Programmable josephson quantum voltage standard ac output characteristic comparison test system and method

Abstract

The application discloses a programmable Josephson quantum voltage standard AC output characteristic comparison test system and method. The application generates synchronous step waves through homologous triggering of two sets of PJVS systems, directly collects difference signals of the two step waves by using a differential sampler, and realizes high-precision comparison of AC output characteristics of the two sets of PJVS systems by combining difference correction and effective value calculation. The application saves a complex intermediate transmission standard, simplifies the comparison process, and improves test efficiency and result accuracy. The application considers theoretical differences caused by parameters such as a PJVS junction parameter, a step number, a bias combination algorithm and a working microwave frequency difference, and further improves test precision by correction, and is suitable for comparison scenes of quantum voltage standard systems of different manufacturers and different parameter configurations.

Description

Technical Field

[0001] This invention belongs to the field of quantum voltage measurement and testing technology, specifically relating to a programmable Josephson quantum voltage standard (PJVS) AC output characteristic comparison test system and method. Background Technology

[0002] Following the reform of the International System of Units (SI), all physical quantities tend to be referenced using quantum mechanics. In the field of AC voltage, the Programmable Josephson Quantum Voltage Standard (PJVS) system, with its ultra-high precision voltage output characteristics, has become one of the mainstream international AC voltage quantization reference standards. However, the transient processes of adjacent quantum voltage steps in the PJVS system are non-quantized. Therefore, in AC metrology applications, differential sampling is actually used to eliminate the influence of transient processes and serve as a method for quantum voltage transfer.

[0003] It is worth noting that different quantum systems need to be compared and verified to ensure their output consistency and measurement accuracy in order to meet the metrological traceability requirements following the reform of the International System of Units (SI). In practical applications, comparative tests of the AC output characteristics of PJVS systems from different laboratories, manufacturers, or with different parameter configurations are required to verify their consistency.

[0004] Existing methods for comparing AC quantum voltage standards primarily employ AC differential measurement schemes. This scheme requires a highly stable AC signal source as an intermediate transfer standard. The differences between the two systems are indirectly obtained by comparing two separate PJVS systems with this transfer standard. However, this approach has several significant drawbacks: First, the stability of the intermediate transfer standard directly affects the accuracy of the comparison results; its own drift introduces additional uncertainty. To ensure accuracy, the transfer standard requires complex calibration and maintenance. Second, the comparison process is cumbersome, requiring two steps to complete the docking test with the transfer standard, resulting in low efficiency. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a programmable Josephson quantum voltage standard AC output characteristic comparison test system and method. It utilizes two programmable Josephson quantum voltage standard (PJVS) systems to generate stepped waves of the same amplitude under the same signal source triggering. The difference signal between the two PJVS systems is collected by a differential sampler and compared with the theoretical voltage value.

[0006] A first aspect of the present invention provides a programmable Josephson quantum voltage standard AC output characteristic comparison test system, comprising:

[0007] Two PJVS systems are used to generate step-approximation AC quantum voltages under the same quantization settings of frequency, number of steps, and amplitude.

[0008] A multi-channel trigger signal source is used to synchronously generate square wave trigger signals;

[0009] An isolated power supply system is used to supply power to the two PJVS systems separately to block interference and drift caused by common ground or common power supply.

[0010] A differential sampler is used to acquire the difference signal output by the two PJVS systems and convert it into a digital signal;

[0011] The host computer controller is used to uniformly configure and coordinate the two PJVS systems, the multi-channel trigger signal source and the differential sampler, and to perform digital signal processing and analysis on the collected differential data and the theoretical voltage data of the two PJVS systems to complete the comparison of AC output characteristics.

[0012] A second aspect of the present invention provides a programmable Josephson quantum voltage standard AC output characteristic comparison test method, applied to the above-mentioned system, comprising the following steps:

[0013] Step 1: Set the quantization parameters to be compared, and send them from the host computer controller to the two PJVS systems and the differential sampler respectively;

[0014] Step 2: Calculate the theoretical voltage array based on the quantization parameters to be compared set in the two PJVS systems, and transmit the obtained data back to the host computer controller. The host computer controller subtracts the two theoretical voltage arrays to obtain the theoretical difference array.

