Researchers Invent A Supercool Mini Thermometer

A team of researchers from the National Institute of Standards and Technology has invented a mini thermometer which can have big potential applications like monitoring the temperature of processor chips in superconductor-based quantum computers, which must stay cold to work properly.

A paper describing this new invention appeared recently in the Applied Physics Letters journal.

The team says that this superconducting thermometer can measures temperatures from 1 Kelvin (minus 272.15 degreeC or minus 457.87 degreeF) to 50 milliKelvin (mK) and potentially 5 mK.

This invention is important as the thermometer is smaller, faster and more convenient than conventional cryogenic thermometers for chip-scale devices and moreover it can be mass produced.

Coming to the size, the thermometer sizes 2.5 by 1.15 millimeters. And talking about usability, it can be embedded in or stuck to another cryogenic microwave device to measure its temperature when mounted on a chip. Further, it can measure temperatures as fast as 5 milliseconds per measure.

“This was a fun idea that quickly grew into something very helpful,” group leader Joel Ullom said. “The thermometer allows researchers to measure the temperature of a wide range of components in their test packages at very little cost and without introducing a large number of additional electrical connections. This has the potential to benefit researchers working in quantum computing or using low-temperature sensors in a wide range of fields.”

Coming to materials used, the thermometer is made of a superconducting niobium resonator coated with silicon dioxide. The coating interacts with the resonator to shift the frequency at which it naturally vibrates. This happens due to atoms “tunneling” between two sites which is a quantum-mechanical effect.

This new thermometer is invented using a new application of the principle that the natural frequency of the resonator depends on the temperature. The thermometer works by mapping changes in frequency to a temperature.

Journal Reference:
J. Wheeler, M. R. Vissers, M. Malnou, J. Hubmayr, J. N. Ullom, J. Gao. Sub-kelvin thermometer for on-chip measurements of microwave devices utilizing two-level systems in superconducting microresonators. Applied Physics Letters, 2020; 117 (19): 192601 DOI: 10.1063/5.0029351

Press Release: National Institute of Standards and Technology (NIST)