JP5263782B2 - Programmable Josephson voltage standard device and control method thereof - Google Patents

Description

  The present invention relates to a control method for suppressing temperature fluctuations of a programmable Josephson voltage standard device and a programmable Josephson voltage standard device having a constant temperature and high accuracy.

  In recent years, with the improvement of measurement accuracy of measuring instruments used in industries such as manufacture of electronic equipment and communication measurement, a high-performance voltage standard is desired. The Josephson voltage standard (JVS) is a device that generates a high-accuracy voltage using the superconducting Josephson effect and includes a large number of Josephson elements. A schematic diagram of the Josephson element is shown in FIG. As shown in FIG. 6, the Josephson element is an element having a sandwich structure in which a thin insulator (I) or a normal conductor (N) 2 is sandwiched between two superconductors (S) 1. When the Josephson element is irradiated with the microwave 3 having a certain frequency (f) and the bias current I is further passed, a constant voltage (V = hf / 2e) determined only by the microwave frequency is applied to both ends of the element. ) Occurs. If no current is passed, the generated voltage becomes completely zero. Here, e and h are the elementary charge and the Planck constant, respectively. Since the microwave frequency can be controlled with very high accuracy, the voltage value obtained can be controlled with very high accuracy. However, in general, the voltage per Josephson element is as small as several tens of μV. Therefore, in order to obtain a required voltage value (10 V or more), a Josephson array in which hundreds of thousands or more Josephson elements are connected in series is constructed and integrated in the chip, and a high voltage of 10 V or more is obtained as a whole. Use as directed. As an example, if the microwave frequency is 16 GHz, about 33 μV per element, about 300,000 elements are required to output 10 V.

In order to obtain voltages of various values from the Josephson array, a device for operating as a digital-analog (D / A) converter has been devised. This is particularly called a programmable Josephson voltage standard (Programmable JVS: PJVS) (see Patent Document 1 and Non-Patent Document 1). A circuit diagram of the PJVS is shown in FIG. As shown in FIG. 7, the Josephson array is divided into a plurality (N) of segments (S # 1, S # 2,... S # N), and a current source for supplying a bias current to each segment. 6 is connected. When a Josephson array is irradiated with microwaves having a frequency (f) from the microwave oscillator 7 and a bias current is further passed, a segment supplied with the current generates a constant high-accuracy voltage. The voltage value of each segment is determined by the number of Josephson elements 5 to be connected. The Josephson element 5 is represented by a cross in the figure. FIG. 8 shows the current-voltage characteristics of the bias current and the generated voltage in the segment. When a current is passed through the segment, a constant voltage step occurs within a certain current range (operation region 8). If the bias current value is set within this range, a constant voltage step can be obtained. Specifically, by switching the bias current value I _bias supplied to each segment between three values, plus, minus, and zero, the voltages generated from the segment are + hfm / 2e, 0, −hfm / 2e (m is It is possible to switch between three states (number of Josephson elements per segment). By performing the same operation individually for all segments, various voltage values can be generated from the array in a programmable manner.

  Since PJVS is realized using superconducting technology, it is necessary to cool the chip to a very low temperature. Conventionally, the cooling method using liquid helium has been the mainstream. This is an excellent cooling technique that can be realized very stably and easily because the entire chip can be uniformly cooled simply by immersing the chip in liquid helium. On the other hand, liquid helium is a depleted resource, and the price has recently been rising, making it difficult to obtain in the future. Therefore, development of cryogenic cooling technology using a refrigerator is being promoted with the aim of lowering costs. FIG. 9 shows how the chip is cooled using a refrigerator. In the cooling method using a refrigerator, a PJVS chip 21 which is an object to be cooled is placed on a chip carrier 24 and firmly fixed to the cooling head 20 using screws 22 or the like. The chip is cooled by being in thermal contact with the cooling head. The chip carrier 24 is provided with a bias current input / voltage output terminal 25 and a microwave input terminal 23 connected to the PJVS chip 21. Since the heat generated in the chip is exhausted only by a thermal path with the cooling head, the cooling characteristics and temperature are likely to be nonuniform in the chip or its peripheral part as compared with the cooling method using liquid helium.