[0015] Step 3: The multi-channel trigger signal source synchronously triggers two sets of PJVS systems to generate their respective step-approximation AC quantum voltages based on the quantization parameters;

[0016] Step 4: After a time delay of Δt, the differential sampler samples the output difference between the two PJVS systems to obtain a digital difference array.

[0017] Step 5: The host computer controller performs array operations to obtain the actual voltage difference array;

[0018] Step 6: Calculate the effective value of the difference voltage based on the actual voltage difference array, compare it with the effective value of the theoretical voltage array of the PJVS system set as reference object 1, calculate the relative deviation, and complete the AC output characteristic consistency assessment.

[0019] Based on the above, the present invention has the following beneficial effects:

[0020] (1) The present invention sets up two PJVS systems. By directly measuring and comparing the output values ​​of the two PJVS systems, the traditional system's AC transmission standard is eliminated, simplifying the structure and testing process of the comparison system, reducing equipment costs and maintenance difficulty, and significantly improving comparison efficiency. Furthermore, the present invention avoids the uncertainty introduced by the drift of the intermediate AC transmission standard, thus improving the accuracy of the comparison results.

[0021] (2) This invention takes into account the theoretical difference caused by parameters such as PJVS junction parameters, number of steps, bias combination algorithm and working microwave frequency difference, and further improves the test accuracy through correction.

[0022] (3) It has strong versatility and is suitable for comparing the AC output characteristics of programmable Josephson quantum voltage standard systems from different manufacturers with different parameter configurations. Attached Figure Description

[0023] Figure 1 A schematic diagram of a programmable Josephson quantum voltage standard AC output characteristic comparison test system;

[0024] Figure 2 This is a schematic diagram of a step-approximation type standard AC quantum voltage. Detailed Implementation

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] This application provides a programmable Josephson quantum voltage standard AC output characteristic comparison test system, in which each module works collaboratively to achieve synchronous control, signal acquisition, and data processing, including:

[0027] The first and second programmable Josephson quantum voltage standard (PJVS) systems, serving as reference object one and reference object two respectively, operate at the same AC quantum voltage frequency f. PJVS The number of steps N in a single cycle and the amplitude V PJVS Under the given quantization conditions, each generates a step-approximation type AC quantum voltage signal.

[0028] The rubidium atomic clock is used to provide a unified, highly stable time reference for multi-channel trigger signal sources and differential samplers, and outputs a 10MHz standard time base signal, thereby ensuring the consistency and traceability of the entire test system in the time dimension.

[0029] A multi-channel trigger signal source is used to synchronously generate three square wave trigger signals under the aforementioned unified time base, including: a first trigger signal, output to the first PJVS system; a second trigger signal, output to the second PJVS system; and a third trigger signal, output to a differential sampler, with a fixed delay Δt relative to the first two signals, used to precisely control the sampling time. The periods of the first and second trigger signals are both 1 / (N×f). PJVS This is used to control the synchronous update of the step voltage of the two PJVS systems.

[0030] The differential sampler has two analog inputs, each connected to the output of one of the two PJVS systems. It is used to directly acquire the difference signal between the two quantum voltage outputs and convert it into a digital signal. Furthermore, it can operate in sample-and-hold mode or integration mode: in sample-and-hold mode, it performs multiple single-point samplings and averages the results at each quantum voltage plateau segment; in integration mode, it continuously integrates the difference signal across the entire plateau segment and outputs the average value to further suppress noise.

[0031] The optical isolation module is connected to the three output terminals of the multi-channel trigger signal source. It is used to block electrical loops through opto-isolation, effectively eliminating ground loops and trigger crosstalk, so as to ensure that the two PJVS systems are completely electrically isolated during the triggering and sampling process.

[0032] An isolated power supply system is used to supply power to the first PJVS system and the second PJVS system separately. The power grounds of each power supply system are not connected to each other, which fundamentally avoids interference and drift caused by common ground or common power supply.

[0033] The host computer controller is used to organize the work of each part; to uniformly configure and coordinate the two PJVS systems, the multi-channel trigger signal source and the differential sampler; and to perform digital signal processing and analysis on the collected differential data and the theoretical voltage data of the two PJVS systems to complete the comparison of AC output characteristics.

