Broadband Quantum-Limited Parametric Amplifier for Astronomy and Quantum Information Technology

Project Information

SPA4AstroQIT

Grant agreement ID: 803862

DOI

10.3030/803862

Project closed

EC signature date 16 August 2018

Start date 1 February 2019

End date 31 January 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 991 678,00

EU contribution

€ 1 991 678,00

Coordinated by

THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
United Kingdom

Periodic Reporting for period 4 - SPA4AstroQIT (Broadband Quantum-Limited Parametric Amplifier for Astronomy and Quantum Information Technology)

Reporting period: 2023-08-01 to 2025-01-31

Summary of the context and overall objectives of the project

Amplifiers are essential in electronic systems, spanning radio, microwave, and mm/sub-mm wave applications. However, even advanced cryogenic HEMT amplifiers struggle with quantum-limited noise, generate significant heat, and degrade above 100 GHz, restricting their use in cutting-edge fields.

Superconducting parametric amplifiers (SPAs) provide a breakthrough alternative. They achieve quantum-limited sensitivity, operate over broad bandwidths, and generate negligible heat. Capable of functioning from radio to THz frequencies, SPAs offer immense potential across multiple domains. This project aimed to advance SPA technology by developing ultra-broadband, quantum-limited amplifiers from microwave to mm/sub-mm wavelengths.

SPAs have wide-ranging applications. In astronomy, they enhance telescope sensitivity, while in satellite communications, their low power consumption is ideal for thermal-constrained environments. In quantum computing, they improve qubit readout fidelity and enable scalable architectures.

This project successfully developed and tested several SPA variants, including JTWPAs, KI-TWPAs, and JSWPAs. We established state-of-the-art lab facilities, built advanced cryogenic measurement systems, and developed a novel theoretical framework for SPA design, including SQUID-based models. Our work led to multiple publications, device wafer fabrications, and collaborations with leading US and European institutions. These amplifiers have already been deployed in real-world experiments, including superconducting qubit readout and the Quantum Sensor for Hidden Sector project searching for axion-like dark matter.

In conclusion, this project has laid the groundwork for next-generation SPA technology. We now aim to extend operations into the mm-wave range and explore functionalities beyond amplification, driving future breakthroughs in quantum science and communications.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

This project was organised into three key work packages:
1. Development of microwave travelling-wave parametric amplifiers (TWPAs)
2. Development of mm-wave TWPAs
3. Demonstration of TWPA-based parametric down-conversion

Despite pandemic-related delays, we achieved key milestones, including commissioning a 10 mK cryogenic system and constructing additional 300 mK and 4 K systems. We also collaborated on an industrially developed 300 mK system for rapid device screening. To enhance efficiency, we implemented an automated measurement system, enabling rapid SPA characterisation and optimising performance.

Work Package I: Microwave TWPAs:

We developed a novel theoretical framework to model and optimise both KI- and JJ-TWPAs, improving prediction accuracy and loss analysis. Using this, we successfully fabricated and tested high-gain, broadband KI-TWPAs, disseminating findings through academic publications and conferences. These amplifiers were deployed for quantum computing and astronomical applications.

For JJ-TWPAs, we doubled bandwidth while reducing the required Josephson junctions by fourfold, enhancing performance. We also developed high-power-handling JJ-TWPAs and unexpectedly innovated JSWPAs, which, though narrower in bandwidth, offer higher yield and stability. These findings contributed to a PhD thesis, career transitions into quantum research, and applications in axion dark matter searches.

Work Package II: Millimetre-Wave TWPAs:

SPAs' scalability makes them ideal for mm-wave systems, reducing noise at critical first-stage amplification. We designed, fabricated, and tested an SPA near 100 GHz, but pandemic-related disruptions slowed progress. To mitigate this, we collaborated with external institutions for testing. Though full high-gain operation was not achieved, we observed crucial nonlinear behaviour, laying the foundation for further development.

Work Package III: TWPA-Based Parametric Down-Converter:

This package aimed to develop a novel parametric mixer that amplifies while down-converting signals, a capability not previously demonstrated. Overcoming design challenges, we successfully implemented this functionality in KITWPAs, marking a likely first in the field. This has major implications for large-pixel mm/sub-mm heterodyne receiver systems.

Impact and Future Prospects:

This project advanced superconducting parametric amplification through theoretical and experimental breakthroughs, leading to multiple publications and a patent filing. The results will impact quantum science, high-frequency electronics, and fundamental physics. The project's success secured an ERC Consolidator Grant, starting in April 2025, to further develop mm-wave SPAs and expand their scientific applications, including quantum computing, neutrino mass measurements, and dark matter searches.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This project pioneered new design methodologies, established cutting-edge experimental setups, and refined fabrication processes. We addressed key engineering challenges, such as custom packaging to mitigate interference and automation systems for accelerated device characterisation. An initial concept, once theoretical, is now a fully operational advanced laboratory, laying the foundation for expanding SPA technology into new frequency regimes and applications.

We achieved the primary goal by test SPAs with an astronomical receiver and delivering prototype devices for qubit-based quantum computation, where they are being evaluated against semiconductor amplifiers. Beyond the original scope, our devices have contributed to fundamental physics experiments, including axion-like dark matter searches and potential applications in neutrino mass determination. While time constraints prevented formal collaborations in that area, this work opens future opportunities.

Key Innovations
• Full-Bandwidth Utilisation: Overcame the traditional idler-mode limitation, enabling full bandwidth use and leading to a patent application.
• Simplified Operation & Integration: Developed a plug-and-play SPA packaging technique, reducing ancillary component needs for seamless deployment.
• Minimised External Interference: Created an operational scheme for efficient real-world use, particularly beneficial for quantum computing applications.
• Expanded Functionality Beyond Amplification: Demonstrated SPAs as both amplifiers and frequency converters, confirming feasibility for extended applications.

By the project’s end, we had generated numerous ideas to enhance SPA performance, extend frequency ranges, and expand functionalities. These advancements will continue under the ERC Consolidator Grant, secured to build on this progress.

The 10mK dilution refrigerator commissioned.

Sample of a KITWPA from the first fabrication batch mounted in a dedicated sample holder.

The 300mK cryogenic system designed and built in-house.