JP 2004-172692 A

C. A. Hamilton, C.I. J. et al. Burroughs, and R.A. L. Kautz, “Josephson D / A Converter with Fundamental Accuracy”, IEEE Transactions on instrumentation and measurement, vol. 44, no. 2, pp. 223-225, April 1995.

  In general, the voltage value of PJVS is 0 V at the minimum and 20 V at the maximum, and any value between them is generated and used. Since the bias current value is fixed within the operating region, the power consumption of the chip increases in proportion to the generated voltage value, and the chip temperature also increases. 10 and 11 are diagrams for explaining problems in the prior art. It will be explained that when the voltage value generated by the array is different, the power and temperature consumed by the array, that is, the entire chip, are also different. The example of FIGS. 10 and 11 is a configuration example of PJVS in which an array having a maximum voltage amplitude of 16 V is equally divided into 16 segments (1 V per segment). Each segment is displayed as a black box. Actually, many Josephson elements are connected inside, and a bias current source is also connected, and three types of voltages of + 1V, 0V, and -1V are switched. Can be output. FIG. 10 and FIG. 11 show examples in which the chip generates heat and the temperature rises when voltages of 2V and 14V are generated in the array, respectively. In FIG. 10, in order to output 2V, + 1V is generated in the segments A and B, and the remaining C to P are set to the zero voltage state. In FIG. 11, in order to output 14V, + 1V is generated in 14 segments A to N, and the remaining O and P are set to a zero voltage state. When the voltage value increases from 2V to 14V, the power consumption of the chip increases and the chip temperature also increases.

FIG. 12 is a diagram showing current-voltage characteristics of bias current and generated voltage in the segments in the array. FIG. 12 shows how the element characteristics (operating region, that is, the range of the bias current at which a constant voltage step is obtained) change depending on the temperature change of the chip. In FIG. 12, for example, the current-voltage characteristics of the bias current and the generated voltage in the segment when the chip temperature is low (for example, when the output voltage is 2 V) are shown by the thin line 30, for example, when the chip temperature is increased (for example, output) The current-voltage characteristics of the bias current and the generated voltage in the segment (when the voltage is 14 V) are shown by a thick line 31. When the output voltage increases (for example, from 2 V to 14 V) and the chip temperature rises, the current-voltage characteristic shifts from the thin line 30 to the thick line 31 as shown by the arrow 32 as shown in FIG. As described above, when the chip temperature rises, the critical current value of the Josephson element decreases, and the bias current operation region in the constant voltage step shifts from the operation region 8 to the operation region 9 having a low current value. Then, at a certain voltage value (for example, when 2 V is generated), even when operating at a point (p, q) with a predetermined bias current _Ibias , at another higher voltage value (for example, when generating 14 V), the chip temperature As a result, the operating region changes from 8 to 9 and the point (p, q) deviates from the operating region and stops operating.

The effect of changing the chip temperature is not only the change of the operating area. As shown in FIGS. 10 and 11, from the voltage output terminal, in addition to the voltage generated in the Josephson array, the difference in the thermoelectromotive force generated at the plus / minus terminal of the lead wire (V _{TEMF +} -V _TEMF− ). Is superimposed as an offset voltage. If the offset voltage is constant, its influence can be measured individually and canceled easily. However, when the temperature of the lead wire near the chip changes depending on the voltage of the chip, there is a problem that the thermoelectromotive force V _TEMF also changes and appears as a change in the offset voltage. If the offset voltage cannot be canceled, the uncertainty (error) of the voltage measurement is increased. The above problem is more serious because the temperature of the chip increases as the voltage value increases.

