The United Nations has declared 2025 the “International Year of Quantum Science and Technology”. Since quantum mechanics was first mentioned 100 years ago, it has been a fundamental pillar of our physical understanding of nature. This initiative aims to recognize the groundbreaking contributions of quantum science to technological development since 1925 and to raise global awareness of its importance for a sustainable future. The “Superposition” (face value CHF 1.20) describes the principle that a quantum system can assume several states simultaneously - only a measurement determines which state is realized. An “Observer effect” (face value CHF 1.90) describes the phenomenon that the measurement of a quantum system changes its state. Only through observation does the system “decide” on a certain state. “Entanglement" (face value CHF 2.50) is one of the most fascinating concepts in quantum physics: two or more quan-tum particles remain connected to each other so that a change in one particle immediately affects the state of the other particle - regardless of the distance.
