A quantum standard for sampled electrical measurements
Short Name: Q-WAVE, Project Number: SIB59
Electrical traceability: Pushing the boundaries of electrical measurements
Rapid advances and faster operating speeds in electronics, from phones to sophisticated medical instruments, have outpaced advances in the technology needed to confirm their performance. For alternating current (AC) inputs, current and voltage switch direction many times per second, creating a repeating cycle. Measurement methods use digitisation to convert the continually changing signal from this cycle into a number. This means sampling voltages at very high speed and assigning numeric values, which creates the potential for inaccurate signal transmission. Ensuring voltages are measured with precision, minimised errors and traceability to the SI is important for cutting-edge electronics.
Quantum devices based on superconducting Josephson junctions that create small but highly reliable voltage outputs have great potential for future industrial voltage standards provided they can be scaled up and used to calibrate transfer devices operating at room temperature.
This project made significant developments in producing traceable voltage standards based on Josephson junctions and improving their accessibility to industrial users.
The project:
- Developed the first prototype quantum voltage standard capable of producing the 1 volt output required by industry, by optimising Josephson junctions and assembling multiple 9000 junction arrays
- Demonstrated the feasibility of photodiodes to generate the precise currents needed to operate Josephson junctions. Light pulses generated at room temperature are transmitted through telecom grade fibre to extremely low cryogenic temperature photodiodes to create the voltage output of the Josephson junction arrays
- Developed and validated the performance of a world leading quantum voltage transfer standard, the DualDAC2. This room temperature pulse waveform generator was used to compare NMI cryogenic voltage standards to ensure European harmonisation for the SI volt
- Investigated algorithms and simulations for determining uncertainties associated with high frequency AC waveform sampling and developed a toolbox to help industrial users to assess measurement uncertainties.
The project demonstrated the feasibility of using superconducting Josephson junctions as precise SI linked calibration standards that match industry requirements for a 1 V AC standard. The DualDAC2, which is superior to anything currently on the market for high-precision AC voltage measurements, is being commercialised by the Finnish company Aivon. This will provide a cost-effective instrument for advanced electronics manufacturers to test components against the SI derived volt, helping users to demonstrate that their components match specifications.
Development of the photodiode and optical fibre concept continues in the EMPIR project 15SIB04 QuADC, to improve accuracy further.
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