  Further, in the conventional liquid helium cooling method, it was easy to keep the chip uniformly at a constant temperature, whereas in the refrigerator cooling, the heat conduction between the chip 21 and the cooling head 20 as shown in FIG. Therefore, uniform cooling is difficult, and the temperature of the chip or its periphery is likely to rise locally and is serious. As already described, if the temperature of the PJVS chip changes even slightly, the critical current value of the Josephson element changes, the bias operation region also changes, and the operation stops. In addition, since the thermoelectromotive force generated on the voltage output lead wire wired in the peripheral portion of the chip also changes depending on the temperature, the obtained voltage value changes accordingly. When implemented using a refrigerator, these problems tend to appear significantly.

  For this reason, the development of PJVS has a voltage as high as 10 to 20 V, and the use of a refrigerator has caused the above problems and makes it difficult to put it into practical use.

  The present invention is intended to solve these problems, and an object of the present invention is to keep constant the power consumption and temperature of the PJVS chip so that they do not depend on the generated voltage value in the PJVS device. Another object of the present invention is to realize a programmable Josephson voltage standard device in which the obtained voltage value is more accurate.

  In order to achieve the above object, the present invention has the following features.

  The method of the present invention is a control method of a programmable Josephson voltage standard apparatus comprising a Josephson array divided into a plurality of segments, wherein the power consumed by the entire Josephson array is controlled by controlling the bias current source in each segment. Is controlled so as to be kept constant regardless of the output voltage. Further, the power consumed by the entire Josephson array is controlled so as to be equal to the power when the maximum voltage is generated regardless of the output voltage. More specifically, the voltage generated by the pair of segments is set to zero by causing a reverse polarity bias current to flow through the paired segments to generate an equal and reverse polarity voltage. Features. Specifically, the segment is divided into two equal parts, and a bias current having a reverse polarity is caused to flow to generate a voltage having an equal and reverse polarity, thereby reducing the voltage generated by the segment to zero. It is characterized by doing.

  The method of the present invention is a control method for a programmable Josephson voltage standard apparatus having a Josephson array divided into a plurality of segments, and selects a segment necessary for obtaining a desired voltage value and supplies a current to the voltage. If there are multiple unselected segments and the number of elements is the same between them, two segments with the same number of elements are formed as one pair, and each segment in the pair is opposite to each other. It is characterized in that a current of a polarity is passed to generate an equal amount and a reverse polarity voltage so that the voltage of the entire pair is zero. In addition, for a segment not selected, the segment is divided into two equal parts, and a bias current having a reverse polarity is caused to flow to generate a voltage having an equal and reverse polarity. Is set to zero.

  The method of the present invention is a control method of a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments, wherein the programmable Josephson voltage standard device is at least one of the divided segments. The book is further divided into sub-segments. In addition, in order to obtain a desired voltage, a part of the sub-segments is selected and a current is supplied to generate a voltage. A plurality of sub-segments that are not selected are divided into two groups. By supplying a current of opposite polarity to the two groups of sub-segments, the voltage across the first and second groups is made zero. The sub-segment is divided so that the number of Josephson elements is proportional to a power of two. In addition, in order to obtain a desired voltage, a part of sub-segments is selected and a current is passed to generate a voltage, and each sub-segment not selected is divided into two equal parts, and each subdivided has a reverse polarity. A bias current is allowed to flow to generate an equal amount of reverse polarity voltage so that the voltage generated by the sub-segment is zero.

  The device of the present invention is a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments, and each segment is maintained so that the power consumed by the entire Josephson array is constant regardless of the output voltage. And a control means for controlling the bias current source. Further, the control means controls the zero voltage generated by the segment pair by generating a voltage of the same polarity and opposite polarity by flowing a reverse polarity bias current to the paired segments. It is characterized by performing. Further, the control means applies a bias current having a reverse polarity to each of the bisected segments to generate an equal amount and a reverse polarity voltage, thereby setting the voltage generated by the segment to zero. Control is performed.

