Researchers in Finland have measured the faintest burst of energy ever recorded by a calorimeter: a single electromagnetic pulse carrying just 0.83 zeptojoules, less than a trillionth of a billionth of a joule. The team, led by Academy Professor Mikko Mottonen at Aalto University with quantum-computing firm IQM and the VTT Technical Research Centre of Finland, reported the result in Nature Electronics.
The device is a bolometer built from a junction of superconducting and normal metal. Superconductivity is so fragile that even a minuscule rise in temperature flips the material to a measurable state, letting the sensor register energy levels that previously slipped below the noise floor.
Because the calorimeter runs at the same millikelvin temperatures as quantum-computer qubits, the researchers say it could read out qubits with less disturbance, count individual photons, and one day help hunt for elusive dark-matter axions arriving from space at unpredictable times.