[0034] In a preferred connection method, the high-end voltage outputs of the two PJVS systems are shorted to each other, and the low-end outputs are respectively connected to the two input terminals of the differential sampler to achieve common-mode suppression and improve the sensitivity of difference measurement.

[0035] Furthermore, the differential sampler employs a Keysight 3458A analog-to-digital converter. Its clock input is connected to a rubidium atomic clock to acquire the required clock signal.

[0036] This application also provides a method for comparing the AC output characteristics of PJVS systems, used in the aforementioned system. Its core lies in: guided by the quantum benchmark requirements following the International System of Units (SI) reform, by synchronously, in-phase, and in-amplitude synthesizing the AC step waves of two programmable Josephson quantum voltage standard systems using co-source triggering, employing a differential sampler to precisely acquire the weak difference signal between the outputs of the two systems, and combining this with the theoretical difference signal from the outputs of the two PJVS systems and calculations of their respective effective values, ultimately achieving a precise comparison of the AC output characteristics of the two PJVS systems. The method includes the following steps:

[0037] Step 1: Set the frequency f of the AC quantum voltage to be compared in the host computer controller. PJVS Number of steps per cycle N, target amplitude V PJVS and the sampling frequency f of the differential sampler sa The relevant parameters are then sent to the two PJVS systems and the differential sampler.

[0038] Step 2: Based on the Josephson quantum voltage formula, calculate the theoretical voltage arrays [V1] and [V2] corresponding to the two PJVS systems respectively and transmit them to the host computer controller. The host computer controller subtracts the two to obtain the theoretical difference array [ΔV1].

[0039] Step 3: The multi-channel trigger signal source synchronously triggers the two PJVS systems to ensure that the two PJVS systems synchronously output the preset quantum voltage step.

[0040] Step 4: The signals triggered by the multi-channel trigger signal source are simultaneously transmitted to the differential sampler after a time delay of Δt, providing a synchronization reference for signal acquisition and avoiding sampling phase misalignment caused by trigger timing deviations. The differential sampler measures the voltage difference in the stable segment of each quantum voltage step and uploads the acquired difference signal to the host computer controller to obtain the digital difference array [V M ].

[0041] Step 5: The host computer controller performs array operations to obtain the voltage difference array [ΔV] = {[V M ]-([V1]-[V2])}.

[0042] Step Six: Using the step wave RMS value calculation method, calculate the theoretical voltage array RMS value [V1] and the actual output difference array [ΔV] of reference object one to obtain the theoretical voltage array RMS value V of reference object one. 1-RMS The difference array ΔV between the actual output and the actual output RMS (i.e., the effective value of ΔV), ΔV RMS With V 1-RMS By comparing the quotients, the relative deviations are obtained, thereby completing the consistency assessment of the AC output characteristics of the two PJVS systems.

[0043] like Figure 1 As shown, based on the same system settings as the above embodiments, this application's test example provides a specific connection diagram of the system, wherein:

[0044] Both the first and second PJVS systems contain a bias current source, a microwave source, and a programmable Josephson array. The two PJVS systems are powered separately by isolated power supply systems. Driven by a microwave frequency f, they each generate a signal based on the quantization parameters to be compared. Figure 2 The step-approximation type standard AC quantum voltage V shown PJVS .

[0045] The low-side output of the standard AC quantum voltage is connected to the two comparison inputs of the differential sampler. The differential sampler converts the input analog signal into a digital signal and outputs it to the host computer controller.

[0046] Based on the same concept as the methods in the above embodiments, this application also provides a specific method implementation demonstration for the above test case system, including the following steps:

[0047] The first step is to define the target AC output parameters of the two sets of PJVS systems to be compared, including core indicators such as AC quantum voltage amplitude, frequency, phase, and number of steps per cycle, to ensure that the target outputs of the two sets of PJVS systems are consistent.

[0048] The selected measuring equipment should be preheated and calibrated to eliminate inherent equipment errors. Measurement parameters should be set according to the target AC signal frequency; for integrating meters, an appropriate integration time must be configured, and for sampling devices, the sampling theorem must be satisfied.