  The apparatus of the present invention is characterized in that at least one of the divided segments is further divided into sub-segments. The control means of the apparatus of the present invention divides a plurality of sub-segments into two groups and supplies currents of opposite polarities to the first group of sub-segments and the second group of sub-segments, whereby the first and first sub-segments are supplied. Control is performed to set the voltage of the two groups to zero. Further, the control means applies a bias current having a reverse polarity to each of the bisected sub-segments to generate an equal and reverse-polarity voltage so that the voltage generated by the sub-segment is zero. It is characterized by performing the control.

In the control method of the programmable Josephson voltage standard device of the present invention, the power consumed by the Josephson array, that is, the chip is constant regardless of the voltage value generated by the PJVS chip, so that the chip temperature is stabilized. As a result, the bias current operating region does not fluctuate. As the chip temperature stabilizes, the thermoelectromotive force (V _{TEMF +} -V _TEMF- ) also does not fluctuate. Therefore, even when using a refrigerator in which uniform cryogenic cooling of the entire chip is difficult, a high arbitrary voltage of 0 to 20 V class can be obtained stably and precisely. In addition, the programmable Josephson voltage standard device of the present invention can keep the chip temperature constant by providing a control unit that keeps the power consumption of the PJVS chip constant regardless of the generated voltage value. If fluctuations in the chip temperature can be suppressed, fluctuations in both the bias current operating region and the thermoelectromotive force can be suppressed. Even when a refrigerator is used, a high arbitrary voltage of 0 to 20 V class can be output stably and precisely.

The figure explaining the programmable Josephson voltage standard apparatus of the 1st Embodiment of this invention. The figure explaining the programmable Josephson voltage standard apparatus of the 1st Embodiment of this invention. The figure explaining the programmable Josephson voltage standard apparatus of the 2nd Embodiment of this invention. The figure explaining the programmable Josephson voltage standard apparatus of the 3rd Embodiment of this invention. The figure explaining the programmable Josephson voltage standard apparatus of the 4th Embodiment of this invention. The schematic diagram of a Josephson element. Programmable Josephson voltage standard circuit diagram. The figure which shows the current-voltage characteristic of the bias current and generated voltage in a PJVS segment. The figure which shows a mode that a PJVS chip | tip is mounted in a refrigerator and it cools. The figure which shows the programmable Josephson voltage standard apparatus of a prior art. The figure which shows the programmable Josephson voltage standard apparatus of a prior art. The figure which shows the current voltage characteristic of the bias current and generated voltage in the segment in an array.

  The present invention is a programmable Josephson voltage standard device that keeps the chip temperature constant by keeping the power consumption of the PJVS chip constant regardless of the generated voltage value. If fluctuations in the chip temperature can be suppressed, fluctuations in both the bias current operating region and the thermoelectromotive force can be suppressed. In the programmable Josephson voltage standard device, the present invention controls the bias current source in each segment for the Josephson array divided into a plurality of segments, thereby reducing the power consumed by the entire Josephson array to the output voltage. Regardless of whether it is constant or not. Hereinafter, embodiments will be described.

(First embodiment)
The first embodiment of the present invention solves the problem by using segments similar to those shown in FIGS. In the first embodiment, a segment necessary for obtaining a desired voltage value is selected and a current is supplied to generate a voltage, and a plurality of segments that have not been selected, that is, a segment in which the voltage remains zero in the related art. If they exist and the number of elements is the same, two segments with the same number of elements are formed as one pair, and currents of opposite polarities are sent to each individual in the pair, and the equivalent and reverse polarity Thus, the voltage of the entire pair is set to zero.
A first embodiment will be described with reference to FIG. 1 and FIG. FIG. 1 and FIG. 2 show solutions for the example of generating voltages of 2V and 14V, respectively. 1 and 2, in a PJVS array that operates as a D / A converter with a maximum amplitude of 16V and 4 bits, while generating voltages of 2V and 14V, respectively, the power consumed by the entire chip is equal to that when 16V is generated. The amount is controlled to be a quantity.

