November 01, 2024 -- Radio Frequency (RF) and microwave power measurements are widely used to support applications across space, defence, and communication. These precise measurements enable engineers to accurately characterise waveforms, components, circuits, and systems.  

Taking this a step further, the NPL and Keysight Technologies collaborated on a groundbreaking research project, exploring RF power at cryogenic temperatures. This resulted in the world’s first successful demonstration of a commercial RF power sensor operating at temperatures as low as 3 kelvin.

This not only marks a significant technological milestone, but it is a critical step forward in supporting quantum development and other applications that require cryogenic conditions. Quantum technology has the potential to achieve major breakthroughs, speeding up computing, communications, and sensing. However, one challenge is that quantum devices such as qubits require operation at cryogenic temperatures. These conditions, while necessary, introduce complexities in maintaining signal integrity and producing precise measurements.

The research focused on utilising Keysight’s N8481S RF power sensor, originally designed for room temperature operation, to perform precise measurements at cryogenic temperatures. The sensor’s thermopile response was meticulously characterised across a range of RF power levels from -35 dBm to 0 dBm in a frequency range from 100 kHz to 10 GHz, ensuring SI traceability through known DC power substitution. This breakthrough opens new possibilities for quantum technologies, where accurate RF power measurements at cryogenic temperatures are crucial.

Dr Murat Celep, NPL Senior Scientist and Science Area Leader, said: “NPL has over 60 years’ expertise in traceable RF and microwave power metrology research. This experience, combined with state-of-the-art cryogenic test facilities at NPL and collaboration with Keysight, has enabled us to demonstrate SI traceable cryogenic power measurements. This is an exciting moment, and we look forward to seeing quantum innovation continue.”

“Our joint efforts have paved the way for advancements in quantum computing and other applications requiring precise RF power measurements at cryogenic temperatures,” said Greg Patschke, General Manager of Keysight’s Aerospace, Defence and Government Solutions Group. “This marks a major milestone, and we are thrilled to have collaborated with the NPL on this groundbreaking research.”

The research results were presented at the 2024 Conference on Precision Electromagnetic Measurements (CPEM) held in Denver, CO, USA, and subsequently published.