[0049] The second step is to calculate the theoretical voltage arrays corresponding to the two PJVS systems according to the Josephson quantum voltage formula, and then transmit this data back to the host computer controller.

[0050] It is worth noting that, due to the operating characteristics of the programmable Josephson array, the transient process of adjacent quantum voltage steps is non-quantized. Therefore, in AC metrology applications, the effective value of the AC quantum voltage step wave is actually used as a reference, and its magnitude can be accurately calculated.

[0051] In view of this, the theoretical difference between the two PJVS systems is calculated as follows:

[0052] Based on Josephson's quantum voltage core formula In the formula, n is an integer representing the quantum step number, here n=1; M is a positive integer representing the number of Josephson singletons in the sub-node array; K J This represents the Josephson constant.

[0053] In fact, the effective forward bias summation M calculated using the above formula, based on a specified voltage value, may not be an integer. Therefore, it is necessary to calculate the theoretical difference by considering the hardware parameter differences between the two PJVS systems. This is based on the target set voltage V. PJVS To deduce the number of effective nodes under ideal conditions Since f is a fixed value during AC synthesis, M needs to be approximated by integers to obtain M1 and M2 (determined by their respective bias combination algorithms); and based on the actual input M1 and M2, the theoretical difference array [ΔV1] between the actual output voltage values ​​of the two PJVS systems can be obtained by formula.

[0054] The third step is to store the waveform data of the step-approximation standard AC quantum voltage generated by the first and second PJVS systems into the host computer. The waveform data includes: the AC frequency f of the standard AC quantum voltage. PJVS Number of steps N, standard AC quantum voltage setting V PJVS And the quantum voltage signal values ​​at each step.

[0055] Fourth, the trigger signal generated by the multi-channel trigger signal source adopts the form of a synchronous pulse, and two synchronous pulses are output in phase simultaneously to ensure that the timing of the trigger signal received by the two PJVS sets is consistent. The trigger signal is transmitted to the differential sampler after a time delay of Δt, providing a synchronization reference for signal acquisition and avoiding sampling phase misalignment caused by trigger timing deviation.

[0056] After receiving the trigger signal, both PJVS systems initiate stepped-wave synthesis based on preset target AC voltage parameters. During AC synthesis, the microwave operating frequency remains fixed, and the number of effective junctions M is changed by sequentially refreshing the bias drive parameters to achieve stepped-wave synthesis. Due to the timing constraints of co-source triggering, the stepped-wave synthesis rhythms of the two systems are completely synchronized, ensuring the validity of the difference signal.

[0057] Step 5: Connect the outputs of the two PJVS systems to the differential sampler using differential input mode to reduce the impact of common-mode interference on the acquisition results.

[0058] Step 6: The host computer controller calculates the valid values ​​of each data point.

[0059] The differential sampler measures the voltage difference between the steady segments of the stepped waves output by the two quantum voltage systems, and uploads the acquired difference signals to the host computer controller to obtain a digital difference array [V]. M The digital difference array [V] acquired by the differential sampler. M Subtracting the theoretical difference array [ΔV1] yields the voltage difference array [ΔV] representing the actual output difference. Using the step-wave RMS calculation method, the RMS value V is calculated from the theoretical voltage array RMS value [V1] and the actual output difference array [ΔV] of the reference object.1-RMS and ΔV RMS .

[0060] In mathematics, the general definition of the effective value of a periodic step wave V(t) with period T is:

[0061]

[0062] A quantum voltage step wave contains N voltage steps within one period, where the voltage of the i-th step is V. i The duration is ΔT, where ΔT = T / N. Therefore, the formula for calculating the effective value of a step wave can be simplified to:

[0063]

[0064] The effective value ΔV of the actual output difference array was obtained through calculation. RMS Then, the effective value of the theoretical voltage array [V1] of the reference object is compared with that of the reference object.

[0065] Comparison result output: The effective value of the theoretical voltage array of reference object one is V. 1-RMS Calculate the relative deviation, evaluate the consistency of the AC output characteristics of the two PJVS systems based on the magnitude of the relative deviation, and complete the comparison of the AC output characteristics of the two PJVS systems.