  First, a current is passed through a PJVS segment necessary for obtaining a voltage to obtain a desired voltage. As shown in FIG. 1, when 2V is generated, + 1V is generated in the segments A and B. When 14V is generated as shown in FIG. 2, a voltage of + 1V is generated in 14 segments A to N. Conventionally, so far, as can be seen from FIGS. 10 and 11, the power consumption of the chip changes in proportion to the generated voltage as it is. Therefore, next, with respect to the segment in the zero voltage state, one pair is formed by two segments, and currents having opposite polarities are caused to flow to generate voltages having opposite polarities and equal amounts. In FIG. 1, for example, seven sets of (C, D), (E, F), (G, H), (I, J), (K, L), (M, N), (O, P) Pairs are created, and each pair is canceled (+ 1V, -1V) or (-1V, + 1V) so that the voltage becomes zero. Similarly in FIG. 2, (O, P) is canceled as a pair. As a result, even in a segment where the voltage is originally zero and the power consumption is zero, power can be consumed in the same manner as in the voltage state segment while the generated voltage is zeroed in pairs. As a result, the same amount of power can be consumed in the chip as when the maximum voltage (16 V) is generated regardless of the generated voltage value, and the chip temperature can be kept constant.

  The above example is an example in which the segment is divided into 16 segments and 1V per segment. However, it is more generally divided into N segments and the voltage per segment is other than 1V. is there.

From the voltage output terminal, in addition to the voltage generated at the Josephson array, the difference in thermoelectromotive force (V _{TEMF +} -V _TEMF- ) generated at the plus and minus terminals of the lead wire is superimposed as an offset voltage. In the example of FIG. 1, the output voltage from the voltage output terminal is
V _OUT = 2V + V _{TEMF +} (T _16V ) −V _TEMF− (T _16V )

In the example of FIG. 2, the output voltage from the voltage output terminal is actually
V _OUT = 14V + V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ) Thus, in FIGS. 1 and 2, the difference in thermoelectromotive force is V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ) in both cases, and the offset voltage is the same (constant regardless of the voltage value). ). Therefore, the influence can be measured and canceled easily.

  If a segment that cannot be paired occurs, it is better to leave the voltage at zero without passing a bias current through the segment. Since there is at most one such segment and the difference in power consumption is small, the temperature variation is considerably improved compared to the conventional one. Further, it is preferably used in combination with the methods of the second to fourth embodiments.

(Second Embodiment)
In the second embodiment, in the first embodiment, one segment in which a pair is not formed is divided into two equal parts, and a bias current having a reverse polarity is applied to each of the segments to make equal amounts. -A voltage of reverse polarity is generated, and the voltage generated while consuming electric power in the segment is set to zero.

  A second embodiment will be described with reference to FIG. FIG. 3 shows that, in a PJVS array that operates as a D / A converter with a maximum amplitude of 16 V and 4 bits, while generating a voltage of −13 V, the power consumed by the entire chip is equal to that when 16 V is generated. It is an example to control. As shown in the figure, −1V is generated in 13 segments A to M. Three zero voltage segments remain (N, O, P), but first select any two (O, P) and cancel them with (+ 1V, -1V) or (-1V, + 1V). To zero voltage. One (segment N) remains, but this is further divided into two and two bias current sources are connected. On the other hand, + 0.5V is generated while -0.5V is generated on the other side. The voltage can be made zero while consuming electric power. As a result, the same amount of power as that when the maximum voltage (16 V) is generated can be consumed in the chip, and the temperature of the chip can be kept constant. The above example is an example in which the segment is divided into 16 segments and 1V per segment. However, it is more generally divided into N segments and the voltage per segment is other than 1V. is there.

From the voltage output terminal, in addition to the voltage generated at the Josephson array, the difference in thermoelectromotive force (V _{TEMF +} -V _TEMF- ) generated at the plus and minus terminals of the lead wire is superimposed as an offset voltage. In the example of FIG. 3, the output voltage from the voltage output terminal is actually
V _OUT = ₋₁₃ V + V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ) Thus, in the case of FIG. 3, the difference in the thermoelectromotive force is V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ), and the offset voltage is set to the voltage value as in the case of the first embodiment. It is constant regardless. Therefore, the influence can be measured and canceled easily.

