration diagram of a Josephson latching logic circuit, and FIG. 1B is a diagram showing current-voltage characteristics of a Josephson junction element;
2A is a diagram showing a DC bias sine AC power supply waveform of a two-phase power supply, and FIG. 2B is a diagram showing a two-phase constant voltage pulsating voltage waveform using Josephson junction characteristics;
FIG. 3 is a diagram showing a conventional Josephson regulator circuit.
4 is a diagram illustrating generation of a pulsating voltage of the pulsating power supply regulator of FIG. 3; FIG.
FIG. 5 is a diagram showing a basic configuration of the present invention.
FIG. 6 is a diagram illustrating a regulator circuit example 1 according to the embodiment.
FIG. 7 is a diagram illustrating generation of a pulsating voltage according to the present invention.
FIG. 8 is a diagram illustrating a regulator circuit example 2 according to the embodiment.
FIG. 9 is a diagram illustrating regulator circuit examples 3 and 4 of the embodiment.
FIG. 10 is a diagram illustrating a logic cell according to the present invention.
FIG. 11 is a conceptual diagram of a two-phase pulsating flow power supply system Josephson integrated circuit configured using the logic cell of the present invention.
[Explanation of symbols]
J, J1, J2 Josephson junction element SQUID multi-junction superconducting interference element IJ, IJ1, IJ2c Josephson junction current IJc, IJ1c, IJ2c Josephson critical current Pi DC-biased sine AC power supply waveform Po pulsating power supply waveform Ip DC Biased sinusoidal alternating current power supply Ir Ir external magnetic field G applied to regulator current Φ SQUID logic gate C logic cell

Claims (3)

An integrated circuit multiphase pulsating power supply regulator using Josephson junction elements includes a multijunction superconducting quantum interference element connected to any one phase of a multiphase DC biased sine AC power supply,
The Josephson critical current of the interference element is injected either by applying an external magnetic field to the interference element by the current itself flowing from the sine AC power supply or by asymmetrically injecting a current to a plurality of interference elements. A superconducting integrated circuit characterized in that the value is equivalently lowered and the connection point voltage of a multi-junction superconducting quantum interference device is output. A superconducting integrated circuit comprising a logic cell structure incorporating the regulator according to claim 1. 3. An integrated circuit, wherein each phase voltage of a multiphase pulsating power supply is supplied to a superconducting quantum interference device having a logic cell structure in which the multi-junction superconducting quantum interference device type regulator of claim 2 is incorporated.

Images