Keysight and National Physical Laboratory Achieve Quantum Milestone with Cryogenic RF Power Measurement Breakthrough

Radio Frequency (RF) and microwave power measurements are widely used to support applications across space, defense, and communication. The precise measurements enable engineers to accurately characterize waveforms, components, circuits, and systems. Taking this a step further, Keysight Technologies and the National Physical Laboratory (NPL) 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 (K). 

This not only marks a significant technological milestone, but it’s 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.  

“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, Defense 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 focused on utilizing 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 characterized 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.

“NPL has over 60 years’ expertise in traceable RF and microwave power metrology research,” said Dr. Murat Celep, Senior Scientist and Science Area Leader at NPL. “This experience, combined with state-of-the-art cryogenic test facilities at NPL and in 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.”

The UK government’s Department for Science, Innovation and Technology (DSIT) supported the research through the UK National Quantum Technologies Program. 

The research results were presented at the 2024 Conference on Precision Electromagnetic Measurements (CPEM) held in Denver, CO, USA, and subsequently published. The citation for the published paper is: M. Celep, S. -H. Shin, M. Stanley, E. Breakenridge, S. Singh and N. Ridler, "SI Traceable RF and Microwave Power Measurements at Cryogenic Temperatures," 2024 Conference on Precision Electromagnetic Measurements (CPEM), Denver, CO, USA, 2024, pp. 1-2, doi: 10.1109/CPEM61406.2024.10646150.