(Third embodiment)
Since PJVS is used as a high-precision D / A converter, higher voltage resolution is required. The third embodiment is particularly suitable for PJVS with increased resolution. In the third embodiment, PJVS has a configuration in which at least one of the divided segments is further divided into sub-segments. In the PJVS configured as described above, in order to obtain a desired voltage, a part of those sub-segments is in a voltage state, and when a zero-voltage state sub-segment exists, an appropriate group is formed from the zero-voltage state sub-segments. Thus, by appropriately setting the polarity of the current source supplied to them, a voltage is generated from each individual in the group, and the voltage of the entire group is set to zero. The third embodiment can be used in combination with the first or second embodiment. The sub-segment is preferably divided so that the number of elements is proportional to the power of two. For example, the number of sub-segment elements is proportional to 2 to the 0th power, 2 to the 0th power, 2 to the 1st power, 2 to the 2nd power, ... 2 to the (m-1) th power (total 2 to the power of m) To.

  A third embodiment will be described with reference to FIG. 1 to 3 are configurations as a 4-bit D / A converter, FIG. 4 is a configuration example in which the resolution is increased to 10 bits while the maximum amplitude remains 16V. FIG. 4 illustrates an example in which a voltage of 13.5V is generated and control is performed so that the power consumed by the entire chip is equal to that at the time of 16V generation. The PJVS segment A is further finely divided into sub-segments so that the number of elements is proportional to the power of two. As shown in FIG. 4, the sub-segments A1 to A7 are divided into seven. In sub-segments A1 to A7, the number of segment elements is 2 to the 0th power, 2 to the 0th power, 2 to the 1st power, 2 to the 2nd power, 2 to the 3rd power, 2 to the 4th power, 2 to the 5th power (all are added) In total, the number of elements is proportional to 2 6. This corresponds to an example in which m = 6 is given as a specific numerical value to m described above. In this configuration, an example in which 13.5 V is generated is shown. + 1V is generated in 13 segments B to N, and + 0.5V is generated in A1 for the seven sub-segments (A1 to A7). As a result, 13.5 V is output. For the remaining segment (O, P), a pair is created and canceled as (+ 1V, -1V) or (-1V, + 1V) to zero voltage. Further, the remaining sub-segments (A2 to A7) are formed into groups, and bias currents are set (A2, A3, A4, A5, A6, A7) = (+ 0.25V, −0.125V, −0.0625V, −0.03125V, −0.015625V, −0.015625V). The sum of the voltages A2 to A7 is zero. In this way, a reverse polarity bias current is supplied to the first group (A2) and the second group (A3, A4, A5, A6, A7) to generate an equal / reverse polarity voltage. While the voltage is generated from each individual in the group, the total voltage of the first and second groups is set to zero. By the above method, while generating 13.5V which is a higher resolution voltage, the same amount of power as that when the maximum voltage (16V) is generated can be consumed in the chip, and the temperature of the chip can be kept constant. It becomes possible to keep.

From the voltage output terminal, in addition to the voltage generated at the Josephson array, the difference in thermoelectromotive force (V _{TEMF +} -V _TEMF- ) generated at the plus and minus terminals of the lead wire is superimposed as an offset voltage. In the example of FIG. 4, the output voltage from the voltage output terminal is actually
V _OUT = −13.5 V + V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ) Thus, in the example of the third embodiment, the difference in the thermoelectromotive force is V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ), and the offset voltage is the first and second embodiments. The same as in the case of. Therefore, the influence can be measured and canceled easily.

