At Aalto University in Espoo, Finland, researchers have just detected the whisper of a whisper—an amount of energy so infinitesimally small that it barely exists in any meaningful way. Using an ultra-sensitive calorimeter built from superconducting and normal conductors, Academy Professor Mikko Möttönen and his team measured an electromagnetic pulse of just 0.83 zeptojoules, marking the first time a calorimetric device has reached such staggering sensitivity. To put this in perspective, a zeptojoule is less than a trillionth of a billionth of a joule—roughly equivalent to the energy needed to lift a single red blood cell one nanometer against Earth's gravity.
This breakthrough matters because precision measurement at quantum scales is the key that unlocks some of physics' most compelling frontiers. Quantum phenomena operate at scales so tiny that traditional tools fail. By pushing the boundaries of what we can measure, scientists open pathways toward more powerful quantum computers, new ways to hunt for dark matter, and the long-sought ability to count individual photons—the fundamental particles that make up light itself.
The innovation lies in a deceptively elegant design. The research team, collaborating with quantum computing company IQM and Finland's Technical Research Centre (VTT), directed a microwave pulse into a sensor made of two types of metal: superconductors that allow electricity to flow without any resistance, and normal conductors that resist electrical flow. This combination creates a exquisitely fragile state. As Möttönen explains, "That combination of metals makes superconductivity such a fragile phenomenon that it weakens immediately if the temperature in the ultracold conductor rises even a little bit. This makes it such a sensitive setup." The slightest temperature fluctuation disrupts the superconducting state, making the device extraordinarily responsive to the tiniest energy pulses. After carefully filtering the signal, the researchers confirmed they had detected that record-breaking 0.83 zeptojoule pulse.
The implications radiate outward in multiple directions. For dark matter research, the team is developing the system to detect dark-matter axions—hypothetical particles that might rain down from space with no warning. "We want to make this setup capable of measuring input that has an arbitrary time of arrival, which is important for things like detecting dark-matter axions in space when you have no idea when they might reach your system," Möttönen says. For quantum computing, the advantage is equally compelling: the calorimeter operates at the millikelvin temperatures already required by qubits, the basic units of quantum information. This means the device can read quantum information without needing to warm up the system or amplify signals—introducing far less disturbance into delicate quantum states. "In the future, our device could be a component for reading out qubits in quantum computers," Möttönen notes.
The research, published in Nature Electronics, was supported by the Future Makers initiative—funded by the Jane and Aatos Erkko Foundation and the Technology Industries of Finland Centennial Foundation—and conducted using OtaNano, Finland's national research infrastructure for nano-, micro- and quantum technologies. It represents not just a technical achievement but a signal that the tools to explore quantum reality and cosmic mysteries are becoming sharper every year.