A newly developed quantum sensor has measured unimaginably small amounts of energy with record-breaking precision. A newly developed technique for measuring unimaginably small amounts of energy could help advance quantum computing and improve the search for dark matter. The method is sensitive enough to detect less than a trillionth of a billionth of a joule and may eventually allow scientists to count individual photons. Quantum mechanics operates at extremely small scales, so researchers are continually developing more precise tools to study particles such as photons, which carry light. Better measurements could improve quantum technologies and help scientists detect hypothetical dark matter particles known as axions. Researchers in Finland recently used an ultra-sensitive heat-based sensor called a calorimeter to measure energy levels below one zeptojoule, equal to one trillionth of a billionth of a joule. For comparison, a zeptojoule is about the amount of energy needed to move a red blood cell upward by one nanometer in Earth’s gravity. The research team was led by Academy Professor Mikko Möttönen at Aalto University in collaboration with quantum computing company IQM and the Technical Research Centre of Finland (VTT). Their findings were published in Nature Electronics. How the Sensor Works Measuring energy at this scale is extremely challenging. To perform the experiment, the researchers sent a microwave pulse into a sensor made from two types of metals: superconductors, which allow electrical signals to move freely, and standard conductors, which create resistance. ‘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,’ says Möttönen, who is also a founder of the quantum computer unicorn IQM. After filtering out background noise, the researchers confirmed that the device detected an electromagnetic pulse carrying