(Fourth embodiment)
In the fourth embodiment, the PJVS has a configuration in which at least one of the divided segments is further finely divided into sub-segments. In the PJVS configured as described above, in order to obtain a desired voltage, when a part of the sub-segments are in a voltage state and there are sub-segments in a zero voltage state, the sub-segments to be zero voltage are divided into two equal parts. A bias current having a reverse polarity is supplied to each of the divided parts to generate a voltage having the same polarity and a reverse polarity, and the voltage generated by the sub-segment is set to zero. The fourth embodiment can be used in combination with the first and second embodiments.

  A fourth embodiment will be described with reference to FIG. FIG. 5 shows that in a PJVS array that operates as a D / A converter with a maximum amplitude of 16 V and 10 bits, a voltage of 13.03125 V is generated, and the power consumed by the entire chip is equal to that when 16 V is generated. This is an example of control.

  An example in which 13.03125V is generated will be described using the same configuration example as that described in the third embodiment. + 1V is generated in 13 segments B to N, and + 0.03125V is generated in A5 for the seven sub-segments (A1 to A7). As a result, 13.03125V is output. For the remaining segment (O, P), a pair is created and canceled as (+ 1V, -1V) or (-1V, + 1V) to zero voltage. For the remaining sub-segments (A1 to 4, 6, and 7), each sub-segment is divided into two equal parts, two bias current sources are connected, while half voltage (positive polarity) is generated. On the other hand, the other half voltage (negative polarity) is generated. As a result, while generating 13.03125 V, the same amount of power as that when the maximum voltage (16 V) is generated can be consumed in the chip, and the temperature of the chip can be kept constant.

From the voltage output terminal, in addition to the voltage generated at the Josephson array, the difference in thermoelectromotive force (V _{TEMF +} -V _TEMF- ) generated at the plus and minus terminals of the lead wire is superimposed as an offset voltage. In the example of FIG. 5, the output voltage from the voltage output terminal is
V _OUT = 13.03125V + V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ) Thus, in the case of the fourth embodiment, the difference in thermoelectromotive force is V _{TEMF +} (T _16V ) −V _TEMF− (T _16V ), and the offset voltage is the first, second, and third implementations. The same as in the case of the form. Therefore, the influence can be measured and canceled easily.

  In carrying out the present invention, the first, second, third, and fourth embodiments can be appropriately combined. In the programmable Josephson voltage standard device of the present invention, the power obtained by obtaining the desired voltage and consumed by the entire Josephson array is equal to or approximately equal to the power when the maximum voltage is generated regardless of the output voltage. It can control to become.

  The examples shown in the embodiment and the like are described for easy understanding of the invention, and are not limited to this embodiment.

  The problem of chip heat generation becomes serious when the voltage value is high (for example, 10 V or more). Applications of PJVS include calibration of Zener diodes, calibration of voltmeters, AC voltage standards, etc., but the required voltage increases year by year, so the apparatus and method of the present invention are useful. In addition, the cooling method using a refrigerator has a problem that nonuniformity is likely to occur in the cooling temperature of the chip. However, the importance is increasing as an alternative technology to the liquid helium cooling method, and the present invention is applied. It is useful.

1. Superconductor (S)
2. Thin insulator (I) or normal conductor (N)
3. Frequency (f) microwave 5. Josephson element 6. Current source 7. Microwave oscillator 8. PJVS segment operating range (Bias current supply possible range)
9. Operating region shifted due to temperature rise 20, Cooling head 21, PJVS chip 22, Screw, etc. 23, Microwave input terminal 24, Chip carrier 25, Bias current input / voltage output terminal 30, Current-voltage characteristics of PJVS segment 31, Current-voltage characteristics changed with temperature rise

Claims (12)

