Researchers from Aalto University and the VTT Finnish Technical Research Center have built an ultra-sensitive bolometer — a thermal radiation detector. Made from a gold-palladium mixture, it facilitates real-time measurement of electromagnetic radiation intensity.

An article about the development published in the journal Communications Physics.

A bolometer works by measuring the thermal effect of radiation. When this appliance heats up, its electrical characteristics change, and this can be fixed with high accuracy. The smaller the bolometer, the less radiation is required to heat it. A small radiation detector has a low heat capacity, so a low radiation intensity gives a stronger signal.

“Quantum computers operate in cryostats, extremely cold containers, where even the smallest amount of excess radiation causes great disturbance. Since nanobolometers are very sensitive, they can accurately measure the level of excess radiation in a cryostat to reduce radiation due to better protection, ”says one of the authors of the work, Mikko Mottenen, professor of quantum technology at Aalto University.

In the course of the work, physicists first built a radiation detector from gold, but it broke after a few weeks  because gold is incompatible with aluminum, which is used as a superconductor in the detector. To overcome this, the group began using an alloy of gold and palladium.

In the course of the study, scientists also developed microwave amplifiers. Their task is to amplify the signal, but they also amplify the noise. The superconducting microwave amplifier created by physicists was able to halve bolometric noise in comparison with the best commercial amplifier currently in use.

Roope Kokkoniemi et al,  Communication Physics 2, 124 (2019)