[0066] In summary, this application enables the comparison of quantum voltage systems, simplifying the measurement process. Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the invention, and are not intended to limit the implementation of the invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of this invention are still within the protection scope of this invention.

Claims

1. A programmable Josephson quantum voltage standard AC output characteristic comparison test system, characterized in that, include: Two PJVS systems are used to generate step-approximation AC quantum voltages under the same quantization settings of frequency, number of steps, and amplitude. A multi-channel trigger signal source is used to synchronously generate square wave trigger signals; An isolated power supply system is used to supply power to the two PJVS systems separately to block interference and drift caused by common ground or common power supply. A differential sampler is used to acquire the difference signal output by the two PJVS systems and convert it into a digital signal; The host computer controller is used to uniformly configure and coordinate the two PJVS systems, multi-channel trigger signal sources and differential samplers, and to perform digital signal processing and analysis on the acquired differential data to complete the comparison of AC output characteristics.

2. The system according to claim 1, characterized in that, Also includes: A rubidium atomic clock is used to provide a unified time reference for the multi-channel trigger signal source and differential sampler; The optical isolation module is used to block the electrical circuit through opto-isolation to ensure complete electrical isolation between the two PJVS systems during triggering and sampling.

3. The system according to claim 1 or 2, characterized in that, The square wave trigger signal includes: The first trigger signal and the second trigger signal are respectively output to the two sets of PJVS systems to control the synchronous update of the step voltage of the two sets of PJVS systems; The third trigger signal, with a fixed time delay Δt relative to the first two signals, is output to the differential sampler to control the sampling time.

4. The system according to claim 3, characterized in that, The operating modes of the differential sampler include: The sample-and-hold mode performs multiple single-point samplings and averages them at each quantum voltage plateau segment. In integral mode, the difference signal is continuously integrated over the entire platform segment and the average value is output.

5. The system according to claim 1, characterized in that, The high-end voltage outputs of the two PJVS systems are shorted to each other, and the low-end voltage outputs are connected to the two input terminals of the differential sampler respectively, so as to achieve common-mode rejection and improve the sensitivity of difference measurement.

6. A programmable Josephson quantum voltage standard AC output characteristic comparison test method, applied to the system as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Set the quantization parameters to be compared, and send them from the host computer controller to the two PJVS systems and the differential sampler respectively; Step 2: Calculate the theoretical voltage array based on the quantization parameters to be compared set in the two PJVS systems, and transmit the obtained data back to the host computer controller. The host computer controller subtracts the two theoretical voltage arrays to obtain the theoretical difference array. Step 3: The multi-channel trigger signal source synchronously triggers two sets of PJVS systems to generate their respective step-approximation AC quantum voltages based on the quantization parameters; Step 4: After a time delay of Δt, the differential sampler samples the output difference between the two PJVS systems to obtain a digital difference array. Step 5: The host computer controller performs array operations to obtain the actual voltage difference array; Step 6: Calculate the effective value of the difference voltage based on the actual voltage difference array, compare it with the effective value of the theoretical voltage array of the PJVS system set as reference object 1, calculate the relative deviation, and complete the AC output characteristic consistency assessment.

7. The method according to claim 6, characterized in that, The quantization parameters to be compared include: AC quantum voltage frequency, number of steps per cycle, target amplitude, and sampling frequency of the differential sampler.

8. The method according to claim 7, characterized in that, Step two specifically involves: The two PJVS systems are based on the Josephson quantum voltage formula, the target voltage, and the bias combination algorithm of each PJVS system. Each system calculates and determines the theoretical voltage array corresponding to the two PJVS systems. The host computer controller then subtracts the two to obtain the theoretical difference.

9. The method according to claim 6, characterized in that, In step five, the digital difference array is subtracted from the theoretical difference array to obtain the actual voltage difference array.

10. The method according to claim 6 or 9, characterized in that, In step six, the calculation method for the effective voltage value includes: Suppose that a period T contains N voltage steps, and the voltage of the i-th step is V. i The duration of the step is ΔT = T / N. For a periodic step wave V(t) with period T, we have: .

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