A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
It is a method of controlling the bias current source in each segment so that the power consumed by the entire Josephson array is kept constant regardless of the output voltage .
For the segment of the pair, by generating equal amounts a and voltages of opposite polarity to flow the opposite polarity of the bias current, to that control method is characterized in that the voltage which the segment pairs are generated zero . A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
It is a method of controlling the bias current source in each segment so that the power consumed by the entire Josephson array is kept constant regardless of the output voltage .
The segment 2 equal portions, by generating the equivalent amount in and opposite polarity voltage to flow a reverse polarity of the bias current for each, characterized in that the voltage to which the segment is generated to zero control method. A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
When a segment necessary for obtaining a desired voltage value is selected and a current is passed to generate a voltage, and there are a plurality of segments that are not selected and the number of elements is equal between them, two equal numbers of elements The segments are formed as one pair, and currents of opposite polarities are passed to each individual in the pair to generate equal and opposite polarity voltages, so that the voltage of the entire pair is zero. Control method. A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
In order to obtain a desired voltage value, select the segment necessary to generate a voltage by supplying current, and for the unselected segment, divide the segment into two equal parts and apply a reverse bias current to each. A control method characterized in that the voltage generated by the segment is made zero by generating equal and opposite polarity voltages. A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
When a segment necessary for obtaining a desired voltage value is selected and a current is passed to generate a voltage, and there are a plurality of segments that are not selected and the number of elements is equal between them, two equal numbers of elements Are formed as one pair, currents having opposite polarities are passed to each individual in the pair to generate equal and opposite polarity voltages, and the voltage of the entire pair is zero,
For a segment that did not form a pair, divide the segment into two equal parts and pass a bias current of opposite polarity to each to generate an equal and opposite polarity voltage. A control method characterized by zeroing. A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
In the programmable Josephson voltage standard device, at least one of the divided segments is further divided into sub-segments,
In order to obtain a desired voltage, a part of the sub-segments is selected and a current is supplied to generate a voltage. A plurality of sub-segments not selected are divided into two groups, and the sub-segments of the first group and the second group A control method characterized in that the voltage of the entire first and second groups is made zero by supplying a reverse polarity current to the sub-segments. 7. The control method according to claim 6 , wherein the sub-segment is divided so that the number of Josephson elements is proportional to a power of two. A control method for a programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments,
In the programmable Josephson voltage standard device, at least one of the divided segments is further divided into sub-segments,
In order to obtain a desired voltage, a part of sub-segments is selected and a current is passed to generate a voltage.
Each sub-segment that is not selected is divided into two equal parts, and a reverse-polarity bias current is applied to each of the divided sub-segments to generate equal and reverse-polarity voltages. A control method characterized by setting zero to zero. A programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments ,
Control means for controlling the bias current source in each segment so as to keep the power consumed by the entire Josephson array constant regardless of the output voltage ,
The control means performs a control to make the voltage generated by the segment pair zero by causing a bias current of reverse polarity to flow and generating an equal and reverse voltage to the paired segments. features and to Help log Lama Bull Josephson voltage standard device. A programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments ,
Control means for controlling the bias current source in each segment so as to keep the power consumed by the entire Josephson array constant regardless of the output voltage ,
The control means applies a bias current of reverse polarity to each of the bisected segments to generate an equal amount of reverse polarity voltage so that the voltage generated by the segment is zero. features and to Help log Lama Bull Josephson voltage standard device be carried out. A programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments ,
Control means for controlling the bias current source in each segment so as to keep the power consumed by the entire Josephson array constant regardless of the output voltage ,
In the programmable Josephson voltage standard device, at least one of the divided segments is further divided into sub-segments,
The control means divides the plurality of sub-segments into two groups, and supplies currents of opposite polarities to the sub-segments of the first group and the sub-segments of the second group, thereby combining the first and second groups. features and to pulp logs Lama Bull Josephson voltage standard apparatus that performs control for the zero. A programmable Josephson voltage standard device comprising a Josephson array divided into a plurality of segments ,
Control means for controlling the bias current source in each segment so as to keep the power consumed by the entire Josephson array constant regardless of the output voltage ,
In the programmable Josephson voltage standard device, at least one of the divided segments is further divided into sub-segments,
The control means applies a bias current having a reverse polarity to each of the equally divided sub-segments to generate an equal amount of a reverse-polarity voltage so that the voltage generated by the sub-segment is zero. features and to pulp logs Lama Bull Josephson voltage standard device be controlled.

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