Superconducting circuits are a leading technology for the realisation of practical quantum computers. However, scaling-up towards full-scale, fault-tolerant quantum computers will involve addressing many challenges concerning, e.g., qubit coherence, reproducibility, stability, cross-talk, control, and readout. In order to achieve this, a new generation of metrological methods and tools will be needed. This project will develop such a suite of tools for superconducting qubits and apply them to state-of-the-art one- and two-qubit circuits. These new tools will underpin further engineering advances and allow for accurate characterisation of qubits and materials, as well as manipulation and read-out.

Objectives:

1. Qubit materials: To investigate new ways of characterising materials of superconducting qubits, to be used for qubit metrology, at temperatures below 1 K. To explore different high-coherence materials and processing steps to facilitate comparisons of material measurement techniques. To develop standardised design and processing procedures for interlaboratory comparisons and reproducibility tests of material measurement techniques.
2. Qubit periphery: To develop, fabricate, and test peripherical devices, such as parametric amplifiers and quantum-accurate Josephson pulse generators, to perform qubit control and read-out operations. To mitigate uncertainties arising from peripherical devices used in the control and read‑out chain.
3. Metrology for single and two-qubit gates: To develop harmonised qubit characterisation routines to unpick mechanisms limiting scalability, coherence, and fidelity. To develop statistical tools for accurate benchmarking with minimised measurement error and overhead.
4. Round Robin: To perform a first Europe-wide Round Robin on basic parameters of single qubits. To develop and validate measurement protocols and recommendations for reproducible characterisation of single qubits, including a best practice guide.
5. Impact: To facilitate the take up of the technology and measurement methods developed in the project by the industrial stakeholders and others, and to engage with industrial stakeholders to understand how to support their future needs for superconducting qubit metrology. To implement a research network to enhance collaboration and to create characterisation abilities for superconducting qubits among European NMIs. To engage standardisation bodies (e.g. CEN‑CENELEC) to identify standardisation needs for superconducting qubits and to initiate corresponding standardisation activities.