Quantum computers concern us all. They represent a significant advance in the way we think about data processing and computer technology and promise breakthroughs in many scientific and industrial fields. They are also - unlike in the past - no longer just the domain of highly specialised researchers and scientists. In view of the expected applications, which could have a massive impact on many areas of people's lives, it was time to write a work on this subject that is both well-founded and generally understandable. One of the main reasons for the high level of interest in quantum computers is their theoretical ability to solve problems that are practically unsolvable for conventional computers. This includes complex simulations in physics, chemistry and materials science, the improvement of algorithms for artificial intelligence, the optimisation of large systems, for example in logistics or financial models, and not least the possibility of breaking existing encryption techniques. The ability to discover and develop new drugs faster by simulating molecular interactions more precisely is another example of the immense potential of quantum computers. The idea that quantum computers are already capable of performing operations that would take thousands of years for the most powerful conventional computer marks a turning point in the world of information processing. This performance advantage, which the first quantum computers have already demonstrated in specialised tasks, underlines the transformative potential of quantum technology Addressing the topic of quantum computing is therefore not only important for scientists, technologists and industry players, but also for politicians, security experts and ultimately for society as a whole. We are at the beginning of an era in which quantum technologies have the potential to fundamentally change our world.