Small Quanta, Big Impact

_{Web special Fraunhofer magazine 1.2025}

A status report from quantum physics, where tiny particles are already achieving great things.

A joke told among quantum physicists goes like this: Heisenberg and Schrödinger are driving in a car when they are stopped by the police. The officer asks Heisenberg, “Do you know how fast you were driving?” Heisenberg thinks for a moment, then answers, “No, but I know exactly where I am.” The police officer gives him a suspicious look, then walks around the car. He opens the trunk and calls out, “Did you know you have a dead cat in your trunk?” Schrödinger sighs in exasperation: “Now I do, you idiot!”

The joke is based on two of the main principles of quantum mechanics. With his uncertainty principle, the young Werner Heisenberg demonstrated in 1925 that in the quantum world, it is impossible to accurately measure both the speed and the position of a particle at the same time. Heisenberg’s formulation of the fundamental laws of quantum mechanics a hundred years ago marked a radical departure from the principles of physics that had appl ied unti l then. Erwin Schrödinger, for his part, demon­strated that particles are not lo­cated in only one specific place; instead, they can be in a state known as superposition. He described matter waves as they spread as being waves of proba­bility. In his famed thought ex­periment, a cat is placed inside a sealed box with a complex radio­active mechanism and is in this kind of superposed state, between living and dead. The act of look­ing to see whether the cat is alive or dead is what determines its actual condition.

These insights radically reshaped our understanding of the world at first – and then our world itself. If not for quantum mechanics, there would be no computers, no lasers, no modern communication technologies. And that is not all. Far from it, in fact: These days, we are able to control the very smallest units of matter individually and put them to use in specific applications – such as com­puters that will soon be able to solve complex problems, highly secure communication and extremely precise measurements in diagnostics or materials research. There is a lot of potential upside, with analysts predicting a market value of up to two trillion U.S. dollars in 2035 for the fields of quantum computing, quantum communi­cations and quantum sensors. Global public-sector in­vestments come to more than 40 billion U.S. dollars, as a recent Fraunhofer study calculated. The importance of advances in this field and the new possibilities it will unlock inspired the United Nations to declare 2025 the International Year of Quantum Science and Technology.